RNA‐binding protein Elavl1/HuR is required for maintenance of cranial neural crest specification

Abstract

Neural crest (NC) cells are a multipotent cell population, unique to the vertebrate species, which gather at the dorsal neural tube and undergo an epithelial-to-mesenchymal transition (EMT). NC then migrate throughout the developing embryo contributing to various cell types such as craniofacial cartilage, neurons, and elements of the peripheral nervous system. While a gene regulatory network (GRN) underlies establishment of NC formation, recent studies suggest a role for post-transcriptional regulation in modulating the output of these regulatory circuits. In this study, we examined RNA-sequencing data from avian embryos at different stages of NC development and found enrichment of Elav1, a transcript encoding for the RNA-binding protein HuR. Using immunohistochemical analyses we characterized the spatiotemporal expression of HuR. We observed HuR expression following the establishment of the neural plate border and upon closure of the neural tube, with an enrichment in expression coinciding with NC formation. Using antisense morpholino oligo to perturb HuR expression, we observed loss of early neural crest specifier FoxD3 and its activator Axud1, as well as the EMT regulator Draxin. In addition, we identified several putative HuR binding sites within the predicted secondary structure of Draxin 3’UTR. RNA pulldown further showed Draxin is a specific target of HuR. Importantly, overexpression of exogenous Draxin was able to rescue NC specification defects observed in HuR knockdowns. Our results demonstrate a critical role for HuR in maintenance of cranial NC specification, at least partially via Draxin mRNA stabilization. Together, these data highlight an important intersection of post-transcriptional regulation with modulation of the neural crest specification GRN.