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Fig. 6
Model of Gdf3 function in early zebrafish development.
(A) In wild-type (WT) embryos, Bmp signaling (blue) is established in a ventral-to-dorsal gradient during blastula and gastrula stages, while Nodal signaling (green) is established along the margin, with strongest expression on the dorsal side. (B) In MZgdf3 embryos, Nodal signaling is weak leading to reduced expression of Nodal target genes including the Bmp inhibitor Chordin. Bmp signaling is increased and leads to an extension of ventral mesoderm markers. However, as Nodal signaling is depleted or lost, the majority of mesoderm and endodermal cell fates fail to be maintained. (C) Proper development of Kupffer’s vesicle includes the generation of asymmetries in cell shape along the anterior-posterior axis of the structure. Anterior cells, closest to the notochord, take on columnar shapes and become more tightly packed, leading to a greater number of cilia in this region. This architecture is required for asymmetric fluid flow in KV and proper dand5 expression. (D) Attenuation of maternal Gdf3 leads to improper cell morphology during KV development, which in turn leads to irregular dand5 expression. Dysregulation of dand5 expression on the left may then inhibit spaw in the left LPM. (E) Removal of Nodal antagonists Lefty1 and Dand5 via ntla morpholino-mediate knockdown does not restore spaw expression in the LPM. This suggests that Gdf3 plays a more direct role in regulating spaw expression, independent of its effects on KV development. Dotted lines (C, D, E) represent lost gene expression.