Speaker
Marcin Zagorski
(Jagiellonian University)
Description
Gene regulatory networks typically have low in-degrees,
whereby any given gene is regulated by few of the genes in
the network. They also tend to have broad distributions for
the out-degree. What mechanisms might be responsible for
these degree distributions? Starting with an accepted
framework of the binding of transcription factors to DNA, we
consider a simple model of gene regulatory dynamics. There,
we show that selection for a target expression pattern leads
to the emergence of minimum connectivities compatible with
the selective constraint. As a consequence, these gene
networks have low in-degree, and functionality is
parsimonious, i.e., is concentrated on a sparse number of
interactions as measured for instance by their essentiality.
Furthermore, we find that mutations of the transcription
factors drive the networks to have broad out-degrees.
Finally, these classes of models are evolvable, i.e.,
significantly different genotypes can emerge gradually under
mutation-selection balance.
