Ontogeny of alpha A and alpha B crystallin polypeptides during Rana temporaria lens development

The ontogeny and localization of alpha A and alpha B polypeptide chains of alpha-crystallin were investigated in the developing lens of Rana temporaria, an anuran amphibian, using the indirect immunofluorescence staining method with heterologous antibodies directed against these two polypeptides. alpha A and alpha B crystallins are primary gene products and are translated by different mRNAs in mammals. Although they show about 6000 amino-acid sequence homology (Bloemendal, 1977), the alpha A cDNA of rat and mouse does not hybridize to alpha B mRNA (Dodemont et al., 1981; King and Piatigorsky, 1983). Antigenically too, alpha A and alpha B polypeptides have been shown to be different. These two polypeptides were isolated from mouse lens native alpha-crystallin by SDS-gel electrophoresis and were injected into young rabbits to raise antibodies. These antibodies were tested by immunoblotting against R. temporaria total lens soluble proteins before their use in the present investigation. Results presented here show that in the developing lens of R. temporaria, alpha A appears earlier than alpha B, suggesting a differential gene activation. In addition, these two polypeptides could not be detected either in the developing lens epithelium or in the epithelium of young froglets (2-3 weeks post-metamorphosis).