A construct in which the Tex101 promoter fragment was cloned in front of a codon-improved cre cassette with the nuclear localization signal from the SV40 large T antigen and the SV40 polyadenylation signal was microinjected in (C57BL/6 x SJL)F2 fertilized eggs. 3 lines were produced and crossed to ROSA26 reporter mice. In two lines (#1 and #5), ectopic activity was detected (all tested tissues stained), but reporter staining in crosses derived from #2 was robust in the testis with no staining in ovary orother tissues. (Spotty staining on the kidney surface was observed). Line 2 was analyzed in further detail.