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Fig. 4
Inhibition of Wnt Signaling Prevents Regeneration of Hair Cells
(A–D) Regeneration of hair cells in normal embryos. New hair cells are regenerated within 24 hr after ablation.
(E–H) In dkk2-overexpressing embryos, where Wnt signaling is inhibited, new hair cells never form (G and H). Scale bar in (E) represents 20 μm.
(I) Proposed mechanism for neuromast size control, based on a regulatory network comprising a negative feedback step.
(J) Sequence of events leading to homeostasis in the case of budding of a new neuromast and in the case of hair cell regeneration. Large circles indicate neuromasts; smaller circles indicate hair cells. Wnt signaling (green) is active whenever Dkk (red) is absent. dkk2 mRNA (orange) is expressed in differentiating and mature hair cells. Dkk2 protein (red) secreted by the hair cells reaches the peripheral cells and inhibits Wnt signaling (i.e., cell proliferation). The size of neuromasts is maintained during both budding and regeneration.
See also Figure S4.