Stem cells and morphogenesis

Stem cells (SCs) can self‐renew and to differentiate along multiple lineages to generate different tissues. In the embryo, multipotent SCs respond to various cues to undergo morphogenesis and produce these tissues. For tissues to function, cells must orient themselves and interact with their neighbors. The skin is an excellent model to explore how an undifferentiated SC generate 3 functional tissues: epidermis, sebaceous gland and hair follicles. Embryonic skin begins as a single layer of multipotent SCs, which adhere to each other and to an underlying basement membrane rich in extracellular matrix. Both cell‐cell and cell‐substratum interactions are essential for the epidermis to form. As development proceeds, these SCs respond to key signals, including Wnts, Bmps, Shh, Notch and Fgfs, to either stratify to produce epidermis or grow downward to generate hair follicles. Basal cells remaining in contact with the basement membrane maintain proliferative potential, while suprabasal cells that are removed from their substratum differentiate. We've begun to dissect how extrinsic signaling to SCs sets off a cascade of changes in transcription that govern cell fate decisions, cell‐cell and cell substratum remodeling, stratification and tissue morphogenesis. When this process is defective, cells fail to integrate morphogenetic signals and polarize the cytoskeleton, resulting in tissue dysfunction.