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Abstract Deletions and malfunctions of the IgLON family of cell adhesion molecules are associated with anatomical, behavioral, and metabolic manifestations of neuropsychiatric disorders. We have previously shown that IgLON genes are expressed in sensory nuclei/pathways and that IgLON proteins modulate sensory processing. Here, we examined the expression of IgLON alternative promoter-specific isoforms during embryonic development and studied the sensory consequences of the anatomical changes when one of the IgLON genes, Negr1, is knocked out. At the embryonal age of E12.5 and E13.5, various IgLONs were distributed differentially and dynamically in the developing sensory areas within the central and peripheral nervous system, as well as in limbs and mammary glands. Sensory tests showed that Negr1 deficiency causes differences in vestibular function and temperature sensitivity in the knockout mice. Sex-specific differences were noted across olfaction, vestibular functioning, temperature regulation, and mechanical sensitivity. Our findings highlight the involvement of IgLON molecules during sensory circuit formation and suggest Negr1’s critical role in somatosensory processing.

Deletions and malfunctions of the IgLON family of cell adhesion molecules are associated with anatomical, behavioral, and metabolic manifestations of neuropsychiatric disorders. We have previously shown that IgLON genes are expressed in sensory nuclei/pathways and that IgLON proteins modulate sensory processing. Here, we examined the expression of IgLON alternative promoter-specific isoforms during embryonic development and studied the sensory consequences of the anatomical changes when one of the IgLON genes, Negr1, is knocked out. At the embryonal age of E12.5 and E13.5, various IgLONs were distributed differentially and dynamically in the developing sensory areas within the central and peripheral nervous system, as well as in limbs and mammary glands. Sensory tests showed that Negr1 deficiency causes differences in vestibular function and temperature sensitivity in the knockout mice. Sex-specific differences were noted across olfaction, vestibular functioning, temperature regulation, and mechanical sensitivity. Our findings highlight the involvement of IgLON molecules during sensory circuit formation and suggest Negr1’s critical role in somatosensory processing. [ABSTRACT FROM AUTHOR]

The immunoglobulin LAMP/OBCAM/NTM (IgLON) family of cell adhesion molecules comprises five members known for their involvement in establishing neural circuit connectivity, fine-tuning, and maintenance. Mutations in IgLON genes result in alterations in these processes and can lead to neuropsychiatric disorders. The two IgLON family members NEGR1 and OPCML share common links with several of them, such as schizophrenia, autism, and major depressive disorder. However, the onset and the underlying molecular mechanisms have remained largely unresolved, hampering progress in developing therapies. NEGR1 and OPCML are evolutionarily conserved in teleosts like the zebrafish (Danio rerio), which is excellently suited for disease modelling and large-scale screening for disease-ameliorating compounds. To explore the potential applicability of zebrafish for extending our knowledge on NEGR1- and OPCML-linked disorders and to develop new therapeutic strategies, we investigated the spatio-temporal expression of the two genes during early stages of development. negr1 and opcml are expressed maternally and subsequently in partially distinct domains of conserved brain regions. Other areas of expression in zebrafish have not been reported in mammals to date. Our results indicate that NEGR1 and OPCML may play roles in neural circuit development and function at stages earlier than previously anticipated. A detailed functional analysis of the two genes based on our findings could contribute to understanding the mechanistic basis of related psychiatric disorders. [ABSTRACT FROM AUTHOR]

In the brain, cell adhesion molecules (CAMs) are critical for neurite outgrowth, axonal fasciculation, neuronal survival and migration, and synapse formation and maintenance. Among CAMs, the IgLON family comprises five members: Opioid Binding Protein/Cell Adhesion Molecule Like (OPCML or OBCAM), Limbic System Associated Membrane Protein (LSAMP), neurotrimin (NTM), Neuronal Growth Regulator 1 (NEGR1), and IgLON5. IgLONs exhibit three N-terminal C2 immunoglobulin domains; several glycosylation sites; and a glycosylphosphatidylinositol anchoring to the membrane. Interactions as homo- or heterodimers in cis and in trans, as well as binding to other molecules, appear critical for their functions. Shedding by metalloproteases generates soluble factors interacting with cellular receptors and activating signal transduction. The aim of this review was to analyse the available data implicating a role for IgLONs in neuropsychiatric disorders. Starting from the identification of a pathological role for antibodies against IgLON5 in an autoimmune neurodegenerative disease with a poorly understood mechanism of action, accumulating evidence links IgLONs to neuropsychiatric disorders, albeit with still undefined mechanisms which will require future thorough investigations. [ABSTRACT FROM AUTHOR]

