As the candidate gene mutations responsible for strain-specific phenotypes, we detected 24 deleterious mutations specific to a single SAMP strain, including the Il4ra p.S540fs frameshift mutation in SAMP6/TaSlc, which is used as a model for osteoporosis, and the Aifm3 p.K582N mutation in SAMP8/TaSlc mice, which display deficits in learning and memory and mitochondrial dysfunction. The gene discussed is XPNPEP1; the disease is osteoporosis.