The Role of Chromosomal Rearrangements in Speciation and Adaptation in Primates– New Tools into Human Welfare Studies?

Comparative genomics has become a powerful tool to study the links between genome evolution and phenotypes. Using genomes of several primate species (human, chimpanzee and macaque) we detected regions of conserved synteny (HSBs) surrounded by evolutionary breakpoint regions (EBRs). Chromosomal rearrangements might act as barriers to gene flow due to a suppression of recombination within reorganized regions, thus facilitating the accumulation of genetic incompatibilities that eventually could lead to speciation. Favouring this view, in human and chimpanzee, we found lower recombination rates in inverted chromosome regions than in collinear chromosomes. Interestingly, human chromosomes 1 and 18, containing human-specific inversions, have genes differentially expressed in cerebral cortex (e.g., USP14 and HSRTS-BETA in human chromosome 18). When we extended these analyses to the macaque genome by estimating recombination rates we found that macaque chromosomes 5 and 9, containing macaque-specific inversions, had lower recombination rates than the rest of the chromosomes. Further, analysing the gene content, we found that defence-response genes, differentially expressed between human and other primates in the reproductive tract, were enriched in rhesus macaque EBRs. Moreover, a cluster of alpha-defensins, which are positively selected in the macaque lineage, was found in the inverted region of macaque chromosome 5. In summary, the study of chromosome evolution in primates is revealing as a powerful tool in pointing to the specific genes and evolutionary mechanisms that could be related to phenotypic differences between humans and their close primate relatives.