|Gorilla Genome Sequence Enables Human Evolution Studies|
|SciMed - Genetics & Genome|
|TS-Si News Service|
|Thursday, 08 March 2012 09:00|
Washington, DC, USA. Scientists have completed the genome sequence for the gorilla the last genus of the living great apes to have its genome decoded.
The findings published in Nature confirm that our closest relative is the chimpanzee, the team show that much of the human genome more closely resembles the gorilla than it does the chimpanzee genome.
This is the first time scientists have been able to compare the genomes of all four living great apes: humans, chimpanzees, gorillas and orang-utans. The study provides a unique perspective on our own origins and is an important resource for research into human evolution and biology, as well as for gorilla biology and conservation. "The gorilla genome is important because it sheds light on the time when our ancestors diverged from our closest evolutionary cousins. It also lets us explore the similarities and differences between our genes and those of gorilla, the largest living primate," says Aylwyn Scally, first author from the Wellcome Trust Sanger Institute.
Using DNA from Kamilah, a female western lowland gorilla, the researchers assembled a gorilla genome sequence and compared it with the genomes of the other great apes. They also sampled DNA sequences from other gorillas in order to explore genetic differences between gorilla species. The team searched more than 11,000 genes in human, chimpanzee and gorilla for genetic changes important in evolution. Humans and chimpanzees are genetically closest to each other over most of the genome, but in many places where this is not the case.
15% of the human genome is closer to the gorilla genome than it is to chimpanzee, and 15% of the chimpanzee genome is closer to the gorilla than human. In all three species, genes relating to sensory perception, hearing and brain development showed accelerated evolution and particularly so in humans and gorillas.
"Our most significant findings reveal not only differences between the species reflecting millions of years of evolutionary divergence, but also similarities in parallel changes over time since their common ancestor," says Dr Chris Tyler-Smith, senior Wellcome author.
"We found that gorillas share many parallel genetic changes with humans including the evolution of our hearing. Scientists had suggested that the rapid evolution of human hearing genes was linked to the evolution of language. Our results cast doubt on this, as hearing genes have evolved in gorillas at a similar rate to those in humans."
This research also illuminates the timing of splits between species. Although we commonly think of species diverging at a single point in time, this does not always reflect reality: species can separate over an extended period of time.
The team found that divergence of gorillas from humans and chimpanzees occurred around ten million years ago. The split between eastern and western gorillas was much more recent, in the last million years or so, and was gradual, although they are now genetically distinct. This split is comparable in some ways to the split between chimpanzees and bonobos, or modern humans and Neanderthals.
"Our research completes the genetic picture for overall comparisons of the great apes," says Dr Richard Durbin, senior author from Wellcome, "After decades of debate, our genetic interpretations are now consistent with the fossil record and provide a way for palaeontologists and geneticists to work within the same framework.
"Our data are the last genetic piece we can gather for this puzzle: there are no other living great ape genera to study." Gorillas survive today in just a few isolated and endangered populations in the equatorial forests of central Africa. They are severely threatened and their numbers are diminishing.
This research not only informs us about human evolution, but highlights the importance of protecting and conserving the full diversity of these remarkable species.
CitationInsights into hominid evolution from the gorilla genome sequence. Aylwyn Scally, Julien Y. Dutheil, LaDeana W. Hillier, Gregory E. Jordan, Ian Goodhead, Javier Herrero, Asger Hobolth, Tuuli Lappalainen, Thomas Mailund, Tomas Marques-Bonet, Shane McCarthy, Stephen H. Montgomery, Petra C. Schwalie, Y. Amy Tang, Michelle C. Ward, Yali Xue, Bryndis Yngvadottir, Can Alkan, Lars N. Andersen, Qasim Ayub, Edward V. Ball, Kathryn Beal, Brenda J. Bradley, Yuan Chen, Chris M. Clee, Stephen Fitzgerald, Tina A. Graves, Yong Gu, Paul Heath, Andreas Heger, Emre Karakoc, Anja Kolb-Kokocinski, Gavin K. Laird, Gerton Lunter, Stephen Meader, Matthew Mort, James C. Mullikin, Kasper Munch, Timothy D. O’Connor, Andrew D. Phillips, Javier Prado-Martinez, Anthony S. Rogers, Saba Sajjadian, Dominic Schmidt, Katy Shaw, Jared T. Simpson, Peter D. Stenson, Daniel J. Turner, Linda Vigilant, Albert J. Vilella, Weldon Whitener, Baoli Zhu, David N. Cooper, Pieter de Jong, Emmanouil T. Dermitzakis, Evan E. Eichler, Paul Flicek, Nick Goldman, Nicholas I. Mundy, Zemin Ning, Duncan T. Odom, Chris P. Ponting, Michael A. Quail, Oliver A. Ryder, Stephen M. Searle, Wesley C. Warren, Richard K. Wilson, Mikkel H. Schierup, Jane Rogers, Chris Tyler-Smith, Richard Durbin. Nature 2012; 483(7388): 169-175. doi:10.1038/nature10842
Gorillas are humans’ closest living relatives after chimpanzees, and are of comparable importance for the study of human origins and evolution. Here we present the assembly and analysis of a genome sequence for the western lowland gorilla, and compare the whole genomes of all extant great ape genera. We propose a synthesis of genetic and fossil evidence consistent with placing the human–chimpanzee and human–chimpanzee–gorilla speciation events at approximately 6 and 10 million years ago. In 30% of the genome, gorilla is closer to human or chimpanzee than the latter are to each other; this is rarer around coding genes, indicating pervasive selection throughout great ape evolution, and has functional consequences in gene expression. A comparison of protein coding genes reveals approximately 500 genes showing accelerated evolution on each of the gorilla, human and chimpanzee lineages, and evidence for parallel acceleration, particularly of genes involved in hearing. We also compare the western and eastern gorilla species, estimating an average sequence divergence time 1.75 million years ago, but with evidence for more recent genetic exchange and a population bottleneck in the eastern species. The use of the genome sequence in these and future analyses will promote a deeper understanding of great ape biology and evolution.
Keywords: Evolution, Genetics, Genomics, Palaeontology.
|Last Updated on Thursday, 08 March 2012 12:46|