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Bioessays 2024 Jan 01;461:e2300179. doi: 10.1002/bies.202300179.
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The early dorsal signal in vertebrate embryos requires endolysosomal membrane trafficking.

Azbazdar Y , De Robertis EM .

Fertilization triggers cytoplasmic movements in the frog egg that lead in mysterious ways to the stabilization of β-catenin on the dorsal side of the embryo. The novel Huluwa (Hwa) transmembrane protein, identified in China, is translated specifically in the dorsal side, acting as an egg cytoplasmic determinant essential for β-catenin stabilization. The Wnt signaling pathway requires macropinocytosis and the sequestration inside multivesicular bodies (MVBs, the precursors of endolysosomes) of Axin1 and Glycogen Synthase Kinase 3 (GSK3) that normally destroy β-catenin. In Xenopus, the Wnt-like activity of GSK3 inhibitors and of Hwa mRNA can be blocked by brief treatment with inhibitors of membrane trafficking or lysosomes at the 32-cell stage. In dorsal blastomeres, lysosomal cathepsin is activated and intriguing MVBs surrounded by electron dense vesicles are formed at the 64-cell stage. We conclude that membrane trafficking and lysosomal activity are critically important for the earliest asymmetries in vertebrate embryonic development.

PubMed ID: 37983969
Article link: Bioessays
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: axin1 bmp4 cer1 chrd ctnnb1 dkk1 frzb frzb2 gdf1 hwa lrp6 nodal nodal1 nodal6 nog tnfsf10 vegt wnt11b wnt8a
GO keywords: multivesicular body [+]

Phenotypes: Xla Wt + hwa (Fig. 4 B, E) [+]

Article Images: [+] show captions