Exon 1 and part of intron 1 (1.9 kb total) were deleted by replacement with a self-excising cassette comprising the following elements: a loxP site, the testis-specific angiotensin I converting enzyme (Ace) promoter, the cre recombinase gene, RNA polymerase II, a neomycin resistance gene, and a second loxP site. (J:243757)