Neuroblastoma is among the most common childhood cancers. Neuroblastoma in advanced stages is one of the most intractable pediatric cancers, notwithstanding the recent therapeutic advances. ALK mutations are among the leading cause of hereditary neuroblastoma and account for more than 14% of the somatically acquired alterations. ALK kinase activity is currently one of the main targets for pharmacological strategies. However, evidence from ALK fusion-positive lung cancer studies has shown that resistance to ALK inhibition arises during the therapy, causing a relapse within several years. IgLONs are membrane-bound proteins involved in cell-to-cell adhesion. The expression of the IgLON family results altered in different cancers. We found that the IgLON member Negr1 is downregulated in neuroblastoma. The ectopic overexpression of Negr1 impairs neuroblastoma growth in vitro and in vivo. Negr1 exists as a GPI-anchored membrane-bound protein and as a soluble protein released upon metalloprotease cleavage. We generated and characterized a panel of Negr1-derived peptides. The treatment with Negr1 protein and derived peptides induce ALK downregulation and halt neuroblastoma progression in vitro and in vivo. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Polycystic ovarian syndrome (PCOS) is a complex heterogeneous condition that affects women of reproductive age, conferring increased cardiovascular morbidity and mortality. The syndrome is characterized by oligomenorrhea, hyperandrogenism, and/or polycystic ovaries and is often associated with obesity and type 2 diabetes. Individuals are predisposed to PCOS by environmental factors and risk variants in genes mostly involved in ovarian steroidogenesis and/or insulin resistance. Genetic risk factors have been identified by both familial and genome-wide (GW) association studies. However, most genetic components are still unknown and missing heritability needs to be elucidated. To learn more about the genetic determinants of PCOS, we performed a GW study in genetically highly homogeneous peninsular families. PATIENTS AND METHODS: We conducted the first GW-linkage and linkage disequilibrium (i.e., linkage + association) study in Italian families with PCOS. RESULTS: We identified several novel risk variants, genes, and pathways potentially implicated in the pathogenesis of PCOS. Specifically, we detected 79 novel variants with significant GW-linkage and/or -association with PCOS across 4 inheritance models (p < 0.00005), of which 50 variants were within 45 novel PCOS-risk genes. CONCLUSIONS: This is the first GW-linkage and linkage disequilibrium study performed in peninsular Italian families and reporting novel genes in PCOS. [ABSTRACT FROM AUTHOR]

In GWAS studies, the neural adhesion molecule encoding the neuronal growth regulator 1 (NEGR1) gene has been consistently linked with both depression and obesity. Although the linkage between NEGR1 and depression is the strongest, evidence also suggests the involvement of NEGR1 in a wide spectrum of psychiatric conditions. Here we show the expression of NEGR1 both in tyrosine- and tryptophan hydroxylase-positive cells. Negr1−/− mice show a time-dependent increase in behavioral sensitization to amphetamine associated with increased dopamine release in both the dorsal and ventral striatum. Upregulation of transcripts encoding dopamine and serotonin transporters and higher levels of several monoamines and their metabolites was evident in distinct brain areas of Negr1−/− mice. Chronic (23 days) escitalopram-induced reduction of serotonin and dopamine turnover is enhanced in Negr1−/− mice, and escitalopram rescued reduced weight of hippocampi in Negr1−/− mice. The current study is the first to show alterations in the brain monoaminergic systems in Negr1-deficient mice, suggesting that monoaminergic neural circuits contribute to both depressive and obesity-related phenotypes linked to the human NEGR1 gene. [ABSTRACT FROM AUTHOR]

Neuronal growth regulator 1 (NEGR1) is a synaptic plasma membrane localized cell adhesion molecule implicated in a wide spectrum of psychiatric disorders. By RNAseq analysis of the transcriptomic changes in the brain of NEGR1-deficient mice, we found that NEGR1 deficiency affects the expression of the Gad2 gene. We show that glutamic acid decarboxylase 65 (GAD65), the Gad2 - encoded enzyme synthesizing the inhibitory neurotransmitter GABA on synaptic vesicles, accumulates non-synaptically in brains of NEGR1-deficient mice. The density of non-synaptic GAD65 accumulations is also increased in NEGR1 deficient cultured hypothalamic neurons, and this effect is rescued by re-expression of NEGR1. By using a novel biosensor of the plasma membrane attachment of GAD65, we demonstrate that GAD65 attaches to the plasma membrane. NEGR1 promotes palmitoylation-dependent clearance of GAD65 from the plasma membrane and targeting of GAD65 to plasma membrane-derived endocytic vesicles. In NEGR1 deficient cultured hypothalamic neurons, the synaptic and extrasynaptic levels of the plasma membrane attached GAD65 are increased, and the synaptic levels of GABA are reduced. NEGR1-deficient mice are characterized by reduced body weight, lower GABAergic synapse densities in the arcuate nucleus, and blunted responsiveness to the reinforcing effects of food rewards. Our results indicate that abnormalities in synaptic GABA synthesis can contribute to brain disorders associated with abnormal expression of NEGR1 in humans., (© 2024 International Society for Neurochemistry.)

Circular RNAs (circRNAs) have been reported to play vital regulatory roles in human diseases. However, the functions of circRNAs in ischemic stroke (IS) are limited. In this study, we aimed to explore the functions and mechanisms of circRNA DLG associated protein 4 (circDLGAP4) in IS development. Oxygen–glucose deprivation (OGD)-treated HCN-2 cells were used to mimic IS environment in vitro. Quantitative real-time polymerase chain reaction (qRT-PCR) assay was used to detect the levels of circDLGAP4, microRNA-503-3p (miR-503-3p) and neuronal growth regulator 1 (NEGR1) mRNA. RNase R assay was conducted to analyze the stability of circDLGAP4. Cell Counting Kit-8 (CCK-8) assay and flow cytometry analysis were adopted for cell viability and death, respectively. Western blot assay was performed for protein levels. Enzyme-linked immunosorbent assay (ELISA) kits were used to examine the concentrations of inflammatory cytokines. Dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay and RNA pull-down assay were employed to analyze the relationships among circDLGAP4, miR-503-3p and NEGR1. CircDLGAP4 level was declined in HCN-2 cells after OGD treatment. CircDLGAP4 overexpression promoted cell viability and suppressed cell death and inflammatory cytokine concentrations in OGD-treated HCN-2 cells. CircDLGAP4 acted as the sponge for miR-503-3p and the impacts of circDLGAP4 overexpression on cell viability, death and inflammation in OGD-treated HCN-2 cells were reversed by miR-503-3p elevation. Furthermore, NEGR1 was the target gene of miR-503-3p. MiR-503-3p inhibition ameliorated OGD-induced HCN-2 cell impairments, but NEGR1 knockdown abolished the effects. CircDLGAP4 alleviated OGD-induced HCN-2 cell damage by regulating miR-503-3p/NEGR1 axis. [ABSTRACT FROM AUTHOR]

