A tissue-specific promoter that can drive a foreign gene to express in the suprabasal urothelial cells of transgenic mice.

Uroplakins are a group of integral membrane proteins that are synthesized as the major differentiation products of urothelium. The luminal portions of these proteins form 12-nm protein particles arranged in a two-dimensional crystalline array. The expression of uroplakin genes is bladder specific and differentiation dependent; little is known, however, about their molecular regulation. Here we describe the cloning of mouse uroplakin II gene and demonstrate, in transgenic mouse experiments, that a 3.6-kb 5'-flanking sequence of this gene can drive a bacterial lacZ (reporter) gene to express in the suprabasal cell layers of the urothelium. The transgene was not expressed in any tested (nonurothelial) epithelial and other tissues (except hypothalamus). These results suggest that most of the cis elements that confer the bladder-specific and differentiation-dependent expression of mouse uroplakin II gene must reside in the 3.6-kb sequence. The availability of a promoter capable of delivering a foreign molecule to the differentiated cell layers of bladder epithelium opens avenues for studying normal and pathological urothelial differentiation in transgenic mice.