UCSF

Purpose

To identify the molecular basis for autosomal recessively inherited congenital non-syndromic pulverulent cataracts in a consanguineous family with four affected children.

Methods

An autozygosity mapping strategy using high density SNP microarrays and microsatellite markers was employed to detect regions of homozygosity. Subsequently good candidate genes were screened for mutations by direct sequencing.

Results

The SNP microarray data demonstrated a 24.96 Mb region of homozygosity at 22q11.21-22q13.2 which was confirmed by microsatellite marker analysis. The candidate target region contained the beta-crystallin gene cluster and direct sequencing in affected family members revealed a novel mutation in CRYBB1 (c.2T>A; p.Met1Lys).

Conclusions

To our knowledge this is the first case of an initiation codon mutation in a human crystallin gene, and only the second report of a CRYBB1 mutation associated with autosomal recessive congenital cataracts. In addition, although a number of genetic causes of autosomal dominant pulverulent cataracts have been identified (including CRYBB1) this is the first gene to have been implicated in autosomal recessive nuclear pulverulent cataract.