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Over 500 noncoding genomic loci are associated with obesity. The majority of these loci reside near genes that are expressed in the hypothalamus in specific neuronal subpopulations that regulate food intake, hindering the ability to identify and functionally characterize them. Here, we carried out integrative single-cell analysis (RNA/ATAC-seq) on both mouse and human male and female hypothalamus to characterize genes and regulatory elements in specific cell subpopulations. Utilizing both transcriptome and regulome data, we identify over 30 different neuronal and non-neuronal cell subpopulations and a shared core of transcription factors that regulate cell cluster-specific genes between mice and humans. We characterize several sex-specific differentially expressed genes and the regulatory elements that control them in specific cell subpopulations. Overlapping cell-specific scATAC peaks with obesity-associated GWAS variants, identifies potential obesity-associated regulatory elements. Using reporter assays and CRISPR editing, we show that many of these sequences, including the top obesity-associated loci (FTOandMC4R), are functional enhancers whose activity is altered due to the obesity-associated variant and regulate known obesity genes. Combined, our work provides a catalog of genes and regulatory elements in hypothalamus cell subpopulations and uses obesity to showcase how integrative single-cell sequencing can identify functional variants associated with hypothalamus-related phenotypes.

Primary cilia are small immotile cellular appendages which mediate diverse types of singling and are found on most mammalian cell types including throughout the central nervous system. Cilia are known to localize certain G protein-coupled receptors (GPCRs) and are critical for mediating the signaling of these receptors. Several of these neuronal GPCRs have recognized roles in feeding behavior and energy homeostasis. Heterologous cell line and model systems likeC. elegansandChlamydomonashave implicated both dynamic GPCR cilia localization and cilia length and shape changes as key for signaling. However, it is unclear if mammalian ciliary GPCRs utilize similar mechanismsin vivoand under what physiological conditions these processes may occur. Here, we use the ciliary GPCRs, melanin concentrating hormone receptor 1 (MCHR1) and neuropeptide-Y receptor 2 (NPY2R) as model ciliary receptors to determine if dynamic localization to cilia occurs. We tested physiological conditions in which these GPCRs have been implicated such as feeding behavior, obesity, and circadian rhythm. Cilia were imaged using confocal microscopy and analyzed with a computer assisted approach allowing for unbiased and high throughput analysis of cilia. We analyzed GPCR positive cilia, cilia frequency as well as cilia length and receptor occupancy. Interestingly we observed changes in ciliary length, receptor occupancy, and cilia frequency under different conditions, but no consistent theme across GPCRs or brain nuclei was observed. A better understanding of the subcellular localization dynamics of ciliary GPCRs could reveal unrecognized molecular mechanisms regulating behaviors like feeding.Significance StatementOften, primary cilia localize specific G protein-coupled receptors (GPCRs) for subcellular signaling. Cell lines and model systems have indicated that cilia deploy dynamic GPCR localization and change their shape or length to modulate signaling. We used mice to assess neuronal cilia GPCRs under physiological conditions associated with both the receptors’ known functions and ciliopathy clinical features like obesity. We show that certain cilia with specific GPCRs appear to dynamically alter their length while others appear relatively stable under these conditions. These results implicate multiple themes across cilia GPCR mediated signaling and indicate that not all cilia modulate GPCR signaling using the same mechanisms. These data will be important for potential pharmacological approaches to target cilia GPCR-mediated signaling.

Circulating corticosteroids orchestrate stress adaptation, including inhibition of inflammation. While pathways governing corticosteroid biosynthesis and intracellular signaling are well understood, less is known about mechanisms controlling plasma corticosteroid transport. Here, we show that hepatocyte KLF15 (Kruppel-like factor 15) controls plasma corticosteroid transport and inflammatory responses through direct transcriptional activation of Serpina6 , which encodes corticosteroid-binding globulin (CBG). Klf15 -deficient mice have profoundly low CBG, reduced plasma corticosteroid binding capacity, and heightened mortality during inflammatory stress. These defects are completely rescued by reconstituting CBG, supporting that KLF15 works primarily through CBG to control plasma corticosterone homeostasis. To understand transcriptional mechanisms, we generated the first KLF15 cistromes using newly engineered Klf15 3xFLAG mice. Unexpectedly, liver KLF15 is predominantly promoter enriched, including Serpina6 , where it binds a palindromic GC-rich motif, opens chromatin, and transactivates genes with minimal associated direct gene repression. Overall, we provide critical mechanistic insight into KLF15 function and identify a hepatocyte-intrinsic transcriptional module that potently regulates systemic corticosteroid transport and inflammation.

Primary cilia are cellular appendages critical for diverse types of Signaling. They are found on most cell types, including cells throughout the CNS. Cilia preferentially localize certain G-protein-coupled receptors (GPCRs) and are critical for mediating the signaling of these receptors. Several of these neuronal GPCRs have recognized roles in feeding behavior and energy homeostasis. Cell and model systems, such asCaenorhabditis elegansandChlamydomonas, have implicated both dynamic GPCR cilia localization and cilia length and shape changes as key for signaling. It is unclear whether mammalian ciliary GPCRs use similar mechanismsin vivoand under what conditions these processes may occur. Here, we assess two neuronal cilia GPCRs, melanin-concentrating hormone receptor 1 (MCHR1) and neuropeptide-Y receptor 2 (NPY2R), as mammalian model ciliary receptors in the mouse brain. We test the hypothesis that dynamic localization to cilia occurs under physiological conditions associated with these GPCR functions. Both receptors are involved in feeding behaviors, and MCHR1 is also associated with sleep and reward. Cilia were analyzed with a computer-assisted approach allowing for unbiased and high-throughput analysis. We measured cilia frequency, length, and receptor occupancy. We observed changes in ciliary length, receptor occupancy, and cilia frequency under different conditions for one receptor but not another and in specific brain regions. These data suggest that dynamic cilia localization of GPCRs depends on properties of individual receptors and cells where they are expressed. A better understanding of subcellular localization dynamics of ciliary GPCRs could reveal unknown molecular mechanisms regulating behaviors like feeding.

