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Séminaires MSC
"Matière et Systèmes Complexes"

                      
Lundi 30 mai 2005 à 11h30
Tour 33, couloir 33-43, 2ème étage, salle de réunion

Marie-Anne Félix

(Institut Jacques-Monod, Paris)

Evolution of a developmental system: the nematode vulva
 
A central problem in biology is to understand the robustness of biological processes when faced with random fluctuations, varying environments or genetic changes, and to evaluate the evolutionary consequences of this robustness. Using well-studied model systems, it is now possible to ask, not only which genes and proteins regulate them, but i) how this is done in a quantitative manner, ii) how stable the system is when faced with perturbations, and iii) what are the evolutionary dynamics of the molecular network within the species and among different species. We address these questions using as a model the molecular network that underlies a simple and well-studied developmental process: vulval precursor cell specification in the nematode worm Caenorhabditis elegans.

In this system, three different developmental cell fates are specified within a row of six cells, using an intercellular signaling network that produces a stable output as the spatial cell fate pattern in this row of six cells. The correct fate pattern is required for normal vulva formation, and therefore for copulation and egg-laying.

We study the precision and evolution of the developmental mechanisms that underlie vulva development in different nematode species and among C. elegans wild isolates, and their evolvability (capacity to evolve) upon random mutation. Striking results are:

  1. the developmental mechanisms that lead to this pattern vary between and within species, whereas the final spatial pattern of vulva precursor cell fates is robust and invariant;
  2. the evolvability of different vulva development features varies between species, and correlates with the features that actually vary among wild isolates of each species or closely related species.