Objective: To investigate whether the positive single nucleotide polymorphisms (SNPs) in previous autism genome-wide association study (GWAS ) are associated with autism in the Chinese Han population. Methods: According to the autism diagnosis of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), 757 Chinese Han children offected with autism and 1436 normal Chinese Han adults were recruited. Five genome-wide significant SNPs reported in previous autism GWAS (rs I620977 in NEGRI, rsI452075 in CADPS, rs325506 near NUDT12, rs10I49470 near COA8 and rs910805 near KIZ) were selected. Besides, another two SNPs (rs9375225 near MMS22L and rs746839 near MROH5) which were in strong linkage disequilibrium with autism GWAS hits were also included. Genotyping for 7 selected SNPs was performed by using Agena MassARRAY SNP genotyping assay. The frequency distribution of genotypes and alleles between the autistic patients and the controls was compared with the Pearson' s χ² test to analyze the association between SNPs and autism. Results: The frequencies of the allele A of rsl620977 in NEGRl (cases vs. controls: 17. 2% vs. 14. 3%), the G carrying genotype (1.4% vs. 26. 0%) and the allele G (17. 2% vs. 14. 3%) of rs746839 near MROH5 in autistic patients were higher than those in normal controls (P < 0. 05). These results remain statistically significant in the male population after Bonferroni correction (P < 0. 007). Conclusion: Rsl620977 in NEGRl and rs746839 near MROH5 are associated with autism in the Chinese Han population. It suggests that these two SNPs might be susceptibility SNPs for autism in the Chinese Han population. [ABSTRACT FROM AUTHOR]

The IgLON family of cell adhesion molecules consists of five members (LSAMP, OPCML, neurotrimin, NEGR1, and IgLON5) discovered as supporters of neuronal development, axon growth and guidance, and synapse formation and maintenance. Tumour suppression properties have recently been emerging based on antiproliferative effects through the modulation of oncogenic pathways. Available evidence endorses a role for non-coding RNAs or microRNAs as relevant controllers of IgLON molecule expression that can impact their critical physiological and pathological roles. Current findings support a function for long non-coding RNAs and microRNAs in the modulation of LSAMP expression in cell senescence, cancer biogenesis, addiction, and pulmonary hypertension. For OPCML, data point to a role for several microRNAs in the control of tumorigenesis. MicroRNAs were detected in neurotrimin-mediated functions in cancer biogenesis and in Schwann cell responses to peripheral nerve injury. For NEGR1, studies have mainly investigated microRNA involvement in neuronal responses to ischaemic injury, although data also exist about tumorigenesis and endothelial cell dysfunction. For IgLON5, information is only available about microRNA involved in myocardial infarction. In conclusion, despite much information being still missing and further research needed, the emerging picture favours a model in which non-coding RNAs exert a crucial role in modulating IgLON expression, ultimately affecting their important physiological functions.

Obesity is a complex disorder with nearly epidemic proportions in many parts of the world. Genome-wide association studies have demonstrated high heritability for obesity and body mass, with associations of certain candidate genes and their variations with respect to race, geographical location/country of origin. However, the functional mechanisms and different ethnic data of these loci are still poorly understood. In this case-control study, we investigated two single nucleotide polymorphisms, rs2815752 in the neuronal growth regulator 1 (NEGR1) gene and rs6548238 in the transmembrane protein 18 (TMEM18) gene, for association in a group of obese residents of Afyonkarahisar province (Turkey). Polymorphisms were genotyped in 172 obese subjects and 77 healthy controls. The results showed no significant differences between the obese subjects and the controls in terms of the allele and genotype frequencies of the NEGR1 gene rs2815752 and the TMEM18 gene rs6548238 polymorphisms. There were no significant associations of the rs2815752 polymorphism in obese subjects and controls with regard to anthropometric measurements and body composition parameters. However, several significant associations were found for the rs6548238 polymorphism with regard to anthropometric measurements and body composition. Consequently, there were no significant differences between the genotype and allele frequencies of NEGR1 gene rs2815752 and TMEM18 gene rs6548238 polymorphisms in the obese group and the controls. There were significant associations for the rs6548238 polymorphism, but not the rs2815752 polymorphism, with the anthropometric measurements and body composition parameters in the group of obese subjects.

