A novel CLRN2 variant: expanding the mutation spectrum and its critical role in isolated hearing impairment.

Background: Biallelic variants in the CLRN2 gene have been reported to cause autosomal recessive profound hearing impairment in humans. CLRN2 belongs to the clarin gene family that encodes a tetraspan protein that contains a cytosolic N-terminus, multiple helical transmembrane domains, and an endoplasmic reticulum membrane retention signal, TKGH, in the C-terminus. The encoded protein may be important in development and homeostasis of the inner ear and retina.

Methods: Here, we present a consanguineous family suffering from autosomal recessive non-syndromic profound hearing impairment (HI). We employed state of the art Whole exome sequencing (WES), Sanger sequencing followed by routine bioinformatics filtration steps and homology modeling to elucidate the effect of mutation at the protein level.

Results: ES followed by Sanger sequencing revealed a novel homozygous nonsense variant in the CLRN2 gene [c.414 C > A; p.Cys138*]. Furthermore, insilico protein modeling of the wildtype and mutated version of the CLRN2 protein revealed large-scale changes that predict to compromise the routine normal function of the protein.

Conclusion: Our finding further extends the mutations spectrum of CLRN2 gene and confirms its important role in hearing homeostasis and with developmental disorder in humans.