Evolution and Development of Metazoans

Group leader


We compare 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 main model is the marine segmented worm Platynereis dumerilii. This annelid species is easily reared in the lab and amenable to most molecular genetic investigation techniques, including transgenesis. This is also a great model for live imaging.

Our main research axes:

  • Was the last common ancestor of bilaterian animals (Urbilateria) a segmented animal?
    We investigate the mechanisms responsible for segment formation in Platynereis. Some genes, such as engrailed, wingless or hedgehog play a similar role in Platynereis as in insects. We are investigating further the roles of the Wnt/β-catenin and Notch signalling pathways

Fig. 1: 3D reconstruction of the expression pattern of engrailed (red) in a 48 h
larva (nuclei, blue).

  • What was the architecture of the nervous system like in Urbilateria?
    Striking similarities are found at the genetic level between the formation of nervous systems in vertebrates and Platynereis. By elucidating the mechanisms of 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 nervous systems of vertebrates.

Fig. 2: 3D reconstruction of the nerve scaffold of a 3-day Platynereis larva. Neurites are labelled with an acetylated tubulin antibody (yellow). Body contour is made with an averaging of nuclei-labelled larvae (cyan).

  • Did Urbilateria possess a blood circulatory system?
    Like most annelids, Platynereis has a closed vascular system. Oxygen is carried from gills to organs by haemoglobin dissolved in the blood. Blood flow is created by the local contractions of vessels. Do these similarities with the blood system of vertebrates indicate a common evolutionary origin? We are investigating the genes that pattern blood vessels and specify the hemogenic cells (that produce the blood haemoglobin).

Fig. 3 :Time-lapse of the embryonic development of Platynereis, seen from the posterior pole (5-35 hrs post-fertilization). Proliferating nuclei are red, quiescent nuclei labelled with a G0/G1 marker are yellow and cell membranes are green. The embryo was injected in the D quadrant, labelling all dorsal cells (down) and revealing the epiboly movements of the ectoderm towards the ventral side (up).

This group is part of the Labex “Who am I?”

Key - words:
Evolution, embryogenesis, segmentation, annelid, nervous system, vascular system, Platynereis, trochophore, teloblast, Evo-Devo, embryo imaging.

Selected Publications 

Gazave E, Lemaitre Q, Balavoine G. (2017) The Notch pathway in the annelid Platynereis: Insights into chaetogenesis and neurogenesis processes. Open Biology, in press

Gazave E, Béhague J, Laplane L, Guillou A, Préau L, Demilly A, Balavoine G, Vervoort M. (2013) Posterior elongation in the annelid Platynereis dumerilii involves stem cells molecularly related to primordial germ cells. Dev Biol. 382:246-67.

Hui JH, McDougall C, Monteiro AS, Holland PW, Arendt D, Balavoine G & Ferrier DE. (2012) Extensive chordate and annelid macrosynteny reveals ancestral homeobox gene organisation. Mol Biol Evol. 29:157–165.

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, 339-342.

Last modified 25 September 2017

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