Biology Seminar - Lionel Christiaen

Abstract:
At macroscopic scales, animal development appears markedly reproducible from one individual to the next, and across generations. However, the molecular and cellular events underlying vertebrate embryogenesis display greater stochastic variability, and species-specific genetic determinism only becomes apparent through multiscale integration. By contrast with their vertebrate relatives and fellow chordates, tunicates display highly stereotyped embryogenesis at single cell resolution, with invariant lineages. Here, I will first explore the underlying molecular mechanisms driving deterministic embryogenesis, with a focus on the cardiopharyngeal lineage in the ascidian Ciona.

Remarkably, Distinct species and populations of Ciona live across variable environmental conditions, especially sea surface temperatures, which the developing embryo seemingly buffers within a defined range, exhibiting robustness that results in a canalized outcome : the tadpole-like swimming larva. I will present our approach aimed at disentangling the molecular and cellular basis of thermal adaptation, with a focus on tempo scaling and developmental canalization.

Finally, once the larva settles and begins metamorphosis, the rules change: post-embryonic development become regulative, the animal acquires the ability to regenerate lost parts, and key functional systems complete development and differentiation, including the digestive, reproductive and circulatory systems. I will present progress in our understanding of post-embryonic regulative development of the whole animal at single cell resolution, with an emphasis on the circulatory system.

Taken together, our studies leverage the unique features of the tunicate model Ciona to reveal fundamental aspects of animal development and evolution, from molecules to populations.

Host: Marianne Bronner