Cre-mediated recombination removed the floxed exon 2 in Dnaja3tm1Jdl, creating a frame-shift that putatively disrupted translation of the Dnaj domain, a glycine-and phenylalanine-rich region, a systein-rich part resembling a zinc finger, and a nonhomologous C-terminal domain. Western blot of mutant MEFs demonstrated that protein production was abolished.