Searching for naïve human pluripotent stem cells

Figure 1 First two cell segregations during preimplatation embryonic development. A: In blue, cells from the inner cell mass (ICM) in the early blastocyst, and white, cells from the trophectoderm; B: At the late blastocyst stage, cells from the ICM segregate into cells from the epiblast (green) and the primitive endoderm (orange).

Figure 2 Maintenance of pluripotency by leukemia inhibitory factor and small molecules. Green arrows indicate activation, red blunted lines indicate inhibition. The pluripotent cell must self-renew without committing to any specific cell type. This may be achieved by promoting self-renewal and inhibiting commitment by LIF; or by small molecules (in italic) which inhibit (1) signaling through the FGF receptor tyrosine kinase, thus inhibiting commitment; and (2) GSK3, promoting self-renewal. Adapted from[33]. LIF: Leukemia inhibitory factor; FGFr: Fibroblast growth factor receptor-specific tyrosine kinase; GSK3: Glycogen synthase kinase 3; MEK: Mitogen-activated protein kinase.