FIG 1.

Transgenic strain breeding diagram. The breeding scheme shown illustrates the generation of testis-specific Ctcfl transgenic mice. In the presence of the gene for Cre recombinase, under the control of a testis-specific promoter, a DNA fragment with a stop signal is deleted to generate a functional rtTA transgene. This experimental design allows the specific expression of Ctcfl transgenes in any tissue, limited only by the availability of the tissue-specific Cre transgenic strain. In our case, we chose a testis-specific promoter to limit the expression of the Ctcfl transgene to the testis.