The melanocortin 4 receptor (MC4R) plays a critical role in the long-term regulation of energy homeostasis, and mutations in the MC4R are the most common cause of monogenic obesity. However, the precise molecular and cellular mechanisms underlying the maintenance of energy balance within MC4R-expressing neurons are unknown. We recently reported that the MC4R localizes to the primary cilium, a cellular organelle that allows for partitioning of incoming cellular signals, raising the question of whether the MC4R functions in this organelle. Here, using mouse genetic approaches, we found that cilia were required specifically on MC4R-expressing neurons for the control of energy homeostasis. Moreover, these cilia were critical for pharmacological activators of the MC4R to exert an anorexigenic effect. The MC4R is expressed in multiple brain regions. Using targeted deletion of primary cilia, we found that cilia in the paraventricular nucleus of the hypothalamus (PVN) were essential to restrict food intake. MC4R activation increased adenylyl cyclase (AC) activity. As with the removal of cilia, inhibition of AC activity in the cilia of MC4R-expressing neurons of the PVN caused hyperphagia and obesity. Thus, the MC4R signaled via PVN neuron cilia to control food intake and body weight. We propose that defects in ciliary localization of the MC4R cause obesity in human inherited obesity syndromes and ciliopathies.

The Melanocortin-4 Receptor (MC4R) plays a critical role in the long-term regulation of energy homeostasis and mutations in MC4R are the most common cause of monogenic obesity. However, the precise molecular and cellular mechanisms underlying the maintenance of energy balance within MC4R expressing neurons are unknown. We recently reported that MC4R localizes to primary cilia, a cellular organelle that allows for partitioning of incoming cellular signals, raising the question of whether MC4R functions there. Here, using mouse genetic approaches, we found that cilia are required specifically on MC4R-expressing neurons to restrain feeding behavior. Moreover, these cilia were critical for pharmacological activators of MC4R to exert an anorexigenic effect. MC4R is expressed in multiple brain regions. Using targeted deletion of primary cilia, we found that cilia in the paraventricular nucleus (PVN) of the hypothalamus are essential to restrict food intake. MC4R activation increases adenylyl cyclase activity. Like removing cilia, inhibiting adenylyl cyclase activity in the cilia of MC4R-expressing neurons of the PVN caused hyperphagia and obesity. Thus, MC4R signals via cilia of PVN neurons to control food intake and body weight. We propose that defects in ciliary localization of MC4R cause obesity in human inherited obesity syndromes and ciliopathies.

Genetic studies in humans and mice have demonstrated that the Melanocortin 4 Receptor (MC4R) is essential for adequate regulation of food intake and body weight. MC4R is expressed in a small population of hypothalamic neurons and very little is known about its molecular and cellular dynamics in vivo. We have recently demonstrated that MC4R localizes to and functions at the primary cilia of select hypothalamic neurons to control energy homeostasis. The primary cilium is a solitary hair-like organelle that serves as an antenna sensing extracellular environment. Defective primary cilia lead to a series of conditions known as ciliopathies, that can manifest through a variety of clinical features, including hyperphagia and obesity. Here we establish that the ciliary localization and the body weight regulating activity of MC4R is dependent on a single-pass transmembrane accessory protein: the Melanocortin Receptor Associated Protein 2 (MRAP2). Specifically, we show that deleting MRAP2 specifically from MC4R neurons (MC4RMRAP2-/-) leads to early onset obesity and hyperphagia. In vitro, co-expression of MRAP2 in ciliated IMCD3 cells increases MC4R localization to the primary cilium. We further demonstrate that MRAP2 and MC4R colocalize specifically at the primary cilium in vivo, and that MC4R fails to localize to the primary cilium when MRAP2 is deleted. These findings highlight the role of the primary cilium in the control of energy homeostasis, and the importance of accessory proteins for the localization of GPCRs to the primary cilium where they exert their function, in this case being critical for the regulation of energy homeostasis.

Author(s): Bernard, Adelaide; Naharros, Irene Ojeda; Bourgain-Guglielmetti, Florence; Ciprin, Jordi; Yue, Xinyu; Zhang, Sumei; McDaid, Erin; Nachury, Maxence; Reiter, Jeremy; Vaisse, Christian | Abstract: ABSTRACT The G protein-coupled receptor MC4R (Melanocortin-4 Receptor) and its associated protein MRAP2 (Melanocortin Receptor-Associated Protein 2) are both essential for the regulation of food intake and body weight in humans and mice. MC4R localizes and functions at the neuronal primary cilium, a microtubule-based organelle that senses and relays extracellular signals. Here, we demonstrate that MRAP2 is critical for the ciliary localization and weight-regulating function of MC4R. Our data reveal that GPCR localization to primary cilia can require specific accessory proteins that may not be present in heterologous cell systems. Our findings also demonstrate the essential role of neuronal primary cilia localization of MC4R for adequate control of energy homeostasis and the obesity-promoting effect of genetic disruption of this pathway.

INTRODUCTION Loss-of-function mutations in one gene copy can lead to reduced amounts of protein and, consequently, human disease, a condition termed haploinsufficiency. It is currently estimated that more than 660 genes cause human disease as a result of haploinsufficiency. The delivery of extra copies of the gene by way of gene therapy is a promising therapeutic strategy to increase gene dosage in such conditions. Recombinant adeno-associated virus (rAAV) provides a promising tool for delivery of transgenes in an efficient and safe way for gene therapy. However, it has some limitations, including an optimal DNA packaging constraint of 4700 base pairs and ectopic expression. RATIONALE Increasing the expression levels of the normal gene copy by directly targeting the endogenous gene regulatory elements that control it could potentially correct haploinsufficiency. CRISPR-mediated activation (CRISPRa), whereby a nuclease-deficient Cas9 (dCas9) is used to target a transcriptional activator to the gene’s regulatory element (promoter or enhancer), could be used for this purpose. Such an approach could overcome the ectopic expression and DNA packaging limitations of rAAV. Using obesity as a model, we tested in mice whether CRISPR-mediated activation of the existing normal copy of two different genes, Sim1 or Mc4r, where loss-of-function mutations that lead to haploinsufficiency are a major cause of human obesity, can rescue their obesity phenotype. RESULTS We first generated a transgenic CRISPRa system using dCas9 fused to a transcriptional activator, VP64, to test whether it can rescue the obesity phenotype in a Sim1 haploinsufficient mouse model. CRISPRa targeting of the Sim1 promoter or its hypothalamus-specific enhancer, which is 270 kilobases away from the gene, in Sim1 haploinsufficient mice increased the expression of the normal copy of Sim1. This up-regulation was sufficient to rescue the obesity phenotype of Sim1 heterozygous mice and led to significantly reduced food intake and body fat content in these mice. We assessed the off-targeting effects of CRISPRa using both RNA sequencing (RNA-seq) and Cas9 chromatin immunoprecipitation sequencing (ChIP-seq) analyses. We found CRISPRa targeting to be highly specific and without any overt changes in the expression of other genes. We also observed that Sim1 up-regulation occurred only in tissues where the regulatory element (promoter or enhancer) that was being targeted was active. Although promoter-CRISPRa–targeted mice up-regulated Sim1 in all the tissues where it is expressed, the enhancer-CRISPRa–targeted mice showed Sim1 up-regulation only in the hypothalamus. We then delivered CRISPRa packaged into rAAV targeting the Sim1 promoter or its hypothalamus-specific enhancer using either Streptococcus pyogenes or the shorter Staphylococcus aureus CRISPRa system. We show that postnatal injection of CRISPRa-rAAV into the hypothalamus can up-regulate Sim1 expression and rescue the obesity phenotype in Sim1 haploinsufficient mice in a long-lasting manner. To further highlight the therapeutic potential of this approach to rescue other haploinsufficient genes, we targeted Mc4r, where haploinsufficiency leads to severe obesity in mice and humans. CRISPRa-rAAV targeting of the Mc4r promoter rescued the obesity phenotype of Mc4r heterozygous mice. CONCLUSION These findings show that the CRISPRa system can rescue a haploinsufficient phenotypein vivo. This CRISPR-mediated activation strategy is different from a conventional gene therapy strategy, as it uses the endogenous regulatory elements to up-regulate the existing functional gene copy. As such, it can overcome the problem of ectopic gene expression. In addition, it could be used for genes that are not amenable to conventional gene therapy because their coding sequences are longer than the rAAV packaging limit. Our results provide a framework to further develop CRISPRa as a potential tool to treat gene dosage–sensitive diseases.

