Molecular Characterization of NRXN1 Deletions from 19,263 Clinical Microarray Cases Identifies Exons Important for Neurodevelopmental Disease Expression

PURPOSE: The purpose of the current study was to assess the penetrance of NRXN1 deletions. METHODS: We compared the prevalence and genomic extent of NRXN1 deletions identified among 19,263 clinically referred cases to that of 15,264 controls. The burden of additional clinically relevant copy-number variations (CNVs) was used as a proxy to estimate the relative penetrance of NRXN1 deletions. RESULTS: We identified 41 (0.21%) previously unreported exonic NRXN1 deletions ascertained for developmental delay/intellectual disability that were significantly greater than in controls (odds ratio (OR) = 8.14; 95% confidence interval (CI): 2.91-22.72; P \u3c 0.0001). Ten (22.7%) of these had a second clinically relevant CNV. Subjects with a deletion near the 3\u27 end of NRXN1 were significantly more likely to have a second rare CNV than subjects with a 5\u27 NRXN1 deletion (OR = 7.47; 95% CI: 2.36-23.61; P = 0.0006). The prevalence of intronic NRXN1 deletions was not statistically different between cases and controls (P = 0.618). The majority (63.2%) of intronic NRXN1 deletion cases had a second rare CNV at a prevalence twice as high as that for exonic NRXN1 deletion cases (P = 0.0035). CONCLUSIONS: The results support the importance of exons near the 5\u27 end of NRXN1 in the expression of neurodevelopmental disorders. Intronic NRXN1 deletions do not appear to substantially increase the risk for clinical phenotypes.Genet Med 19 1, 53-61

A fourth case of Feingold syndrome type 2: psychiatric presentation and management

Feingold syndrome (FGLDS1) is an autosomal dominant disorder caused by mutations in the MYCN oncogene on the short arm of chromosome 2 (2p24.1). It is characterised by microcephaly, digital abnormalities, oesophageal and duodenal atresias, and often learning disability or mental retardation. In 2011, individuals sharing the skeletal abnormalities of FGLDS1 but lacking mutations in MYCN, were found to harbour hemizygous deletions of the MIR17HG gene on chromosome 13q31.3. These individuals share many of the characteristics of FGLDS1 except for gastrointestinal atresia. The condition was termed Feingold syndrome type 2 (FGLDS2). We describe the presentation and management of a fourth known case of FGLDS2 in an 18-year-old girl with microcephaly, short stature, mildly dysmorphic features, digital malformations and significant cognitive and psychiatric symptoms. Comparative genomic hybridisation array testing confirmed a 7.4 Mb microdeletion in chromosome region 13q31.1q.31.3 corresponding to the MIR17HG gene