Association Analysis Between a Novel Allelic Variant in B–Crystallin Splice Site and Cataract

Abstract

Abstract: : Purpose:αB–crystallin (CRYAB) is one of the crystallin family members which are major components of soluble protein in human lens and play essential role in maintaining lens transparency. We investigated a novel allelic variant in an αB–crystallin splice site, 324+4(T>G), which may affect the integrity of the αB–crystallin protein, for its association with cataract. Methods:We collected whole blood samples from 116 cataract patients and 114 sex and age matched normal controls. All subjects were Hong Kong Chinese. DNA was extracted and PCR was used to amplify the gene segment including exon 2 of αB–crystallin and its adjacent splice sites. The PCR products were genotyped by direct sequencing. The data was analyzed by Pearson chi–square test. Results:Among the 116 cataract patients, 87(75%) were TT genotype, 24(20.7%) were TG, and 5(4.3%) were GG. The T frequency was 85.3% and G frequency was 14.7%. In the normal control group, 78(68.4%) were TT, 31(27.2%) were TG, and 5 (4.4%) were GG. The T frequency was 82% and G frequency 18%. Both TT genotype and T allele frequency were higher in patient than in controls, although the difference was not significant (p =0.27 and p =0.33 respectively). Conclusions:The αB–crystallin T allele may be related to cataractgeneisis, which is a complex process involving multiple genetic and environmental factors. Study of the T allele in different morphological and age group of cataract patients is in progress to further understand its association with cataract. Effects of the T allele on the αB–crystallin function should be investigated.

Keywords: cataract • genetics