Effects of age and genetic growth rate on the crystallin composition of the chick lens.

This two part study continues and extends our examination of the effects of age and of genetically determined intrinsic growth rate on the overall protein composition of chick lens epithelia, lens fiber masses and whole lenses. Water-soluble proteins were analyzed by SDS-polyacrylamide and 2-dimensional gel electrophoresis. First, detailed age-related changes in protein expression between day 4 of embryonic development and the 8-week adult stage are described for one normal chick strain. Secondly, comparisons are made between day-old post-hatch chicks of four different genotypes: two genetically unrelated chick strains with a high growth rate and propensity for hyperplasia of the lens epithelium and two unrelated slow-growing strains, both with normal lens morphology. We find that the beta/delta-crystallin ratio in lens epithelia and fiber masses is higher in both the slow- than in both the fast-growing strains. The data emphasizes the importance of quantitative and non-coordinate changes in crystallin polypeptide expression during lens growth and development, and implicates growth rate as a modifier of the pattern of crystallin expression.