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The cuticles of ecdysozoan animals are barriers to material loss and xenobiotic insult. Key to this barrier is lipid content, the establishment of which is poorly understood. Here, we show that the p-glycoprotein PGP-14 functions coincidentally with the sphingomyelin synthase SMS-5 to establish a polar lipid barrier within the pharyngeal cuticle of the nematode C. elegans. We show that PGP-14 and SMS-5 are coincidentally expressed in the epithelium that surrounds the anterior pharyngeal cuticle where PGP-14 localizes to the apical membrane. pgp-14 and sms-5 also peak in expression at the time of new cuticle synthesis. Loss of PGP-14 and SMS-5 dramatically reduces pharyngeal cuticle staining by Nile Red, a key marker of polar lipids, and coincidentally alters the nematode's response to a wide-range of xenobiotics. We infer that PGP-14 exports polar lipids into the developing pharyngeal cuticle in an SMS-5-dependent manner to safeguard the nematode from environmental insult. Author summary: An infinite number of small molecules have the potential to threaten life. Not surprisingly then, animals have evolved multiple mechanisms to defend against such threats. One defense mechanism employed by many animals is the creation of an outer protective layer called the cuticle. Lipids within the cuticle act as a barrier to retard small molecule passage into the underlying tissues. Water-loving small molecules cannot traverse a lipid barrier and fat-loving molecules can get trapped within the barrier. How this lipid barrier is established is incompletely understood. Here, we describe our discovery of a conserved protein called PGP-14 that is expressed in the tissue that makes the cuticle that protects the mouth and pharynx of the nematode worm C. elegans. We show that PGP-14 peaks in expression at the end of new cuticle synthesis and is necessary for lipid deposition within it. Without PGP-14, many small molecules adversely accumulate within the animal and consequently kill it. Hence, PGP-14 is a key component employed by the animal to help protect it from small molecule threats. [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) are ubiquitous organelles that facilitate neutral lipid storage in cells, including energy-dense triglycerides. They are found in all investigated metazoan embryos where they are thought to provide energy for development. Intriguingly, early embryos of diverse metazoan species asymmetrically allocate LDs amongst cellular lineages, a process which can involve massive intracellular redistribution of LDs. However, the biological reason for asymmetric lineage allocation is unknown. To address this issue, we utilize the Drosophila embryo where the cytoskeletal mechanisms that drive allocation are well characterized. We disrupt allocation by two different means: Loss of the LD protein Jabba results in LDs adhering inappropriately to glycogen granules; loss of Klar alters the activities of the microtubule motors that move LDs. Both mutants cause the same dramatic change in LD tissue inheritance, shifting allocation of the majority of LDs to the yolk cell instead of the incipient epithelium. Embryos with such mislocalized LDs do not fully consume their LDs and are delayed in hatching. Through use of a dPLIN2 mutant, which appropriately localizes a smaller pool of LDs, we find that failed LD transport and a smaller LD pool affect embryogenesis in a similar manner. Embryos of all three mutants display overlapping changes in their transcriptome and proteome, suggesting that lipid deprivation results in a shared embryonic response and a widespread change in metabolism. Excitingly, we find abundant changes related to redox homeostasis, with many proteins related to glutathione metabolism upregulated. LD deprived embryos have an increase in peroxidized lipids and rely on increased utilization of glutathione-related proteins for survival. Thus, embryos are apparently able to mount a beneficial response upon lipid stress, rewiring their metabolism to survive. In summary, we demonstrate that early embryos allocate LDs into specific lineages for subsequent optimal utilization, thus protecting against oxidative stress and ensuring punctual development. Author summary: Embryos of diverse animal species sort their lipid droplets into specific cell lineages early in development. Here we prevent Drosophila embryo's ability to undergo this asymmetric inheritance through two separate genetic perturbations. We then investigate the effects on subsequent embryogenesis, finding developmental delays and an inability to consume the mislocalized lipid droplets. We find a similar delay for embryos which receive fewer lipid droplets from their mothers. To understand how embryos respond to limited access to lipid droplets, we investigate the global transcriptome and proteome in the mutants and find alterations to the expression of hundreds of metabolism genes, including for enzymes that transport sugar across cell membranes, break down fat, or protect against oxidative stress. We test if the upregulated genes have beneficial functions for lipid-deprived embryos. We find that zygotic knock down of the upregulated oxidative stress response genes GSS and GSTT4 as well as the lipase ATGL lowers hatching success in LD-deprived genetic backgrounds, but not wild type. In summary, we find that early lipid droplet lineage sorting sets the stage for metabolic success in subsequent embryogenesis. [ABSTRACT FROM AUTHOR]

Ferroptosis is an iron-dependent form of regulated cell death associated with uncontrolled membrane lipid peroxidation and destruction. Previously, we showed that dietary dihomo-gamma-linolenic acid (DGLA; 20: 3(n-6)) triggers ferroptosis in the germ cells of the model organism, Caenorhabditis elegans. We also demonstrated that ether lipid-deficient mutant strains are sensitive to DGLA-induced ferroptosis, suggesting a protective role for ether lipids. The vinyl ether bond unique to plasmalogen lipids has been hypothesized to function as an antioxidant, but this has not been tested in animal models. In this study, we used C. elegans mutants to test the hypothesis that the vinyl ether bond in plasmalogens acts as an antioxidant to protect against germ cell ferroptosis as well as to protect from whole-body tert-butyl hydroperoxide (TBHP)-induced oxidative stress. We found no role for plasmalogens in either process. Instead, we demonstrate that ether lipid-deficiency disrupts lipid homeostasis in C. elegans, leading to altered ratios of saturated and monounsaturated fatty acid (MUFA) content in cellular membranes. We demonstrate that ferroptosis sensitivity in both wild type and ether-lipid deficient mutants can be rescued in several ways that change the relative abundance of saturated fats, MUFAs and specific polyunsaturated fatty acids (PUFAs). Specifically, we reduced ferroptosis sensitivity by (1) using mutant strains unable to synthesize DGLA, (2) using a strain carrying a gain-of-function mutation in the transcriptional mediator MDT-15, or (3) by dietary supplementation of MUFAs. Furthermore, our studies reveal important differences in how dietary lipids influence germ cell ferroptosis versus whole-body peroxide-induced oxidative stress. These studies highlight a potentially beneficial role for endogenous and dietary MUFAs in the prevention of ferroptosis. Author summary: Ferroptosis is a regulated form of cell death driven by excess production of lipid peroxides. Understanding ferroptosis is important because this type of cell death is associated with disease states such as neurodegeneration and various renal, liver, and lung diseases. In addition, with more knowledge of regulatory mechanisms, induction of ferroptosis could be harnessed to control tumor growth. To examine specific lipid contributions to ferroptosis sensitivity, we used mutant strains of the small roundworm Caenorhabditis elegans exhibiting a range of altered lipid compositions to examine how cellular and dietary lipids influence ferroptosis and oxidative stress sensitivity. We found that the accumulation of lipid peroxides correlates with cell death but that plasmalogens, a subset of ether lipids that are proposed to act as cellular antioxidants, do not protect from ferroptosis or oxidative stress. Instead, ether lipid biosynthesis contributes to lipid homeostasis in membranes. In their absence, membrane saturated fatty acids are increased, while membrane monounsaturated fatty acids (MUFAs) are less abundant. Restoring membrane MUFAs reduces lipid peroxides and contributes to cellular resistance to ferroptotic cell death. These studies suggest that dietary MUFAs could prevent ferroptosis in disease. [ABSTRACT FROM AUTHOR]

Epidemiological and clinical studies have found associations between depression and cardiovascular disease risk factors, and coronary artery disease patients with depression have worse prognosis. The genetic relationship between depression and these cardiovascular phenotypes is not known. We here investigated overlap at the genome-wide level and in individual loci between depression, coronary artery disease and cardiovascular risk factors. We used the bivariate causal mixture model (MiXeR) to quantify genome-wide polygenic overlap and the conditional/conjunctional false discovery rate (pleioFDR) method to identify shared loci, based on genome-wide association study summary statistics on depression (n = 450,619), coronary artery disease (n = 502,713) and nine cardiovascular risk factors (n = 204,402–776,078). Genetic loci were functionally annotated using FUnctional Mapping and Annotation (FUMA). Of 13.9K variants influencing depression, 9.5K (SD 1.0K) were shared with body-mass index. Of 4.4K variants influencing systolic blood pressure, 2K were shared with depression. ConjFDR identified 79 unique loci associated with depression and coronary artery disease or cardiovascular risk factors. Six genomic loci were associated jointly with depression and coronary artery disease, 69 with blood pressure, 49 with lipids, 9 with type 2 diabetes and 8 with c-reactive protein at conjFDR < 0.05. Loci associated with increased risk for depression were also associated with increased risk of coronary artery disease and higher total cholesterol, low-density lipoprotein and c-reactive protein levels, while there was a mixed pattern of effect direction for the other risk factors. Functional analyses of the shared loci implicated metabolism of alpha-linolenic acid pathway for type 2 diabetes. Our results showed polygenic overlap between depression, coronary artery disease and several cardiovascular risk factors and suggest molecular mechanisms underlying the association between depression and increased cardiovascular disease risk. Author summary: Studies have found associations between depression and both cardiovascular disease risk factors and worse cardiovascular disease prognosis. It is unknown if shared genetic factors contribute to these associations. We applied novel statistical tools for polygenic architectures to investigate if there are common genes for depression, coronary artery disease and cardiovascular risk factors (body mass index, blood pressure, lipids, type 2 diabetes and c-reactive protein). We used the statistical methods the bivariate causal mixture model (MiXeR) and the conditional/conjunctional false discovery rate (pleioFDR) to quantify genome-wide overlap and to identify shared genetic variants. We found extensive genetic overlap. Depression shared 68% of genetic variants with body mass index and 14% and with systolic blood pressure. We also identified 79 unique genomic variants associated with depression and coronary artery disease or the risk factors. Variants associated with increased risk for depression also increased the risk of coronary artery disease, some of the lipids and c-reactive protein levels, while there was a mixed pattern of direction for the other risk factors. Further analyses identified shared genetic variants found in metabolism of alpha-linolenic pathway for type 2 diabetes. [ABSTRACT FROM AUTHOR]

