Ronan Duchesne

Complex Systems Master's Program, iXXi, École Normale Supérieure de Lyon, France

Systems Biology

" systems biology is a biology-based inter-disciplinary field of study that focuses on complex interactions within biological systems, using a holistic approach " (wikipedia)

My research is focused on the study of the interactions between the components of biological systems, and their unexpected emerging properties. This relatively recent approach is referred to as Systems Biology, and I have been applying it to two domains of the life sciences so far: Development on one hand, and Ecology on the other one. You can find an overview of my past research projects below.

As for the future, there are two main directions that I am interested in. On one hand is the application of the methods of Networks Science to elucidate the governing rules of biological networks structure and of their dynamics. On the other hand is theoretical biology, i.e. the research of optimally complex mathematical representations of biological phenomena.

Structural modeling of ecological foodwebs

Under the supervision of Franck Jabot (Laboratory of Engineering for Complex Systems, IRSTEA Clermont-Ferrand, FRANCE)

Foodwebs, the networks of feeding interactions among ecosystems, are known to be structured and far-from-random. Yet, only little is known about the principles that underlie their structure, which has mainly been tackled through model selection. This leaves us with a bunch of structural models, ranked upon their ability to reproduce the structure of actual foodwebs. These models are starting to be used for predicting the dynamics of actual ecosystems, which is based on the implicit assumption that the best model to predict the structure of an ecosystem is also the best one for predicting its dynamics.

The goal of my internship was to challenge this hypothesis by establishing two rankings of foodweb structural models:

Then, a simple comparison of the two rankings would allow us to discard, or accept the initial hypothesis.

Modeling the genetic control of the Drosophila dorsal closure

Under the supervision of Stéphane Vincent (LBMC, ENS Lyon) and Vincent Calvez (UMPA, ENS Lyon)

Dorsal Closure is an extensively studied morphogenetic process of the Drosophila embryonic development, in which two epidermal cell sheets move together to close an opening in the dorsal side of the embryo. This movement is synchronized throughout the tissue, and it has been proved recently that the differenciation of the cells responsible for this process is under the control of a coherent FeedForward Loop between the Junk (Jnk) and Decapentaplegic (Dpp) pathways.

In the course of my internship, we generated a mathematical model of this genetic network in order to better understand its dynamic function. Using the properties of the FFL, and the fact that Dpp is a morphogen (i.e. it can move through tissues and has a concentration-dependent activity), we asked if the network was sufficient to display a synchrony in the activation of the targets of the network.