IDENTIFICATION OF A LENS-SPECIFIC REGULATORY REGION (LSR) OF THE MURINE ALPHA-B-CRYSTALLIN GENE

Previous studies have shown that the - 661/+ 44 sequence of the murine alpha B-crystallin gene contains a muscle-preferred enhancer (- 426/- 257) and can drive the bacterial chloramphenicol acetyltransferase (CAT) gene in the lens, skeletal muscle and heart of transgenic mice. Here we show that transgenic mice carrying a truncated - 164/ + 44 fragment of the alpha B-crystallin gene fused to the CAT gene expressed exclusively in the lens; by contrast mice carrying a - 426/+ 44 fragment of the alpha B gene fused to CAT expressed highly in the lens, skeletal muscle and heart, and slightly in the lung, brain, kidney, spleen and liver. DNase I protection experiments indicated that the - 147/- 118 sequence is protected by nuclear proteins from alpha TN4-1 lens cell line, but not by nuclear proteins from myotubes of the C2C12 cell line. Site directed mutagenesis of this sequence decreased promoter activity in transiently-transfected lens cells, consistent with this sequence being a lens-specific regulatory region (LSR). We conclude that the - 426/- 257 enhancer is required for expression in skeletal muscle, heart and possibly other tissues, and that the - 164/+ 44 sequence of the alpha B-crystallin gene is sufficient for expression in the lens of transgenic mice.