Fat stored in the form of lipid droplets has long been considered a defining characteristic of cytoplasm. However, recent studies have shown that nuclear lipid droplets occur in multiple cells and tissues, including in human patients with fatty liver disease. The function(s) of stored fat in the nucleus has not been determined, and it is possible that nuclear fat is beneficial in some situations. Conversely, nuclear lipid droplets might instead be deleterious by disrupting nuclear organization or triggering aggregation of hydrophobic proteins. We show here that nuclear lipid droplets occur normally in C. elegans intestinal cells and germ cells, but appear to be associated with damage only in the intestine. Lipid droplets in intestinal nuclei can be associated with novel bundles of microfilaments (nuclear actin) and membrane tubules that might have roles in damage repair. To increase the normal, low frequency of nuclear lipid droplets in wild-type animals, we used a forward genetic screen to isolate mutants with abnormally large or abundant nuclear lipid droplets. Genetic analysis and cloning of three such mutants showed that the genes encode the lipid regulator SEIP-1/seipin, the inner nuclear membrane protein NEMP-1/Nemp1/TMEM194A, and a component of COPI vesicles called COPA-1/α-COP. We present several lines of evidence that the nuclear lipid droplet phenotype of copa-1 mutants results from a defect in retrieving mislocalized membrane proteins that normally reside in the endoplasmic reticulum. The seip-1 mutant causes most germ cells to have nuclear lipid droplets, the largest of which occupy more than a third of the nuclear volume. Nevertheless, the nuclear lipid droplets do not trigger apoptosis, and the germ cells differentiate into gametes that produce viable, healthy progeny. Thus, our results suggest that nuclear lipid droplets are detrimental to intestinal nuclei, but have no obvious deleterious effect on germ nuclei. Author summary: Several human disorders such as obesity are associated with abnormal fat storage. Cells normally store fat in cytoplasmic organelles called lipid droplets. However, recent studies have shown that fat can also form inside of the cell nucleus, and the effects of nuclear fat are not known. Here we use the cell biology and genetics of the model organism C. elegans to study the causes and consequences of nuclear fat. We show that intestinal cells can contain nuclear fat, particularly during high-low-high changes in cytoplasmic fat that involve de novo fat synthesis. Nuclear fat is associated with multiple changes in intestinal nuclei that appear to represent damage and repair. Germ nuclei that normally differentiate into oocytes can also contain nuclear fat. In germ cells, however, even high levels of nuclear fat appear to cause little or no damage. Our results suggest that intestinal nuclei and germ cell nuclei might have different responses to nuclear fat in part because they differ in chromosomal organization at the nuclear envelope. [ABSTRACT FROM AUTHOR]

Fish oil supplementation is widely used for reducing serum triglycerides (TAGs) but has mixed effects on other circulating cardiovascular biomarkers. Many genetic polymorphisms have been associated with blood lipids, including high- and low-density-lipoprotein cholesterol (HDL-C, LDL-C), total cholesterol, and TAGs. Here, the gene-diet interaction effects of fish oil supplementation on these lipids were analyzed in a discovery cohort of up to 73,962 UK Biobank participants, using a 1-degree-of-freedom (1df) test for interaction effects and a 2-degrees-of-freedom (2df) test to jointly analyze interaction and main effects. Associations with P < 1×10−6 in either test (26,157; 18,300 unique variants) were advanced to replication in up to 7,284 participants from the Atherosclerosis Risk in Communities (ARIC) Study. Replicated associations reaching 1df P < 0.05 (2,175; 1,763 unique variants) were used in meta-analyses. We found 13 replicated and 159 non-replicated (UK Biobank only) loci with significant 2df joint tests that were predominantly driven by main effects and have been previously reported. Four novel interaction loci were identified with 1df P < 5×10−8 in meta-analysis. The lead variant in the GJB6-GJB2-GJA3 gene cluster, rs112803755 (A>G; minor allele frequency = 0.041), shows exclusively interaction effects. The minor allele is significantly associated with decreased TAGs in individuals with fish oil supplementation, but with increased TAGs in those without supplementation. This locus is significantly associated with higher GJB2 expression of connexin 26 in adipose tissue; connexin activity is known to change upon exposure to omega-3 fatty acids. Significant interaction effects were also found in three other loci in the genes SLC12A3 (HDL-C), ABCA6 (LDL-C), and MLXIPL (LDL-C), but highly significant main effects are also present. Our study identifies novel gene-diet interaction effects for four genetic loci, whose effects on blood lipids are modified by fish oil supplementation. These findings highlight the need and possibility for personalized nutrition. Author summary: We utilized the unprecedentedly large genotype and phenotype dataset in the UK Biobank to perform a genome-wide association study (GWAS) which accounts for the interplay between genotype and dietary intake. We examined the interaction effects of fish oil supplementation on levels of blood lipids (LDL-C, HDL-C, TAGs, and total cholesterol). Our findings were replicated in the Atherosclerosis Risk in Communities (ARIC) Study. We found that at the genetic variant rs112803755 (A>G), the minor allele (G) is associated with a decrease in TAGs among individuals with fish oil supplementation, but is associated with an increase in TAGs among those without supplementation. In other words, only individuals carrying the minor allele benefit from fish oil supplementation in reducing TAG levels. We further analyzed rs112803755 with functional genomics data from the Genotype-Tissue Expression (GTEx) project to identify potential target genes, and found a connexin coding gene which has been previously reported to respond to cellular omega-3 levels. This research suggests that inter-personal variation in TAG response to fish oil supplementation is in part explained by genotype, and that fish oil dose adjustment based on genotype should be investigated as a means to protect against cardiovascular disease risk. [ABSTRACT FROM AUTHOR]

Apolipoprotein B-containing lipoproteins (B-lps) are essential for the transport of hydrophobic dietary and endogenous lipids through the circulation in vertebrates. Zebrafish embryos produce large numbers of B-lps in the yolk syncytial layer (YSL) to move lipids from yolk to growing tissues. Disruptions in B-lp production perturb yolk morphology, readily allowing for visual identification of mutants with altered B-lp metabolism. Here we report the discovery of a missense mutation in microsomal triglyceride transfer protein (Mtp), a protein that is essential for B-lp production. This mutation of a conserved glycine residue to valine (zebrafish G863V, human G865V) reduces B-lp production and results in yolk opacity due to aberrant accumulation of cytoplasmic lipid droplets in the YSL. However, this phenotype is milder than that of the previously reported L475P stalactite (stl) mutation. MTP transfers lipids, including triglycerides and phospholipids, to apolipoprotein B in the ER for B-lp assembly. In vitro lipid transfer assays reveal that while both MTP mutations eliminate triglyceride transfer activity, the G863V mutant protein unexpectedly retains ~80% of phospholipid transfer activity. This residual phospholipid transfer activity of the G863V mttp mutant protein is sufficient to support the secretion of small B-lps, which prevents intestinal fat malabsorption and growth defects observed in the mttpstl/stl mutant zebrafish. Modeling based on the recent crystal structure of the heterodimeric human MTP complex suggests the G865V mutation may block triglyceride entry into the lipid-binding cavity. Together, these data argue that selective inhibition of MTP triglyceride transfer activity may be a feasible therapeutic approach to treat dyslipidemia and provide structural insight for drug design. These data also highlight the power of yolk transport studies to identify proteins critical for B-lp biology. Author summary: Cardiovascular disease affects about a third of the world's population and is mediated by the buildup of lipids (primarily derived from plasma lipoproteins) in the wall of blood vessels. An essential protein required for the synthesis of the lipoproteins, from insects to humans, is microsomal triglyceride transfer protein (MTP). This protein transfers lipids, including triglycerides and phospholipids, to apolipoprotein B (APOB) for the assembly of ApoB-containing lipoproteins. Here we report a mutation in MTP that blocks the transfer of triglycerides but not phospholipids. Modeling based on the recent crystal structure of the MTP complex suggests the G865V mutation may block access to the region of the protein that binds triglyceride. In zebrafish, the residual phospholipid transfer activity of the mutant protein is sufficient to support secretion of small ApoB-containing lipoproteins and prevent a number of serious health conditions observed in humans harboring null MTP mutations (e.g., intestinal fat malabsorption, growth retardation). These results suggest that selective inhibitors of MTP that can mimic this mutation may be a feasible therapeutic approach to treat dyslipidemias in humans. [ABSTRACT FROM AUTHOR]

