Structural and functional evidence for a singular repertoire of BMP receptor signal transducing proteins in the lophotrochozoan Crassostrea gigas suggests a shared ancestral BMP/activin pathway

• Published in: FEBS Journal
• Main Authors: Herpin, Amaury, Lelong, Christophe, Becker, Thomas, Rosa, Frederic, Favrel, Pascal, Cunningham, Charles
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2005
• Subjects: Crassostrea gigas
• Online Access: http://dx.doi.org/10.1111/j.1742-4658.2005.04761.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1742-4658.2005.04761.x; https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1742-4658.2005.04761.x

The transforming growth factor β (TGF‐β) superfamily includes bone morphogenetic proteins, activins and TGF‐β sensu stricto ( s.s ). These ligands, which transduce their signal through a heteromeric complex of type I and type II receptors, have been shown to play a key role in numerous biological processes including early embryonic development in both deuterostomes and ecdyzozoans. Lophochotrozoans, the third major group of bilaterian animals, have remained in the background of the molecular survey of metazoan development. We report the cloning and functional study of the central part of the BMP pathway machinery in the bivalve mollusc Crassostrea gigas ( Cg‐ BMPR1 type I receptor and Cg‐ TGFβsfR2 type II receptor), showing an unusual functional mode of signal transduction for this superfamily. The use of the zebrafish embryo as a reporter organism revealed that Cg‐ BMPR1, Cg‐ TGFβsfR2, Cg‐ ALR I, an activin Type I receptor or their dominant negative acting truncated forms, when overexpressed during gastrulation, resulted in a range of phenotypes displaying severe disturbance of anterioposterior patterning, due to strong modulations of ventrolateral mesoderm patterning. The results suggest that Cg‐ BMPR1, and to a certain degree Cg‐ TGFβsfR2 proteins, function in C. gigas in a similar way to their zebrafish orthologues. Finally, based on phylogenetic analyses, we propose an evolutionary model within the complete TGF‐β superfamily. Thus, evidence provided by this study argues for a possible conserved endomesoderm/ectomesoderm inductive mechanism in spiralians through an ancestral BMP/activin pathway in which the singular, promiscuous and probably unique Cg‐ TGFβsfR2 would be the shared type II receptor interface for both BMP and activin ligands.