Cell adhesion molecules (CAMs) play crucial roles in the genesis and progress of tumor. We investigated the effects of single nucleotide polymorphisms (SNPs) of CAMs, neuronal growth regulator 1 (NEGR1), and Otoancorin (OTOA) on lung cancer susceptibility in Chinese nonsmoking females. Logistic regression and Cox regression analyses were conducted to investigate the effects of SNPs and environmental factors. For rs3102911, genotype TT carriers decreased the risk of lung cancer with an odds ratio (OR) of 0.635. AA genotypes of rs741718 increased the risk of lung cancer with an OR of 3.527. In stratified analysis, genotype AA carriers of rs741718 had a high susceptibility to lung adenocarcinoma compared with GG and AG genotypes. Analyses of association between SNPs and clinical characteristics revealed that rs3102911 as a protective factor and rs741718 as a risk factor influenced the lung cancer occurrence and progression in nonsmoking females. [ABSTRACT FROM AUTHOR]

In the large GWAS studies, NEGR1 gene has been one of the most significant gene loci for body mass phenotype. The purpose of the current study was to clarify the role of NEGR1 in the maintenance of systemic metabolism, including glucose homeostasis, by using both male and female Negr1−/− mice receiving a standard or high fat diet (HFD). We found that 6 weeks of HFD leads to higher levels of blood glucose in Negr1−/− mice. In the glucose tolerance test, HFD induced phenotype difference only in male mice; Negr1−/− male mice displayed altered glucose tolerance, accompanied with upregulation of circulatory branched-chain amino acids (BCAA). The general metabolomic profile indicates that Negr1−/− mice are biased towards glyconeogenesis, fatty acid synthesis, and higher protein catabolism, all of which are amplified by HFD. Negr1 deficiency appears to induce alterations in the efficiency of energy storage; reduced food intake could be an attempt to compensate for the metabolic challenge present in the Negr1−/− males, particularly during the HFD exposure. Our results suggest that the presence of functional Negr1 allows male mice to consume more HFD and prevents the development of glucose intolerance, liver steatosis, and excessive weight gain.

Obesity is a complex disorder with nearly epidemic proportions in many parts of the world. Genome-wide association studies have demonstrated high heritability for obesity and body mass, with associations of certain candidate genes and their variations with respect to race, geographical location/country of origin. However, the functional mechanisms and different ethnic data of these loci are still poorly understood. In this case-control study, we investigated two single nucleotide polymorphisms, rs2815752 in the neuronal growth regulator 1 (NEGR1) gene and rs6548238 in the transmembrane protein 18 (TMEM18) gene, for association in a group of obese residents of Afyonkarahisar province (Turkey). Polymorphisms were genotyped in 172 obese subjects and 77 healthy controls. The results showed no significant differences between the obese subjects and the controls in terms of the allele and genotype frequencies of the NEGR1 gene rs2815752 and the TMEM18 gene rs6548238 polymorphisms. There were no significant associations of the rs2815752 polymorphism in obese subjects and controls with regard to anthropometric measurements and body composition parameters. However, several significant associations were found for the rs6548238 polymorphism with regard to anthropometric measurements and body composition. Consequently, there were no significant differences between the genotype and allele frequencies of NEGR1 gene rs2815752 and TMEM18 gene rs6548238 polymorphisms in the obese group and the controls. There were significant associations for the rs6548238 polymorphism, but not the rs2815752 polymorphism, with the anthropometric measurements and body composition parameters in the group of obese subjects. [ABSTRACT FROM AUTHOR]

Neural adhesion proteins are crucial in the development and maintenance of functional neural connectivity. Growing evidence suggests that the IgLON family of neural adhesion molecules LSAMP, NTM, NEGR1, and OPCML are important candidates in forming the susceptibility to schizophrenia (SCZ). IgLON proteins have been shown to be involved in neurite outgrowth, synaptic plasticity and neuronal connectivity, all of which have been shown to be altered in the brains of patients with the diagnosis of schizophrenia. Here we optimized custom 50-isoform-specific TaqMan gene-expression analysis for the transcripts of human IgLON genes to study the expression of IgLONs in the dorsolateral prefrontal cortex (DLPFC) of schizophrenic patients (n D 36) and control subjects (n D 36). Uniform 50-region and a single promoter was confirmed for the human NEGR1 gene by in silico analysis. IgLON5, a recently described family member, was also included in the study. We detected significantly elevated levels of the NEGR1 transcript (1.33-fold increase) and the NTM 1b isoform transcript (1.47-fold increase) in the DLPFC of schizophrenia patients compared to healthy controls. Consequent protein analysis performed in male subjects confirmed the increase in NEGR1 protein content both in patients with the paranoid subtype and in patients with other subtypes. In-group analysis of patients revealed that lower expression of certain IgLON transcripts, mostly LSAMP 1a and 1b, could be related with concurrent depressive endophenotype in schizophrenic patients. Additionally, our study cohort provides further evidence that cannabis use may be a relevant risk factor associated with suicidal behaviors in psychotic patients. In conclusion, we provide clinical evidence of increased expression levels of particular IgLON family members in the DLPFC of schizophrenic patients. We propose that alterations in the expression profile of IgLON neural adhesion molecules are associated with brain circuit disorganization in neuropsychiatric disorders, such as schizophrenia. In the light of previously published data, we suggest that increased level of NEGR1 in the frontal cortex may serve as molecular marker for a wider spectrum of psychiatric conditions. [ABSTRACT FROM AUTHOR]

IgLON proteins are GPI anchored adhesion molecules that control neurite outgrowth. In particular, Negr1 down-regulation negatively influences neuronal arborization in vitro and in vivo. In the present study, we found that the metalloprotease ADAM10 releases Negr1 from neuronal membrane. Ectodomain shedding influences several neuronal mechanisms, includingsurvival, synaptogenesis and the formation of neurite trees. By combining morphological analysis and virus-mediated selective protein silencing in primary murine cortical neurons, we found that pharmacologically inhibition of ADAM10 results in an impairment of neurite tree maturation that can be rescued upon treatment with soluble Negr1. Furthermore, we report that released Negr1 influences neurite outgrowth in a P-ERK1/2 and FGFR2 dependent manner. Together our findings suggest a role for Negr1 in regulating neurite outgrowth through the modulation of FGFR2 signalling pathway. Given the physiological and pathological role of ADAM10, Negr1 and FGFR2, the regulation of Negr1 shedding may play a crucial role in sustaining brain function and development.

