The Interactive Fly
Evolutionarily conserved developmental pathways
The regulation of dorsal-ventral polarityis controlled in the fly by Decapentaplegic, acting downstream of dorsal.DPP is required for ectodermal dorsal-ventral polarity and the subdivisionof the mesoderm. In Xenopus, the DPP homolog BMP-4 inhibits two differentiationevents: the induction of dorsalmesoderm (Spemann's organizer) and the dorsalization of ventral mesoderm.BMP-4 knockout mice show no mesoderm formation.
In spite of their phylogenetically conserved function, the maternal mechanisms by which sog and dpp are activated in abutting territories in fly embryos (i. e., direct transcriptional threshold responses to the Dorsal morphogen gradient) appear to differ fundamentally from those leading to the complementary activation of chordin and BMP-4 in frog embryos (i.e., Wnt and Activin-like induction of goosecoid expression in the Spemann organizer leading to chordin expression dorsally, and FGF plus a low Activin-like signal inducing BMP-4 expression ventrally). In contrast, once the primary zygotic response genes sog/chordin and dpp/BMP-4 are expressed in abutting territories, they specify neural vs. non-neural ectoderm through a highly conserved mechanism. SOG functions by preventing DPP from autoactivating (reinforcing its own expression). How does SOG function as a DPP antagonist? As Chordin has been shown to bind BMP-4 with high affinity, the mechanism of Chordin/Sog function may be to bind and sequester BMP-4/DPP in an inactive form (See SOG for references).
Drosophila Homologs in other species ---------- -------------------Decapentaplegic Xenopus: BMP4 Mammals: BMP2 and BMP4 Short gastrulation Xenopus: ChordinTolloid C. elegans: hch-1 Mammalian: BMP-1Tolloid related-1 (tolkin) C. elegans: hch-1 Mammalian: BMP-1Twisted gastrulation Xenopus: xTwisted gastrulationThick veins Mammalian: type I TGF-ß receptorPunt Mammalian: type II TGF-ß receptorSaxophone Mammalian: type I TGF-ß receptorMedea C. elegans: Sma-4 Xenopus: XSMad1 Human: SMad4, also known as DPC4 Mothers against DPP C. elegans: Sma-1, Sma-2 and Sma-3 Xenopus: XMad1 and XMad2 Human: MadR1, DPC4, hMAD3 and hMAD4
date revised: 13 Oct 96
Developmental Pathways conserved in Evolution
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