Background Three-dimensional optical (3DO) body scanning has been proposed for automatic anthropometry. However, conventional measurements fail to capture detailed body shape. More sophisticated shape features could better indicate health status. Objectives The objectives were to predict DXA total and regional body composition, serum lipid and diabetes markers, and functional strength from 3DO body scans using statistical shape modeling. Methods Healthy adults underwent whole-body 3DO and DXA scans, blood tests, and strength assessments in the Shape Up! Adults cross-sectional observational study. Principal component analysis was performed on registered 3DO scans. Stepwise linear regressions were performed to estimate body composition, serum biomarkers, and strength using 3DO principal components (PCs). 3DO model accuracy was compared with simple anthropometric models and precision was compared with DXA. Results This analysis included 407 subjects. Eleven PCs for each sex captured 95% of body shape variance. 3DO body composition accuracy to DXA was: fat mass R2 = 0.88 male, 0.93 female; visceral fat mass R2 = 0.67 male, 0.75 female. 3DO body fat test-retest precision was: root mean squared error = 0.81 kg male, 0.66 kg female. 3DO visceral fat was as precise (%CV = 7.4 for males, 6.8 for females) as DXA (%CV = 6.8 for males, 7.4 for females). Multiple 3DO PCs were significantly correlated with serum HDL cholesterol, triglycerides, glucose, insulin, and HOMA-IR, independent of simple anthropometrics. 3DO PCs improved prediction of isometric knee strength (combined model R2 = 0.67 male, 0.59 female; anthropometrics-only model R2 = 0.34 male, 0.24 female). Conclusions 3DO body shape PCs predict body composition with good accuracy and precision comparable to existing methods. 3DO PCs improve prediction of serum lipid and diabetes markers, and functional strength measurements. The safety and accessibility of 3DO scanning make it appropriate for monitoring individual body composition, and metabolic health and functional strength in epidemiological settings.This trial was registered at clinicaltrials.gov as NCT03637855.

Genome wide association studies (GWAS) in obesity have identified a large number of noncoding loci located near genes expressed in the central nervous system. However, due to the difficulties in isolating and characterizing specific neuronal subpopulations, few obesity-associated SNPs have been functionally characterized. Leptin responsive neurons in the hypothalamus are essential in controlling energy homeostasis and body weight. Here, we combine FACS-sorting of leptin-responsive hypothalamic neuron nuclei with genomic and epigenomic approaches (RNA-seq, ChIP-seq, ATAC-seq) to generate a comprehensive map of leptin-response specific regulatory elements, several of which overlap obesity-associated GWAS variants. We demonstrate the usefulness of our leptin-response neuron regulome, by functionally characterizing a novel enhancer near Socs3, a leptin response-associated transcription factor. We envision our data to serve as a useful resource and a blueprint for functionally characterizing obesity-associated SNPs in the hypothalamus.

Most monogenic cases of obesity in humans have been linked to mutations in genes encoding members of the leptin-melanocortin pathway. Specifically, mutations in MC4R, the melanocortin-4 receptor gene, account for 3-5% of all severe obesity cases in humans1-3. Recently, ADCY3 (adenylyl cyclase 3) gene mutations have been implicated in obesity4,5. ADCY3 localizes to the primary cilia of neurons 6 , organelles that function as hubs for select signaling pathways. Mutations that disrupt the functions of primary cilia cause ciliopathies, rare recessive pleiotropic diseases in which obesity is a cardinal manifestation 7 . We demonstrate that MC4R colocalizes with ADCY3 at the primary cilia of a subset of hypothalamic neurons, that obesity-associated MC4R mutations impair ciliary localization and that inhibition of adenylyl cyclase signaling at the primary cilia of these neurons increases body weight. These data suggest that impaired signaling from the primary cilia of MC4R neurons is a common pathway underlyinggenetic causes of obesity in humans.

Neurons expressing agouti-related protein (AgRP) are essential for feeding. The majority of these neurons are located outside the blood-brain barrier (BBB), allowing them to directly sense circulating metabolic factors. Here, we show that, in adult mice, AgRP neurons outside the BBB (AgRPOBBB) were rapidly ablated by peripheral administration of monosodium glutamate (MSG), whereas AgRP neurons inside the BBB and most proopiomelanocortin (POMC) neurons were spared. MSG treatment induced proliferation of tanycytes, the putative hypothalamic neural progenitor cells, but the newly proliferated tanycytes did not become neurons. Intriguingly, AgRPOBBB neuronal number increased within a week after MSG treatment, and newly emerging AgRP neurons were derived from post-mitotic cells, including some from the Pomc-expressing cell lineage. Our study reveals that the lack of protection by the BBB renders AgRPOBBB vulnerable to lesioning by circulating toxins but that the rapid re-emergence of AgRPOBBB is part of a reparative process to maintain energy balance.