IgLON family is composed of five genes: Lsamp, Ntm, Opcml, Negr1, and Iglon5; encoding for five highly homologous neural adhesion proteins that regulate neurite outgrowth and synapse formation. In the current study we performed in silico analysis revealing that Ntm and Opcml display similar genomic structure as previously reported for Lsamp, characterized by two alternative promotors 1a and 1b. Negr1 and Iglon5 transcripts have uniform 5′ region, suggesting single promoter. Iglon5, the recently characterized family member, shares high level of conservation and structural qualities characteristic to IgLON family such as N-terminal signal peptide, three Ig domains, and GPI anchor binding site. By using custom 5′-isoform-specific TaqMan gene-expression assay, we demonstrated heterogeneous expression of IgLON transcripts in different areas of mouse brain and several-fold lower expression in selected tissues outside central nervous system. As an example, the expression of IgLON transcripts in urogenital and reproductive system is in line with repeated reports of urogenital tumors accompanied by mutations in IgLON genes. Considering the high levels of intra-family homology shared by IgLONs, we investigated potential compensatory effects at the level of IgLON isoforms in the brains of mice deficient of one or two family members. We found that the lack of IgLONs is not compensated by a systematic quantitative increase of the other family members. On the contrary, the expression of Ntm 1a transcript and NEGR1 protein was significantly reduced in the frontal cortex of Lsamp-deficient mice suggesting that the expression patterns within IgLON family are balanced coherently. The actions of individual IgLONs, however, can be antagonistic as demonstrated by differential expression of Syp in deletion mutants of IgLONs. In conclusion, we show that the genomic twin-promoter structure has impact on both anatomical distribution and intra-family interactions of IgLON family members. Remarkable variety in the activity levels of 1a and 1b promoters both in the brain and in other tissues, suggests complex functional regulation of IgLONs by alternative signal peptides driven by 1a and 1b promoters. [ABSTRACT FROM AUTHOR]

The regulatory roles for non-coding RNAs, the long non-coding RNAs and microRNAs, are emerging as crucial determinants of central nervous system development and function. Neuronal growth regulator 1 (NEGR1) is a cell adhesion molecule that has been shown to play an important role in neurite outgrowth during neuronal development. Precise expression of the Negr1 gene is crucial for proper brain development and is dysregulated during brain injury. Hence, we attempted to elucidate the non-coding RNAs that control Negr1 gene expression. A long non-coding RNA, BC048612, transcribed from the bidirectional GC-rich Negr1 gene promoter was found to influence Negr1 mRNA expression. In vitro knockdown of the long non-coding RNA resulted in significant down-regulation of Negr1 mRNA expression, NEGR1 protein levels and neurite length whereas over-expression enhanced Negr1 mRNA expression, NEGR1 protein levels and increased neurite length. Meanwhile, another non-coding RNA, microRNA-203, was found to target the 3′ untranslated region of the Negr1 mRNA. Inhibition of microRNA-203 led to increased expression of Negr1 mRNA, elevated NEGR1 protein levels and increased neurite length. Conversely, microRNA-203 over-expression decreased the level of Negr1 mRNA, NEGR1 protein and neurite length. Neither microRNA-203 nor the long non-coding RNA, BC048612 could influence each other's expression. Hence, the long non-coding RNA, BC048612, and microRNA-203 were determined to be positive and negative regulators of Negr1 gene expression respectively. These processes have a direct effect on NEGR1 protein levels and neurite length, thus highlighting the importance of the regulatory non-coding RNAs in modulating Negr1 gene expression for precise neuronal development. [ABSTRACT FROM AUTHOR]

Inguinal white adipose tissue (iWAT) is essential for the beneficial effects of exercise training on metabolic health. The underlying mechanisms for these effects are not fully understood, and here, we test the hypothesis that exercise training results in a more favorable iWAT structural phenotype. Using biochemical, imaging, and multi-omics analyses, we find that 11 days of wheel running in male mice causes profound iWAT remodeling including decreased extracellular matrix (ECM) deposition and increased vascularization and innervation. We identify adipose stem cells as one of the main contributors to training-induced ECM remodeling, show that the PRDM16 transcriptional complex is necessary for iWAT remodeling and beiging, and discover neuronal growth regulator 1 (NEGR1) as a link between PRDM16 and neuritogenesis. Moreover, we find that training causes a shift from hypertrophic to insulin-sensitive adipocyte subpopulations. Exercise training leads to remarkable adaptations to iWAT structure and cell-type composition that can confer beneficial changes in tissue metabolism., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

