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Development 2003 Oct 01;13020:4919-29. doi: 10.1242/dev.00706.
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Glypican 4 modulates FGF signalling and regulates dorsoventral forebrain patterning in Xenopus embryos.

Galli A , Roure A , Zeller R , Dono R .

Heparan sulphate proteoglycans such as glypicans are essential modulators of intercellular communication during embryogenesis. In Xenopus laevis embryos, the temporal and spatial distribution of Glypican 4 (Gpc4) transcripts during gastrulation and neurulation suggests functions in early development of the central nervous system. We have functionally analysed the role of Xenopus Gpc4 by using antisense morpholino oligonucleotides and show that Gpc4 is part of the signalling network that patterns the forebrain. Depletion of GPC4 protein results in a pleiotropic phenotype affecting both primary axis formation and early patterning of the anterior central nervous system. Molecular analysis shows that posterior axis elongation during gastrulation is affected in GPC4-depleted embryos, whereas head and neural induction are apparently normal. During neurulation, loss of GPC4 disrupts expression of dorsal forebrain genes, such as Emx2, whereas genes marking the ventral forebrain and posterior central nervous system continue to be expressed. This loss of GPC4 activity also causes apoptosis of forebrain progenitors during neural tube closure. Biochemical studies establish that GPC4 binds FGF2 and modulates FGF signal transduction. Inhibition of FGF signal transduction, by adding the chemical SU5402 to embryos from neural plate stages onwards, phenocopies the loss of gene expression and apoptosis in the forebrain. We propose that GPC4 regulates dorsoventral forebrain patterning by positive modulation of FGF signalling.

PubMed ID: 12930779
Article link: Development

Species referenced: Xenopus laevis
Genes referenced: egr2 emx2 fgf2 fgf8 foxg1 gpc1 gpc4 gsc hoxb9 hoxc9-like mapk1 myc nkx2-1 nog otx2 smad1 sox2 tbx2 tbxt tub uqcc6
Morpholinos: gpc4 MO2

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