Haploinsufficiency, having only one functional copy of a gene, leads to a wide range of human disease and has been associated with over 300 genes. Here, we tested whether CRISPR activation (CRISPRa) could rescue a haploinsufficient disease in vivo. Haploinsufficiency of Sim1, a transcription factor involved in the leptin pathway, results in severe obesity in humans and mice. CRISPRa targeting of either the Sim1 promoter or its ~270kb distant hypothalamic enhancer using transgenic mice, rescued the obesity phenotype in Sim1 heterozygous mice. Interestingly, despite using a ubiquitous promoter for CRISPRa, Sim1 was upregulated only in tissues where the promoter or enhancer are active, suggesting that cis-regulatory elements can determine CRISPRa tissue-specificity. To further relate this to therapy, we injected CRISPRa adeno associated virus into the hypothalamus, leading to reversal of the obesity phenotype. This therapeutic strategy could be used to rescue numerous diseases resulting from altered gene dosage.

The ciliopathies Bardet – Biedl syndrome and Alström syndrome cause obesity. How ciliary dysfunction leads to obesity has remained mysterious, partly because of a lack of understanding of the physiological roles of primary cilia in the organs and pathways involved in the regulation of metabolism and energy homeostasis. Historically, the study of rare monogenetic disorders that present with obesity has informed our molecular understanding of the mechanisms involved in nonsyndromic forms of obesity. Here, we present a framework, based on genetic studies in mice and humans, of the molecular and cellular pathways underlying long-term regulation of energy homeostasis. We focus on recent progress linking these pathways to the function of the primary cilia with a particular emphasis on the roles of neuronal primary cilia in the regulation of satiety.

Objective Hyperphagia is a central feature of inherited disorders (e.g., Prader–Willi Syndrome) in which obesity is a primary phenotypic component. Hyperphagia may also contribute to obesity as observed in the general population, thus raising the potential importance of common underlying mechanisms and treatments. Substantial gaps in understanding the molecular basis of inherited hyperphagia syndromes are present as are a lack of mechanistic of mechanistic targets that can serve as a basis for pharmacologic and behavioral treatments. Design and Methods International conference with 28 experts, including scientists and caregivers, providing presentations, panel discussions, and debates. Results The reviewed collective research and clinical experience provides a critical body of new and novel information on hyperphagia at levels ranging from molecular to population. Gaps in understanding and tools needed for additional research were identified. Conclusions This report documents the full scope of important topics reviewed at a comprehensive international meeting devoted to the topic of hyperphagia and identifies key areas for future funding and research.

Most of our understanding of G protein–coupled receptor (GPCR) activation has been focused on the direct interaction between diffusible ligands and their seven-transmembrane domains. However, a number of these receptors depend on their extracellular N-terminal domain for ligand recognition and activation. To dissect the molecular interactions underlying both modes of activation at a single receptor, we used the unique properties of the melanocortin-4 receptor (MC4R), a GPCR that shows constitutive activity maintained by its N-terminal domain and is physiologically activated by the peptide α-melanocyte stimulating hormone (αMSH). We find that activation by the N-terminal domain and αMSH relies on different key residues in the transmembrane region. We also demonstrate that agouti-related protein, a physiological antagonist of MC4R, acts as an inverse agonist by inhibiting N terminus–mediated activation, leading to the speculation that a number of constitutively active orphan GPCRs could have physiological inverse agonists as sole regulators.

Haplo-insufficiency of the bHLH (basic helix-loop-helix) transcription factor single-minded 1 (SIM1) causes severe obesity in mice and humans. We hypothesized that common genetic variations in/near SIM1 could exert more subtle effects on its function and associate with human adiposity. First, SIM1 coding regions were sequenced in severely obese subjects, and two common nonsynonymous single-nucleotide polymorphisms (nsSNPs) in complete linkage disequilibrium (LD) were identified: Pro352Thr (rs3734354) and Ala371Val (rs3734355). We next carried out a SNP association study of five adiposity traits (BMI, % body fat, abdominal visceral and subcutaneous fat, and leptin concentrations) in 1,699 whites and 1,173 blacks. TagSNPs covering SIM1 and nearby conserved regions, and the only common nsSNP in SIM1's binding partner aryl-hydrocarbon receptor nuclear translocator 2 (ARNT2) (Gly679Ser/rs4072568), were investigated. The effects of rs3734355/4 on SIM1 activity were tested using an in vitro reporter assay. We replicated previous observations that homozygosity for the 371Val allele was associated with higher BMI in white males (P = 0.003). Together with previous findings in white males (combined n = 3,479), BMI was increased by 1.10 kg/m(2) in 371Val homozygotes (95% confidence interval (CI): 0.25-1.95 kg/m(2), P = 0.01). In vitro, the 352Thr-371Val haplotype impaired SIM1 transcriptional activity by 22% (P0.0001). TagSNP analysis of SIM1 revealed two SNPs in the 3' region (rs9390322 and rs7746743) and another in intron 5 (rs3734353) to be significantly associated with various adiposity measures in ethnicity- and sex-specific manners after multiple testing correction. In white males, rs4072568 in ARNT2 was also associated with BMI (P = 9 × 10(-4)) and % body fat (P = 0.001). Our findings implicate heritable defects of the SIM1-ARNT2 axis in the predisposition to human obesity.

Background Heterozygous mutations in melanocortin-4 receptor (MC4R) are the most frequent genetic cause of obesity. Bariatric surgery is a successful treatment for severe obesity. The mechanisms of weight loss after bariatric surgery are not well understood. Methods Ninety-two patients who had Roux-en-Y gastric bypass (RYGB) surgery were screened for MC4R mutations. We compared percent excess weight loss (%EWL) in the four MC4R mutation carriers with that of two control groups: 8 matched controls and with the remaining 80 patients who underwent RYGB. Results Four patients were heterozygous for functionally significant MC4R mutations. In patients with MC4R mutations, the %EWL after RYGB (66% EWL) was not significantly different compared to matched controls (70% EWL) and non-matched controls (60% EWL) after 1 year of follow-up. Conclusions This study suggests that patients with heterozygous MC4R mutations also benefit from RYGB and that weight loss may be independent of the presence of such mutations.

