Do principles of control define a unique class of cells?
The fact that so many characteristic behaviors of stem cells and stem cell systems – homeostasis in the face of the production of differentiated progeny; rapid tissue regeneration; developmental expansion; self-regulation; and niche dependence – emerge simply as a result of feedback regulation of self-renewal suggests that the ability to be regulated by such feedback might serve as a good defining characteristic of stemness. Alas, we have no such luck here. As it happens, cells that are not considered stem cells also show this behavior, namely the so-called ‘transit-amplifying cells’ that lie downstream of stem cells in tissue lineages, and are distinguished by an apparently limited potential for self-renewal. For example, in the olfactory epithelium, qualitatively similar feedback effects are mediated by two different TGFβ family members upon the stem cell and its molecularly distinct descendant, respectively [7]. That descen dant, the immediate neuronal progenitor, behaves like a typ
Related Questions
- What group of people joined together on the basis of common principles, who seek to control government and public policy?
- Can the Access Control Lists (ACLs) or class maps be used to define the traffic that needs to be rate-limited or shaped?
- Can I/O cells be reconfigured in a way that ensures that the status of the pin is always under control?
