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Trabajo presentado en el V Congreso de la Sociedad Española de Biología Evolutiva (SESBE 2016), celebrado en Murcia del 18 al 21 de enero de 2016., One of the interesting evolutionary challenges is to discover the genetic bases of adaptive phenotypes, but the strongest challenges are complex adaptations. Some are being solved through the genetic analysis for specific adaptations, even for complex traits (like the short stature of Negritos), opening the field for complexity. Gene products function in molecular networks, as such, the position within the network may determine the strength of selection applied to the gene. This analysis indicates how evolution is shaping the complex interactions inherent to molecular pathways and networks. The analysis may be applied to the pathway level (with a low number of interacting units but a very detailed molecular knowledge), the entire metabolome, or even the whole interactome. We present here all these cases in order to relate selection to the specificity of reactions and their function. At the level of the human interactome, selection has not acted equally throughout evolutionary history: genes with higher number of interactions are more likely to have been targeted by recent positive selection during recent human evolution. Our results indicate that the relationship between centrality and the impact of adaptive evolution highly depends on the evolutionary time-scale. Most likely, network adaptation occurs through intraspecific adaptive leaps affecting key network genes, followed by the fine tuning of adaptations in less important network regions. This analysis goes beyond the identification of single cases of adaptation and opens the scope of understanding how natural selection works within the biomolecular complexity of life.

Trabajo presentado en la 4th Meeting of the Spanish Society of the Evolutionary Biology (SESBE 2013) celebrada en Barcelona del 27 al 29 de noviembre de 2013.

Trabajo presentado en la XIII Jornada de Biologia Evolutiva, celebrada en Barcelona el 2 de julio de 2013., Genes are subject to disparate selective pressures: they evolve under different strengths of purifying selection and are differently affected by positive selection. However, the biological mechanisms underlying such differences have not been fully understood yet. While most of the studies focused on describing the factors that make a protein more or less constrained in its evolution, the determinants of the impact of positive selection are to be discovered. Genes and proteins often function as parts of rather complex networks of interacting molecules. Therefore, understanding evolutionary forces acting on individual genes will likely benefit from considering their position in such systems. Several lines of evidence indicate that the strength of purifying selection acting on genes is affected by their relative position in molecular networks while much less is known for positive selection. Nevertheless, some observations suggest that the impact of positive selection on genes is also affected by the position of their encoded proteins in molecular networks. Analysis of a few individual pathways suggests that positive selection preferentially targets genes that exert a high degree of control over the overall behaviour of the pathway, i.e. at “privileged” positions. On the other hand, it has been found that genes that have evolved under positive selection since the human-chimp split tended to encode proteins acting at the periphery of the human Protein Interaction Network (PIN). This analysis, however, relied only on the human genome and on the at the time incomplete chimpanzee genome, which limited the power of positive selection inferences. The current availability of genomic data (including the complete genomes of several mammals, plus 1000 human genomes) allows to infer the action of positive selection with an unprecedented power. In agreement with previous results, we observed that purifying selection act at the core of the PIN while genes affected by ancient positive selection (as inferred from comparison of 10 mammalian genomes) tend to act at its periphery. However, the opposite trend was observed for positive selection acting on human populations: signatures of recent positive selection are more likely to be observed for genes acting at the centre of the human PIN.

Poster presentado en la 4th Meeting of the Spanish Society for Evolutionary Biology (SESBE 2013) celebrada en Barcelona del 27 al 29 de noviembre de 2013.