Neurexin Research Articles

Molecular Analysis of Cluster Headache

Cluster headache (CH) is characterized by severe, recurrent, unilateral attacks of extreme intensity and brief duration. Variants in a myriad of genes were studied in sporadic CH patients, often with conflicting results. We studied gene mutations in some candidate genes, hypocretin receptor 2, Clock, and alcohol dehydrogenase 4 (ADH4), in 54 unrelated sporadic CH patients and in 200 controls in 8 kindreds/families that included more affected and nonaffected cases. Furthermore, we performed the whole-genome scanning by comparative genomic hybridization, searching for rearrangements associated with DNA gain or loss in a subset of sporadic and familial CH and control participants. The analysis of candidate genes revealed that only allele and genotype frequency of the 2 ADH4 mutations resulted significantly between sporadic CH and controls; the same mutations were homozygous in CH patients from 2 families. The comparative genomic hybridization analysis revealed 2 novel rearrangements that involved the intron regions of thyrotropin-releasing hormone-degrading enzyme and neurexin 3 (NRXN3) genes, respectively. The first arrangement was present either in CH or in controls, whereas the second one was specifically found in some sporadic and familial CH cases. Our data (although obtained on a small number of cases) confirm the genetic heterogeneity of CH, suggesting that mutations in the ADH4 gene and a novel rearrangement involving NRXN3 gene might be related to CH in a subset of cases.

A common cognitive, psychiatric, and dysmorphic phenotype in carriers of NRXN1 deletion.

Deletions in the 2p16.3 region that includes the neurexin (NRXN1) gene are associated with intellectual disability and various psychiatric disorders, in particular, autism and schizophrenia. We present three unrelated patients, two adults and one child, in whom we identified an intragenic 2p16.3 deletion within the NRXN1 gene using an oligonucleotide comparative genomic hybridization array. The three patients presented dual diagnosis that consisted of mild intellectual disability and autism and bipolar disorder. Also, they all shared a dysmorphic phenotype characterized by a long face, deep set eyes, and prominent premaxilla. Genetic analysis of family members showed two inherited deletions. A comprehensive neuropsychological examination of the 2p16.3 deletion carriers revealed the same phenotype, characterized by anxiety disorder, borderline intelligence, and dysexecutive syndrome. The cognitive pattern of dysexecutive syndrome with poor working memory and reduced attention switching, mental flexibility, and verbal fluency was the same than those of the adult probands. We suggest that in addition to intellectual disability and psychiatric disease, NRXN1 deletion is a risk factor for a characteristic cognitive and dysmorphic profile. The new cognitive phenotype found in the 2p16.3 deletion carriers suggests that 2p16.3 deletions might have a wide variable expressivity instead of incomplete penetrance.

Replication of previous genome-wide association studies of psychiatric diseases in a large schizophrenia case–control sample from Spain

Genome wide association studies (GWAS) has allowed the discovery of some interesting risk variants for schizophrenia (SCZ). However, this high-throughput approach presents some limitations, being the most important the necessity of highly restrictive statistical corrections as well as the loss of statistical power inherent to the use of a Single Nucleotide Polymorphism (SNP) analysis approach. These problems can be partially solved through the use of a polygenic approach. We performed a genotyping study in SCZ using 86 previously associated SNPs identified by GWAS of SCZ, bipolar disorder (BPD) and autistic spectrum disorder (ASD) patients. The sample consisted of 3063 independent cases with DSM-IV-TR diagnosis of SCZ and 2847 independent controls of European origin from Spain. A polygenic score analysis was also used to test the overall effect on the SCZ status. One SNP, rs12290811, located in the ODZ4 gene reached statistical significance (p=1.7×10−4, Allelic odds ratio=1.21), a value very near to those reported in previous GWAS of BPD patients. In addition, 4 SNPs were close to the significant threshold: rs3850333, in the NRXN1 gene; rs6932590, at MHC; rs2314398, located in an intergenic region on chromosome 2; and rs1006737, in the CACNA1C gene. We also found that 74% of the studied SNPs showed the same tendency (risk or protection alleles) previously reported in the original GWAS (p<0.001). Our data strengthen the polygenic component of susceptibility to SCZ. Our findings show ODZ4 as a risk gene for SCZ, emphasizing the existence of common vulnerability in psychosis.

