2-year post-doctoral funding: robustness of ascidian embryogenesis to environmental and experimental variation

The tunicate team at CRBM (Montpellier, France), headed by Patrick Lemaire, is offering a 2-year post-doctoral fellowship (or a 3-year PhD fellowship for an exceptional candidate) to study the robustness of animal embryonic development to genetic and environmental perturbations, using quantitative live imaging of ascidian embryos. A short video describes a recent piece of work of the team relevant to the project.

Why ascidians?

Ascidians are a group of marine invertebrates. Their embryonic cell lineages and early embryonic stage morphologies have remained essentially identical since the group’s emergence about 400 million years ago. This suggests that they are subject to very strong developmental or evolutionary constraints (Lemaire et al. 2011). Ascidian embryogenesis is also very robust to environmental perturbations of temperature and salinity. The extreme evolutionary and environmental robustness of embryonic geometries and cell lineages contrasts with a rapid genetic divergence between species and intra- and inter-specific variability in gene expression.

What is the project?

The proposed experimental project will provide a quantitative assessment of the developmental robustness of a critical morphogenetic process, ascidian gastrulation (1, 3, 5), to two key environmental parameters (water temperature and salinity) and to genetic perturbations of the morphogenetic driving force apparatus (myosin II, Rho kinase, …). The project will study the magnitude of environmental or genetic variations compatible with the production of a viable larva. It will seek to identify the least – and most – robust developmental processes and time points, i. e. those that collapse first, or resist best to the perturbations. Finally, it will characterize the structure of the natural and experimentally-induced variability in the geometry and mechanical properties of embryos. This may lead to the identification of developmental modules.

The project will involve advanced light-sheet imaging of live micro-injected embryos of the ascidian Phallusia mammillata, followed by the computational and statistical analysis of the acquired developmental movies (see 2, 4).

Who funds the project, and how to apply?

The project is funded by an ANR-NSF binational project grant and will be conducted in collaboration with 3 other teams: Prof. Atef Asnacios (MSC, Paris), Prof. Edwin Munro (U. Chicago, USA) and Prof. Madhav Mani (Northwestern University, Evanston, USA).

Expected candidates will have a PhD in cell and developmental biology, an excellent track record of publications and oral communications, strong skills in fluorescent live imaging and some experience in the computational analysis of large datasets. To apply, send Patrick Lemaire (patrick.lemaire[at]crbm.cnrs.fr) by May 11, 2022 at the latest a motivation letter, a CV and the names and contact details of 2 academic referees including the PhD supervisor. A working knowledge of English (B2) is needed, there is no prerequisite in French.

References

1. Fiuza U.-M. and Lemaire, P. (2021) Mechanical and genetic control of ascidian endoderm invagination during gastrulation, Semin Cell Dev Biol 120:108-118
2. Guignard L. *, Fiuza U.-M. *, Leggio B., Laussu J., Faure E., Michelin G., Biasuz K., Hufnagel L., Malandain G. #, Godin C. #, Lemaire P.# (2020) Contact-area dependent cell communications and the morphological invariance of ascidian embryogenesis. Science, 369 :6500 eaar5663
3. Fiuza U-M, Negishi T., Rouan A., Yasuo H.#, Lemaire P. # (2020) Nodal and Eph signalling relay drives the transition between apical constriction and apico-basal shortening during ascidian endoderm invagination. Development 147: dev186965
4. Leggio, B; Laussu J; Carlier, A; Godin, C; Lemaire, P and Faure, E (2019) MorphoNet: An interactive online morphological browser to explore complex multi-scale data. Nat Commun.10(1):2812
5. Lemaire P. (2011) Evolutionary crossroads in developmental biology: the tunicates, Development, 138(11):2143-52
6. Sherrard, K., Robin, FB, Lemaire, P., and Munro, E. (2010) Sequential activation of apical and basolateral myosin drives endoderm invagination during ascidian gastrulation, Current Biology, 20(17):1499-510.

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