Characterization of Pumilio gene expression during early neural crest development.

Neural crest cells are multipotent cells present in vertebrate embryos that give rise to a wide array of cell types and tissues. A growing number of studies have identified post-transcriptional regulatory events that are essential for multiple stages of neural crest development, though a thorough characterization of the post-transcriptional regulators controlling these events is currently lacking. From single cell RNA-sequencing data, we identified members of the Pumilio family of RNA-binding proteins, PUM1 and PUM2, as candidate post-transcriptional regulators of neural crest development. Using hybridization chain reaction (HCR) in avian embryos (Gallus gallus), we characterized the spatiotemporal expression of Pumilio family mRNAs during early stages of cranial neural crest development. We show that Pum1 and Pum2, though expressed throughout the three germ layers, were enriched in ectodermally-derived tissues, and following neurulation, Pum1 and Pum2 show distinct expression patterns. We observed that Pum1 displayed a more uniform expression throughout the neural tube and neural crest during neural crest specification and the epithelial-mesenchymal transition (EMT). In contrast, Pum2 was enriched in neural crest cells poised to undergo EMT. We thus hypothesize that PUM1 and PUM2, often speculated to be functionally redundant, may play distinct roles at key steps of neural crest development.