A targeting vector was designed to insert a loxP-flanked stop cassette upstream of exon 8 of the lysine (K)-specific methyltransferase 2A (Kmt2a) gene. A cassette containing 6.5-kb fragment of murine CREB binding protein (Cbp) cDNA, a Simian virus 40 polyadenylation signal (SV40 pA), and a puromycin resistance sequence (puro) was inserted into exon 8.