Xenopus XsalF: anterior neuroectodermal specification by attenuating cellular responsiveness to Wnt signaling |
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Authors: | Onai Takayuki Sasai Noriaki Matsui Masaru Sasai Yoshiki |
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Affiliation: | Organogenesis and Neurogenesis Group, Center for Developmental Biology, RIKEN, Kobe 650-0047, Japan. |
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Abstract: | Here we show that XsalF, a frog homolog of the Drosophila homeotic selector spalt, plays an essential role for the forebrain/midbrain determination in Xenopus. XsalF overexpression expands the domain of forebrain/midbrain genes and suppresses midbrain/hindbrain boundary (MHB) markers and anterior hindbrain genes. Loss-of-function studies show that XsalF is essential for the expression of the forebrain/midbrain genes and for the repression of the caudal genes. Interestingly, XsalF functions by antagonizing canonical Wnt signaling, which promotes caudalization of neural tissues. XsalF is required for anterior-specific expressions of GSK3beta and Tcf3, genes encoding antagonistic effectors of Wnt signaling. Loss-of-function phenotypes of GSK3beta and Tcf3 mimic those of XsalF while injections of GSK3beta and Tcf3 rescue loss-of-function phenotypes of XsalF. These findings suggest that the forebrain/midbrain-specific gene XsalF negatively controls cellular responsiveness to posteriorizing Wnt signals by regulating region-specific GSK3beta and Tcf3 expression. |
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