Mutation screening of the neurexin 1 gene in thai patients with intellectual disability and autism spectrum disorder.

Neurexin 1 has two major protein isoforms using alternative promoters, coding for the alpha-neurexin 1 (α-NRXN1) and beta-neurexin 1 (β-NRXN1) genes. This study is to explore the possibility that variants of the NRXN1 gene predispose to intellectual disability (ID) and autism spectrum disorder (ASD). The coding regions in 24 exons and exon-intron boundaries of the NRXN1 gene were investigated in 115 Thai patients with ID and ASD by direct DNA sequencing. Nine novel variants of the NRXN1 gene were identified. Four novel variants were found in the β-NRXN1 gene, one variant of six GGC repeats in exon 1, and three variants at the 5'UTR. Five novel variants were identified in the α-NRXN1 gene, four intronic variants and one missense variant in exon 14 (c.2713T>A or p.F905I). Mutation screening of the NRXN1gene in patients with ID and ASD may be useful to identify potential variants predisposing to ID and ASD. However, further studies utilizing protein functional analysis of the novel variants are required for a more definite conclusion.

Fraternal Twins With Autism, Severe Cognitive Deficit, and Epilepsy: Diagnostic Role of Chromosomal Microarray Analysis

A 7-year-old child presented with atypical absence epilepsy. He also had autism and severe cognitive deficit. As part of his diagnostic workup, a chromosomal microarray analysis was performed, which showed novel biallelic deletions in the neurexin 1 gene (NRXN1). His fraternal twin sister, who also had autism and cognitive impairment, was subsequently found to have the same biallelic deletions. Deletions included a 272-282kb loss at band 2p16.3 in one allele and a smaller 135-174-kb loss on the second allele. Neurexin 1 (NRXN1) is a cell adhesion protein, forming a synaptic complex with neuroligin. This signals a pathway that is critical for activity-dependent synaptic transmission. Mutations in this gene have been associated with autism and neurodevelopmental delay. Although there are many reports of heterozygous mutations with variable expressivity, only 3 cases with biallelic NRXN1 mutations have been previously reported, all of which have a more severe phenotype. We report 2 siblings with biallelic deletions, both of which affect the promoter region and exons 1-5 in the α-NRXN1 isoform, which has a role in the Ca(2+)-dependent release of neurotransmitters in the central nervous system. Our cases expand the phenotype of biallelic α NRXN 1 mutations and emphasize the important role of NRXN1 in autism and intellectual disability. Chromosomal microarray analysis should be the clinical standard in all specialties for first-tier genetic testing in autistic spectrum disorders.

Copy number variant study of bipolar disorder in Canadian and UK populations implicates synaptic genes

Genome-wide single nucleotide polymorphism (SNP) data from 936 bipolar disorder (BD) individuals and 940 psychiatrically healthy comparison individuals of North European descent were analyzed for copy number variation (CNV). Using multiple CNV calling algorithms, and validating using in vitro molecular analyses, we identified CNVs implicating several candidate genes that encode synaptic proteins, such as DLG1, DLG2, DPP6, NRXN1, NRXN2, NRXN3, SHANK2, and EPHA5, as well as the neuronal splicing regulator RBFOX1 (A2BP1), and neuronal cell adhesion molecule CHL1. We have also identified recurrent CNVs on 15q13.3 and 16p11.2-regions previously reported as risk loci for neuropsychiatric disorders. In addition, we performed CNV analysis of individuals from 215 BD trios and identified de novo CNVs involving the NRXN1 and DRD5 genes. Our study provides further evidence of the occasional involvement of genomic mutations in the etiology of BD, however, there is no evidence of an increased burden of CNVs in BD. Further, the identification of CNVs at multiple members of the neurexin gene family in BD individuals, supports the role of synaptic disruption in the etiology of BD.