The melanocortin 4 receptor (MC4R) is a G-protein-coupled receptor (GPCR) and a key molecule in the regulation of energy homeostasis. At least 159 substitutions in the coding region of human MC4R (hMC4R) have been described experimentally; over 80 of those occur naturally, and many have been implicated in obesity. However, assessment of the presumably functionally essential residues remains incomplete. Here we have performed a complete in silico mutagenesis analysis to assess the functional essentiality of all possible nonnative point mutants in the entire hMC4R protein (332 residues). We applied SNAP, which is a method for quantifying functional consequences of single amino acid (AA) substitutions, to calculate the effects of all possible substitutions at each position in the hMC4R AA sequence. We compiled a mutability score that reflects the degree to which a particular residue is likely to be functionally important. We performed the same experiment for a paralogue human melanocortin receptor (hMC1R) and a mouse orthologue (mMC4R) in order to compare computational evaluations of highly related sequences. Three results are most salient: 1) our predictions largely agree with the available experimental annotations; 2) this analysis identified several AAs that are likely to be functionally critical, but have not yet been studied experimentally; and 3) the differential analysis of the receptors implicates a number of residues as specifically important to MC4Rs vs. other GPCRs, such as hMC1R.—Bromberg, Y., Overton, J., Vaisse, C., Leibel, R. L., Rost, B. In silico mutagenesis: a case study of the melanocortin 4 receptor.

The pro-opiomelanocotin (POMC) plays a key role in body weight regulation, where its derived peptides mediate leptin action via the hypothalamic melanocortin 4 receptor (MC4R). The pathogenic effects of POMC mutations have been challenged in obesity. Our aim was to assess the relevance of POMC mutations in a cohort of French obese and nonobese children. Direct sequencing of the POMC gene was performed in 322 obese and 363 control unrelated children. Functional studies for the novel Phe144Leu mutation included the response to alpha-melanocyte stimulating hormone (alphaMSH) and a competitive binding assay. POMC mutations were identified in 3.72% of obese [95% confidence interval (CI): 1.66-5.80] and 2.20% of control (95% CI: 0.69-3.71) subjects. The novel mutation located in the alphaMSH region of the POMC gene (Phe144Leu) was found in one obese child and was transmitted by the obese father. Functional studies showed that MC4R activation in response to Leu144alphaMSH was almost completely abolished due to a dramatically altered binding of Leu144alphaMSH to MC4R. The frequency of POMC mutations is not significantly different between obese and control children in our cohort. The novel heterozygous mutation Phe144Leu leading to the absence of melanocortin signaling was associated with early-onset obesity suggesting its pathogenic role.

Objective Elevated levels of serum leptin are associated with increased adiposity and production of pro-inflammatory cytokines. Both cytokines and body adiposity have been shown to predict cardiovascular events and mortality. The primary objective of the present study is to explore the associations between serum leptin and all-cause mortality and mortality from cardiovascular disease (CVD) over a span of 10 years, controlling for body adiposity and proinflammatory cytokines. Methods The Health, Aging and Body Composition (Health ABC) study is a prospective cohort of 3,075 older adults aged 70 to 79 years. This analysis includes 2,919 men and women with complete serum leptin and vital status data. Data on all-cause mortality and incident cardiovascular events (including Coronary Heart Disease and Congestive Heart Failure) were collected over 10 years of follow-up (mean 8.4 years). Results Women with leptin in quartile 2 and 3 were at lower risk of all-cause mortality, and those with leptin in quartile 2 were at lower risk of mortality from CVD as compared to women with lowest leptin values when adjusted for age, race, site, years of education, alcohol use, smoking, and physical activity. When these associations were additionally adjusted for body fat, C-reactive protein and pro-inflammatory cytokines, women with leptin values in quartile 3 were at lower risk of all-cause mortality and women with leptin in quartile 2 and 3 were at lower risk of mortality from CVD than women with lowest leptin values. These associations were not significant among men after adjusting for body fat and cytokines. Conclusions The present study suggests that moderately elevated concentrations of serum leptin are independently associated with lower risk of all-cause mortality and CVD-related mortality among older women. Among men, serum leptin is not associated with reduced risk of all-cause and CVD mortality after controlling for body fat and cytokines.

Context: Ketosis-prone diabetes (KPD) is mostly observed in males of West African descent and is characterized by phasic or permanent insulin dependence without apparent autoimmune process. Objective: KPD subjects display a propensity to hyperglycemia-induced acute insulin deficiency, suggesting that they exhibit a propensity to oxidative stress in β-cells. The enzyme glucose-6-phosphate dehydrogenase (G6PD) is a defense mechanism against oxidative stress, and G6PD deficiency, an X-linked genetic disorder with male predominance, is frequent in West Africans. We hypothesized that mutations in the G6PD gene could predispose to KPD. Design: We studied G6PD erythrocyte enzyme activity and the insulin secretory reserve (glucagon-stimulated C peptide) in a cohort of hospitalized West Africans with KPD (n = 59) or type 2 diabetes (T2DM; n = 59) and in normoglycemic controls (n = 55). We also studied the G6PD gene in an extended population of KPD patients (n = 100), T2DM patients (n = 59), and controls (n = 85). ...

Bone remodelling, the mechanism by which vertebrates regulate bone mass, comprises two phases, namely resorption by osteoclasts and formation by osteoblasts; osteoblasts are multifunctional cells also controlling osteoclast differentiation. Sympathetic signalling via beta2-adrenergic receptors (Adrb2) present on osteoblasts controls bone formation downstream of leptin. Here we show, by analysing Adrb2-deficient mice, that the sympathetic nervous system favours bone resorption by increasing expression in osteoblast progenitor cells of the osteoclast differentiation factor Rankl. This sympathetic function requires phosphorylation (by protein kinase A) of ATF4, a cell-specific CREB-related transcription factor essential for osteoblast differentiation and function. That bone resorption cannot increase in gonadectomized Adrb2-deficient mice highlights the biological importance of this regulation, but also contrasts sharply with the increase in bone resorption characterizing another hypogonadic mouse with low sympathetic tone, the ob/ob mouse. This discrepancy is explained, in part, by the fact that CART ('cocaine amphetamine regulated transcript'), a neuropeptide whose expression is controlled by leptin and nearly abolished in ob/ob mice, inhibits bone resorption by modulating Rankl expression. Our study establishes that leptin-regulated neural pathways control both aspects of bone remodelling, and demonstrates that integrity of sympathetic signalling is necessary for the increase in bone resorption caused by gonadal failure.

As a mediator of the effects of leptin, the melanocortin-4 receptor (MC4R) is an essential component of the central regulation of long-term energy homeostasis. Heterozygous mutations in this receptor are the most frequent genetic cause of severe obesity in children. The very rare described carriers of homozygous MC4R mutations for whom clinical data were available had a residual receptor activity thus not allowing for the description of the full extent of the role of MC4R in humans. Here, we present the clinical and biological features of a patient with complete absence of MC4R activity and compare the clinical and endocrine characteristics of this patient with those previously observed in leptin receptor-deficient patients. Our data suggest that in humans, the MC4R mediates most of the anorectic effects of leptin in early childhood. In contrast, MC4R does not mediate the effect of leptin on linear growth and other endocrine axes. In addition, complete MC4R deficiency is not a cause of relative hyperinsulinemia as recently observed in children with heterozygous MC4R mutations.

