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SeMoVi - June 9th, 2010

14h00 - 15h00 Stéphane RobinAgroParisTech / INRA 
Using "null" models to study biological networks
15h00 - 15h30 Pause café
15h30 - 16h30 Hubert CharlesINSA de LYON 

Exploring the regulatory network of Buchnera aphidicola, a case-study of genome evolution in a symbiotic context

16h30 - 17h00 Discussion générale


Stéphane Robin, AgroParisTech / INRA
Using "null" models to study biological networks

Network analysis is now one of the most active parts of computational biology. Most methods refer to some modelling of the network(s) under study, although the meaning of `modelling' varies quite a lot. In this talk, we will present some methods where the model is neither a mechanistic description of how the network behaves, nor a realistic description of the way it has been build. `Null' models can be seen as naive and yet reasonably faithful descriptions of what is observed. Such a model must account for some information, and enable us to discover some other information. We will consider the problem of motif detection in interaction or metabolic network. We will present several random graph models that can be used as null models. We will then show how they can be used to detect exceptional patterns in a network, or to compare networks based on patterns frequencies.