Practice question

Dishevelled protein acts as key adaptor upstream of beta-catenin in Wnt pathway hierarchy. In sea urchin oocytes before fertilization, Dishevelled protein and mRNA are anchored to vegetal cortex via interactions with actin-associated proteins, cortically localized vesicles, and cytoskeletal scaffolds. This pre-fertilization localization establishes asymmetry inherited by micromeres after fourth unequal cleavage. Vegetal cortical Dishevelled locally inhibits GSK-three, permitting beta-catenin accumulation vegetally and activating endomesoderm genes. If Dishevelled were localized animally or in blastocoel, vegetal specification would fail, animalizing embryo and altering endomesoderm patterning strongly.