Novel unconventional variants expand the allelic spectrum of OPHN1 gene

Abstract

Mutations in the OPHN1 gene cause a rare X‐linked recessive neurodevelopmental disorder characterized by intellectual disability, variably associated with cerebellar hypoplasia and distinctive facial appearance. In most of cases so far reported, the identified genomic variants involve the region encoding the central RhoGAP domain of the oligophrenin‐1 protein, and are predicted to result in a complete loss of function. By using a NGS‐based diagnostic approach, we identified three male and a female patients from two unrelated families carrying novel non‐disruptive OPHN1 variants (the in‐frame c.116_127 deletion and the missense c.2129C>T change, respectively), affecting either the BAR domain or the C‐terminus proline‐rich domain of the protein. Clinical and neuroimaging findings in the patients recapitulated the main features of OPHN1‐related syndrome, including developmental delay, intellectual disability, behavioral disorder, dysmorphic features, seizures, cerebellar hypoplasia, and ventriculomegaly. Yet, we observed a wide variability even among affected siblings, confirming the lack of clear genotype–phenotype correlation. Our results expand the allelic spectrum of OPHN1 and illustrate the challenges for clinical interpretation of non‐disruptive variants affecting X‐linked genes.

Effect of the OPHN1 novel variant c.1025+1 G>A on RNA splicing: insights from a minigene assay

“…Numerous clinical studies have documented the association of the OPHN1 gene with neurodevelopmental disorders. To date, over 100 cases of intellectual developmental delay linked to mutations in the OPHN1 gene have been reported [ 22 ], encompassing more than 20 distinct mutation variants [ 23 ] known to contribute to conditions such as intellectual disability and autism(Supplementary Table 1 ). Billuart et al [ 11 ] identified a 1-bp deletion in the OPHN1 gene in a family case with X-linked syndromic intellectual developmental disorder.…”

Neuronal Cytoskeleton in Intellectual Disability: From Systems Biology and Modeling to Therapeutic Opportunities

“…In humans, LOF mutations in OPHN1 cause syndromic XLID, in which ID is associated with epilepsy, ventriculomegaly, and cerebellar hypoplasia [ 167 , 168 , 169 ].…”