DEVELOPMENTAL REGULATION OF THE CHICKEN BETA-B1-CRYSTALLIN PROMOTER IN TRANSGENIC MICE

The cis-elements responsible for the high-level, lens-specific express ion of the chicken beta B1-crystallin gene were investigated by genera ting mice harboring beta B1-crystallin promoter/chloramphenicol acetyl transferase (CAT) transgenes. Deletion of promoter sequences -434/-15 3 and -152/-127 as well as site-directed mutagenesis of the PL1 (-116/ -102) and PL2 (-90/-76) elements significantly decreased CAT gene expr ession in the lenses of adult transgenic mice. Transfection studies us ing multimerized PLI and PL2 elements fused to the chicken B-actin bas al promoter indicated that PL1 is a general activating element while P L2 is involved in the lens-specificity of the chicken beta B1-crystall in promoter. CAT histochemistry demonstrated that the chicken beta B1- crystallin promoter (-434/+30) was active in both primary and secondar y lens fiber cells from 12.5 days post coitum (dpc) until adulthood, A ctivity of the -152/+30/CAT transgene was relatively low and confined to the primary lens fiber cells of 16.5 dpc mice. Together, these data suggest that the reduced activity of this promoter in the adult lens is due both to this developmentally restricted expression pattern and a reduction in promoter activity, RNA hybridization studies demonstrat ed that the chicken beta B1-crystallin/CAT (-434/+30) transgene was ex pressed at similar levels in the same cells as the endogenous mouse be ta B1-crystallin gene in 16.5 dpc transgenic mouse embryos. These data show a strict conservation of the lens-specific spatial and temporal regulation of the chicken and mouse beta B1-crystallin genes.