Ancient Infection - retroviral evidence preserved in modern primates

Scientists at the University of Michigan report the discovery of a novel retoviral derived sequences around the centromeres of extant catarrhines including humans. Named "K222," it exists as a single copy in baboons, gorilla, orangutans, and chimpanzees; but in humans, nine copies are found in the pericentromeres of nine different chromosomes. The introduction of this sequence into modern primate genomes can be traced to an ancestral retroviral infection of the germ line that occurred approximately 25 million years ago, after the split of Old World and New World primates---explaining the absence of this catarrhine symplesiomorphy among platyrrhines. The fact that only humans present multiple copies of K222, and all pericentromeric, suggests chromosomal recombination near the centromere within the last 6 million years of hominin evolution. As centromeres are generally considered immune to recombination during gametogenesis, pericentromeric recombination as a human autapomorphy could have interesting implications for studies in health and medicine.

Fig. 1 - Two catarrhines (photo credit Barry Bland)

Source from the journal Genome Biology