IgLON proteins are GPI anchored adhesion molecules that control neurite outgrowth. In particular, Negr1 down-regulation negatively influences neuronal arborization in vitro and in vivo. In the present study, we found that the metalloprotease ADAM10 releases Negr1 from neuronal membrane. Ectodomain shedding influences several neuronal mechanisms, including survival, synaptogenesis, and the formation of neurite trees. By combining morphological analysis and virus-mediated selective protein silencing in primary murine cortical neurons, we found that pharmacologically inhibition of ADAM10 results in an impairment of neurite tree maturation that can be rescued upon treatment with soluble Negr1. Furthermore, we report that released Negr1 influences neurite outgrowth in a P-ERK1/2 and FGFR2 dependent manner. Together our findings suggest a role for Negr1 in regulating neurite outgrowth through the modulation of FGFR2 signaling pathway. Given the physiological and pathological role of ADAM10, Negr1, and FGFR2, the regulation of Negr1 shedding may play a crucial role in sustaining brain function and development. [ABSTRACT FROM AUTHOR]

Neural growth regulator 1 ( Negr1) is among the first common variants that have been associated with the regulation of body mass index. Using AAV technology directed to manipulate Negr1 expression in vivo, we find that decreased expression of Negr1 in periventricular hypothalamic areas leads to increases in body weight, presumably via increased food intake. Moreover, we observed that both increased and decreased levels of Negr1 lead to reduced locomotor activity and body temperature. In sum, our results provide further support for a role of hypothalamic expressed Negr1 in the regulation of energy balance. [ABSTRACT FROM AUTHOR]

Obesity has reached epidemic proportions globally and has become the cause of several major health risks worldwide. Presently, more than 100 loci have been related to obesity and metabolic traits in humans by genome-wide association studies. The complex genetic architecture behind obesity has triggered a need for the development of better animal models than rodents. The pig has emerged as a very promising biomedical model to study human obesity traits. In this study, we have characterized the expression patterns of six obesity-related genes, leptin ( LEP) , leptin receptor ( LEPR) , melanocortin 4 receptor ( MC4R) , fat mass and obesity associated ( FTO) , neuronal growth regulator 1 ( NEGR) 1 and adiponectin ( ADIPOQ) , in seven obesity-relevant tissues (liver; muscle; pancreas; hypothalamus; and retroperitoneal, subcutaneous and mesenteric adipose tissues) in two pig breeds (production pigs and Göttingen minipigs) that deviate phenotypically and genetically from each other with respect to obesity traits. We observe significant differential expression for LEP, LEPR and ADIPOQ in muscle and in all three adipose tissues. Interestingly, in pancreas, LEP expression is only detected in the fat minipigs. FTO shows significant differential expression in all tissues analyzed, and NEGR1 shows significant differential expression in muscle, pancreas, hypothalamus and subcutaneous adipose tissue. The MC4R transcript can be detected only in hypothalamus. In general, the expression profiles of the investigated genes are in accordance with those observed in human studies. Our study shows that both the differences between the investigated breeds and the phenotypic state with respect to obesity/leanness play a large role for differential expression of the obesity-related genes. [ABSTRACT FROM AUTHOR]

Genome-wide association studies (GWAS) have identified a total of about 40 single nucleotide polymorphisms (SNPs) that show significant linkage to body mass index, a widely utilised surrogate measure of adiposity. However, only 8 of these associations have been confirmed by follow-up GWAS using more sophisticated measures of adiposity (computed tomography). Among these 8, there is a SNP close to the gene FTO which has been the subject of considerable work to diagnose its function. The remaining 7 SNPs are adjacent to, or within, the genes NEGR1, TMEM18, ETV5, FLJ35779, LINGO2, SH2B1 and GIPR, most of which are less well studied than FTO, particularly in the context of obesity. This article reviews the available data on the functions of these genes, including information gleaned from studies in humans and animal models. At present, we have virtually no information on the putative mechanism associating the genes FLJ35779 and LINGO2 to obesity. All of these genes are expressed in the brain, and for 2 of them (SH2B1 and GIPR), a direct link to the appetite regulation system is known. SH2B1 is an enhancer of intracellular signalling in the JAK-STAT pathway, and GIPR is the receptor for an appetite-linked hormone (GIP) produced by the alimentary tract. NEGR1, ETV5 and SH2B1 all have suggested roles in neurite outgrowth, and hence SNPs adjacent to these genes may affect development of the energy balance circuitry. Although the genes have central patterns of gene expression, implying a central neuronal connection to energy balance, for at least 4 of them (NEGR1, TMEM18, SH2B1 and GIPR), there are also significant peripheral functions related to adipose tissue biology. These functions may contribute to their effects on the obese phenotype. © 2013 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Aims/hypothesis: Genome-wide association studies (GWAS) have identified numerous single-nucleotide polymorphisms associated with obesity, consequently implying a role in adipocyte biology for many closely residing genes. We investigated the functional relevance of such genes in human adipocytes. Methods: We selected eight genes ( BDNF, MAF, MTCH2, NEGR1, NPC1, PTER, SH2B1 and TMEM18) from obesity GWAS and analysed their effect in human adipogenesis using small interfering (si)RNA-mediated knockdown, their regulation by metabolic agents in adipocytes and pre-adipocytes, and gene expression in paired samples of human fat biopsies (68 non-obese, 165 obese) by quantitative real-time PCR. Results: We show a two- to threefold upregulation of MAF, MTCH2 and NEGR1 and a two- to fourfold downregulation of BDNF and PTER during adipogenesis. Knockdown of BDNF (mean ± SEM; 83.8 ± 4.7% of control; p = 0.0002), MTCH2 (72.7 ± 9.5%; p = 0.0006), NEGR1 (70.2 ± 5.7%; p < 0.0001) and TMEM18 (70.8 ± 6.1%; p < 0.0001) significantly inhibited adipocyte maturation, while knockdown of the other proteins had no effect. Insulin slightly induced MAF (1.65-fold; p = 0.0009) and MTCH2 (1.72-fold; p < 0.0001), while it suppressed BDNF (59.6%; p = 0.0009), NEGR1 (58.0%; p = 0.0085) and TMEM18 (69.3%; p = 0.0377) in adipocytes. The synthetic glucocorticoid dexamethasone suppressed MAF (45.7%; p = 0.0022), BDNF (66.6%; p = 0.0012) and TMEM18 (63.5%; p = 0.0181), but induced NEGR1 (3.2-fold; p = 0.0117) expression. Furthermore, MTCH2, NEGR1 and TMEM18 were differentially expressed in subcutaneous and visceral adipose tissue. TMEM18 expression was decreased in the adipose tissue of obese patients, and negatively correlated with anthropometric variables and adipocyte size. Conclusions/interpretation: Our results imply a regulatory role for TMEM18, BDNF, MTCH2 and NEGR1 in adipocyte differentiation and biology. In addition, we show a variation of MAF expression during adipogenesis, while NPC1, PTER and SH2B1 were not regulated. [ABSTRACT FROM AUTHOR]