Association study of common polymorphisms in MSRA, TFAP2B, MC4R, NRXN3, PPARGC1A, TMEM18, SEC16B, HOXB5 and OLFM4 genes with obesity-related traits among Portuguese children

At least 52 genetic loci were associated with obesity-related traits. However, little is known about the genetic basis of obesity among children. This study aims to test whether 10 polymorphisms in obesity-related genes methionine sulfoxide reductase A (MSRA), transcription factor AP-2 beta (TFAP2B), melanocortin 4 receptor (MC4R), neurexin 3 (NRXN3), peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PPARGC1A), transmembrane protein 18 (TMEM18), homolog of S. cerevisiae Sec16 (SEC16B), homeobox B5 (HOXB5) and olfactomedin 4 (OLFM4) are associated with the risk of obesity in Portuguese children. A total of 730 children aging from 6 to 12 years old, recruited randomly from public schools in Portugal, were analysed. Anthropometric measurements were obtained and children were classified into three phenotypic groups, normal weight (n=256), overweight (n=320) and obese (n=154), according to the International Obesity Task Force cutoffs. Polymorphisms were genotyped by allelic discrimination TaqMan assays. The MC4R rs12970134 polymorphism was nominally associated with body mass index (BMI) (P=0.035), BMI Z-score (P=0.043) and waist circumference (P=0.020), and borderline associated with weight (P=0.053). Near nominal associations were also found for the PPARGC1A rs8192678 polymorphism with weight (P=0.061), and for the MSRA rs545854 polymorphism with BMI (P=0.055) and BMI Z-score (P=0.056). Furthermore, logistic regression showed that MC4R rs12970134 and TFAP2B rs987237 were nominally, respectively, associated (P=0.029) and borderline associated (P=0.056) with the obese phenotype. This study highlighted the possible association of MC4R, PPARGC1A, MSRA and TFAP2B polymorphisms with several obesity-related traits in a sample of Portuguese children. The two significant associated TFAP2B rs987237 and MC4R rs12970134 polymorphisms showed an opposite direction of effect to that in the original reports.

Incomplete penetrance of NRXN1 deletions in families with schizophrenia

Neurexin 1 (NRXN1) is a presynaptic neuronal adhesion molecule that interacts with postsynaptic neuroligins in both glutamatergic and GABAergic synapses and is important in synaptic formation and function. NRXN1 deletions increase the risk of schizophrenia, so our aims were to explore this in our family sample, to distinguish de novo from inherited mutations, to examine transmission to affected and unaffected siblings and to estimate penetrance. We performed copy number analyses in NRXN1 using data from Illumina BeadArrays from 635 subjects with schizophrenia (276 in genotyped families), 487 of their unaffected parents and 309 unaffected siblings as well as 635 normal controls, all from the CBDB/NIMH Genetic Study of Schizophrenia. Deletions called by software were confirmed by quantitative PCR and comparative genome hybridization. There were deletions in 15 individuals in 11 families, including de novo exonic deletions in one case and one unaffected sibling. We observed no deletions in controls, 7 deletions in cases (1.10%), and an unexpectedly high deletion frequency in parents (n=5, 1.02%) and siblings (n=3, 0.97%). Three families showed inheritance from an unaffected parent, and in two families an unaffected parent did not transmit to the affected offspring. Thus we have added to the evidence that NRXN1 deletions are more frequent in patients with schizophrenia than in healthy individuals. However, the presence of de novo deletions in unaffected relatives and transmission from and to unaffected family members demonstrated that while the deletions may well have been necessary for some carriers to develop schizophrenia, they were not always sufficient.

Identification of Candidate Single-Nucleotide Polymorphisms in NRXN1 Related to Antipsychotic Treatment Response in Patients with Schizophrenia