Nonautoimmune ketosis-prone diabetic syndromes are increasingly frequent in nonwhite populations. We have characterized a cohort of patients of sub-Saharan African origin who had ketosis-prone type 2 diabetes (n = 111), type 1 diabetes (n = 21), and type 2 diabetes (n = 88) and were admitted to a hospital for management of uncontrolled diabetes. We compared epidemiological, clinical, and metabolic features at diabetes onset and measured insulin secretion (glucagon-stimulated C-peptide) and insulin action (short intravenous insulin tolerance test) during a 10-year follow-up. Ketosis-prone type 2 diabetes shows a strong male predominance, stronger family history, higher age and BMI, and more severe metabolic decompensation than type 1 diabetes. In ketosis-prone type 2 diabetes, discontinuation of insulin therapy with development of remission of insulin dependence is achieved in 76% of patients (non-insulin dependent), whereas only 24% of patients remain insulin dependent. During evolution, ketosis-prone type 2 diabetes exhibit specific beta-cell dysfunction features that distinguish it from type 1 and type 2 diabetes. The clinical course of non-insulin-dependent ketosis-prone type 2 diabetes is characterized by ketotic relapses followed or not by a new remission. Progressive hyperglycemia precedes and is a strong risk factor for ketotic relapses (hazard ratio 38). The probability for non-insulin-dependent ketosis-prone type 2 diabetes to relapse is 90% within 10 years, of whom approximately 50% will become definitively insulin dependent. Insulin sensitivity is decreased in equal proportion in both ketosis-prone type 2 diabetes and type 2 diabetes, but improves significantly in non-insulin-dependent ketosis-prone type 2 diabetes, only after correction of hyperglycemia. In conclusion, ketosis-prone type 2 diabetes can be distinguished from type 1 diabetes and classical type 2 diabetes by specific features of clinical pathophysiology and also by the natural history of beta-cell dysfunction and insulin resistance reflecting a propensity to glucose toxicity.

Heterozygous mutations in the coding sequence of the serpentine melanocortin 4 receptor (MC4R) are the most frequent genetic cause of severe human obesity. Since haploinsufficiency has been proposed as a causal mechanism of obesity associated with these mutations, reduction in gene transcription caused by mutations in the transcriptionally essential regions of the MC4R promoter may also be a cause of severe obesity in humans. To test this hypothesis we defined the minimal promoter region of the human MC4R and evaluated the extent of genetic variation in this region compared with the coding region in two cohorts of severely obese subjects. 5′RACE followed by functional promoter analysis in multiple cell lines indicates that an 80-bp region is essential for the transcriptional activity of the MC4R promoter. Systematic screening of 431 obese children and adults for mutations in the coding sequence and the minimal core promoter of MC4R reveals that genetic variation in the transcriptionally essential region of the MC4R promoter is not a significant cause of severe obesity in humans.

Common genetic variants 3′ of MC4R within two large linkage disequilibrium (LD) blocks spanning 288 kb have been associated with common and rare forms of obesity. This large association region has not been refined and the relevant DNA segments within the association region have not been identified. In this study, we investigated whether common variants in the MC4R gene region were associated with adiposity-related traits in a biracial population-based study. Single nucleotide polymorphisms (SNPs) in the MC4R region were genotyped with a custom array and a genome-wide array and associations between SNPs and five adiposity-related traits were determined using race-stratified linear regression. Previously reported associations between lower BMI and the minor alleles of rs2229616/Val103Ile and rs52820871/Ile251Leu were replicated in white female participants. Among white participants, rs11152221 in a proximal 3′ LD block (closer to MC4R) was significantly associated with multiple adiposity traits, but SNPs in a distal 3′ LD block (farther from MC4R) were not. In a case-control study of severe obesity, rs11152221 was significantly associated. The association results directed our follow-up studies to the proximal LD block downstream of MC4R. By considering nucleotide conservation, the significance of association, and proximity to the MC4R gene, we identified a candidate MC4R regulatory region. This candidate region was sequenced in 20 individuals from a study of severe obesity in an attempt to identify additional variants, and the candidate region was tested for enhancer activity using in vivo enhancer assays in zebrafish and mice. Novel variants were not identified by sequencing and the candidate region did not drive reporter gene expression in zebrafish or mice. The identification of a putative insulator in this region could help to explain the challenges faced in this study and others to link SNPs associated with adiposity to altered MC4R expression.

Glycodelin is an endometrial protein with proposed immunomodulatory activity during human embryonic nidation. In this review we describe the effects of ovarian hormones on glycodelin transcription, synthesis, and secretion by human epithelial cells and focus on the importance of glycodelin in implantation. We demonstrate that glycodelin transcription, synthesis, and secretion by human epithelial cells are stimulated by progestins and antiprogestins but not by estrogen. Sequences localized within a 403-base-pair region flanking the 5' human glycodelin gene promoter appear to be responsible for transcriptional activation of this gene mediated by progesterone receptor-ligand complexes. Relax in, purported to enhance glycodelin production in vivo and in prior in vitro studies, had no stimulatory effect on the expression of this gene in vitro in our models.

One of the most abundant protein products of human secretory endometrium is glycodelin, a glycoprotein previously referred to as PP14. Although the precise function of this protein is unknown, its unique glycosylation pattern is believed to affect immunomodulatory activity during human embryonic implantation and inhibition of sperm-egg binding after ovulation. Having confirmed the expression of glycodelin in secretory endometrial glands, we used purified endometrial epithelial cell cultures to demonstrate the hormonal regulation of glycodelin synthesis and secretion. The findings were corroborated by transiently transfecting glycodelin gene promoter-reporter constructs into human epithelioid HeLa and Ishikawa cells. Our results indicate that glycodelin protein production by endometrial epithelial cells is directly up-regulated 4- to 9-fold by progestins and antiprogestins in vitro. Transcriptional regulation of the glycodelin gene promoter expressed in HeLa cells is progesterone receptor-dependent. As observed in the primary endometrial cells, progestins and antiprogestins both act as agonists on the in vitro expression of this endometrial gene. Our findings provide insight into the regulation of this abundant endometrial protein and raise interesting questions about the physical nature of the interaction of agonist- and antagonist-bound progesterone receptors with the glycodelin gene promoter.

