Figure 3.

Hau-gremlin is required for normal O fate in the O–P equivalence group and is a BMP2/4-specific antagonist. Panels A–D are ventral views of the germinal plate; panels E–G are dorsal views of the right germinal band.

(A) Hau-pax6a expression in the o bandlet was blocked in the right side, injected with Hau-gremlin ASMO (open arrowheads) but is normal in the left side (black arrowheads), injected with a control MO.

(B) Hau-pax6a expression in the o bandlet is rescued (compare arrowheads on left and right) by co-injecting ASMO-resistant Hau-gremlin mRNA with Hau-gremlin ASMO.

(C) Hau-pax6a expression was detected in the nominal o bandlet (black arrowheads) and the nominal p bandlet (red arrowheads) on the right side, co-injected with Hau-alk3/6^K253R mRNA (encoding a dominant negative receptor) and Hau-gremlin ASMO.

(D) Injection of Hau-alk3/6^K253R mRNA alone similarly induces ectopic Hau-pax6a expression in the p bandlet (red arrowheads) in addition to normal Hau-pax6a expression in the nominal o bandlet (black arrowheads).

(E) Misexpressing Hau-BMP2/4a, Hau-BMP2/4b or Hau-BMP5-8 in the n bandlet induced ectopic Hau-six1/2a expression in the adjacent nominal o bandlet. The differing efficacies indicate that Hau-BMP2/4a and Hau-BMP2/4b are not as efficient as Hau-BMP5-8 in inducing Hau-six1/2a expression.

(F) Ectopic Hau-six1/2a expression induced by misexpressing Hau-BMP2/4a or Hau-BMP2/4b in the n bandlet was enhanced in germinal bands containing Hau-gremlin ASMO.

(G) Injecting N teloblasts with equimolar mixtures of Hau-gremlin plus Hau-bmp2/4a or Hau-bmp2/4b failed to induce ectopic Hau-six1/2a expression in the adjacent o bandlet, but equimolar mixtures of Hau-gremlin plus Hau-bmp5-8 induced Hau-six1/2a expression in the nominal o bandlet. Scale bar, A–D: 50 µm; E–G: 30 µm.