Transgenic Cre recombinase expression in germ cells and early embryogenesis directs homogeneous and ubiquitous deletion of loxP-flanked gene segments.

We report on the establishment of a transgenic mouse line expressing Cre recombinase under control of the c-kit promoter. Expression of Cre recombinase was only observed in late spermatogenesis and oogenesis, however, Cre-mediated deletion of floxed gene segments occurred at this stage as well as in early embryogenesis. As a consequence of this, a chimeric distribution of loxed alleles was found in a large fraction of these mice. The chimerism was very homogeneous in different organs and tissues of the same individual but varied between different individual offspring. The potential uses for this mouse line are discussed.