miR-133a-3p and miR-338-3p shape neural crest derivatives in zebrafish

Neural crest cells are a transient, multipotent population that gives rise to diverse structures during vertebrate embryonic development, including craniofacial cartilage and pigment cells. Although the transcriptional regulation of neural crest development is well characterized, the role of microRNAs remains less understood. Using a double-transgenic zebrafish model expressing fluorescent reporters under the sox10 promoter, combined with fluorescence-activated cell sorting and RNA sequencing, we identified microRNAs enriched in neural crest cells. We focused on miR-133a-3p and miR-338-3p, previously linked to tumor suppression, to explore their developmental roles. The overexpression of either microRNA led to craniofacial cartilage malformations and reduced melanophore number, accompanied by decreased expression of key regulators including sox9b, sox10, and runx3 Reporter assays confirmed direct targeting of the sox9b 3'untranslated region. In addition, miR-338-3p overexpression increased neural crest cell numbers, suggesting a role in proliferation. These findings uncover novel functions for miR-133a-3p and miR-338-3p in vertebrate craniofacial and pigment cell development, highlighting shared regulatory features between embryogenesis and tumorigenesis.