The commonly used immunodeficient mice are athymic nude mice, severe combined immune deficiency (SCID) mice, non-obese diabetes–severe combined immune deficiency (NOD-SCID) mice, and NOD-PrkdcscidIL2rgnull mice, such as NOD.Cg-PrkdcscidIl2rgtm1Sug/ShiJic mouse (NOG) and NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ mouse (NSG). The gene discussed is CTSG; the disease is diabetes mellitus.