High impact information on scw

• We propose that the use of broadly distributed Dpp homodimers and spatially restricted Dpp/Scw heterodimers produces the biphasic signal that is responsible for specifying the two dorsal tissue types [1].
• Facilitated transport of a Dpp/Scw heterodimer by Sog/Tsg leads to robust patterning of the Drosophila blastoderm embryo [1].
• Although scw is expressed uniformly during blastoderm stages, its effect on development appears graded and is restricted to the dorsal side of the embryo [2].
• From this stage onward, activation by Scw is no longer required, and Dpp suffices to induce high levels of pMad [3].
• This demonstrates that Mad phosphorylation requires simultaneous activation by Scw and Dpp [3].

Biological context of scw

• These studies suggest that the Dpp/Scw activity gradient directly specifies at least three distinct thresholds of gene expression in the dorsal ectoderm of gastrulating embryos [4].
• Direct visualisation in the Drosophila embryo of Sog, a Dpp/Scw inhibitor, has now revealed a graded distribution established by degradation and endocytosis [5].
• This prevents Dpp/Screw from initiating a signal transduction event in the receiving cell [6].

Regulatory relationships of scw

• It appears that a major function of dCBP in the embryo is to regulate upstream components of the Dpp/Screw pathway by Smad-independent mechanisms, as well as acting as a Smad coactivator on downstream target genes [6].

Other interactions of scw

• Drosophila Tbx6-related gene, Dorsocross, mediates high levels of Dpp and Scw signal required for the development of amnioserosa and wing disc primordium [7].
• Smad proteins, the intracellular transducers of the signal, fail to become activated by phosphorylation in dCBP mutants, leading to diminished Dpp/Screw-target gene expression [6].
• We further show that Screw, a second BMP2/4-related gene product, Tolloid, a BMP1-related protein, and the zinc finger-containing protein Schnurri, are required to allow full levels of tinman induction during this process [8].

References