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M. B. Melo, A. Santana, M. Waiswol, E. S. Arcieri, F. Richeti, C. A. Longui, J. P. C. Vasconcellos; New Mutation in the Alpha A-Crystallin Gene Causing Autosomal Dominant Congenital Cataract. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1337.
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Congenital cataracts are one of the most treatable causes of visual impairment and blindness during infancy, with an estimated prevalence of 1 to 6 cases per 10,000 live births. As many as half of all congenital cataract cases may have a genetic cause either as part of a systemic disease or as a nonsyndromic Mendelian trait. All three types of Mendelian inheritance have been reported for cataract; however, autosomal dominant transmission seems to be the most frequent. Studies have reported about fifteen genes that are actually involved in the formation of congenital cataract. There is an intimate relation between crystallin genes and lens transparency, and therefore they are excellent candidate genes for inherited cataract. The purpose of this study was to investigate mutations in the alpha A, gamma C and gamma D-crystallin genes (CRYAA, CRYGC and CRYGD,respectively) in a Brazilian family with autosomal dominant congenital nuclear cataract.
A two-generation Brazilian family was referred to Santa Casa de São Paulo Ophthalmology Departament. The coding regions and intron/exon boundaries of the CRYAA, CRYGC and CRYGD genes were amplified by PCR and directly sequenced.
The Brazilian family with three affected individuals and one unaffected individual was evaluated. Sequence analysis of the CRYAA gene revealed, in exon 1, a point mutation leading to the substitution of an arginine to a cysteine at amino acid 12 (ARG12CYS) that could be identified only in affected individuals, hence, segregating with the disease.
We have identified, in alpha A-crystallin, a mutation causing congenital nuclear cataract in a Brazilian family, which, to our knowledge, is being reported for the first time. The affected residue has been conserved through evolution and supports literature data that reports the involvement of the amino acid ARG in the functional integrity of the lens.
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