Practice question

Cortical rotation generates aligned microtubule tracks between vegetal pole and future dorsal side allowing kinesin-directed transport of membrane-associated proteins and mRNAs. Critical cargo includes Dishevelled protein, Wnt11 mRNA and glycogen synthase kinase binding protein that inhibits GSK3 locally. Accumulation dorsally results in local stabilization of beta-catenin which then enters nuclei of dorsal vegetal and marginal blastomeres forming Nieuwkoop center. BMP and noggin not transported dorsally in this cytoskeletal event, FGF more uniform. Therefore molecule accumulating dorsally during rotation is beta-catenin via upstream regulators. This illustrates conserved developmental logic of morphogen gradients patterning embryonic axes through Wnt and BMP antagonism.