A Testis-Specific Expression of Cre Recombinase in Transgenic Mice Testis by Kap147/Kpn Hybrid Promoter

Gene targeting technology has been widely applied to gene function analysis. In order to precisely study gene function in specific tissues during a specific developmental period, tissue specific or inducible promoter driven Cre recombinase to guide gene knockout or silence are often used. To study the in vitro and in vivo functions of the hybrid promoter Kap147/Kpn and to facilitate the study of gene function using Cre/loxp system, the transgenic mice of Cre recombinase guided by the heterozygous promoter Kap147/Kpn were constructed. Co-transfection assay, in vitro cell culture experiments and dihydrotestosterone induction confirmed Kap147/Kpn promoter is cell specific and androgen inducible. Reverse transcription PCR and fluorescence quantitative PCR confirmed the testis-specific Cre gene expression in the offspring Cre-F0-2 and kidney-specific Cre gene expression in the offsprings of Cre-F0-1 and Cre-F0-6. In addition, fluorescence quantitative PCR assay showed that the amount of Cre mRNA in adult mice of Cre-F0-2 offsprings was 20−30 times higher than that in the newborn or senile mice, which is in accordance with the amount of androgen in mice, suggesting that the activity of Kap147/Kpn chimeric promoter is probably regulated by androgen. Hormone induction experiment showed that 15 mg/(kg·d) DHT accelerated the expression of Cre mRNA of about 1.7-fold in testis, and 100 mg/(kg·d) CAP reduced the expression by about 50%, which thereby demonstrated that the Kap147/Kpn hybrid promoter was androgen inducible in Cre-F0-2 transgenic mice. Upon breeding the Kap147/Kpn-Cre mice (Cre-F0-2) with double-fluorescent Cre reporter mouse (B6.129 (Cg)-Gt (ROSA) 26Sor), frozen sections from male double transgenic mice showed bright green fluorescence only in testis where Cre recombinase specifically expressed. This model mouse Cre-F0-2 with tissue specific Cre recombinase in the testis would provide a novel useful tool for studying the physiological significance of genes expressed in the testis.