RTT iPSCs expressed pluripotency markers Sox2, Oct4, Tra1-60, and Tra1-81 and maintained hESC-like morphology upon passaging for at least 42 passages with normal karyotype (46, XX), and were pluripotent as indicated by teratoma formation (Figs. 1B, S1A and S1B). The gene discussed is SOX2; the disease is teratoma.