Neurexins are presynaptic neuronal adhesion molecules that interact with postsynaptic neuroligins to form an inter-synaptic complex required for synaptic specification and efficient neurotransmission. Deletions and point mutations in the neurexin 1 (NRXN1) gene are associated with a broad spectrum of neuropsychiatric and neurodevelopmental disorders, including autism, intellectual disability, epilepsy, developmental delay, and schizophrenia. Recently, small nucleotide polymorphisms in NRXN1 have been associated with antipsychotic drug response in patients with schizophrenia. Based on previous suggestive evidence of an impact on clozapine response in patients with schizophrenia, we conducted an association study of NRXN1 polymorphisms (rs12467557 and rs10490162) with antipsychotic treatment response in 54 patients with schizophrenia in a double blind, placebo-controlled NIMH inpatient crossover trial and examined for association with risk for schizophrenia in independent case-control and family-based clinical cohorts. Pharmacogenetic analysis in the placebo controlled trial revealed significant association of rs12467557and rs10490162 with drug response, whereby individuals homozygous for the A allele, at either SNP, showed significant improvement in positive symptoms, general psychopathology, thought disturbance, and negative symptoms, whereas patients carrying the G allele showed no overall response. Although we did not find evidence of the same NRXN1 SNPs being associated with results of the NIMH sponsored CATIE trial, other SNPs showed weakly positive signals. The family and case-control analyses for schizophrenia risk were negative. Our results provide confirmatory evidence of genetically determined differences in drug response in patients with schizophrenia related to NRXN1 variation. Furthermore, these findings potentially implicate NRXN1 in the therapeutic actions of antipsychotic drugs.

Etiological yield of SNP microarrays in idiopathic intellectual disability

Intellectual disability (ID) has a prevalence of 3% and is classified according to its severity. An underlying etiology cannot be determined in 75–80% in mild ID, and in 20–50% of severe ID. After it has been shown that copy number variations involving short DNA segments may cause ID, genome-wide SNP microarrays are being used as a tool for detecting submicroscopic copy number changes and uniparental disomy. This study was performed to investigate the presence of copy number changes in patients with ID of unidentified etiology. Affymetrix® 6.0 SNP microarray platform was used for analysis of 100 patients and their healthy parents, and data were evaluated using various databases and literature. Etiological diagnoses were made in 12 patients (12%). Homozygous deletion in NRXN1 gene and duplication in IL1RAPL1 gene were detected for the first time. Two separate patients had deletions in FOXP2 and UBE2A genes, respectively, for which only few patients have recently been reported. Interstitial and subtelomeric copy number changes were described in 6 patients, in whom routine cytogenetic tools revealed normal results. In one patient uniparental disomy type of Angelman syndrome was diagnosed. SNP microarrays constitute a screening test able to detect very small genomic changes, with a high etiological yield even in patients already evaluated using traditional cytogenetic tools, offer analysis for uniparental disomy and homozygosity, and thereby are helpful in finding novel disease-causing genes: for these reasons they should be considered as a first-tier genetic screening test in the evaluation of patients with ID and autism.

CaMKII phosphorylation of neuroligin-1 regulates excitatory synapses

Neuroligins are postsynaptic cell adhesion molecules that are important for synaptic function through their trans-synaptic interaction with neurexins (NRXNs). The localization and synaptic effects of neuroligin-1 (NL-1, also called NLGN1) are specific to excitatory synapses with the capacity to enhance excitatory synapses dependent on synaptic activity or Ca(2+)/calmodulin kinase II (CaMKII). Here we report that CaMKII robustly phosphorylates the intracellular domain of NL-1. We show that T739 is the dominant CaMKII site on NL-1 and is phosphorylated in response to synaptic activity in cultured rodent neurons and sensory experience in vivo. Furthermore, a phosphodeficient mutant (NL-1 T739A) reduces the basal and activity-driven surface expression of NL-1, leading to a reduction in neuroligin-mediated excitatory synaptic potentiation. To the best of our knowledge, our results are the first to demonstrate a direct functional interaction between CaMKII and NL-1, two primary components of excitatory synapses.

Impaired Hippocampal Neuroligin-2 Function by Chronic Stress or Synthetic Peptide Treatment is Linked to Social Deficits and Increased Aggression

Neuroligins (NLGNs) are cell adhesion molecules that are important for proper synaptic formation and functioning, and are critical regulators of the balance between neural excitation/inhibition (E/I). Mutations in NLGNs have been linked to psychiatric disorders in humans involving social dysfunction and are related to similar abnormalities in animal models. Chronic stress increases the likelihood for affective disorders and has been shown to induce changes in neural structure and function in different brain regions, with the hippocampus being highly vulnerable to stress. Previous studies have shown evidence of chronic stress-induced changes in the neural E/I balance in the hippocampus. Therefore, we hypothesized that chronic restraint stress would lead to reduced hippocampal NLGN-2 levels, in association with alterations in social behavior. We found that rats submitted to chronic restraint stress in adulthood display reduced sociability and increased aggression. This occurs along with a reduction of NLGN-2, but not NLGN-1 expression (as shown with western blot, immunohistochemistry, and electron microscopy analyses), throughout the hippocampus and detectable in different layers of the CA1, CA3, and DG subfields. Furthermore, using synthetic peptides that comprise sequences in either NLGN-1 (neurolide-1) or NLGN-2 (neurolide-2) involved in the interaction with their presynaptic partner neurexin (NRXN)-1, intra-hippocampal administration of neurolide-2 led also to reduced sociability and increased aggression. These results highlight hippocampal NLGN-2 as a key molecular substrate regulating social behaviors and underscore NLGNs as promising targets for the development of novel drugs for the treatment of dysfunctional social behaviors.

