Beta cell-specific ablation of target gene using Cre-loxP system in transgenic mice.

Tissue-specific inactivation of a gene using the Cre-loxP system has been used as an important tool to define its role in which the inactivation of the gene in every cell type results in an embryonic lethality. The expression of Cre recombinase (Cre) can be regulated by controlling the timing or spatial distribution of Cre expression via tissue-specific promoters, ligand-inducible promoters, and ligand-dependent Cre fusion proteins. The rat insulin promoter (RIP) has been used in this study to drive the expression of Cre, specifically in the beta cells. The Cre coding sequence was ligated with the RIP and the isolated RIP-Cre transgene was microinjected into one cell embryo to establish a transgenic mouse line. Tissue specificity of the rat insulin promoter was demonstrated by reverse transcriptase polymerase chain reaction using total RNA from pancreas and other tissues of the RIP-Cre transgenic mice. In addition, the efficiency and specificity of RIP was further analyzed by crossbreeding the RIP-Cre transgenic mice with reporter mice bearing a beta-actin-loxP-CAT-loxP-lacZ transgene. In these mice, lacZ is expressed only after excision of the floxed-CAT gene by Cre-mediated recombination. Here, we present the data for beta cell-specific expression of lacZ in the bigenic mice, as proof of concept in a mouse model for targeting beta cell-specific gene(s). The RIP-Cre transgenic mice will be used as a potential tool for targeting the excision of beta cell-specific gene(s) to study their role in islet cell physiology.