Syndecan-1 regulates BMP signaling and dorso-ventral patterning of the ectoderm during early Xenopus development

Abstract
Extracellular regulation of growth factor signaling is a key event for embryonic patterning. Heparan sulfate proteoglycans (HSPG) are among the molecules that regulate this signaling during embryonic development. Here we study the function of syndecan1 (Syn1), a cell-surface HSPG expressed in the non-neural ectoderm during early development of Xenopus embryos. Overexpression of Xenopus Syn1 (xSyn1) mRNA is Sufficient to reduce BMP signaling, induce chordin expression and rescue dorso-ventral patterning in ventrailized embryos. Experiments using chordin morpholinos established that xSyn1 mRNA can inhibit BM P signaling in the absence of chordin. Knockdown of xSyn1 resulted in a reduction of BMP signaling and expansion of the neural plate with the concomitant reduction of the non-neural ectoderm. Overexpression of xSyn1 mRNA in xSyn1 morphant embryos resulted in a biphasic effect, with BMP being inhibited at high concentrations and activated at low concentrations of xSyn1. Interestingly, the function of xSyn1 on dorso-ventral patterning and BMP signaling is specific for this HSPG. In summary, we report that xSyn1 regulates dorso-ventral patterning of the ectoderm through modulation of BMP signaling. (C) 2009 Elsevier Inc. All rights reserved.
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Keywords
Syndecan1, HSPG, BMP signaling, Dorso-ventral patterning, Ectoderm, Chordin, HEPARAN-SULFATE PROTEOGLYCANS, BONE MORPHOGENETIC PROTEIN-2, SPEMANN ORGANIZER, TWISTED GASTRULATION, EXTENSION MOVEMENTS, INTEGRIN ACTIVITY, AXIS FORMATION, BINDING, CHORDIN, GROWTH
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