Sequence analysis of 17NRXN1deletions

Genome instability plays fundamental roles in human evolution and phenotypic variation within our population. This instability leads to genomic rearrangements that are involved in a wide variety of human disorders, including congenital and neurodevelopmental disorders, and cancers. Insight into the molecular mechanisms governing such genomic rearrangements may increase our understanding of disease pathology and evolutionary processes. Here we analyse 17 carriers of non-recurrent deletions in the NRXN1 gene, which have been associated with neurodevelopmental disorders, e.g. schizophrenia, autism and epilepsies. 17 non-recurrent NRXN1 deletions identified by GWA were sequenced to map the breakpoints of each. Meme … etc. was used to identify shared patterns between the deletions and compare these were previously studies on non-recurrent deletions. We discovered two novel sequence motifs shared between all 17 NRXN1 deletions and a significantly higher AT nucleotide content at the breakpoints, compared to the overall nucleotide content on chromosome 2. We found different alteration of sequence at the breakpoint; small insertions and duplications giving rise to short microhomology sequences. No single mechanism seems to be implicated in the deletion events, but the results suggest that NHEJ, FoSTeS or MMBIR is implicated. The two novel sequence motifs together with a high AT content in all in NRXN1 deletions may lead to increased instability leading to a increase susceptibility to a single stranded structures. This favours potentially repaired by NHEJ mechanism of double strand breaks or may leading to replication errors. © 2013 Wiley Periodicals, Inc.

The Tissue-Specific RNA Binding Protein T-STAR Controls Regional Splicing Patterns of Neurexin Pre-mRNAs in the Brain

The RNA binding protein T-STAR was created following a gene triplication 520–610 million years ago, which also produced its two parologs Sam68 and SLM-1. Here we have created a T-STAR null mouse to identify the endogenous functions of this RNA binding protein. Mice null for T-STAR developed normally and were fertile, surprisingly, given the high expression of T-STAR in the testis and the brain, and the known infertility and pleiotropic defects of Sam68 null mice. Using a transcriptome-wide search for splicing targets in the adult brain, we identified T-STAR protein as a potent splicing repressor of the alternatively spliced segment 4 (AS4) exons from each of the Neurexin1-3 genes, and exon 23 of the Stxbp5l gene. T-STAR protein was most highly concentrated in forebrain-derived structures like the hippocampus, which also showed maximal Neurexin1-3 AS4 splicing repression. In the absence of endogenous T-STAR protein, Nrxn1-3 AS4 splicing repression dramatically decreased, despite physiological co-expression of Sam68. In transfected cells Neurexin3 AS4 alternative splicing was regulated by either T-STAR or Sam68 proteins. In contrast, Neurexin2 AS4 splicing was only regulated by T-STAR, through a UWAA-rich response element immediately downstream of the regulated exon conserved since the radiation of bony vertebrates. The AS4 exons in the Nrxn1 and Nrxn3 genes were also associated with distinct patterns of conserved UWAA repeats. Consistent with an ancient mechanism of splicing control, human T-STAR protein was able to repress splicing inclusion of the zebrafish Nrxn3 AS4 exon. Although Neurexin1-3 and Stxbp5l encode critical synaptic proteins, T-STAR null mice had no detectable spatial memory deficits, despite an almost complete absence of AS4 splicing repression in the hippocampus. Our work identifies T-STAR as an ancient and potent tissue-specific splicing regulator that uses a concentration-dependent mechanism to co-ordinately regulate regional splicing patterns of the Neurexin1-3 AS4 exons in the mouse brain.

