Outside the niche, stem cells differentiate

because the absence of signals lead to differentiation, stem cells hard to propagate

what are the signals how is range controled

�the intrinsic state of the cell (stem-ness)

�outside signals

�Self-renewing signals: very complex

1. inhibit differentiation

2. control proliferation

3. are local and niches have a limited capacity

4. include the main developmental pathways: Notch, Hedgehog, BMP, FGF and Wnt