Identification of a lens-specific regulatory region (LSR) of the murine αB-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.