Most of exon 1 and all of exon 2 were replaced with the coding sequence for Foxj1, an IRES2-tdtomato, and an FRT flanked neo cassette. Flp mediated recombination removed the neo cassette. Expression of tdtomato is detected in the node in heterozygous embryos. Expression of Foxj1 mRNA is detected in homozygous embryos at E7.5-8.