A targeting construct was made containing exon 3 of the mitogen-activated protein kinase 8 interacting protein 1 (Mapk8ip1 or Jip1) gene. Codon 103 in exon 3 was mutated from a Threonine (ACT) to an Alanine (GCC) (T103A), and a loxP-flanked neomycin (neo) resistance cassette was placed downstream of exon 3. Cre mediated recombination removed the neo cassette.