Increasing Hif-2α expression by generating Hif-2α knockin mice was reported to enhance expression of the pluripotent transcription factor Oct-4 through direct promoter binding, whereas the loss of Hif-2α results in a severe deficiency of embryonic PGCs in the genital ridge (Covello et al., 2006) and subsequent azoospermia (Scortegagna et al., 2005). The gene discussed is EPAS1; the disease is Azoospermia.