Pumilio Regulates the Epithelial-Mesenchymal Transition and Gastrulation During Zebrafish Development
Damoulis, Vanessa Ann
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The pumilio family of RNA binding proteins act as translational repressors to control developmental patterning events of invertebrates, germline stem cell maintenance, and neuronal growth through deadenylation, inhibition of translational elongation, and allow access of microRNAs to their targets. pumilio proteins have yet to be identified and functionally characterized in the zebrafish, Danio rerio. Here, three putative pumilio homologs in zebrafish are identified by their characteristic PUF (pumilio and FBF) binding domains and found to be expressed during early development and enriched in the immature oocytes of the adult ovary. Loss of each homolog results in developmental defects, arising from improper formation of the shield and dorsal organizer structures during the first steps of gastrulation. Gastrulation events necessitate both proper patterns of gene signaling and cell motility, as gained by epithelial-to-mesenchymal transitions (EMT), to occur. In pum1 morphants, both the presentation of wild-type signaling gradients and EMT events are inhibited. Through in silico and in vivo analysis, acvr1b, an Activin receptor, was identified as a target for pum1. acvr1b assists in patterning the gastrulating embryo and, through control of miR-200a expression, inhibits EMT events. Thus, pum1 through its direct translational repression of acvr1b is able to modulate levels of miR-200a and control both patterning and EMT events in the early vertebrate embryo.