Identification of co-segregating GJA3 and CRYBA1 missense variants in a Chinese family with congenital cataract: a possible digenic etiology

TL;DR

A Chinese family with congenital cataract was studied to find genetic causes, revealing two rare gene variants that may work together to cause the condition.

Contribution

The study identifies two co-segregating missense variants in GJA3 and CRYBA1 as possible digenic contributors to congenital cataract in a Chinese family.

Findings

Two rare missense variants in GJA3 and CRYBA1 were found to co-occur in all affected family members.

The variants are predicted to be damaging and are classified as variants of uncertain significance according to ACMG guidelines.

No other rare, protein-altering variants in known cataract genes were found in the affected individuals.

Abstract

Congenital cataract (CC), defined as lens opacity present at birth or in early infancy, is a major cause of reversible childhood blindness and shows marked genetic heterogeneity. This study aimed to investigate the genetic basis of CC in a multigenerational Chinese family.

A four-generation family with CC was clinically characterized. Whole-exome sequencing was performed in the proband, followed by stepwise variant filtering based on minor allele frequency, predicted functional impact, known CC-associated genes, and an autosomal dominant inheritance model. Candidate variants were annotated and classified according to ACMG guidelines. Sanger sequencing was used to validate variants in two additional affected relatives.

Two heterozygous missense variants were identified in known CC-associated genes: GJA3 c.776C > A (p.Ser259Tyr) and CRYBA1 c.346A > T (p.Ile116Phe). Both were extremely rare or absent in population databases and predicted to be damaging by multiple in silico tools. Sanger sequencing confirmed that the two variants co-occurred in all three affected family members tested, and no other rare, protein-altering variants meeting the filtering criteria were found in established cataract genes.

According to ACMG guidelines, both variants remain classified as variants of uncertain significance, but their rarity, predicted functional impact and consistent co-occurrence in affected individuals support them as strong candidate variants that may jointly contribute to CC in this family and expand the spectrum of GJA3- and CRYBA1-associated changes.

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