The cis regulatory elements of the alphaA-crystallin promoter responsible for the lens-specific expression of this gene and for its developmental regulation were further characterized. The results indicated that sequence -88 to +46 of the murine alphaA-crystallin gene contains the cis regulatory elements for lens-specific expression and for correct developmental regulation of this gene in vivo. The alphaA-crystallin promoter (-366/+46) which has become a very useful tool to target gene expression to the lens, is being used to study how foreign gene expression in the lens affects the phenotype of the lens or the rest of the eye. Aldose reductase mRNA levels were found to be significantly increased in the lens of a transgenic mouse line that carries the alphaA-crystallin promoter fused to the SV40 large T antigen. That mouse line develops a complete cataract as early as embryonic day 14. Several fusion genes containing the alphaA-crystallin promoter fused to growth factors, oncogenes, interferon, or ribozymes are currently being used to study the effect of their expression in the eye.