Brachyury establishes the embryonic mesodermal progenitor niche

  1. David Kimelman1
  1. Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA

    Abstract

    Formation of the early vertebrate embryo depends on a Brachyury/Wnt autoregulatory loop within the posterior mesodermal progenitors. We show that exogenous retinoic acid (RA), which dramatically truncates the embryo, represses expression of the zebrafish brachyury ortholog no tail (ntl), causing a failure to sustain the loop. We found that Ntl functions normally to protect the autoregulatory loop from endogenous RA by directly activating cyp26a1 expression. Thus, the embryonic mesodermal progenitors uniquely establish their own niche—with Brachyury being essential for creating a domain of high Wnt and low RA signaling—rather than having a niche created by separate support cells.

    Keywords

    Footnotes

    • Received June 23, 2010.
    • Accepted November 1, 2010.
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