A team led by Oregon Health & Science University has sequenced and annotated the genome of the only ape whose DNA had yet to be sequenced — the gibbon, an endangered small ape that inhabits the tropical forests of Southeast Asia. Tomàs Marqués-Bonet ICREA Research Professor and leader of the Comparative Genomics team at Institut de Biologia Evolutiva (UPF/CSIC) and the (CNAG) –based in the PCB– has led the Spanish contribution to the study.

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The team’s work, published in Nature (doi:10.1038/nature13679), gives scientists new insight into the evolution of the gibbon genome and its extraordinary number of chromosomal rearrangements. Chromosomal rearrangements are structural changes in the DNA that are often problematic in other species — including causing cancer in humans — but seem to have happened in gibbons at a very high frequency. The genome sequencing work also provides new details on the family tree and evolutionary history of the gibbon lineage that has been a longstanding source of debate.

Additionally, the team uncovered some genetic clues on how gibbon species over millions of years developed longer arms and powerful shoulder and arm tendons — important for these tree-dwelling primates whose main mode of locomotion is swinging from tree to tree in the dense tropical forest.

Finally, like the DNA sequencing of other apes and non-human primates, the team’s work gives science new insight into the human genome — since apes are so genetically similar to humans. Unraveling primate genomes is vitally important as researchers try to understand the genetic factors in human health and disease.

“This is the last ape to be sequenced and the end of an era in human comparative genomics,” said Tomàs Marquès-Bonet. “Now we have tools — the genomes — for all the closest species to humans.”

As part of the project, the CNAG carried out the sequencing of several whole genomes of different gibbon species using next-generation sequencing and revealed more about the order in which the four different gibbon genera — or a group of species — diverged from each other. While in most cases it is possible to determine the order in which different species diverged from each other, this is not the case for gibbons. Evolutionary biologists within the team found that the four gibbon genera diverged almost instantaneously about four million years ago. That prevents scientists from determining the order in which they separated from each other.

Gibbons, together with the other apes — orangutans, gorillas, chimpanzees and bonobos — are the closest relatives to humans. Humans and these apes all belong to the “superfamily” called Hominoidea. But unlike other apes and humans, gibbons have undergone a high number of chromosomal rearrangements as they have evolved.

“Reading the gibbon DNA is a milestone in the field of genetic sequencing because it is a species with extraordinary features that will give us the keys to understanding genomic rearrangements and translate this knowledge into clinics.” said Ivo Gut, director of the CNAG and co-author on the paper.

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