Targeting the GDF-15 gene and generation of GDF-15-/-lacZknockin mice. a, Structure of the GDF-15 gene and strategy for disrupting its structure. b and c, Southern blot and PCR analysis of tail DNA derived from the progeny of heterozygous mutant mice showing genotypes of wild-type, heterozygous, and GDF-15 deficient mice. d, Western blot analysis of kidney protein extract from all genotypes tested with a peptide antibody against GDF-15 confirms the absence of GDF-15 in the knockout mice and a gene-dosage effect of reduced protein levels in heterozygous mice. Five ng of recombinant GDF-15 was used as a control.