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Fig. 8 The strategy of stemness maintenance and expansion of hindbrain boundary cells. (A) Scheme of temporal gene expression in the boundary cell population before and after 32?hpf. (B,C) Scheme depicting transverse representations of the hindbrain boundaries before and after 32?hpf. Magnifications of cells (bottom) displaying the mechanisms of Her9 action. Before 32?hpf (B), Her9 inhibits neurogenic genes and cell cycle genes, such as cdkn1ca, keeping boundary cells as progenitors dividing symmetric proliferative. Upon her9 decline (C), Notch3/DeltaD trigger asymmetric divisions. One cell is kept as a progenitor through Notch3 activity, whereas the other cell expresses both neurogenic genes and cdkn1ca, promoting neurogenesis and cell cycle exit.