The genes encoding the functionally related hepatocyte nuclear factors HNF-1α and HNF-4α play a critical role in normal pancreatic β-cell function. Mutations in these liver-enriched transcription factors result in two forms of early-onset type 2 diabetes (maturity-onset diabetes of the young [MODY]), M0DY3 and M0DY1, which are characterized by impaired glucose-stimulated insulin secretion, early disease onset, and autosomal dominant inheritance. The transcriptional hierarchy of HNFs suggests that other proteins of the regulatory cascade might be responsible for other forms of MODY and/or late-onset type 2 diabetes. In this study, we show that HNF-3α, -3β, -3γ, -4γ, and -6 are expressed in pancreatic β-cells. We report the identification and characterization of simple tandem repeat DNA polymorphisms in the genes encoding HNF-3α, -3β, -3γ, -4γ, and -6 and the mapping of HNF-6 to chromosome bands 15q21.1–21.2 by fluorescence in situ hybridization. These markers will be useful to study the role of genetic variation in these genes in the pathogenesis of type 2 diabetes.

Haploinsufficiency of the single-minded homology 1 (SIM1) gene in humans and mice leads to severe obesity, suggesting that altered expression of SIM1, by way of regulatory elements such as enhancers, could predispose individuals to obesity. Here, we identified transcriptional enhancers that could regulate SIM1, using comparative genomics coupled with zebrafish and mouse transgenic enhancer assays. Owing to the dual role of Sim1 in hypothalamic development and in adult energy homeostasis, the enhancer activity of these sequences was annotated from embryonic to adult age. Of the seventeen tested sequences, two SIM1 candidate enhancers (SCE2 and SCE8) were found to have brain-enhancer activity in zebrafish. Both SCE2 and SCE8 also exhibited embryonic brain-enhancer expression in mice, and time course analysis of SCE2 activity showed overlapping expression with Sim1 from embryonic to adult age, notably in the hypothalamus in adult mice. Using a deletion series, we identified the critical region in SCE2 that is needed for enhancer activity in the developing brain. Sequencing this region in obese and lean cohorts revealed a higher prevalence of single nucleotide polymorphisms (SNPs) that were unique to obese individuals, with one variant reducing developmental-enhancer activity in zebrafish. In summary, we have characterized two brain enhancers in the SIM1 locus and identified a set of obesity-specific SNPs within one of them, which may predispose individuals to obesity.

The central melanocortin system is essential for the regulation of long-term energy homeostasis in humans. Rodent experiments suggest that this system also affects glucose metabolism, in particular by modulating peripheral insulin sensitivity independently of its effect on adiposity. Rare patients with complete genetic defects in the central melanocortin system can provide insight into the role of this system in glucose homeostasis in humans. We here describe the eighth individual with complete proopiomelanocortin (POMC) deficiency and the first with coincidental concomitant type 1 diabetes, which provides a unique opportunity to determine the role of melanocortins in glucose homeostasis in human. Direct sequencing of the POMC gene in this severely obese patient with isolated adrenocorticotropic hormone deficiency identified a homozygous 5' untranslated region mutation -11C>A, which we find to abolish normal POMC protein synthesis, as assessed in vitro. The patient's insulin requirements were as expected for his age and pubertal development. This unique patient suggests that in humans the central melanocortin system does not seem to affect peripheral insulin sensitivity, independently of its effect on adiposity.

Summary: Diabetic obesity is associated with increased fracture risk in adults and adolescents. We find in both adolescent and adult mice dramatically inferior mechanical properties and structural quality of cortical bone, in agreement with the human fracture data, although some aspects of the response to obesity appear to differ by age. Introduction: The association of obesity with bone is complex and varies with age. Diabetic obese adolescents and adult humans have increased fracture risk. Prior studies have shown reduced mechanical properties as a result of high-fat diet (HFD) but do not fully address size-independent mechanical properties or structural quality, which are important to understand material behavior. Methods: Cortical bone from femurs and tibiae from two age groups of C57BL/6 mice fed either HFD or low-fat diet (LFD) were evaluated for structural and bone turnover changes (SEM and histomorphometry) and tested for bending strength, bending stiffness, and fracture toughness. Leptin, IGF-I, and non-enzymatic glycation measurements were also collected. Results: In both young and adult mice fed on HFD, femoral strength, stiffness, and toughness are all dramatically lower than controls. Inferior lamellar and osteocyte alignment also point to reduced structural quality in both age groups. Bone size was largely unaffected by HFD, although there was a shift from increasing bone size in obese adolescents to decreasing in adults. IGF-I levels were lower in young obese mice only. Conclusions: While the response to obesity of murine cortical bone mass, bone formation, and hormonal changes appear to differ by age, the bone mechanical properties for young and adult groups are similar. In agreement with human fracture trends, adult mice may be similarly susceptible to bone fracture to the young group, although cortical bone in the two age groups responds to diabetic obesity differently. © 2010 The Author(s).

The hypothalamus plays a major role in the long-term regulation of body weight in humans. Within the hypothalamus, the leptin–melanocortin system is critical for energy balance, as animal and human studies have shown that disruption of this pathway, which senses peripheral energy stores and signals satiety, leads to the most severe forms of human obesity. The monogenic causes of obesity identified so far in this pathway are very heterogeneous and account for less than 5% of severe obesity. The genetic basis of the remaining 95% of obesity is likely to be even more heterogeneous and polygenic. The melanocortin 4-receptor (MC4R) is the most specialized molecule for body weight maintenance within this system as the clinical phenotype of MC4R deficiency is limited to obesity. Indeed, heterozygous MC4R mutations are the most common cause of monogenic obesity. In addition, novel mechanisms are emerging as important for pathogenicity of obesity, such as abnormal hypothalamic development, alterations in neuronal plasticity, and dysfunction of the primary cilium. This chapter focuses on obesity caused by mutations in genes that have a physiologic role in the hypothalamic leptin–melanocortin system of energy balance.

Bariatric surgery is often successful for treatment of severe obesity. The mechanisms of weight loss after bariatric surgery and the role of central energy homeostatic pathways in this weight loss process are not well understood. The study of individuals with complete loss of function of genes important in the leptin-melanocortin system may help establish the significance of these pathways for weight loss after bariatric surgery. We describe the outcome of bariatric surgery in an adolescent with compound heterozygosity and complete functional loss of both alleles of the melanocortin 4 receptor (MC4R). The patient underwent laparoscopic adjustable gastric banding and truncal vagotomy at years of age, which resulted in initial, but not long-term weight loss. Our experience with this patient suggests that complete MC4R deficiency impairs response to gastric banding and results in poor weight loss after this surgery.

