Postnatal male germ-cell expression of cre recombinase in Tex101-iCre transgenic mice.

We have generated a transgenic mouse line that expresses improved Cre recombinase (iCre) under the control of the testis-expressed gene 101 (Tex101) promoter. This transgenic mouse line was named Tex101-iCre. Using the floxed ROSA reporter mice, we found that robust Cre recombinase activity was detected in postnatal testes with weak or no activity in other tissues. Within the testis, Cre recombinase was active in spermatogenic cells as early as the prospermatogonia stage at day 1 after birth. In 30- and 60-day-old mice, positive Cre recombinase activity was detected not only in prospermatogonia but also in spermatogenic cells at later stages of spermatogenesis. There was little or no Cre activity in interstitial cells. Breeding wild-type females with homozygous floxed fibroblast growth factor receptor 2 (Fgfr2) males carrying the Tex101-iCre transgene did not produce any progeny with the floxed Fgfr2 allele. All the progeny inherited a recombined Fgfr2 allele, indicating that complete deletion of the floxed Fgfr2 allele by Tex101-iCre can be achieved in the male germline. Furthermore, FGFR2 protein was not detected in spermatocytes and spermatids of adult Fgfr2(fl/fl) ;Tex101-iCre mice. Taken together, our results suggest that the Tex101-iCre mouse line allows the inactivation of a floxed gene in spermatogenic cells in adult mice, which will facilitate the functional characterization of genes in normal spermatogenesis and male fertility.