Background Microdeletions in the NRXN1 gene have been associated with a

Background Microdeletions 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. 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. Keywords: Copy number variants, Autism spectrum disorders, NRXN1, Neurodevelopmental disorders, Epilepsy, Microcephaly, Neurexins Background Neurexin 1 (NRXN1; 2p16.3) is a member of a small Nr2f1 family of proteins, which also includes neurexin 2 and neurexin 3, originally identified as synaptic transmembrane receptors for the black-widow spider toxin -latrotoxin [1]. Neurexins play a role in synapse maturation by fine-tuning synaptic properties and regulating synaptic transmission through conversation with neuroligins [2] and mediate trans-synaptic interactions that help to shape the synapse [3]. Each neurexin gene (NRXN1-3) produces two major isoforms, – and -, with different extracellular but comparable intracellular and transmembrane structures [4]. -NRXNs, which act as synaptic organisers, have six LNS (Laminin G, NRXN, Sex-hormone-binding globulin) domains, with three intercalated epidermal growth factor (EGF)-like domains and have been shown to interact with neurexophilins [5] and LRRTM proteins [6], as VE-821 well as regulating some calcium channels VE-821 [7]; -NRXNs have a single LNS domain, lack EGF-like sequences and contain fewer laminin G domains [8]. Nrxn1 also undergoes considerable option splicing, which is temporally and spatially controlled by neuronal activity via calcium/calmodulin-dependent kinase IV signalling [9]. Deletions within NRXN1 have been identified in individuals diagnosed with a range of neurodevelopmental disorders (NDD): including intellectual disability, developmental delay, speech and language delay [10, 11] autism spectrum disorders (ASD) [12C17] schizophrenia [18C21], and when homozygously deleted, early-onset epilepsy [22] or Pitt-Hopkins-like Syndrome [23]. A family with NRXN1 deletions, schizophrenia and type 1 diabetes has been explained [24], which is plausible because neurexin 1 is usually expressed in -cells of pancreas [25]. Although deletions in NRXN2 have not been reported, rare deletions in NRXN3 have been recognized in ASD [26]. The above studies have mainly focused on the detection of CNVs in groups of patients with specific phenotypes. However, it is progressively recognised that NRXN1 deletions may be risk factors for a variety of clinical disorders. In the present study, we statement intragenic NRXN1 deletions detected during diagnostic cytogenetic screening of sequential referrals using a custom aCGH platform including dense protection of the NRXN1 locus, and describe the phenotype of these patients and the size and position of their deletions. Materials Diagnostic referral cases The tested cohort consisted of patients referred to Guys and St Thomas NHS Foundation Trust from regional paediatricians and other health specialists, as well as from genetics centres both in and outside the region (SE Thames). Array CGH analysis was initiated to determine the causes of developmental delay, neurocognitive disability, learning difficulties, behavioural abnormalities or birth defects or to confirm a clinical diagnosis of a suspected syndrome. All patient assessments were carried out as part of standard clinical care, either as clinical referrals for array CGH screening following a normal karyotype, or those having array CGH as a first-line VE-821 test in place of karyotyping. All data were anonymised. Array CGH analysis Testing was carried out at a regional cytogenetics CPA.