Tsg was identified in Drosophila as being required to specify the dorsal-most structures in the embryo, for example amnioserosa. Biochemical experiments have revealed three key properties of Tsg: it can synergistically inhibit Dpp/BMP action in both Drosophila and vertebrates by forming a tripartite complete between itself, SOG/chordin and a BMP ligand; Tsg seems to enhance the Tld/BMP-1-mediated cleavage rate of SOG/chordin and may change the preference of site utilisation; Tsg can promote the dissociation of chordin cysteine-rich-containing fragments from the ligand to inhibit BMP signalling [1,2].

1: Dorsal midline fate in Drosophila embryos requires twisted gastrulation, a gene encoding a secreted protein related to human connective tissue growth factor. Mason ED, Konrad KD, Webb CD, Marsh JL; Genes Dev 1994;8:1489-1501. PMID:7958834

2: Twisted gastrulation is a conserved extracellular BMP antagonist. Ross JJ, Shimmi O, Vilmos P, Petryk A, Kim H, Gaudenz K, Hermanson S, Ekker SC, O'Connor MB, Marsh JL; Nature 2001;410:479-483. PMID:11260716