Nanog is a member of the homeobox family of DNA binding transcription factors and has been shown to maintain embryonic stem (ES) cell self-renewal independently of leukemia inhibitory factor (LIF)/Stat3. Nanog mRNA is present in pluripotent mouse and human cell lines, and absent from differentiated cells. Functionally, Nanog works together with other key pluripotent factors (Oct4, Sox2, and Lin28) to reprogram human fibroblasts and generate induced pluripotent stem (iPS) cells. These key factors form a regulatory network to support or limit each other's expression level, which maintains the properties of ES cells. Affinity purified rabbit anti-Nanog can be used to demonstrate pluripotency of ES and IPS cells. There are two kinds of variants could recognized by NANOG, one is normal form (~39kd), the other is post-translation modified form (~48kd) (21136380 ). Nanog exists two isoforms with molecular weight 34.4 kDa and 31.9 kDa. (PMID: 21969378)