A cre/ERT2-Frt-Kanamycin-Frt sequence was inserted by recombineering methods (in bacterial cells) in the first methionine position of the Aspm gene located in a BAC (BAC RP-24-26-F8). The Kana selection marker was deleted by activation of Flpe in the EL250 E.coli cells. Purified BAC DNA was injected into FVB zygotes. No founder information is available.