Toward Systems Biology

May 30 - 31, June 1, 2011


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General Architecture of a Genetic Regulation Network. Applications to Embryologic and Immunologic Control

The general architecture of a genetic regulation network consists of strong connected components of its interaction graph, to which are attached three kinds of sub-structures:

  • a set of up-trees, issued from the sources of the interaction graph of the network, made either of small RNAs (like the microRNAs, translational inhibitors), or of genes repressors and/or inductors, self-expressed without any other genes controlling them;
  • a set of circuits in the core (in graph sense) of the strong connected components of the interaction graph. These circuits are unique or multiple, reduced to one gene or made of several ones, negative (having an odd number of negative interactions) or positive, and disjoint of intersected;
  • a set of down-trees going to the sinks of the interaction graph, i.e., to genes controlled, but not controlling any other genes.

The various state configurations it is possible to observe in the above sub-structures correspond to different dynamical behaviours. We show that these dynamics have in general a small number of attractors, corresponding to the functions of the tissue they represent in the Delbrück's paradigm. Examples of such dynamics will be given in embryology (feather morphogenesis in chicken, gastrulation and wings morphogenesis in Drosophila) as well as in immunology (rearrangements of the genes of the TCR receptors in mice).

Jacques Demongeot, TIMC