Molecular and clinical characterization of 25 individuals with exonic deletions of NRXN1 and comprehensive review of the literature

This study aimed to elucidate the observed variable phenotypic expressivity associated with NRXN1 (Neurexin 1) haploinsufficiency by analyses of the largest cohort of patients with NRXN1 exonic deletions described to date and by comprehensively reviewing all comparable copy number variants in all disease cohorts that have been published in the peer reviewed literature (30 separate papers in all). Assessment of the clinical details in 25 previously undescribed individuals with NRXN1 exonic deletions demonstrated recurrent phenotypic features consisting of moderate to severe intellectual disability (91%), severe language delay (81%), autism spectrum disorder (65%), seizures (43%), and hypotonia (38%). These showed considerable overlap with previously reported NRXN1-deletion associated phenotypes in terms of both spectrum and frequency. However, we did not find evidence for an association between deletions involving the β-isoform of neurexin-1 and increased head size, as was recently published in four cases with a deletion involving the C-terminus of NRXN1. We identified additional rare copy number variants in 20% of cases. This study supports a pathogenic role for heterozygous exonic deletions of NRXN1 in neurodevelopmental disorders. The additional rare copy number variants identified may act as possible phenotypic modifiers as suggested in a recent digenic model of neurodevelopmental disorders.

CNV Analysis in Tourette Syndrome Implicates Large Genomic Rearrangements in COL8A1 and NRXN1

Tourette syndrome (TS) is a neuropsychiatric disorder with a strong genetic component. However, the genetic architecture of TS remains uncertain. Copy number variation (CNV) has been shown to contribute to the genetic make-up of several neurodevelopmental conditions, including schizophrenia and autism. Here we describe CNV calls using SNP chip genotype data from an initial sample of 210 TS cases and 285 controls ascertained in two Latin American populations. After extensive quality control, we found that cases (N = 179) have a significant excess (P = 0.006) of large CNV (>500 kb) calls compared to controls (N = 234). Amongst 24 large CNVs seen only in the cases, we observed four duplications of the COL8A1 gene region. We also found two cases with ∼400kb deletions involving NRXN1, a gene previously implicated in neurodevelopmental disorders, including TS. Follow-up using multiplex ligation-dependent probe amplification (and including 53 more TS cases) validated the CNV calls and identified additional patients with rearrangements in COL8A1 and NRXN1, but none in controls. Examination of available parents indicates that two out of three NRXN1 deletions detected in the TS cases are de-novo mutations. Our results are consistent with the proposal that rare CNVs play a role in TS aetiology and suggest a possible role for rearrangements in the COL8A1 and NRXN1 gene regions.

Increased genome instability in human DNA segments with self-chains: homology-induced structural variations via replicative mechanisms

Environmental factors including ionizing radiation and chemical agents have been known to be able to induce DNA rearrangements and cause genomic structural variations (SVs); however, the roles of intrinsic characteristics of the human genome, such as regional genome architecture, in SV formation and the potential mechanisms underlying genomic instability remain to be further elucidated. Recently, locus-specific observations showed that 'self-chain' (SC), a group of short low-copy repeats (LCRs) in the human genome, can induce autism-associated SV mutations of the MECP2 and NRXN1 genes. In this study, we conducted a genome-wide analysis to investigate SCs and their potential roles in genomic SV formation. Utilizing a vast amount of human SV data, we observed a significant biased distribution of human germline SV breakpoints to SC regions. Notably, the breakpoint distribution pattern is different between SV types across deletion, duplication, inversion and insertion. Our observations were coincident with a mechanism of SC-induced DNA replicative errors, whereas SC may sporadically be used as substrates of nonallelic homologous recombination (NAHR). This contention was further supported by our consistent findings in somatic SV mutations of cancer genomes, suggesting a general mechanism of SC-induced genome instability in human germ and somatic cells.

