A transgenic construct was generated that contained cre/ERT, beta-globin intron, LacZtag, and SV40polyA coding sequences under control of an apical ectodermal ridge (AER)-specific 520 bp Msx2 promoter. The purified construct was injected into Swiss Webster zygotes. Nine founders were generated with eight transmitting the transgene. Four expressed cre/ERT in the apical ectodermal ridge (AER). Studies were performed using one line (no. 27) that showed the strongest expression. (J:62572)