Apart from studying normal T cell development, disease-specific iPSCs can be generated from somatic cells (non-T cells) of patients with inherited diseases affecting the immune system such as X-linked Severe Combined Immunodeficiency (SCID-X1) with the Interleukin-2 receptor gamma chain (IL-2Rγ) mutation (51) or recombination-activating gene 1 (RAG1) mutations (52) to study abnormal T cell development in these disease models. The gene discussed is RAG1; the disease is hereditary disease.