Lipid droplets (LD) are affected in multiple human disorders. These highly dynamic organelles are involved in many cellular roles. While their intracellular dispersion is crucial to ensure their function and other organelles-contact, underlying mechanisms are still unclear. Here we show that Spastin, one of the major proteins involved in Hereditary Spastic Paraplegia (HSP), controls LD dispersion. Spastin depletion in zebrafish affects metabolic properties and organelle dynamics. These functions are ensured by a conserved complex set of splice variants. M1 isoforms determine LD dispersion in the cell by orchestrating endoplasmic reticulum (ER) shape along microtubules (MTs). To further impact LD fate, Spastin modulates transcripts levels and subcellular location of other HSP key players, notably Seipin and REEP1. In pathological conditions, mutations in human Spastin M1 disrupt this mechanism and impacts LD network. Spastin depletion influences not only other key proteins but also modulates specific neutral lipids and phospholipids, revealing an impact on membrane and organelle components. Altogether our results show that Spastin and its partners converge in a common machinery that coordinates LD dispersion and ER shape along MTs. Any alteration of this system results in HSP clinical features and impacts lipids profile, thus opening new avenues for novel biomarkers of HSP. Author summary: Hereditary spastic paraplegia is a group of inherited diseases characterized by spasticity and gait disorder. Spastin mutations represent the most common cause of hereditary spastic paraplegia. While Spastin was initially defined as a microtubule severing protein, alternative isoforms impact organelles. In the present work, we identify how Spastin combines the specificity of different splice variants to coordinate endoplasmic reticulum shape and lipid droplet dispersion. When mutated, Spastin impairs this synchronization between organelle dynamics, and affects other proteins involved in hereditary spastic paraplegia, notably REEP1 and Seipin. The coordination of lipid droplet dispersion and reticulum shaping under the control of Spastin is a unique trafficking model, affected in the different forms of hereditary spastic paraplegia. The impact of Spastin on this machinery results in the alteration of the lipid profile, particularly phospholipids and neutral lipids in muscle and brain. These potential biomarkers open new therapeutic avenues in hereditary spastic paraplegia. [ABSTRACT FROM AUTHOR]

Phosphoribosyl pyrophosphate synthetase (PRPS) is a rate-limiting enzyme whose function is important for the biosynthesis of purines, pyrimidines, and pyridines. Importantly, while missense mutations of PRPS1 have been identified in neurological disorders such as Arts syndrome, how they contribute to neuropathogenesis is still unclear. We identified the Drosophila ortholog of PRPS (dPRPS) as a direct target of RB/E2F in Drosophila, a vital cell cycle regulator, and engineered dPRPS alleles carrying patient-derived mutations. Interestingly, while they are able to develop normally, dPRPS mutant flies have a shortened lifespan and locomotive defects, common phenotypes associated with neurodegeneration. Careful analysis of the fat body revealed that patient-derived PRPS mutations result in profound defects in lipolysis, macroautophagy, and lysosome function. Significantly, we show evidence that the nervous system of dPRPS mutant flies is affected by these defects. Overall, we uncovered an unexpected link between nucleotide metabolism and autophagy/lysosome function, providing a possible mechanism by which PRPS-dysfunction contributes to neurological disorders. [ABSTRACT FROM AUTHOR]

Ageing populations pose one of the main public health crises of our time. Reprogramming gene expression by altering the activities of sequence-specific transcription factors (TFs) can ameliorate deleterious effects of age. Here we explore how a circuit of TFs coordinates pro-longevity transcriptional outcomes, which reveals a multi-tissue and multi-species role for an entire protein family: the E-twenty-six (ETS) TFs. In Drosophila, reduced insulin/IGF signalling (IIS) extends lifespan by coordinating activation of Aop, an ETS transcriptional repressor, and Foxo, a Forkhead transcriptional activator. Aop and Foxo bind the same genomic loci, and we show that, individually, they effect similar transcriptional programmes in vivo. In combination, Aop can both moderate or synergise with Foxo, dependent on promoter context. Moreover, Foxo and Aop oppose the gene-regulatory activity of Pnt, an ETS transcriptional activator. Directly knocking down Pnt recapitulates aspects of the Aop/Foxo transcriptional programme and is sufficient to extend lifespan. The lifespan-limiting role of Pnt appears to be balanced by a requirement for metabolic regulation in young flies, in which the Aop-Pnt-Foxo circuit determines expression of metabolic genes, and Pnt regulates lipolysis and responses to nutrient stress. Molecular functions are often conserved amongst ETS TFs, prompting us to examine whether other Drosophila ETS-coding genes may also affect ageing. We show that five out of eight Drosophila ETS TFs play a role in fly ageing, acting from a range of organs and cells including the intestine, adipose and neurons. We expand the repertoire of lifespan-limiting ETS TFs in C. elegans, confirming their conserved function in ageing and revealing that the roles of ETS TFs in physiology and lifespan are conserved throughout the family, both within and between species. [ABSTRACT FROM AUTHOR]

Schnyder corneal dystrophy (SCD) is a rare genetic eye disease characterized by corneal opacification resulted from deposition of excess free cholesterol. UbiA prenyltransferase domain-containing protein-1 (UBIAD1) is an enzyme catalyzing biosynthesis of coenzyme Q10 and vitamin K2. More than 20 UBIAD1 mutations have been found to associate with human SCD. How these mutants contribute to SCD development is not fully understood. Here, we identified HMGCR as a binding partner of UBIAD1 using mass spectrometry. In contrast to the Golgi localization of wild-type UBIAD1, SCD-associated mutants mainly resided in the endoplasmic reticulum (ER) and competed with Insig-1 for HMGCR binding, thereby preventing HMGCR from degradation and increasing cholesterol biosynthesis. The heterozygous Ubiad1 G184R knock-in (Ubiad1G184R/+) mice expressed elevated levels of HMGCR protein in various tissues. The aged Ubiad1G184R/+ mice exhibited corneal opacification and free cholesterol accumulation, phenocopying clinical manifestations of SCD patients. In summary, these results demonstrate that SCD-associated mutations of UBIAD1 impair its ER-to-Golgi transportation and enhance its interaction with HMGCR. The stabilization of HMGCR by UBIAD1 increases cholesterol biosynthesis and eventually causes cholesterol accumulation in the cornea. [ABSTRACT FROM AUTHOR]

Increasing seed oil content is one of the most important breeding goals for soybean due to a high global demand for edible vegetable oil. However, genetic improvement of seed oil content has been difficult in soybean because of the complexity of oil metabolism. Determining the major variants and molecular mechanisms conferring oil accumulation is critical for substantial oil enhancement in soybean and other oilseed crops. In this study, we evaluated the seed oil contents of 219 diverse soybean accessions across six different environments and dissected the underlying mechanism using a high-resolution genome-wide association study (GWAS). An environmentally stable quantitative trait locus (QTL), GqOil20, significantly associated with oil content was identified, accounting for 23.70% of the total phenotypic variance of seed oil across multiple environments. Haplotype and expression analyses indicate that an oleosin protein-encoding gene (GmOLEO1), colocated with a leading single nucleotide polymorphism (SNP) from the GWAS, was significantly correlated with seed oil content. GmOLEO1 is predominantly expressed during seed maturation, and GmOLEO1 is localized to accumulated oil bodies (OBs) in maturing seeds. Overexpression of GmOLEO1 significantly enriched smaller OBs and increased seed oil content by 10.6% compared with those of control seeds. A time-course transcriptomics analysis between transgenic and control soybeans indicated that GmOLEO1 positively enhanced oil accumulation by affecting triacylglycerol metabolism. Our results also showed that strong artificial selection had occurred in the promoter region of GmOLEO1, which resulted in its high expression in cultivated soybean relative to wild soybean, leading to increased seed oil accumulation. The GmOLEO1 locus may serve as a direct target for both genetic engineering and selection for soybean oil improvement. [ABSTRACT FROM AUTHOR]

Berardinelli-Seip congenital generalized lipodystrophy is associated with increased bone mass suggesting that fat tissue regulates the skeleton. Because there is little mechanistic information regarding this issue, we generated "fat-free" (FF) mice completely lacking visible visceral, subcutaneous and brown fat. Due to robust osteoblastic activity, trabecular and cortical bone volume is markedly enhanced in these animals. FF mice, like Berardinelli-Seip patients, are diabetic but normalization of glucose tolerance and significant reduction in circulating insulin fails to alter their skeletal phenotype. Importantly, the skeletal phenotype of FF mice is completely rescued by transplantation of adipocyte precursors or white or brown fat depots, indicating that adipocyte derived products regulate bone mass. Confirming such is the case, transplantation of fat derived from adiponectin and leptin double knockout mice, unlike that obtained from their WT counterparts, fails to normalize FF bone. These observations suggest a paucity of leptin and adiponectin may contribute to the increased bone mass of Berardinelli-Seip patients. [ABSTRACT FROM AUTHOR]

The article discusses the authors' perspective on the study "Genome-wide association study reveals sex-specific genetic architecture of facial attractiveness" by B. Hu and colleagues. They discuss the results of the study which suggested that single nucleotide polymorphism (SNP) is associated with rated facial attractiveness.

