This transgene expresses Cre recombinase under the control of a human beta-actin promoter, which is active in all embryonic cells at or before the blastocyst stage. Line number 2 contains a single copy of the transgene inserted into intron 4 of Tmem163 (chr1:129,442,346; NCBI37/mm9) with three intronic deletions of 2.2, 7.3 and 3.2 kb, respectively, surrounding the transgene integration site.