Fig. 16.5.

Model for regulation of cell division and fate specification by SHH in the cerebellum. In the cerebellum, GNPs can divide so that their spindles are parallel to the pial surface (left of dashed line) or perpendicular to the pial surface (right). (a) During a parallel division, both daughter cells are exposed to the same level of SHH (blue circles) and retain their GNP fate, resulting in a nonterminal SCD (green cells). In the absence of SHH, both daughter cells undergo a fate change, causing terminal SCD (yellow cells). (b) During a perpendicular division, SHH is exposed locally to one daughter cell and not the other, resulting in an ACD that produces daughter cells with different cell fates (yellow versus green)