Expression Of Amylase Genes In Transgenic Mice.

Abstract

The amylase multigene family is a useful model system for the study of evolution and regulation of gene expression. I have characterized two nonallelic murine pancreatic amylase genes, Amy-2.1$\sp{y}$ and Amy-2.2$\sp{y}$, whose promoter sequences are 30% divergent. They provide an example of closely related genes that have diverged in one aspect of regulation (response to insulin) and remained similar in others (tissue specificity and glucocorticoid regulation). Their sequences have been compared with regard to both evolutionary history and functional homology. To localize sequences required for pancreas-specific and hormone-dependent activation, three lines of transgenic mice were established using different constructs of the Amy-2.2$\sp{y}$ gene: an entire Amy-2.2$\sp{y}$ gene, a minigene, and an amylase-chloramphenicol acetyltransferase fusion gene. In all of these lines, the transgene was expressed at high levels, exclusively in the pancreas, in a hormone-dependent manner. These experiments indicate that cis-acting DNA sequences mediating the regulation of this gene are located within 227 basepairs of the 5$\sp\prime$ flanking sequence, and suggest that transcription is the process regulated. Transgenic mice carrying constructs of an Amy-1 (salivary amylase) gene have also been produced. This gene has two promoters active in different tissues, located 7 kilobases (parotid promoter) and 4.5 kilobases (liver promoter) upstream of the structural gene. One of the transferred constructs contains an entire Amy-1 gene, including both promoters. It appears to be expressed from the liver but not the parotid promoter, in the single transgenic line examined. The other two constructs juxtapose the parotid promoter, in either orientation, to the 5$\sp\prime$ flanking region of the Amy-2.2$\sp{y}$ minigene mentioned above. Several of these lines express the transgene in the pancreas.