Identification and characterization of six β-crystallin gene mutations associated with congenital cataract in Chinese families.

backgroundThis study aims to identify the underlying genetic defects of β-crystallin (CRYB) genes responsible for congenital cataracts in a group of Chinese families.

methodsDetailed family history and clinical data of six Chinese families with autosomal dominant congenital cataracts were recorded. Targeted exome sequencing was applied to detect the underlying genetic defects for the families. Generated variants were confirmed by PCR and sanger sequencing. Afterward, bioinformatic analysis through several computational predictive programs was performed to assess impacts of mutations on protein structure and function.

resultsA total of 53 participants (23 affected and 30 unaffected) from six unrelated Chinese families were recruited. Cataract phenotypes covered nuclear, total, posterior polar, pulverulent, snowflake-like, and zonular. Through targeted exome sequencing, six mutations in four β-crystallin genes were revealed which included five missense mutations CRYBB1 p.Q70P, CRYBB2 p.E23Q, CRYBB2 p.A49V, CRYBB2 R188C, CRYBA4 p.M14K and one splice mutation CRYBB3 c.75+1 G>A. In silico results predicted pathogenic for all four missense variants except variant CRYBB2-p.A49V yielded results as tolerant. The CRYBB3 c.75+1 G>A splice site mutation was predicted to be deleterious by leading to a broken splice site, a premature stop codon, and subsequently resulting in a short peptide of 113 amino acids, which may affect protein features.

conclusionThe obtained results expanded mutational and phenotype spectrum of β-crystallin genes and offer clues for pathogenesis of congenital cataracts. The data also demonstrated that targeted exome sequencing is valuable for providing molecular diagnostic information for congenital cataract patients.