This allele is a derivative of Fgf4tm1.2Mrt where the exons 2 and 3 were removed by Cre-mediated recombination by crossing mice carrying the Fgf4tm1.2Mrt allele with mice expressing Cre recombinase under the control of a beta-actin promoter (TgNACTB-Cre)2Mrt). (J:61886)