Overweight and obesity are rapidly expanding health problems in children and adolescents. Obesity is associated with greater bone mineral content that might be expected to protect against fracture, which has been observed in adults. Paradoxically, however, the incidence of bone fractures has been found to increase in overweight and obese children and adolescents. Prior studies have shown some reduced mechanical properties as a result of high-fat diet (HFD) but do not fully address size-independent measures of mechanical properties, which are important to understand material behavior. To clarify the effects of HFD on the mechanical properties and microstructure of bone, femora from C57BL/6 mice fed either a HFD or standard laboratory chow (Chow) were evaluated for structural changes and tested for bending strength, bending stiffness and fracture toughness. Here, we find that in young, obese, high-fat fed mice, all geometric parameters of the femoral bone, except length, are increased, but strength, bending stiffness, and fracture toughness are all reduced. This increased bone size and reduced size-independent mechanical properties suggests that obesity leads to a general reduction in bone quality despite an increase in bone quantity; yield and maximum loads, however, remained unchanged, suggesting compensatory mechanisms. We conclude that diet-induced obesity increases bone size and reduces size-independent mechanical properties of cortical bone in mice. This study indicates that bone quantity and bone quality play important compensatory roles in determining fracture risk.

Summary Objective X-linked nephrogenic diabetes insipidus (XNDI), caused by mutations in the V2 vasopressin receptor (V2R), is clinically distinguished from central diabetes insipidus (CDI) by elevated serum vasopressin (AVP) levels and unresponsiveness to 1-desamino-8-d-arginine vasopressin (DDAVP). We report two infants with XNDI, and present the characterization and functional rescue of a novel V2R mutation. Patients Two male infants presented with poor growth and hypernatraemia. Both patients had measurable pretreatment serum AVP and polyuria that did not respond to DDAVP, suggesting NDI. However, both also had absent posterior pituitary bright spot on MRI, which is a finding more typical of CDI. Methods The AVPR2 gene encoding V2R was sequenced. The identified novel missense mutation was re-created by site-directed mutagenesis and expressed in HEK293 cells. V2R activity was assessed by the ability of transfected cells to produce cAMP in response to stimulation with DDAVP. Membrane localization of V2R was assessed by fluorescence microscopy. Results Patient 1 had a deletion of AVPR2; patient 2 had the novel mutation L57R. In transiently transfected HEK293 cells, DDAVP induced detectable but severely impaired L57R V2R activity compared to cells expressing wild-type V2R. Fluorescence microscopy showed that myc-tagged wild-type V2R localized to the cell membrane while L57R V2R remained intracellular. A nonpeptide V2R chaperone, SR121463, partially rescued L57R V2R function by allowing it to reach the cell membrane. Conclusions L57R V2R has impaired in vitro activity that can be partially improved by treatment with a V2R chaperone. The posterior pituitary hyperintensity may be absent in infants with XNDI.

There is a strong genetic component to human obesity. Most genes that influence an individual’s predisposition to gain weight are not yet known. However, a glimpse into the long-term regulation of body weight has come from studying extreme human obesity caused by single gene defects. These monogenic obesity disorders have confirmed that the hypothalamic leptin-melanocortin system is critical for energy balance in humans because disruption of these pathways causes the most severe obesity phenotypes. Approximately 20 different genes and at least 3 different mechanisms implicated in monogenic causes of obesity have been identified, however, they account for less than 5% of all severe obesity. This suggests that the genetic basis for human obesity is likely to be extremely heterogeneous, with contribution from numerous different genes acting by various, yet undiscovered, molecular mechanisms.

Differential hybridization of cDNAs corresponding to mRNAs expressed in the human endometrium during the secretory phase or during the first trimester of pregnancy, but not during the proliferative phase, allowed us to isolate and characterize cDNAs encoding human placental protein 14 (PP14). The cDNA was used to isolate the PP14 gene from a human genomic library. The entire gene encompasses 5.05 kb divided into seven exons by six introns. The human PP14 gene shows identical organization with the ovine β-lactoglobulin gene, as expected from protein homology. Sequencing of 3 kb of the 5′-flanking region of the gene allowed us to characterize a 400-bp duplication of the PP14 gene lying at position –2,660. This duplication was homologous to 100 bp of exon 4 and 300 bp of intron 4, including 180 bp corresponding exactly to the right arm of an Alu element lying on the complementary strand. This homology suggests that this duplication may have arisen through a retroposition event.

Ketosis-prone diabetes (KPD) is a phenotypically defined form of diabetes characterized by male predominance and severe insulin deficiency. Neurogenin3 (NGN3) is a proendocrine gene, which is essential for the fate of pancreatic beta cells. Mice lacking ngn3 develop early insulin-deficient diabetes. Thus, we hypothesized that gender and variants in NGN3 could predispose to KPD. We have studied clinical and metabolic parameters according to gender in patients with KPD (n = 152) and common type 2 diabetes (T2DM) (n = 167). We have sequenced NGN3 in KPD patients and screened gene variants in T2DM and controls (n = 232). In KPD, male gender was associated with a more pronounced decrease in beta-cell insulin secretory reserve, assessed by fasting C-peptide [mean (ng/ml) +/- s.d., M: 1.1 +/- 0.6, F: 1.5 +/- 0.9; p = 0.02] and glucagon-stimulated C-peptide [mean (ng/ml) +/- s.d., M: 2.2 +/- 1.1, F: 3.1 +/- 1.7; p = 0.03]. The rare affected females were in an anovulatory state. We found two new variants in the promoter [-3812T/C (af: 2%) and -3642T/C (af: 1%)], two new coding variants [S171T (af: 1%) and A185S (af: 1%)] and the variant already described [S199F (af: 69%)]. These variants were not associated with diabetes. Clinical investigation revealed an association between 199F and hyperglycaemia assessed by glycated haemoglobin [HbA1c (%, +/-s.d.) S199: 12.6 +/- 1.6, S199F: 12.4 +/- 1.4 and 199F: 14.1 +/- 2.2; p = 0.01]. In vitro, the P171T, A185S and S199F variants did not reveal major functional alteration in the activation of NGN3 target genes. In conclusion, male gender, anovulatory state in females and NGN3 variations may influence the pathogenesis of KPD in West Africans. This has therapeutic implications for potential tailored pharmacological intervention in this population.