Date : 21/4/2010

Internship proposal for : Master 1 or Master 2

Laboratory

Institut Jacques Monod
UMR 7592
15 rue Hélène Brion 75205 Paris
Director : Giuseppe Baldacci
Website : http://www.ijm.fr/en/ijm/research/research-groups/nematode/
Main discipline : Molecular biology

Mentor

Marie-Anne Félix
email : This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
phone : +33 157278067

Subjects / Tools-Methodologies

1 : evolution/laser cell ablation
2 : intercellular signaling/microscopy
3 : Caenorhabditis/

Summary of lab's interests

Our team combines evolutionary, ecological and quantitative approaches to laboratory biology of a major model organism. The nematode worm C. elegans has become one of the major lab model organisms, yet little is known of its biology in the wild. Of particular interest is its mode of reproduction with selfing hermaphrodites and facultative males. In order to understand the biology of Caenorhabditis nematodes outside the laboratory, especially their outcrossing rate, population structure and ecology, we collect and study natural populations of C. elegans and other Caenorhabditis species (many of them new). After first isolating C. elegans from compost heaps, we recently found that C. elegans mostly proliferates in rotting fruits. We now aim to study the ecology and the structure of diversity of these natural populations. To study a model developmental system in its evolutionary context, we chose to focus on vulva formation, one of the best-studied developmental process in C. elegans. Vulva cell fate specification is an example of a biological system that is robust to stochastic noise and environmental change(for all precursor cell fates except one). Most biological processes are studied in the laboratory under one standard condition in one reference genetic background. In contrast, we aim to study the impact of environmental and genetic variation on vulva development. We explore the impact of the environment on the system (both on its output and on the signaling pathway activities leading to cell fate specification) and its evolvability upon random mutation. The observed buffering of the system\'s output to environmental variation results in buffering of some genetic variation, thus allowing for evolution in the process without change in its output. We reveal and study such cryptic evolution within C. elegans and among different Caenorhabditis species using various experimental approaches.

Summary of project

Evolution of an intercellular signaling network in the Caenorhabditis genus C. elegans vulva precursor cell fate patterning is a model developmental system. In this system, a row of six precursor cells, P(3-8).p, are competent to form vulval tissue. The spatial cell fate pattern (3°-3°-2°-1°-2°-3° fates from P3.p to P8.p) is organized in response to a LIN-3/EGF signal emitted by the gonadal anchor cell, located closest to P6.p. Cell fate patterning involves a well-characterized network of intercellular signaling pathways, including EGF/Ras and Notch and multiple feedback loops and crosstalk (ref. 1). The system output - the cell fate pattern - is quasi-invariant in the Caenorhabditis genus. However, quantitative evolution in this signaling network has been demonstrated by scoring of cell fate patterns after ablation of the anchor cell during the induction process (ref. 2). In the past few years, twelve new species of Caenorhabditis have been discovered (unpublished) and their phylogenetic relationship established by our collaborators (K. Kiontke and D. Fitch, unpublished). The project is to perform anchor cell ablations in these new species and score the resulting cell fate patterns. Changes in cell fate patterns and putative changes in the signaling network will then be mapped onto the Caenorhabditis phylogeny. The denser sampling with the additional species will provide information as to the direction of evolution in the signaling network. This project will be associated with results obtained in the lab through mathematical modeling of the network in intact and ablated animals (Hoyos et al., submitted). The ablation project may thus be followed by testing predicted quantitative variation in the signaling pathways by molecular genetic means. 1. Sternberg PW (2005). Vulval development. WormBook, ed. The C. elegans Research Community, doi/10.1895/wormbook.1.6.1, www.wormbook.org. 2. Félix, M.-A. (2007). Cryptic quantitative evolution of the vulva intercellular network in Caenorhabditis. Curr. Biol. 17, 103-114.