The following sequence was inserted into intron 5: a loxP site, an FRT site flanked neomycin resistance gene cassette, the 3' end of Map3k7 intron 5, Map3k7 exons 6-17 cDNA, human GH poly(A) signal sequences, and an F3 site flanked puromycin resistance gene cassette. Exon 6 was replaced with a version carrying a mutation changing aspartic acid codon 175 (GAT) to alanine (GCT) (p.D175A). The neo and puro cassettes were removed through subsequent Flp-mediated recombination. This allele will express the wild-type peptide from the inserted mini-gene unless conditional Cre-mediated deletion removes the mini-gene, in which case the peptide with the D175A mutation will be expressed. The mutation renders the peptide kinase-dead.