Fig. 5 S1

Notch signaling regulates proneuromast formation downstream of the MAPK pathway and shroom3 is dispensable for rosette formation.

(A–B') MAPK is required to maintain di-pERK1/2 expression in the primordium. (B') The MAPK inhibitor PD0325901 leads to a strong reduction of di-pERK1/2 expression. PD0325901 downregulates the Fgf targets pea3 (C–C'), fgfr1 (D–D'), notch3 (E–E') and the Notch target her4 (F–F'). (G–I) Loss of shroom3 by induction of DNshroom3 using the cldnb promoter does not disrupt proneuromast formation (H) or maintenance of deposited neuromasts (I). (J) shroom1 is expressed in the trailing region of the wildtype primordium, is downregulated in NICD (J') and highly upregulated in mib1^ta52b primordia (J'') showing that shroom1 is inhibited by Notch signaling. shroom2a expression is also inhibited by Notch signaling. shroom2a expression is barely detectable in wildtype (K) and NICD (K) primordia but upregulated in mib1^ta52b primordia. We currently do not understand why shroom genes are upregulated in mib1 primordia, as at least shroom3 is regulated by Fgf. All scale bars are 25 μm.