In the large GWAS studies, NEGR1 gene has been one of the most significant gene loci for body mass phenotype. The purpose of the current study was to clarify the role of NEGR1 in the maintenance of systemic metabolism, including glucose homeostasis, by using both male and female Negr1−/− mice receiving a standard or high fat diet (HFD). We found that 6 weeks of HFD leads to higher levels of blood glucose in Negr1−/− mice. In the glucose tolerance test, HFD induced phenotype difference only in male mice; Negr1−/− male mice displayed altered glucose tolerance, accompanied with upregulation of circulatory branched-chain amino acids (BCAA). The general metabolomic profile indicates that Negr1−/− mice are biased towards glyconeogenesis, fatty acid synthesis, and higher protein catabolism, all of which are amplified by HFD. Negr1 deficiency appears to induce alterations in the efficiency of energy storage; reduced food intake could be an attempt to compensate for the metabolic challenge present in the Negr1−/− males, particularly during the HFD exposure. Our results suggest that the presence of functional Negr1 allows male mice to consume more HFD and prevents the development of glucose intolerance, liver steatosis, and excessive weight gain. [ABSTRACT FROM AUTHOR]

Abstract Background Genome-wide association studies (GWAS) are useful to reveal an association between single nucleotide polymorphisms and different measures of obesity. A multitude of new loci has recently been reported, but the exact function of most of the according genes is not known. The aim of our study was to start elucidating the function of some of these genes. Methods We performed an expression analysis of fourteen genes, namely BDNF, ETV5, FAIM2, FTO, GNPDA2, KCTD15, LYPLAL1, MCR4, MTCH2, NEGR1, NRXN3, TMEM18, SEC16B and TFAP2B, via real-time RT-PCR in adipose tissue of the kidney capsule, the mesenterium and subcutaneum as well as the hypothalamus of obese Zucker diabetic fatty (ZDF) and Zucker lean (ZL) rats at an age of 22 weeks. Results All of our target genes except for SEC16B showed the highest expression in the hypothalamus. This suggests a critical role of these obesity-related genes in the central regulation of energy balance. Interestingly, the expression pattern in the hypothalamus showed no differences between obese ZDF and lean ZL rats. However, LYPLAL1, TFAP2B, SEC16B and FAIM2 were significantly lower expressed in the kidney fat of ZDF than ZL rats. NEGR1 was even lower expressed in subcutaneous and mesenterial fat, while MTCH2 was higher expressed in the subcutaneous and mesenterial fat of ZDF rats. Conclusion The expression pattern of the investigated obesity genes implies for most of them a role in the central regulation of energy balance, but for some also a role in the adipose tissue itself. For the development of the ZDF phenotype peripheral rather than central mechanisms of the investigated genes seem to be relevant.

The members of the IgLON superfamily of cell adhesion molecules facilitate fundamental cellular communication during brain development, maintain functional brain circuitry, and are associated with several neuropsychiatric disorders such as depression, autism, schizophrenia, and intellectual disabilities. Usage of alternative promoter-specific 1a and 1b mRNA isoforms in Lsamp, Opcml, Ntm, and the single promoter of Negr1 in the mouse and human brain has been previously described. To determine the precise spatiotemporal expression dynamics of Lsamp, Opcml, Ntm isoforms, and Negr1, in the developing brain, we generated isoform-specific RNA probes and carried out in situ hybridization in the developing (embryonic, E10.5, E11.5, 13.5, 17; postnatal, P0) and adult mouse brains. We show that promoter-specific expression of IgLONs is established early during pallial development (at E10.5), where it remains throughout its differentiation through adulthood. In the diencephalon, midbrain, and hindbrain, strong expression patterns are initiated a few days later and begin fading after birth, being only faintly expressed during adulthood. Thus, the expression of specific IgLONs in the developing brain may provide the means for regionally specific functionality as well as for specific regional vulnerabilities. The current study will therefore improve the understanding of how IgLON genes are implicated in the development of neuropsychiatric disorders. [ABSTRACT FROM AUTHOR]

