Abstract
One of the earliest events in neural crest development takes place at the neural plate border and consists in the induction of Pax3 expression by posteriorizing Wnt·β-catenin signaling. The molecular mechanism of this regulation is not well understood, but several observations suggest a role for posteriorizing Cdx transcription factors (Cdx1/2/4) in this process. Cdx genes are known as integrators of posteriorizing signals from Wnt, retinoic acid, and FGF pathways. In this work, we report that Wnt-mediated regulation of murine Pax3 expression is indirect and involves Cdx proteins as intermediates. We show that Pax3 transcripts co-localize with Cdx proteins in the posterior neurectoderm and that neural Pax3 expression is reduced in Cdx1-null embryos. Using Wnt3a-treated P19 cells and neural crest-derived Neuro2a cells, we demonstrate that Pax3 expression is induced by the Wnt-Cdx pathway. Co-transfection analyses, electrophoretic mobility shift assays, chromatin immunoprecipitation, and transgenic studies further indicate that Cdx proteins operate via direct binding to an evolutionarily conserved neural crest enhancer of the Pax3 proximal promoter. Taken together, these results suggest a novel neural function for Cdx proteins within the gene regulatory network controlling neural crest development.
Highlights
Cdx transcription factors are known to convey the posteriorizing signals from the canonical Wnt pathway
We found that murine Pax3 is an indirect Wnt target and that Cdx proteins can directly activate neural Pax3 expression at least via the previously described NCE2 [13]
Pax3 Neural Expression Is Regulated by Cdx Proteins—To determine whether Pax3 is a Cdx target gene, we evaluated its expression in e8.5 Cdx1-null embryos
Summary
Cdx transcription factors are known to convey the posteriorizing signals from the canonical Wnt pathway. Co-transfection analyses, electrophoretic mobility shift assays, chromatin immunoprecipitation, and transgenic studies further indicate that Cdx proteins operate via direct binding to an evolutionarily conserved neural crest enhancer of the Pax proximal promoter Taken together, these results suggest a novel neural function for Cdx proteins within the gene regulatory network controlling neural crest development. Cdx gene expression is regulated by posteriorizing signals from Wnt, retinoic acid (RA), and fibroblast growth factor (FGF) pathways in multiple species [27,28,29,30,31,32,33,34,35,36,37,38]. Our data strengthen the idea that Cdx members are involved in both NT and NCC development in a tissue-autonomous manner downstream of Wnt signals
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