Identification of a Protein-truncating Variant in SCAPER Gene Causing Syndromic form of Intellectual Disability

Intellectual disability (ID) is characterized by impairments in cognitive functioning and adaptive behavior. Globally, it affects 1-3% of the general population, with an increased prevalence in consanguineous families. It is a clinically heterogeneous disorder that can manifest as a variable phenotype. Intellectual developmental disorder and retinitis pigmentosa (IDDRP) is a rare syndrome in which patients present with both ID and retinitis pigmentosa.

This study examined a consanguineous family to identify disease-associated pathogenic mutations and elucidate their potential functional impact in patients with IDDRP.

Clinical assessment of the patients revealed characteristics consistent with both intellectual disability (ID) and retinitis pigmentosa. Individuals affected by IDDRP were subjected to whole exome sequencing (WES), and the identified candidate pathogenic variants were validated by Sanger sequencing. Computational analyses were conducted to evaluate the impact of these mutations on the protein structure and function.

WES identified a protein-truncating variant, c.2605A>T (p.Lys869Ter), in the Sphase cyclin A-associated protein in the endoplasmic reticulum (SCAPER) gene. SCAPER has previously been reported to cause IDDRP. In silico analyses revealed structural and interactional alterations in the SCAPER protein. This variant is novel in the Pakistani population and has not been previously reported. This variant exhibits an autosomal recessive mode of inheritance and segregates among the investigated affected and unaffected family members.

The present study expands the spectrum of disease-causing variants in SCAPER and will contribute to a better understanding of the genetic etiology of IDDRP.