COINTEGRATION AND EXPRESSION OF BACTERIAL AND GENOMIC TRANSGENES IN THE PANCREATIC AND INTESTINAL TISSUES OF TRANSGENIC MICE

Previous studies in the mammary gland have reported the 'rescue' of po orly expressed cDNA transgenes by their co-integration with a genomic sequence specifically expressed in the mammary tissue. To determine wh ether a highly expressed genomic sequence co-integrated with a cDNA se quence can rescue expression in other tissues, the expression of a bac terial gene, celE', encoding endoglucanase E' (EGE'), was investigated in the pancreatic and intestinal epithelia of transgenic mice. To res cue pancreatic expression, the human growth hormone genomic sequence w as co-integrated with the bacterial gene, whereas to rescue intestinal expression, the genomic sequence encoding the intestinal fatty acid b inding protein was used. In both studies the number of transgenics exp ressing celE' was significantly increased (60%) by the use of a genomi c sequence, but only in the intestinal tissues was the level of celE' expression improved. However, this improvement was modest, representin g at maximum only a doubling in the levels of ECE'. Thus permissive in tegration or rescue may be general, but the overall level of rescue is often insubstantial compared to the endogenous expression of the tran sgene genomic DNA. (C) 1997 Elsevier Science B.V.