The Interactive Fly

Evolutionarily conserved developmental pathways

Dorsal-ventral polarity - Decapentaplegic: interacting proteins, receptors and downstream targets

The regulation of dorsal-ventral polarity is controlled in the fly by Decapentaplegic, acting downstream of dorsal. DPP is required for ectodermal dorsal-ventral polarity and the subdivision of the mesoderm. In Xenopus, the DPP homolog BMP-4 inhibits two differentiation events: the induction of dorsal mesoderm (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: Chordin

Tolloid                     C. elegans: hch-1
                            Mammalian: BMP-1

Tolloid related-1 (tolkin)  C. elegans: hch-1
                            Mammalian: BMP-1


Twisted gastrulation        Xenopus: xTwisted gastrulation

Thick veins                 Mammalian: type I TGF-ß receptor

Punt                        Mammalian: type II TGF-ß receptor

Saxophone                   Mammalian: type I TGF-ß receptor

Medea                       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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