Pronodal acts via FGFR3 to govern duration of Shh expression in the prechordal mesoderm

Pamela S. Ellis, Sarah Burbridge, Sandrine Soubes, Kyoji Ohyama, Nadav Ben-Haim, Canhe Chen, Kim Dale, Michael M. Shen, Daniel Constam, Marysia Placzek (Lead / Corresponding author)

    Research output: Contribution to journalArticlepeer-review

    11 Citations (Scopus)
    137 Downloads (Pure)

    Abstract

    The secreted glycoprotein sonic hedgehog (Shh) is expressed in the prechordal mesoderm, where it plays a crucial role in induction and patterning of the ventral forebrain. Currently little is known about how Shh is regulated in prechordal tissue. Here we show that in the embryonic chick, Shh is expressed transiently in prechordal mesoderm, and is governed by unprocessed Nodal. Exposure of prechordal mesoderm microcultures to Nodal-conditioned medium, the Nodal inhibitor CerS, or to an ALK4/5/7 inhibitor reveals that Nodal is required to maintain both Shh and Gsc expression, but whereas Gsc is largely maintained through canonical signalling, Nodal signals through a non-canonical route to maintain Shh. Further, Shh expression can be maintained by a recombinant Nodal cleavage mutant, proNodal, but not by purified mature Nodal. A number of lines of evidence suggest that proNodal acts via FGFR3. ProNodal and FGFR3 co-immunoprecipitate and proNodal increases FGFR3 tyrosine phosphorylation. In microcultures, soluble FGFR3 abolishes Shh without affecting Gsc expression. Further, prechordal mesoderm cells in which Fgfr3 expression is reduced by Fgfr3 siRNA fail to bind to proNodal. Finally, targeted electroporation of Fgfr3 siRNA to prechordal mesoderm in vivo results in premature Shh downregulation without affecting Gsc. We report an inverse correlation between proNodal-FGFR3 signalling and pSmad1/5/8, and show that proNodal-FGFR3 signalling antagonises BMPmediated pSmad1/5/8 signalling, which is poised to downregulate Shh. Our studies suggest that proNodal/FGFR3 signalling governs Shh duration by repressing canonical BMP signalling, and that local BMPs rapidly silence Shh once endogenous Nodal-FGFR3 signalling is downregulated.

    Original languageEnglish
    Pages (from-to)3821-3832
    Number of pages12
    JournalDevelopment
    Volume142
    Issue number22
    Early online date28 Sept 2015
    DOIs
    Publication statusPublished - 15 Nov 2015

    Keywords

    • BMP
    • Forebrain ventral midline
    • Nodal
    • Prechordal mesoderm
    • Sonic hedgehog

    ASJC Scopus subject areas

    • Developmental Biology
    • Molecular Biology

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