The Atoh7 (Math5) and cre recombinase cDNAs, separated by an internal ribosomal entry site (IRES) and followed by an SV40 polyadenylation sequence, were cloned into a plasmid upstream of a 2.4 kb fragment of the mouse Crx gene that contained the promoter and proximal regulatory region. The linearized purified transgene was injected into fertilized oocytes. 2 founders and 2 lines were obtained, crossed to GFP reporter mice and analyzed for GFP and cre expression. A representative line, 251, was chosen for further analysis.