Research

 

 

 

 

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:

 

Fig. 1 : Reconstruction 3D du profil d’expression du gène engrailed (rouge) chez une larve de 48h (noyaux en bleu).

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 engrailedwingless 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. 2 : Reconstruction 3D de l’architecture neurale d’une larve de 3 jours de Platynereis. Les neurites sont marqués avec un anticorps contre la α-tubuline acetylée (jaune).
Les contours du corps sont créés par moyennage de plusieurs larves marquées au niveau des noyaux (cyan)

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. 3 : Film du développement embryonnaire de Platynereis, vu depuis le pole postérieur (5-35 hrs après fécondation). Les noyaux des cellules en prolifération sont rouges, ceux des cellules quiescentes révélées par un marqueur de la phase G0/G1 sont jaunes et les membranes sont vertes. L’embryon a été injecté dans le quadrant D, marquant ainsi toutes les cellules dorsales (en bas) et révélant les mouvements d’épibolie de l’ectoderme vers la face ventrale (en haut).

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).

 

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

 

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