Molecular mechanisms of chromosomal rearrangement during primate evolution

Breakpoint analysis of the large chromosomal rearrangements which have occurred during primate evolution promises to yield new insights into the underlying mechanisms of mutagenesis. Comparison of these evolutionary breakpoints with those that are disease-associated in humans, and which occur during either meiotic or mitotic cell division, should help to identify basic mechanistic similarities as well as differences. It has recently become clear that segmental duplications (SDs) have had a very significant impact on genome plasticity during primate evolution. In comparisons of the human and chimpanzee genomes, SDs have been found in flanking regions of 70-80% of inversions and similar to 40% of deletions/duplications. A strong spatial association between primate-specific breakpoints and SDs has also become evident from comparisons of human with other mammalian genomes. The lineage-specific hyperexpansion of certain SDs observed in the genomes of human, chimpanzee, gorilla and gibbon is indicative of the intrinsic instability of some SDs in primates. However, since many primate-specific breakpoints map to regions lacking SDs, but containing interspersed high-copy repetitive sequence elements such as SINEs, LINEs, LTRs, alpha-satellites and (AT) (n) repeats, we may infer that a range of different molecular mechanisms have probably been involved in promoting chromosomal breakage during the evolution of primate genomes.