Involvement of Frizzled-10 in Wnt-7a signaling during chick limb development

Authors

  • Yasuhiko Kawakami,

    1. Department of Molecular Biology, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan.
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    • †Present address: Gene Expression Laboratory, Salk Institute, La Jolla, CA 92037, USA.

  • Naoyuki Wada,

    1. Department of Molecular Biology, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan.
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  • Shin-ichiro Nishimatsu,

    1. Department of Molecular Biology, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan.
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  • Tsutomu Nohno

    1. Department of Molecular Biology, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan.
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    • *Author to whom all correspondence should be addressed.


Abstract

The dorsal ectoderm of the limb bud is known to regulate anterior–posterior patterning as well as dorsal– ventral patterning during vertebrate limb morphogenesis. Wnt-7a, expressed in the dorsal ectoderm, encodes a key molecule implicated in these events. In the present study, chicken frizzled-10 (Fz-10) encoding a Wnt receptor was used to study mechanisms of Wnt-7a signaling during chick limb patterning, because its expression is restricted to the posterior-distal region of the dorsal limb bud. Fz-10 transcripts colocalize with Sonic hedgehog (Shh) in the dorsal side of stages 18–23 chick limb buds. It was demonstrated that Fz-10 interacts with Wnt-7a to induce synergistically the expression of Wnt-responsive genes, such as Siamois and Xnr3, in Xenopus animal cap assays. In the chick limb bud, Fz-10 expression is regulated by Shh and a signal from the dorsal ectoderm, presumably Wnt-7a, but not by signals from the apical ectodermal ridge. These results suggest that Fz-10 acts as a receptor for Wnt-7a and has a positive effect on Shh expression in the chick limb bud.

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