Molecular genetics of cataract

Studies on hereditary congenital cataracts have led to the identification of genes involved in formation of these cataracts. Knowledge of the structure and function of a particular gene and the effect of disease-associated mutations on its function are providing insights into the mechanisms of cataract. Identification of the disease gene requires both the relevant clinical data as well as genetic data on the entire pedigree in which the disease is found to occur. Genes for hereditary cataract have been mapped by genetic linkage analysis, in which one examines the inheritance pattern of DNA markers throughout the genome in all individuals of the pedigree, and compares those with the inheritance of the disease. Cosegregation of a set of markers with disease implies that the disease gene is present at the same chromosomal location as those markers. The genes so far identified for hereditary cataracts in both humans and animal models encode structural lens proteins, gap junction proteins, membrane proteins and regulatory proteins involved in lens development. Understanding of the mechanisms of hereditary cataract may also help us understand the manner in which environmental and nutritional factors act on the lens to promote opacification.