• Circ_HECW2 acted as a sponge of miR-30e-5p. • Circ_HECW2 regulated NEGR1 expression by miR-30e-5p. • Circ_HECW2 regulated LPS-triggered EndoMT in HBMECs by the miR-30e-5p/NEGR1 axis. Endothelial-mesenchymal transition (EndoMT) plays a critical role in the dysfunction of the blood–brain barrier (BBB). Circular RNAs (circRNAs) function as crucial regulatory factors in EndoMT. Nevertheless, the underlying mechanisms of circRNA HECW2 (circ_HECW2, hsa_circ_0057583) in lipopolysaccharide (LPS)-induced EndoMT remain largely unclear. The levels of circ_HECW2, miR-30e-5p and neuronal growth regulator 1 (NEGR1) were detected by quantitative real-time polymerase chain reaction (qRT-PCR) or western blot. Ribonuclease (RNase) R and Actinomycin D assays were performed to validate the stability of circ_HECW2. Cell colony formation, proliferation and apoptosis were tested by a standard colony formation assay, the 3-(4,5-dimethylthiazol-2yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)–2H-tetrazolium (MTS) assay and flow cytometry, respectively. Targeted relationships among circ_HECW2, miR-30e-5p and NEGR1 were verified by a dual-luciferase reporter assay. Our data indicated that LPS increased circ_HECW2 expression and reduced miR-30e-5p expression in human brain microvascular endothelial cells (HBMECs). Circ_HECW2 silencing promoted cell proliferation and suppressed cell apoptosis and EndoMT in LPS-treated HBMECs. Mechanistically, circ_HECW2 directly interacted with miR-30e-5p by binding to miR-30e-5p. MiR-30e-5p was a functional mediator of circ_HECW2 in regulating LPS-induced cell EndoMT. Furthermore, Circ_HECW2 regulated NEGR1 expression through functioning as a miR-30e-5p sponge. Moreover, miR-30e-5p overexpression repressed the EndoMT of LPS-treated HBMECs by targeting NEGR1. Collectively, our current study demonstrated that circ_HECW2 silencing suppressed LPS-triggered HBMEC EndoMT at least in part through the regulation of the miR-30e-5p/NEGR1 axis, illuminating a promising strategy for EndoMT inhibition. [ABSTRACT FROM AUTHOR]

Neuronal growth regulator 1 (NEGR1), a member of the immunoglobulin superfamily cell adhesion molecule subgroup IgLON, has been involved in neuronal growth and connectivity. Genetic variants, in or near the NEGR1 locus, have been associated with obesity and, more recently, with learning difficulties, intellectual disability, and psychiatric disorders. Here, we described the only second report of NEGR1 gene disruption in 1p31.1 microdeletion in two patients. Patient 1 is a 14-year-old female with neurological and psychiatric features present also in her family. Patient 2 is a 5-month-old infant showing global hypotonia as unique neurological features till now. This patient also carries 7p22.1 duplication, of paternal origin, that could be responsible for some malformations present in the child. We hypothesize a role of NEGR1 in producing the phenotype of our patients and compare them with other cases previously reported in the literature and DECIPHER database to better identify a possible genotype-phenotype correlation. [ABSTRACT FROM AUTHOR]

Nowadays, diagnosis of neurodegenerative disorders is mainly based on neuroimaging and clinical symptoms, although postmortem neuropathological confirmation remains the gold standard diagnostic technique. Therefore, cerebrospinal fluid (CSF) proteome is considered a valuable molecular repository for diagnosing and targeting the neurodegenerative process. It is well known that olfactory dysfunction is among the earliest features of synucleinopathies such as Parkinson's disease (PD). Consequently, we consider that the application of tissue proteomics in primary olfactory structures is an ideal approach to explore early pathophysiological changes, detecting olfactory proteins that might be tested in CSF as potential biomarkers. Data mining of mass spectrometry-generated datasets has revealed that 30% of the olfactory bulb (OB) proteome is also localized in CSF. In this chapter, we describe a method that utilizes label-free quantitative proteomics and computational analysis to characterize human OB proteomes and potential cerebrospinal fluid (CSF) biomarkers associated with neurodegenerative syndromes. For that, we applied peptide fractionation methods, followed by tandem mass spectrometry (nanoLC-MS/MS), in silico analysis, and semi-quantitative orthogonal techniques in OB derived from PD subjects. After obtaining the differential OB proteome across Lewy-type alpha-synucleinopathy (LTS) stages and further validating the method, this workflow was applied to probe changes in NEGR1 (neuronal growth regulator 1) and GNPDA2 (glucosamine-6-phosphate deaminase 2) protein levels in CSF derived from parkinsonian subjects with respect to controls, observing an inverse correlation between both proteins and α-synuclein, the principal component analysis of Lewy pathology.

Long non-coding RNAs and microRNAs control gene expression to determine central nervous system development and function. Neuronal growth regulator 1 (NEGR1) is a cell adhesion molecule that plays an important role in neurite outgrowth during neuronal development and its precise expression is crucial for correct brain development. The data described here is related to the research article titled "A long non-coding RNA, BC048612 and a microRNA, miR-203 coordinate the gene expression of Neuronal growth regulator 1 (NEGR1) adhesion protein" [1]. This data article contains detailed bioinformatics analysis of genetic signatures at the Negr1 gene locus retrieved from the UCSC genome browser. This approach could be adopted to identify putative regulatory non-coding RNAs in other tissues and diseases.