A peptide from the extracellular region of the synaptic protein α Neurexin stimulates angiogenesis and the vascular specific tyrosine kinase Tie2

Neurexin (NRXN) and Neuroligin (NLGN) are trans-synaptic proteins involved in vascular biology. NRXN is encoded in long (α) and short (β) isoforms. We have shown that βNRXN modulates blood vessel development in synergy with VEGFA and associates with NLGN. On the other hand αNRXN is also expressed in blood vessels but does not interact with NLGN or act in synergy with VEGFA, thus demonstrating a differential role.To find clues into the vascular functions of αNRXN, we chose a 7 aa motif that is part of its extracellular region and was formerly selected through a proteomic search for interactors of the vascular receptor Tie2. Next we (a) synthetized and modeled such peptide in order to determine its biological activity towards Tie2 in in vitro and in vivo angiogenesis assays and (b) evaluated if αNRXN and Tie2 physically associate in situ during vascular development.We used biochemical and cellular assays to prove that the synthetic αNRXN peptide (a) modulates the angiogenic phenotype of cultured endothelial cells and angiogenesis in vivo and (b) efficiently stimulates Tie2 phosphorylation and downstream mediators in endothelial cells. Moreover, we show that αNRXN and Tie2 can be reciprocally immunoprecipitated from chicken blood vessels at late stages of vascular development.These data have a double significance, i.e. provide a novel tool to modulate Tie2 and further suggest the involvement of the NRXN family of synaptic protein in the vascular system through their interaction with a fundamental vascular player.

Exon‐disrupting deletions of NRXN1 in idiopathic generalized epilepsy

Neurexins are neuronal adhesion molecules located in the presynaptic terminal, where they interact with postsynaptic neuroligins to form a transsynaptic complex required for efficient neurotransmission in the brain. Recently, deletions and point mutations of the neurexin 1 (NRXN1) gene have been associated with a broad spectrum of neuropsychiatric disorders. This study aimed to investigate if NRXN1 deletions also increase the risk of idiopathic generalized epilepsies (IGEs). We screened for deletions involving the NRXN1 gene in 1,569 patients with IGE and 6,201 controls using high-density oligonucleotide microarrays. We identified exon-disrupting deletions of NRXN1 in 5 of 1,569 patients with IGE and 2 of 6,201 control individuals (p = 0.0049; odds ratio (OR) 9.91, 95% confidence interval (CI) 1.92-51.12). A complex familial segregation pattern in the IGE families was observed, suggesting that heterozygous NRXN1 deletions are susceptibility variants. Intriguingly, we identified a second large copy number variant in three of five index patients, supporting an involvement of heterogeneous susceptibility alleles in the etiology of IGE. We conclude that exon-disrupting deletions of NRXN1 represent a genetic risk factor in the genetically complex predisposition of common IGE syndromes.

NRXN1 deletions identified by array comparative genome hybridisation in a clinical case series - further understanding of the relevance of NRXN1 to neurodevelopmental disorders.

BackgroundMicrodeletions in the NRXN1 gene have been associated with a range of neurodevelopmental disorders, including autism spectrum disorders, schizophrenia, intellectual disability, speech and language delay, epilepsy and hypotonia.ResultsIn the present study we performed array CGH analysis on 10,397 individuals referred for diagnostic cytogenetic analysis, using a custom oligonucleotide array, which included 215 NRXN1 probes (median spacing 4.9 kb). We found 34 NRXN1 deletions (0.33% of referrals) ranging from 9 to 942 kb in size, of which 18 were exonic (0.17%). Three deletions affected exons also in the beta isoform of NRXN1. No duplications were found. Patients had a range of phenotypes including developmental delay, learning difficulties, attention deficit hyperactivity disorder (ADHD), autism, speech delay, social communication difficulties, epilepsy, behaviour problems and microcephaly. Five patients who had deletions in NRXN1 had a second CNV implicated in neurodevelopmental disorder: a CNTNAP2 and CSMD3 deletion in patients with exonic NRXN1 deletions, and a Williams-Beuren syndrome deletion and two 22q11.2 duplications in patients with intronic NRXN1 deletions.ConclusionsExonic deletions in the NRXN1 gene, predominantly affecting the alpha isoform, were found in patients with a range of neurodevelopmental disorders referred for diagnostic cytogenetic analysis. The targeting of dense oligonucleotide probes to the NRXN1 locus on array comparative hybridisation platforms provides detailed characterisation of deletions in this gene, and is likely to add to understanding of the importance of NRXN1 in neural development.