We have continued to characterize the structure, expression and evolution of crystallin genes of the eye lens. Sequences have been obtained for the BetaB-1, Beta A3/1- and Beta2-crystallin chicken cDNAs. Gene sequences have been derived for chicken and human alphaA-crystallin chicken betaB-1 and BetaA3/A1-crystallin, and chicken Delta-crystallin. Both chicken Delta-crystallin polypeptides were shown to be generated from the Delta1 mRNA by a translational or co-translational mechanism. Transfection experiments demonstrated that the alternative RNA splicing of the murine AlphaA-crystallin gene is neither tissue- nor species-specific. Crystallin promoters were analyzed by fusion to the bacterial chloramphenicol acetyl transferase (CAT) gene in the pSVO-CAT expression vector. Cell-free transcription experiments using a Hela cell extract was used to identify the core promoter of the chicken delta- and murine alphaA-crystallin promoters. Transient transfection experiments using cultured lens epithelia and production of transgenic mice demonstrated tissue-specific and developmental controls operating in the crystallin promoters. Both positive and putative negative regulatory sequences were indicated. The murine alphaA-crystallin promoter (sequences -364 to +45) when fused to the SV40 T-antigen gene neoplastically transformed lens cells in transgenic mice. Thus, these experiments initiate genetic engineering in the visual system.
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