Targeting strategy for disruption of the Tefm gene. LoxP sites flanking exon 2 of the Tefm gene together with puromycin selection marker (PuroR) were inserted into the mouse genome by homologous recombination. The PuroR cassette was excised by mating with Flp-recombinase mice to obtain heterozygous floxed Tefm mice (Tefm+/loxP). Whole-body and tissue-specific Tefm knockout mice were obtained by crossing Tefm+/loxP with different Cre-recombinase mice. 