Dipteran or “true” flies occupy nearly every terrestrial habitat, and have evolved to feed upon a wide variety of sources including fruit, pollen, decomposing animal matter, and even vertebrate blood. Here we analyze the molecular, genetic and cellular basis of odor response in the tsetse fly Glossina morsitans, which feeds on the blood of humans and their livestock, and is a vector of deadly trypanosomes. The G. morsitans antenna contains specialized subtypes of sensilla, some of which line a sensory pit not found in the fruit fly Drosophila. We characterize distinct patterns of G. morsitans Odor receptor (GmmOr) gene expression in the antenna. We devise a new version of the “empty neuron” heterologous expression system, and use it to functionally express several GmmOrs in a mutant olfactory receptor neuron (ORN) of Drosophila. GmmOr35 responds to 1-hexen-3-ol, an odorant found in human emanations, and also alpha-pinene, a compound produced by malarial parasites. Another receptor, GmmOr9, which is expressed in the sensory pit, responds to acetone, 2-butanone and 2-propanol. We confirm by electrophysiological recording that neurons of the sensory pit respond to these odorants. Acetone and 2-butanone are strong attractants long used in the field to trap tsetse. We find that 2-propanol is also an attractant for both G. morsitans and the related species G. fuscipes, a major vector of African sleeping sickness. The results identify 2-propanol as a candidate for an environmentally friendly and practical tsetse attractant. Taken together, this work characterizes the olfactory system of a highly distinct kind of fly, and it provides an approach to identifying new agents for controlling the fly and the devastating diseases that it carries. [ABSTRACT FROM AUTHOR]

Balancing selection provides a plausible explanation for the maintenance of deleterious alleles at moderate frequency in livestock, including lethal recessives exhibiting heterozygous advantage in carriers. In the current study, a leg weakness syndrome causing mortality of piglets in a commercial line showed monogenic recessive inheritance, and a region on chromosome 15 associated with the syndrome was identified by homozygosity mapping. Whole genome resequencing of cases and controls identified a mutation causing a premature stop codon within exon 3 of the porcine Myostatin (MSTN) gene, similar to those causing a double-muscling phenotype observed in several mammalian species. The MSTN mutation was in Hardy-Weinberg equilibrium in the population at birth, but significantly distorted amongst animals still in the herd at 110 kg, due to an absence of homozygous mutant genotypes. In heterozygous form, the MSTN mutation was associated with a major increase in muscle depth and decrease in fat depth, suggesting that the deleterious allele was maintained at moderate frequency due to heterozygous advantage (allele frequency, q = 0.22). Knockout of the porcine MSTN by gene editing has previously been linked to problems of low piglet survival and lameness. This MSTN mutation is an example of putative balancing selection in livestock, providing a plausible explanation for the lack of disrupting MSTN mutations in pigs despite many generations of selection for lean growth. [ABSTRACT FROM AUTHOR]

The Drosophila protocadherins Dachsous and Fat regulate growth and tissue polarity by modulating the levels, membrane localization and polarity of the atypical myosin Dachs. Localization to the apical junctional membrane is critical for Dachs function, and the adapter protein Vamana/Dlish and palmitoyl transferase Approximated are required for Dachs membrane localization. However, how Dachs levels are regulated is poorly understood. Here we identify the early girl gene as playing an essential role in Fat signaling by limiting the levels of Dachs protein. early girl mutants display overgrowth of the wings and reduced cross vein spacing, hallmark features of mutations affecting Fat signaling. Genetic experiments reveal that it functions in parallel with Fat to regulate Dachs. early girl encodes an E3 ubiquitin ligase, physically interacts with Dachs, and regulates its protein stability. Concomitant loss of early girl and approximated results in accumulation of Dachs and Vamana in cytoplasmic punctae, suggesting that it also regulates their trafficking to the apical membrane. Our findings establish a crucial role for early girl in Fat signaling, involving regulation of Dachs and Vamana, two key downstream effectors of this pathway. [ABSTRACT FROM AUTHOR]

Signaling pathways that control the activities in non-photosynthetic plastids, important sites of plant metabolism, are largely unknown. Previously, we demonstrated that WRKY2 and WRKY34 transcription factors play an essential role in pollen development downstream of mitogen-activated protein kinase 3 (MPK3) and MPK6 in Arabidopsis. Here, we report that GLUCOSE-6-PHOSPHATE/PHOSPHATE TRANSLOCATOR 1 (GPT1) is a key target gene of WRKY2/WRKY34. GPT1 transports glucose-6-phosphate (Glc6P) into plastids for starch and/or fatty acid biosynthesis depending on the plant species. Loss of function of WRKY2/WRKY34 results in reduced GPT1 expression, and concomitantly, reduced accumulation of lipid bodies in mature pollen, which leads to compromised pollen viability, germination, pollen tube growth, and male transmission in Arabidopsis. Pollen-specific overexpression of GPT1 rescues the pollen defects of wrky2 wrky34 double mutant. Furthermore, gain-of-function activation of MPK3/MPK6 enhances GPT1 expression; whereas GPT1 expression is reduced in mkk4 mkk5 double mutant. Together, this study revealed a cytoplasmic/nuclear signaling pathway capable of coordinating the metabolic activities in plastids. High-level expression of GPT1 at late stages of pollen development drives Glc6P from cytosol into plastids, where Glc6P is used for fatty acid biosynthesis, an important step of lipid body biogenesis. The accumulation of lipid bodies during pollen maturation is essential to pollen fitness and successful reproduction. [ABSTRACT FROM AUTHOR]

The human 1q21.1 deletion of ten genes is associated with increased risk of schizophrenia. This deletion involves the β-subunit of the AMP-activated protein kinase (AMPK) complex, a key energy sensor in the cell. Although neurons have a high demand for energy and low capacity to store nutrients, the role of AMPK in neuronal physiology is poorly defined. Here we show that AMPK is important in the nervous system for maintaining neuronal integrity and for stress survival and longevity in Drosophila. To understand the impact of this signaling system on behavior and its potential contribution to the 1q21.1 deletion syndrome, we focused on sleep, an important role of which is proposed to be the reestablishment of neuronal energy levels that are diminished during energy-demanding wakefulness. Sleep disturbances are one of the most common problems affecting individuals with psychiatric disorders. We show that AMPK is required for maintenance of proper sleep architecture and for sleep recovery following sleep deprivation. Neuronal AMPKβ loss specifically leads to sleep fragmentation and causes dysregulation of genes believed to play a role in sleep homeostasis. Our data also suggest that AMPKβ loss may contribute to the increased risk of developing mental disorders and sleep disturbances associated with the human 1q21.1 deletion. [ABSTRACT FROM AUTHOR]

The control of the size of internal tubular organs, such as the lungs or vascular system, is critical for proper physiological activity and to prevent disease or malformations. This control incorporates the intrinsic physical anisotropy of tubes to generate proportionate organs that match their function. The exact mechanisms underlying tube size control and how tubular anisotropy is translated at the cellular level are still not fully understood. Here we investigate these mechanisms using the Drosophila tracheal system. We show that the apical polarity protein Crumbs transiently accumulates anisotropically at longitudinal cell junctions during tube elongation. We provide evidence indicating that the accumulation of Crumbs in specific apical domains correlates with apical surface expansion, suggesting a link between the anisotropic accumulation of Crumbs at the cellular level and membrane expansion. We find that Src42A is required for the anisotropic accumulation of Crumbs, thereby identifying the first polarised cell behaviour downstream of Src42A. Our results indicate that Src42A regulates a mechanism that increases the fraction of Crb protein at longitudinal junctions, and genetic interaction experiments are consistent with Crb acting downstream of Src42A in controlling tube size. Collectively, our results suggest a model in which Src42A would sense the inherent anisotropic mechanical tension of the tube and translate it into a polarised Crumbs accumulation, which may promote a bias towards longitudinal membrane expansion, orienting cell elongation and, as a consequence, longitudinal growth at the tissue level. This work provides new insights into the key question of how organ growth is controlled and polarised and unveils the function of two conserved proteins, Crumbs and Src42A, with important roles in development and homeostasis as well as in disease, in this biological process. [ABSTRACT FROM AUTHOR]

Antimicrobial peptides act as a host defense mechanism and regulate the commensal microbiome. To obtain a comprehensive view of genes contributing to long-term memory we performed mRNA sequencing from single Drosophila heads following behavioral training that produces long-lasting memory. Surprisingly, we found that Diptericin B, an immune peptide with antimicrobial activity, is upregulated following behavioral training. Deletion and knock down experiments revealed that Diptericin B and another immune peptide, Gram-Negative Bacteria Binding Protein like 3, regulate long-term but not short-term memory or instinctive behavior in Drosophila. Interestingly, removal of DptB in the head fat body and GNBP-like3 in neurons results in memory deficit. That putative antimicrobial peptides influence memory provides an example of how some immune peptides may have been repurposed to influence the function of nervous system. [ABSTRACT FROM AUTHOR]

