FIGURE 2. Controls of asymmetric stem-cell division.
From the following article:
Asymmetric and symmetric stem-cell divisions in development and cancer
Sean J. Morrison and Judith Kimble
Nature 441, 1068-1074(29 June 2006)
doi:10.1038/nature04956
Three simple mechanisms are shown, but others are plausible. For molecular details, see recent reviews1, 2, 3, 4, 12, 17, 31. a, Asymmetric localization of cell polarity regulators (red) initiates the asymmetric division. Shown is asymmetric assembly of the PAR–aPKC complex at one end of the dividing cell. Stem cells are orange, differentiated cells are green. b, Cell fate determinants (red) can be segregated to the cytoplasm of one daughter cell, as shown here, or they can be associated with the membrane, centrosome or another cellular constituent that is differentially distributed to the daughters. c, Regulated orientation of the mitotic spindle retains only one daughter in the stem-cell niche (red), such that only that daughter cell has access to extrinsic signals necessary for maintaining stem-cell identity. This mechanism achieves an asymmetric outcome, even though the division itself is intrinsically symmetric. In an alternative but similar model, the daughter cell placed away from the niche is exposed to signals that induce differentiation.