Here I am again with my #SystemsBiology notes.
In this lecture the professor has taught us the basis of Network analysis, but what I find particularly interesting is that these concepts are applicable to so many fields!

But how are networks useful when we are talking about genomes? Well, for example researchers built networks to try to understand why the deletion of some genes that are in common to both yeasts and mice (like Map2k1) don't impact the yeasts' fitness, but if deleted in mice they cause embryonic lethality.

Researchers discovered that this might be due to the fact that during evolution these genes became more and more connected: if we consider each gene as a node of a network, the betweennes centrality of genes that are not essential in yeasts but are essential in mice increased a lot, suggesting that those genes in complex organisms became crucial in some biological pathways or protein complexes. For example, in mice Map2k1 is a member of the Ksr1 scaffold protein complex, while in yeasts it is not part of any protein complex.

From this discovery, they derived the centrality-lethality rule: in complex organisms, if a gene is highly connected it is probably also essential.

Source:
Kim, J., Kim, I., Han, S. et al. Network rewiring is an important mechanism of gene essentiality change. Sci Rep 2, 900 (2012). https://doi.org/10.1038/srep00900