Genome-wide association studies have shown that pleiotropy is a common phenomenon that can potentially be exploited for enhanced detection of susceptibility loci. We propose heritability informed power optimization (HIPO) for conducting powerful pleiotropic analysis using summary-level association statistics. We find optimal linear combinations of association coefficients across traits that are expected to maximize non-centrality parameter for the underlying test statistics, taking into account estimates of heritability, sample size variations and overlaps across the traits. Simulation studies show that the proposed method has correct type I error, robust to population stratification and leads to desired genome-wide enrichment of association signals. Application of the proposed method to publicly available data for three groups of genetically related traits, lipids (N = 188,577), psychiatric diseases (Ncase = 33,332, Ncontrol = 27,888) and social science traits (N ranging between 161,460 to 298,420 across individual traits) increased the number of genome-wide significant loci by 12%, 200% and 50%, respectively, compared to those found by analysis of individual traits. Evidence of replication is present for many of these loci in subsequent larger studies for individual traits. HIPO can potentially be extended to high-dimensional phenotypes as a way of dimension reduction to maximize power for subsequent genetic association testing. [ABSTRACT FROM AUTHOR]

Basement membranes (BMs) are thin sheet-like specialized extracellular matrices found at the basal surface of epithelia and endothelial tissues. They have been conserved across evolution and are required for proper tissue growth, organization, differentiation and maintenance. The major constituents of BMs are two independent networks of Laminin and Type IV Collagen in addition to the proteoglycan Perlecan and the glycoprotein Nidogen/entactin (Ndg). The ability of Ndg to bind in vitro Collagen IV and Laminin, both with key functions during embryogenesis, anticipated an essential role for Ndg in morphogenesis linking the Laminin and Collagen IV networks. This was supported by results from in vitro and cultured embryonic tissues experiments. However, the fact that elimination of Ndg in C. elegans and mice did not affect survival strongly questioned this proposed linking role. Here, we have isolated mutations in the only Ndg gene present in Drosophila. We find that while, similar to C.elegans and mice, Ndg is not essential for overall organogenesis or viability, it is required for appropriate fertility. We also find, alike in mice, tissue-specific requirements of Ndg for proper assembly and maintenance of certain BMs, namely those of the adipose tissue and flight muscles. In addition, we have performed a thorough functional analysis of the different Ndg domains in vivo. Our results support an essential requirement of the G3 domain for Ndg function and unravel a new key role for the Rod domain in regulating Ndg incorporation into BMs. Furthermore, uncoupling of the laminin and Collagen IV networks is clearly observed in the larval adipose tissue in the absence of Ndg, indeed supporting a linking role. In light of our findings, we propose that BM assembly and/or maintenance is tissue-specific, which could explain the diverse requirements of a ubiquitous conserved BM component like Nidogen. [ABSTRACT FROM AUTHOR]

Increasing evidence suggests that dysregulation of lipid metabolism is associated with neurodegeneration in retinal diseases such as age-related macular degeneration and in brain disorders such as Alzheimer’s and Parkinson’s diseases. Lipid storage organelles (lipid droplets, LDs), accumulate in many cell types in response to stress, and it is now clear that LDs function not only as lipid stores but also as dynamic regulators of the stress response. However, whether these LDs are always protective or can also be deleterious to the cell is unknown. Here, we investigated the consequences of LD accumulation on retinal cell homeostasis under physiological and stress conditions in Drosophila and in mice. In wild-type Drosophila, we show that dFatp is required and sufficient for expansion of LD size in retinal pigment cells (RPCs) and that LDs in RPCs are required for photoreceptor survival during aging. Similarly, in mice, LD accumulation induced by RPC-specific expression of human FATP1 was non-toxic and promoted mitochondrial energy metabolism in RPCs and non-autonomously in photoreceptor cells. In contrast, the inhibition of LD accumulation by dFatp knockdown suppressed neurodegeneration in Aats-metFB Drosophila mutants, which carry elevated levels of reactive oxygen species (ROS). This suggests that abnormal turnover of LD may be toxic for photoreceptors cells of the retina under oxidative stress. Collectively, these findings indicate that FATP-mediated LD formation in RPCs promotes RPC and neuronal homeostasis under physiological conditions but could be deleterious for the photoreceptors under pathological conditions. [ABSTRACT FROM AUTHOR]

It is uncertain which β4-galactosyltransferase (β4GalT; gene name, B4galt), β4GalT-5 and/or β4GalT-6, is responsible for the production of lactosylceramide (LacCer) synthase, which functions in the initial step of ganglioside biosynthesis. Here, we generated conditional B4galt5 knockout (B4galt5 cKO) mice, using Nestin-Cre mice, and crossed these with B4galt6 KO mice to generate B4galt5 and 6 double KO (DKO) mice in the central nervous system (CNS). LacCer synthase activity and major brain gangliosides were completely absent in brain homogenates from the DKO mice, although LacCer synthase activity was about half its normal level in B4galt5 cKO mice and B4galt6 KO mice. The DKO mice were born normally but they showed growth retardation and motor deficits at 2 weeks and died by 4 weeks of age. Histological analyses showed that myelin-associated proteins were rarely found localized in axons in the cerebral cortex, and axonal and myelin formation were remarkably impaired in the spinal cords of the DKO mice. Neuronal cells, differentiated from neurospheres that were prepared from the DKO mice, showed impairments in neurite outgrowth and branch formation, which can be explained by the fact that neurospheres from DKO mice could weakly interact with laminin due to lack of gangliosides, such as GM1a. Furthermore, the neurons were immature and perineuronal nets (PNNs) were poorly formed in DKO cerebral cortices. Our results indicate that LacCer synthase is encoded by B4galt5 and 6 genes in the CNS, and that gangliosides are indispensable for neuronal maturation, PNN formation, and axonal and myelin formation. [ABSTRACT FROM AUTHOR]

Fusarium graminearum is a fungal pathogen that causes Fusarium head blight (FHB) in wheat and barley. Autophagy is a highly conserved vacuolar degradation pathway essential for cellular homeostasis in which Atg9 serves as a multispanning membrane protein important for generating membranes for the formation of phagophore assembly site. However, the mechanism of autophagy or autophagosome formation in phytopathogens awaits further clarifications. In this study, we identified and characterized the Atg9 homolog (FgAtg9) in F. graminearum by live cell imaging, biochemical and genetic analyses. We find that GFP-FgAtg9 localizes to late endosomes and trans-Golgi network under both nutrient-rich and nitrogen starvation conditions and also show its dynamic actin-dependent trafficking in the cell. Further targeted gene deletion of FgATG9 demonstrates that it is important for growth, aerial hyphae development, and pathogenicity in F. graminearum. Furthermore, the deletion mutant (ΔFgatg9) shows severe defects in autophagy and lipid metabolism in response to carbon starvation. Interestingly, small GTPase FgRab7 is found to be required for the dynamic trafficking of FgAtg9, and co-immunoprecipitation (Co-IP) assays show that FgAtg9 associates with FgRab7 in vivo. Finally, heterologous complementation assay shows that Atg9 is functionally conserved in F. graminearum and Magnaporthe oryzae. Taken together, we conclude that FgAtg9 is essential for autophagy-dependent development and pathogenicity of F. graminearum, which may be regulated by the small GTPase FgRab7. [ABSTRACT FROM AUTHOR]

Tri-methylation on histone H3 lysine 4 (H3K4me3) is associated with active gene expression but its regulatory role in transcriptional activation is unclear. Here we used Caenorhabditis elegans to investigate the connection between H3K4me3 and gene expression regulation during aging. We uncovered around 30% of H3K4me3 enriched regions to show significant and reproducible changes with age. We further showed that these age-dynamic H3K4me3 regions largely mark gene-bodies and are acquired during adult stages. We found that these adult-specific age-dynamic H3K4me3 regions are correlated with gene expression changes with age. In contrast, H3K4me3 marking established during developmental stages remained largely stable with age, even when the H3K4me3 associated genes exhibited RNA expression changes during aging. Importantly, the genes associated with changes in H3K4me3 and RNA levels with age are enriched for functional groups commonly implicated in aging biology. Therefore, our findings suggested divergent roles of H3K4me3 in gene expression regulation during aging, with important implications on aging-dependent pathophysiologies. [ABSTRACT FROM AUTHOR]

Polymyxin is the last line of defense against severe infections caused by carbapenem-resistant gram-negative pathogens. The emergence of transferable MCR-1/2 polymyxin resistance greatly challenges the renewed interest in colistin (polymyxin E) for clinical treatments. Recent studies have suggested that Moraxella species are a putative reservoir for MCR-1/2 genetic determinants. Here, we report the functional definition of ICR-Mo from M. osloensis, a chromosomally encoded determinant of colistin resistance, in close relation to current MCR-1/2 family. ICR-Mo transmembrane protein was prepared and purified to homogeneity. Taken along with an in vitro enzymatic detection, MALDI-TOF mass spectrometry of bacterial lipid A pools determined that the ICR-Mo enzyme might exploit a possible “ping-pong” mechanism to accept the hosphothanolmine (PEA) moiety from its donor hosphatidylthanolamine (PE) and then transfer it to the 1(or 4’)-phosphate position of lipid A via an ICR-Mo-bound PEA adduct. Structural decoration of LPS-lipid A by ICR-Mo renders the recipient strain of E. coli resistant to polymyxin. Domain swapping assays indicate that the two domains of ICR-Mo cannot be functionally-exchanged with its counterparts in MCR-1/2 and EptA, validating its phylogenetic position in a distinct set of MCR-like genes. Structure-guided functional mapping of ICR-Mo reveals a PE lipid substrate recognizing cavity having a role in enzymatic catalysis and the resultant conference of antibiotic resistance. Expression of icr-Mo in E. coli significantly prevents the formation of reactive oxygen species (ROS) induced by colistin. Taken together, our results define a member of a group of intrinsic colistin resistance genes phylogenetically close to the MCR-1/2 family, highlighting the evolution of transferable colistin resistance. [ABSTRACT FROM AUTHOR]

