Map2k1^{tm1(Map2k1,Map2k2)Chrn}

A cDNA of Map2k1 (tagged with Myc and flanked by loxP sites), an frt-flanked neomycin selection cassette, and a cDNA of Map2k2 were inserted into the first exon of Mek1. Western blot analysis showed that both endogenous Map2k1 protein and the Myc-tagged Map2k1 protein are expressed in heterozygous embryonic stem (ES) cells. (J:258488)