Most common pathologies in humans are not caused by the mutation of a single gene, rather they are
complex diseases
that arise due to the dynamic interaction of many genes and
environmental factors. This plethora of interacting genes generates a
complexity landscape that masks the real effects associated with the
disease. To construct dynamic maps of gene interactions (also called
genetic regulatory networks) we need to understand the interplay
between thousands of genes. Several issues arise in the analysis of
experimental data related to gene function: on the one hand, the nature
of measurement processes generates highly noisy signals; on the other
hand, there are far more variables involved (number of genes and
interactions among them) than experimental samples. Another source of
complexity is the highly nonlinear character of the underlying
biochemical dynamics. To overcome some of these limitations, we
generated an optimized method based on the implementation of a Maximum
Entropy Formalism (MaxEnt) to deconvolute a genetic regulatory network
based on the most probable meta-distribution of gene–gene interactions.
We tested the methodology using experimental data for Papillary Thyroid
Cancer (PTC) and Thyroid Goiter tissue samples. The optimal MaxEnt
regulatory network was obtained from a pool of 25,593,993 different
probability distributions. The group of observed interactions was
validated by several (mostly
in silico) means and sources. For
the associated Papillary Thyroid Cancer Gene Regulatory Network
(PTC-GRN) the majority of the nodes (genes) have very few links
(interactions) whereas a small number of nodes are highly connected.
PTC-GRN is also characterized by high clustering coefficients and
network heterogeneity. These properties have been recognized as
characteristic of topological robustness, and they have been largely
described in relation to biological networks. A number of biological
validity outcomes are discussed with regard to both the inferred model
and the PTC.