Human GWAS of obesity have been successful in identifying loci associated with adiposity, but for the most part, these are non-coding SNPs whose function, or even whose gene of action, is unknown. To help identify the genes on which these human BMI loci may be operating, we conducted a high throughput screen in Drosophila Melanogaster. Starting with 78 BMI loci from two recently published GWAS meta-analyses, we identified fly orthologs of all nearby genes (± 250KB). We crossed RNAi knockdown lines of each gene with flies containing tissue-specific drivers to knock down (KD) the expression of the genes only in the brain and the fat body. We then raised the flies on a control diet and compared the amount of fat/triglyceride in the tissue-specific KD group compared to the driver-only control flies. 16 of the 78 BMI GWAS loci could not be screened with this approach, as no gene in the 500-kb region had a fly ortholog. Of the remaining 62 GWAS loci testable in the fly, we found a significant fat phenotype in the KD flies for at least one gene for 26 loci (42%) even after correcting for multiple comparisons. By contrast, the rate of significant fat phenotypes in RNAi KD found in a recent genome-wide Drosophila screen (Pospisilik et al. (2010) is ~5%. More interestingly, for 10 of the 26 positive regions, we found that the nearest gene the one that showed a significant phenotype in the fly. Specifically, our screen suggests that for the 10 human BMI SNPs rs11057405, rs205262, rs9925964, rs9914578, rs2287019, rs11688816, rs13107325, rs7164727, rs17724992, and rs299412, the functional genes may NOT be the nearest ones (CLIP1, C6orf106, KAT8, SMG6, QPCTL, EHBP1, SLC39A8, ADPGK /ADPGK-AS1, PGPEP1, KCTD15, respectively), but instead, the specific nearby cis genes are the functional target (namely: ZCCHC8, VPS33A, RSRC2; SPDEF, NUDT3; PAGR1; SETD1, VKORC1; SGSM2, SRR; VASP, SIX5; OTX1; BANK1; ARIH1; ELL; CHST8, respectively). The study also suggests further functional experiments to elucidate mechanism of action for genes evolutionarily conserved for fat storage. [ABSTRACT FROM AUTHOR]

PIKfyve, VAC14, and FIG4 form a complex that catalyzes the production of PI(3,5)P2, a signaling lipid implicated in process ranging from lysosome maturation to neurodegeneration. While previous studies have identified VAC14 and FIG4 mutations that lead to both neurodegeneration and coat color defects, how PIKfyve regulates melanogenesis is unknown. In this study, we sought to better understand the role of PIKfyve in melanosome biogenesis. Melanocyte-specific PIKfyve knockout mice exhibit greying of the mouse coat and the accumulation of single membrane vesicle structures in melanocytes resembling multivesicular endosomes. PIKfyve inhibition blocks melanosome maturation, the processing of the melanosome protein PMEL, and the trafficking of the melanosome protein TYRP1. Taken together, these studies identify a novel role for PIKfyve in controlling the delivery of proteins from the endosomal compartment to the melanosome, a role that is distinct from the role of PIKfyve in the reformation of lysosomes from endolysosomes. [ABSTRACT FROM AUTHOR]

The mechanisms by which the sensory environment influences metabolic homeostasis remains poorly understood. In this report, we show that oxygen, a potent environmental signal, is an important regulator of whole body lipid metabolism. C. elegans oxygen-sensing neurons reciprocally regulate peripheral lipid metabolism under normoxia in the following way: under high oxygen and food absence, URX sensory neurons are activated, and stimulate fat loss in the intestine, the major metabolic organ for C. elegans. Under lower oxygen conditions or when food is present, the BAG sensory neurons respond by repressing the resting properties of the URX neurons. A genetic screen to identify modulators of this effect led to the identification of a BAG-neuron-specific neuropeptide called FLP-17, whose cognate receptor EGL-6 functions in URX neurons. Thus, BAG sensory neurons counterbalance the metabolic effect of tonically active URX neurons via neuropeptide communication. The combined regulatory actions of these neurons serve to precisely tune the rate and extent of fat loss to the availability of food and oxygen, and provides an interesting example of the myriad mechanisms underlying homeostatic control. [ABSTRACT FROM AUTHOR]

Forkhead box (FOXO) proteins are evolutionarily conserved, stress-responsive transcription factors (TFs) that can promote or counteract cell death. Mutations in FOXO genes are implicated in numerous pathologies, including age-dependent neurodegenerative disorders, such as Parkinson’s disease (PD). However, the complex regulation and downstream mechanisms of FOXOs present a challenge in understanding their roles in the pathogenesis of PD. Here, we investigate the involvement of FOXO in the death of dopaminergic (DA) neurons, the key pathological feature of PD, in Drosophila. We show that dFOXO null mutants exhibit a selective loss of DA neurons in the subgroup crucial for locomotion, the protocerebral anterior medial (PAM) cluster, during development as well as in adulthood. PAM neuron-targeted adult-restricted knockdown demonstrates that dFOXO in adult PAM neurons tissue-autonomously promotes neuronal survival during aging. We further show that dFOXO and the bHLH-TF 48-related-2 (FER2) act in parallel to protect PAM neurons from different forms of cellular stress. Remarkably, however, dFOXO and FER2 share common downstream processes leading to the regulation of autophagy and mitochondrial morphology. Thus, overexpression of one can rescue the loss of function of the other. These results indicate a role of dFOXO in neuroprotection and highlight the notion that multiple genetic and environmental factors interact to increase the risk of DA neuron degeneration and the development of PD. [ABSTRACT FROM AUTHOR]

Bacterial morphology is a complex trait that is highly sensitive to changes in the environment. For heterotrophic organisms, such as Escherichia coli, increases in nutrient levels are frequently accompanied by several-fold increases in both size and growth rate. Despite the dramatic nature of these changes, how alterations in nutrient availability translate into changes in growth and morphology remains a largely open question. To understand the signaling networks coupling nutrient availability with size and shape, we examined the impact of deletions in the entirety of non-essential central carbon metabolic genes on E. coli growth rate and cell size. Our data reveal the presence of multiple metabolic nodes that play important yet distinctive roles in dictating biosynthetic capacity and shaping cell morphology. Specifically, perturbations of acetyl-CoA metabolism impact cell size and division through changes in fatty acid synthesis. Additionally, we identify a genetic pathway linking glucose levels to cell width through the signaling molecule cyclic-AMP. Together our findings highlight a surprising diversity of factors and mechanisms contributing to growth potential and cell morphology, providing a foundation for further studies. [ABSTRACT FROM AUTHOR]

The Th-inducing POK (Th-POK, also known as ZBTB7B or cKrox) transcription factor is a key regulator of lineage commitment of immature T cell precursors. It is yet unclear the physiological functions of Th-POK besides helper T cell differentiation. Here we show that Th-POK is restrictedly expressed in the luminal epithelial cells in the mammary glands that is upregulated at late pregnancy and lactation. Lineage restrictedly expressed Th-POK exerts distinct biological functions in the mammary epithelial cells and T cells in a tissue-specific manner. Th-POK is not required for mammary epithelial cell fate determination. Mammary gland morphogenesis in puberty and alveologenesis in pregnancy are phenotypically normal in the Th-POK-deficient mice. However, Th-POK-deficient mice are defective in triggering the onset of lactation upon parturition with large cellular lipid droplets retained within alveolar epithelial cells. As a result, Th-POK knockout mice are unable to efficiently secret milk lipid and to nurse the offspring. Such defect is mainly attributed to the malfunctioned mammary epithelial cells, but not the tissue microenvironment in the Th-POK deficient mice. Th-POK directly regulates expression of insulin receptor substrate-1 (IRS-1) and insulin-induced Akt-mTOR-SREBP signaling. Th-POK deficiency compromises IRS-1 expression and Akt-mTOR-SREBP signaling in the lactating mammary glands. Conversely, insulin induces Th-POK expression. Thus, Th-POK functions as an important feed-forward regulator of insulin signaling in mammary gland lactation. [ABSTRACT FROM AUTHOR]

Animals use taste to sample and ingest essential nutrients for survival. Free fatty acids (FAs) are energy-rich nutrients that contribute to various cellular functions. Recent evidence suggests FAs are detected through the gustatory system to promote feeding. In Drosophila, phospholipase C (PLC) signaling in sweet-sensing cells is required for FA detection but other signaling molecules are unknown. Here, we show Gr64e is required for the behavioral and electrophysiological responses to FAs. GR64e and TRPA1 are interchangeable when they act downstream of PLC: TRPA1 can substitute for GR64e in FA but not glycerol sensing, and GR64e can substitute for TRPA1 in aristolochic acid but not N-methylmaleimide sensing. In contrast to its role in FA sensing, GR64e functions as a ligand-gated ion channel for glycerol detection. Our results identify a novel FA transduction molecule and reveal that Drosophila Grs can act via distinct molecular mechanisms depending on context. [ABSTRACT FROM AUTHOR]

