Evolution and Development of Metazoans
- Guillaume BALAVOINE
Tel.: +33 (0)157278002
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Our group compares the genetic networks that regulate the developmental patterning of key aspects of the body plan across metazoans, in order to reconstruct the early stages of animal evolution.
Our current model is the marine annelid Platynereis dumerilii. This annelid species is easily reared in the lab and amenable to most molecular genetic investigation techniques. Annelids are part of the Trochozoans, the large third branch of the bilaterian tree, alongside deuterostomes (vertebrates, echinoderms, ...) and ecdysozoans (arthropods, nematodes, ...).
Fig. 1: The head of the annelid Platynereis dumerilii. Picture by Nicolas Dray
The main research axes are:
- Was the last common ancestor of bilaterian animals (Urbilateria) a segmented animal ? We are trying to identify the genes responsible for segment formation in Platynereis. Some of these genes, such as engrailed, wingless or hedgehog apparently play in Platynereis a role similar to that in insects. We are investigating the roles of the Wnt/?-catenin, Hedgehog and Notch signalling pathways in segment formation.
Fig. 2: Expression patterns of 2 genes involved in segment formation in a Platynereis trochophore larva: NK4 in green and Lbx in red. Confocal microscopy picture. Work done by Bruno Hudry, Martine Le Gouar and Nicolas Dray.
- What was the architecture of the nervous system like and how did it form in Urbilateria? Striking similarities are found at the genetic level between the formation of nervous systems in vertebrates on one hand and Platynereis on the other. Insects such as Drosophila look more derived in this respect. By elucidating the mechanisms of neurogenesis and nervous system patterning in an annelid, we hope we will be able to bridge the gap between protostomes and deuterostomes, to reconstitute ancestral characteristics and eventually to understand the origin of the complex and concentrated nervous system of vertebrates.
Fig. 3: Formation of the nervous system in the posterior growth zone of Platynereis. The nerves are labelled with an anti-acetylated tubulin antibody (in green) and differentiating neural cells are labelled with a synaptotagmin RNA probe (in red). Confocal microscopy 3D movie. Work done by Pierre Kerner.
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Selection of Publications
Demilly A, Simionato E, Ohayon D, Kerner P, Garcès A, Vervoort M. (2011) Coe genes are expressed in differentiating neurons in the central nervous system of protostomes. PLoS One. 6(6):e21213.
Janssen R, Le Gouar M, Pechmann M, Poulin F, Bolognesi R, Schwager EE, Hopfen C, Colbourne JK, Budd GE, Brown SJ, Prpic NM, Kosiol C, Vervoort M, Damen WG, Balavoine G, McGregor AP. (2010) Conservation, loss, and redeployment of Wnt ligands in protostomes: implications for understanding the evolution of segment formation. BMC Evol Biol 10:374.
Dray N, Tessmar-Raible K, Le Gouar M, Vibert L, Christodoulou F, Schipany K, Guillou A, Zantke J, Snyman H, Béhague J, Vervoort M, Arendt D, Balavoine G. (2010) Hedgehog signaling regulates segment formation in the annelid Platynereis. Science 329:339-42.
Richards G., Simionato E., Perron M., Adamska M., Vervoort M., & Degnan B.M. (2008). Evolutionary origins of the neurogenic circuit: evidence from sponges. Curr Biol 18:1156-61.
Denes, A.S., Jekely, G., Steinmetz, P.R.H., Raible, F., Snyman, H., Prud'homme, B., Ferrier, D.E.K. Balavoine, G. & Arendt, D. (2007) Molecular Architecture of Annelid Nerve Cord Supports Common Origin of Nervous System Centralization in Bilateria. Cell 129:1–12.
Last modified 4 November 2015