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Presenting Author(s) Tsutomu Nohno
Abstract Title Wnt3a and Wnt10a involved in AER formation in the chick limb bud.
Full author List Tsutomu Nohno, Tomohiro Narita, Shunsuke Sasaoka,Kiyoshi Udagawa
Text of abstract Members of the Wnt family are known to participate in limb morphogenesis through different signaling activity. Wnt5a, Wnt11, Wnt7a, and Wnt3a show region specific expression in the developing limb, and have differential effects on limb chondrogenesis and myogenesis. Wnt3a was indicated to play a role in induction and maintenance of the apical ectodermal ridge of the chick limb bud, since Wnt3a is expressed in the presumptive limb ectoderm before FGF8 expression, and induced in the non-limb ectoderm by FGF10, in addition to the fact that mouse Wnt3a could induce AER when misexpressed in the chick limb bud. However, the chicken Wnt3a is unable to induce FGF8 when misexpressed in the limb ectoderm. In contrast to the mouse Wnt3a, chicken Wnt3a lacks typical signal peptide sequence in the N-terminal region that is required for efficient extracellular secretion. Chicken Wnt3a has poor activity to accumulate b-catenin in CEF compared to mouse Wnt3a. Wnt10a is expressed intensely in the AER and weakly in the non-ridge limb ectoderm. Overexpression of Wnt10a resulted in ectodermal expansion of FGF8 expression outside of the AER, through b-catenin accumulation in the cytoplasmic fraction, as demonstrated by Western blotting. Chimeric analysis has indicated identical activity between the mouse and chicken Wnt3a within the mature region of the peptide. These results suggest that Wnt10a, but not Wnt3a, is involved in FGF8 expression in the chick AER through b-catenin signaling pathway.
Which session is your work most relevant to: Limb initiation