Adipose tissue lipolysis occurs during the development of heart failure as a consequence of chronic adrenergic stimulation. However, the impact of enhanced adipose triacylglycerol hydrolysis mediated by adipose triglyceride lipase (ATGL) on cardiac function is unclear. To investigate the role of adipose tissue lipolysis during heart failure, we generated mice with tissue-specific deletion of ATGL (atATGL-KO). atATGL-KO mice were subjected to transverse aortic constriction (TAC) to induce pressure-mediated cardiac failure. The cardiac mouse lipidome and the human plasma lipidome from healthy controls (n = 10) and patients with systolic heart failure (HFrEF, n = 13) were analyzed by MS-based shotgun lipidomics. TAC-induced increases in left ventricular mass (LVM) and diastolic LV inner diameter were significantly attenuated in atATGL-KO mice compared to wild type (wt) -mice. More importantly, atATGL-KO mice were protected against TAC-induced systolic LV failure. Perturbation of lipolysis in the adipose tissue of atATGL-KO mice resulted in the prevention of the major cardiac lipidome changes observed after TAC in wt-mice. Profound changes occurred in the lipid class of phosphatidylethanolamines (PE) in which multiple PE-species were markedly induced in failing wt-hearts which was attenuated in atATGL-KO hearts. Moreover, selected heart failure-induced PE species in mouse hearts were also induced in plasma samples from patients with chronic heart failure. TAC-induced cardiac PE induction resulted in decreased PC/ PE-species ratios associated with increased apoptotic marker expression in failing wt-hearts, a process absent in atATGL-KO hearts. Perturbation of adipose tissue lipolysis by ATGL-deficiency ameliorated pressure-induced heart failure and the potentially deleterious cardiac lipidome changes that accompany this pathological process, namely the induction of specific PE species. Non-cardiac ATGL-mediated modulation of the cardiac lipidome may play an important role in the pathogenesis of chronic heart failure. [ABSTRACT FROM AUTHOR]

The cell envelope of mycobacteria is a highly unique and complex structure that is functionally equivalent to that of Gram-negative bacteria to protect the bacterial cell. Defects in the integrity or assembly of this cell envelop must be sensed to allow the induction of stress response systems. The promoter that is specifically and most strongly induced upon exposure to ethambutol and isoniazid, first line drugs that affect cell envelope biogenesis, is the iniBAC promoter. In this study, we set out to identify the regulator of the iniBAC operon in Mycobacterium marinum using an unbiased transposon mutagenesis screen in a constitutively iniBAC-expressing mutant background. We obtained multiple mutants in the mce1 locus as well as mutants in an uncharacterized putative transcriptional regulator (MMAR_0612). This latter gene was shown to function as the iniBAC regulator, as overexpression resulted in constitutive iniBAC induction, whereas a knockout mutant was unable to respond to the presence of ethambutol and isoniazid. Experiments with the M. tuberculosis homologue (Rv0339c) showed identical results. RNAseq experiments showed that this regulatory gene was exclusively involved in the regulation of the iniBAC operon. We therefore propose to name this dedicated regulator iniBAC Regulator (IniR). IniR belongs to the family of signal transduction ATPases with numerous domains, including a putative sugar-binding domain. Upon testing different sugars, we identified trehalose as an activator and metabolic cue for iniBAC activation, which could also explain the effect of the mce1 mutations. In conclusion, cell envelope stress in mycobacteria is regulated by IniR in a cascade that includes trehalose. [ABSTRACT FROM AUTHOR]

Fatty liver is a major health problem worldwide. People with hereditary deficiency of hormone-sensitive lipase (HSL) are reported to develop fatty liver. In this study, systemic and tissue-specific HSL-deficient mice were used as models to explore the underlying mechanism of this association. We found that systemic HSL deficient mice developed fatty liver in an age-dependent fashion between 3 and 8 months of age. To further explore the mechanism of fatty liver in HSL deficiency, liver-specific HSL knockout mice were created. Surprisingly, liver HSL deficiency did not influence liver fat content, suggesting that fatty liver in HSL deficiency is not liver autonomous. Given the importance of adipose tissue in systemic triglyceride metabolism, we created adipose-specific HSL knockout mice and found that adipose HSL deficiency, to a similar extent as systemic HSL deficiency, causes age-dependent fatty liver in mice. Mechanistic study revealed that deficiency of HSL in adipose tissue caused inflammatory macrophage infiltrates, progressive lipodystrophy, abnormal adipokine secretion and systemic insulin resistance. These changes in adipose tissue were associated with a constellation of changes in liver: low levels of fatty acid oxidation, of very low density lipoprotein secretion and of triglyceride hydrolase activity, each favoring the development of hepatic steatosis. In conclusion, HSL-deficient mice revealed a complex interorgan interaction between adipose tissue and liver: the role of HSL in the liver is minimal but adipose tissue deficiency of HSL can cause age-dependent hepatic steatosis. Adipose tissue is a potential target for treating the hepatic steatosis of HSL deficiency. [ABSTRACT FROM AUTHOR]

Fat represents a calorically potent food source that yields approximately twice the amount of energy as carbohydrates or proteins per unit of mass. The highly palatable taste of free fatty acids (FAs), one of the building blocks of fat, promotes food consumption, activates reward circuitry, and is thought to contribute to hedonic feeding underlying many metabolism-related disorders. Despite a role in the etiology of metabolic diseases, little is known about how dietary fats are detected by the gustatory system to promote feeding. Previously, we showed that a broad population of sugar-sensing taste neurons expressing Gustatory Receptor 64f (Gr64f) is required for reflexive feeding responses to both FAs and sugars. Here, we report a genetic silencing screen to identify specific populations of taste neurons that mediate fatty acid (FA) taste. We find neurons identified by expression of Ionotropic Receptor 56d (IR56d) are necessary and sufficient for reflexive feeding response to FAs. Functional imaging reveals that IR56d-expressing neurons are responsive to short- and medium-chain FAs. Silencing IR56d neurons selectively abolishes FA taste, and their activation is sufficient to drive feeding responses. Analysis of co-expression with Gr64f identifies two subpopulations of IR56d-expressing neurons. While physiological imaging reveals that both populations are responsive to FAs, IR56d/Gr64f neurons are activated by medium-chain FAs and are sufficient for reflexive feeding response to FAs. Moreover, flies can discriminate between sugar and FAs in an aversive taste memory assay, indicating that FA taste is a unique modality in Drosophila. Taken together, these findings localize FA taste within the Drosophila gustatory center and provide an opportunity to investigate discrimination between different categories of appetitive tastants. [ABSTRACT FROM AUTHOR]

Lipid and lipoprotein subclasses are associated with metabolic and cardiovascular diseases, yet the genetic contributions to variability in subclass traits are not fully understood. We conducted single-variant and gene-based association tests between 15.1M variants from genome-wide and exome array and imputed genotypes and 72 lipid and lipoprotein traits in 8,372 Finns. After accounting for 885 variants at 157 previously identified lipid loci, we identified five novel signals near established loci at HIF3A, ADAMTS3, PLTP, LCAT, and LIPG. Four of the signals were identified with a low-frequency (0.005

Dietary fatty acids can be incorporated directly into phospholipids. This poses a specific challenge to cellular membranes since their composition, hence properties, could greatly vary with different diets. That vast variations in diets are tolerated therefore implies the existence of regulatory mechanisms that monitor and regulate membrane compositions. Here we show that the adiponectin receptor AdipoR2, and its C. elegans homolog PAQR-2, are essential to counter the membrane rigidifying effects of exogenously provided saturated fatty acids. In particular, we use dietary supplements or mutated E. coli as food, together with direct measurements of membrane fluidity and composition, to show that diets containing a high ratio of saturated to monounsaturated fatty acids cause membrane rigidity and lethality in the paqr-2 mutant. We also show that mammalian cells in which AdipoR2 has been knocked-down by siRNA are unable to prevent the membrane-rigidifying effects of palmitic acid. We conclude that the PAQR-2 and AdipoR2 proteins share an evolutionarily conserved function that maintains membrane fluidity in the presence of exogenous saturated fatty acids. [ABSTRACT FROM AUTHOR]

Given the relevance of beige adipocytes in adult humans, a better understanding of the molecular circuits involved in beige adipocyte biogenesis has provided new insight into human brown adipocyte biology. Genetic mutations in SLC39A13/ZIP13, a member of zinc transporter family, are known to reduce adipose tissue mass in humans; however, the underlying mechanisms remains unknown. Here, we demonstrate that the Zip13-deficient mouse shows enhanced beige adipocyte biogenesis and energy expenditure, and shows ameliorated diet-induced obesity and insulin resistance. Both gain- and loss-of-function studies showed that an accumulation of the CCAAT/enhancer binding protein-β (C/EBP-β) protein, which cooperates with dominant transcriptional co-regulator PR domain containing 16 (PRDM16) to determine brown/beige adipocyte lineage, is essential for the enhanced adipocyte browning caused by the loss of ZIP13. Furthermore, ZIP13-mediated zinc transport is a prerequisite for degrading the C/EBP-β protein to inhibit adipocyte browning. Thus, our data reveal an unexpected association between zinc homeostasis and beige adipocyte biogenesis, which may contribute significantly to the development of new therapies for obesity and metabolic syndrome. [ABSTRACT FROM AUTHOR]

