Rabbit Anti-Human CRYAA Polyclonal Antibody

PURPOSE: To determine the genetic basis for congenital total white cataract with microcornea in three affected siblings. DESIGN: Prospective interventional case series. METHODS: Clinical ophthalmic examination, venous blood sampling for linkage analyses, and diagnostic testing of identified candidate gene(s). RESULTS: Three siblings had congenital total white cataract with microcornea; the parents and seven other siblings were asymptomatic. Linkage analysis mapped the phenotype to Hsa 21q22.3, the region of the gene for the alpha-A component of alpha-crystallin (CRYAA), with a logarithm of odds (LOD) score of 2.5. Diagnostic CRYAA sequencing revealed a novel homozygous non-sense mutation (R54C) in the three affected individuals only. One other sibling and the two parents were heterozygotes; these individuals had punctuate lenticular opacities evident by careful slit-lamp biomicroscopy which were not present in the noncarriers, all of whom had unremarkable ophthalmic examinations. CONCLUSION: R54C is the second reported recessive CRYAA mutation associated with congenital cataract and the first with described morphology: punctuate lenticular opacities in carriers and congenital total white cataract with microcornea in homozygotes. The microcornea may have been caused by an inductive effect on the developing cornea from the abnormal lens and/or reduced CRYAA molecular chaperoning of the cornea.

alpha A-crystallin is a lens chaperone that plays an essential role in the transparency and refractive properties of the lens. Mutations in alpha A-crystallin have been associated with the development of hereditary cataracts. The R49C mutation of alpha A-crystallin (alpha A-R49C) was identified in a four-generation Caucasian family with hereditary cataracts. The alpha A-R49C protein forms larger-than-normal oligomers in the lens and has decreased solubility. This aberrant alpha A-R49C oligomerization suggests that protein folding is altered. However, whether activation of the unfolded protein response (UPR) occurs during crystallin mutation-induced cataract formation and whether the UPR causes cell death under these conditions is unclear. We investigated UPR activation in an in vivo mouse model of alpha A-R49C using immunoblot analysis of lens extracts. We found that expression of the endoplasmic reticulum (ER) chaperone, BiP, was 5-fold higher in homozygous alpha A-R49C lenses than in wild type lenses. Analysis of proteins typically expressed during the UPR revealed that ATF-4 and CHOP levels were also higher in homozygous lenses than in wild type lenses, while the opposite was true of ATF-6 and XBP-1. Taken together, these findings show that mutation of alpha A-crystallin induces activation of the UPR during cataract formation. They also suggest that the UPR is an important mediator of cell death observed in homozygous alpha A-R49C lenses. (C) 2010 Elsevier Inc. All rights reserved.