Cre recombinase expression is driven by a mouse endothelial-specific receptor tyrosine kinase promoter/enhancer. Recombinase activity is detected in endothelial cells during embryogenesis and adulthood. Expression was also detected in hematopoietic cells. The promoter has also been reported to be active in female germ cells. A low frequency of deletion events are also observed by inheritance from the male germline. The transgene integrated into chromosome 13 causing a 241.3 Kb deletion and disrupting the following genes: Mtrr (5-methyltetrahydrofolate-homocysteine methyltransferase reductase), Fastkd3 (FAST kinase domains 3), 1700001L19Rik, Adcy2 (adenylate cyclase 2). The deletion results in a functional knock-out of Mtrr, Adcy2 and Fastkd3 in homozygous mice. Founder line 12 has a copy number of greater than 10.