Individuals choose their mates so as to maximize reproductive success, and one important component of this choice is assessment of traits reflecting mate quality. Little is known about why specific traits are used for mate quality assessment nor about how they reflect it. We have previously shown that global manipulation of insulin signaling, a nutrient-sensing pathway governing investment in survival versus reproduction, affects female sexual attractiveness in the fruit fly, Drosophila melanogaster. Here we demonstrate that these effects on attractiveness derive from insulin signaling in the fat body and ovarian follicle cells, whose signals are integrated by pheromone-producing cells called oenocytes. Functional ovaries were required for global insulin signaling effects on attractiveness, and manipulations of insulin signaling specifically in late follicle cells recapitulated effects of global manipulations. Interestingly, modulation of insulin signaling in the fat body produced opposite effects on attractiveness, suggesting a competitive relationship with the ovary. Furthermore, all investigated tissue-specific insulin signaling manipulations that changed attractiveness also changed fecundity in the corresponding direction, pointing to insulin pathway activity as a reliable link between fecundity and attractiveness cues. The cues themselves, cuticular hydrocarbons, responded distinctly to fat body and follicle cell manipulations, indicating independent readouts of the pathway activity from these two tissues. Thus, here we describe a system in which female attractiveness results from an apparent connection between attractiveness cues and an organismal state of high fecundity, both of which are created by lowered insulin signaling in the fat body and increased insulin signaling in late follicle cells. [ABSTRACT FROM AUTHOR]

Reference 1 Francis M, Li C, Sun Y, Zhou J, Li X, Brenna JT, et al. (2021) Genome-wide association study of fish oil supplementation on lipid traits in 81,246 individuals reveals new gene-diet interaction loci. The ARIC datasets used for the analyses in this manuscript were obtained from dbGaP through dbGaP accession study number phs000280.v3.p1. [Extracted from the article]

Preventing obesity requires a precise balance between deposition into and mobilization from fat stores, but regulatory mechanisms are incompletely understood. Drosophila Split ends (Spen) is the founding member of a conserved family of RNA-binding proteins involved in transcriptional regulation and frequently mutated in human cancers. We find that manipulating Spen expression alters larval fat levels in a cell-autonomous manner. Spen-depleted larvae had defects in energy liberation from stores, including starvation sensitivity and major changes in the levels of metabolic enzymes and metabolites, particularly those involved in β-oxidation. Spenito, a small Spen family member, counteracted Spen function in fat regulation. Finally, mouse Spen and Spenito transcript levels scaled directly with body fat in vivo, suggesting a conserved role in fat liberation and catabolism. This study demonstrates that Spen is a key regulator of energy balance and provides a molecular context to understand the metabolic defects that arise from Spen dysfunction. [ABSTRACT FROM AUTHOR]

Phenotypic variance heterogeneity across genotypes at a single nucleotide polymorphism (SNP) may reflect underlying gene-environment (G×E) or gene-gene interactions. We modeled variance heterogeneity for blood lipids and BMI in up to 44,211 participants and investigated relationships between variance effects (Pv), G×E interaction effects (with smoking and physical activity), and marginal genetic effects (Pm). Correlations between Pv and Pm were stronger for SNPs with established marginal effects (Spearman’s ρ = 0.401 for triglycerides, and ρ = 0.236 for BMI) compared to all SNPs. When Pv and Pm were compared for all pruned SNPs, only BMI was statistically significant (Spearman’s ρ = 0.010). Overall, SNPs with established marginal effects were overrepresented in the nominally significant part of the Pv distribution (Pbinomial <0.05). SNPs from the top 1% of the Pm distribution for BMI had more significant Pv values (PMann–Whitney = 1.46×10−5), and the odds ratio of SNPs with nominally significant (<0.05) Pm and Pv was 1.33 (95% CI: 1.12, 1.57) for BMI. Moreover, BMI SNPs with nominally significant G×E interaction P-values (Pint<0.05) were enriched with nominally significant Pv values (Pbinomial = 8.63×10−9 and 8.52×10−7 for SNP × smoking and SNP × physical activity, respectively). We conclude that some loci with strong marginal effects may be good candidates for G×E, and variance-based prioritization can be used to identify them. [ABSTRACT FROM AUTHOR]

It is now established that the central nervous system plays an important role in regulating whole body metabolism and energy balance. However, the extent to which sensory systems relay environmental information to modulate metabolic events in peripheral tissues has remained poorly understood. In addition, it has been challenging to map the molecular mechanisms underlying discrete sensory modalities with respect to their role in lipid metabolism. In previous work our lab has identified instructive roles for serotonin signaling as a surrogate for food availability, as well as oxygen sensing, in the control of whole body metabolism. In this study, we now identify a role for a pair of pheromone-sensing neurons in regulating fat metabolism in C. elegans, which has emerged as a tractable and highly informative model to study the neurobiology of metabolism. A genetic screen revealed that GPA-3, a member of the Gα family of G proteins, regulates body fat content in the intestine, the major metabolic organ for C. elegans. Genetic and reconstitution studies revealed that the potent body fat phenotype of gpa-3 null mutants is controlled from a pair of neurons called ADL(L/R). We show that cAMP functions as the second messenger in the ADL neurons, and regulates body fat stores via the neurotransmitter acetylcholine, from downstream neurons. We find that the pheromone ascr#3, which is detected by the ADL neurons, regulates body fat stores in a GPA-3-dependent manner. We define here a third sensory modality, pheromone sensing, as a major regulator of body fat metabolism. The pheromone ascr#3 is an indicator of population density, thus we hypothesize that pheromone sensing provides a salient 'denominator' to evaluate the amount of food available within a population and to accordingly adjust metabolic rate and body fat levels. [ABSTRACT FROM AUTHOR]

Joint genetic models for multiple traits have helped to enhance association analyses. Most existing multi-trait models have been designed to increase power for detecting associations, whereas the analysis of interactions has received considerably less attention. Here, we propose iSet, a method based on linear mixed models to test for interactions between sets of variants and environmental states or other contexts. Our model generalizes previous interaction tests and in particular provides a test for local differences in the genetic architecture between contexts. We first use simulations to validate iSet before applying the model to the analysis of genotype-environment interactions in an eQTL study. Our model retrieves a larger number of interactions than alternative methods and reveals that up to 20% of cases show context-specific configurations of causal variants. Finally, we apply iSet to test for sub-group specific genetic effects in human lipid levels in a large human cohort, where we identify a gene-sex interaction for C-reactive protein that is missed by alternative methods. [ABSTRACT FROM AUTHOR]

The general transcription factor TBP (TATA-box binding protein) and its associated factors (TAFs) together form the TFIID complex, which directs transcription initiation. Through RNAi and mutant analysis, we identified a specific TBP family protein, TRF2, and a set of TAFs that regulate lipid droplet (LD) size in the Drosophila larval fat body. Among the three Drosophila TBP genes, trf2, tbp and trf1, only loss of function of trf2 results in increased LD size. Moreover, TRF2 and TAF9 regulate fatty acid composition of several classes of phospholipids. Through RNA profiling, we found that TRF2 and TAF9 affects the transcription of a common set of genes, including peroxisomal fatty acid β-oxidation-related genes that affect phospholipid fatty acid composition. We also found that knockdown of several TRF2 and TAF9 target genes results in large LDs, a phenotype which is similar to that of trf2 mutants. Together, these findings provide new insights into the specific role of the general transcription machinery in lipid homeostasis. [ABSTRACT FROM AUTHOR]

The heart has emerged as an important organ in the regulation of systemic lipid homeostasis; however, the underlying mechanism remains poorly understood. Here, we show that Drosophila cardiomyocytes regulate systemic lipid metabolism by producing apolipoprotein B-containing lipoproteins (apoB-lipoproteins), essential lipid carriers that are so far known to be generated only in the fat body. In a Drosophila genetic screen, we discovered that when haplo-insufficient, microsomal triglyceride transfer protein (mtp), required for the biosynthesis of apoB-lipoproteins, suppressed the development of diet-induced obesity. Tissue-specific inhibition of Mtp revealed that whereas knockdown of mtp only in the fat body decreases systemic triglyceride (TG) content on normal food diet (NFD) as expected, knockdown of mtp only in the cardiomyocytes also equally decreases systemic TG content on NFD, suggesting that the cardiomyocyte- and fat body-derived apoB-lipoproteins serve similarly important roles in regulating whole-body lipid metabolism. Unexpectedly, on high fat diet (HFD), knockdown of mtp in the cardiomyocytes, but not in fat body, protects against the gain in systemic TG levels. We further showed that inhibition of the Drosophila apoB homologue, apolipophorin or apoLpp, another gene essential for apoB-lipoprotein biosynthesis, affects systemic TG levels similarly to that of Mtp inhibition in the cardiomyocytes on NFD or HFD. Finally, we determined that HFD differentially alters Mtp and apoLpp expression in the cardiomyocytes versus the fat body, culminating in higher Mtp and apoLpp levels in the cardiomyocytes than in fat body and possibly underlying the predominant role of cardiomyocyte-derived apoB-lipoproteins in lipid metabolic regulation. Our findings reveal a novel and significant function of heart-mediated apoB-lipoproteins in controlling lipid homeostasis. [ABSTRACT FROM AUTHOR]