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Transgenic Xenopus Embryos Reveal That Anterior Neural Development Requires Continued

Summary: Transgenic Xenopus Embryos Reveal That Anterior
Neural Development Requires Continued
Suppression of BMP Signaling after Gastrulation
Katharine O. Hartley,* Zoše Hardcastle, Rosalind V. Friday,*
Enrique Amaya,*,1
and Nancy Papalopulu,1
*Department of Zoology and Department of Anatomy, Wellcome/CRC Institute, University
of Cambridge, Tennis Court Road, Cambridge CB2 1QR, United Kingdom
In vertebrates, BMP signaling before gastrulation suppresses neural development. Later in development, BMP signaling
specifies a dorsal and ventral fate in the forebrain and dorsal fate in the spinal cord. It is therefore possible that a change in
the competence of the ectoderm to respond to BMP signaling occurs at some point in development. We report that exposure
of the anterior neural plate to BMP4 before gastrulation causes suppression of all neural markers tested. To determine the
effects of BMP4 after gastrulation, we misexpressed BMP4 using a Pax-6 promoter fragment in transgenic frog embryos and
implanted beads soaked in BMP4 in the anterior neural plate. Suppression of most anterior neural markers was observed.
We conclude that most neural genes continue to require suppression of BMP signaling into the neurula stages. Additionally,
we report that BMP4 and BMP7 are abundantly expressed in the prechordal mesoderm of the neurula stage embryo. This
poses the paradox of how the expression of most neural genes is maintained if they can be inhibited by BMP signaling. We
show that at least one gene in the anterior neural plate suppresses the response of the ectoderm to BMP signaling. We
propose that the suppressive effect of BMP signaling on the expression of neural genes coupled with localized suppressors
of BMP signaling result in the fine-tuning of gene expression in the anterior neural plate. © 2001 Academic Press


Source: Amaya, Enrique - Healing Foundation Centre & Developmental Biology, Faculty of Life Sciences, University of Manchester


Collections: Biology and Medicine