New gene-editing system enables large-scale studies of gene function.
The first comprehensive comparison of the genetic blueprints of humans and chimpanzees shows our closest living relatives share 96 percent of our DNA sequence, an international research consortium reported today.
Led by scientists from the Broad Institute of MIT and Harvard University, and the Washington University School of Medicine, the Chimpanzee Sequencing and Analysis Consortium reported its findings in the Sept. 1 issue of the journal Nature.
"We now have a nearly complete catalog of the genetic changes that occurred during the evolution of the modern human and chimpanzee species from our common ancestor," said the study's lead author, Tarjei S. Mikkelsen of the Broad Institute. "By cross-referencing this catalog against clinical observations and other biological data, we can begin to identify the specific changes that underlie the unique traits of the human species."
"The evolutionary comparison of the human and chimpanzee genomes has major implications for biomedicine," said Eric Lander, director of the Broad Institute and a co-leader of the research team. "It provides a crucial baseline for human population genetic analysis. By identifying recent genetic changes and regions with unusually high or low variation, it can point us to genes that vary as a response to infectious agents and environmental pressures."
The research provides key information for human medicine because at least some genetic changes reflect either responses to recent infectious agents or evolutionary changes relevant to human health.
Researchers found that more than 50 genes present in the human genome are missing or partially deleted from the chimpanzee genome. For example, three key genes involved in inflammation appear to be deleted in the chimpanzee genome, possibly explaining some of the known differences between the immune and inflammatory responses of chimpanzees and humans.
The corresponding number of gene deletions in the human genome is not yet precisely known, but humans appear to have lost the function of the caspase-12 gene, which produces an enzyme that may affect the progression of Alzheimer's disease.
The research also demonstrates that humans and chimpanzees have accumulated more potentially deleterious mutations in their genomes over the course of evolution than have mice, rats and other rodents. While such mutations can cause diseases that may erode a species' overall fitness, they may have also made primates more adaptable to rapid environmental changes and enabled them to achieve unique evolutionary adaptations.
The researchers further note that a few classes of genes are changing unusually quickly in both humans and chimpanzees compared with other mammals. These classes include genes involved in perception of sound, transmission of nerve signals, production of sperm and cellular transport of ions. The rapid evolution of these genes may have contributed to the special characteristics of primates.
The data behind these conclusions, as well as all future data from the Chimpanzee Sequencing and Analysis Consortium, are in the public domain. As a result, scientists worldwide can contribute to understanding human evolutionary history and applying these data to biomedical research.
The 67 researchers who took part in the Chimpanzee Sequencing and Analysis Consortium share authorship of the Nature paper. The sequencing and assembly of the chimpanzee genome was done at the Broad Institute and at the Washington University School of Medicine. In addition to those centers, the consortium included researchers from institutions elsewhere in the United States, as well as in Israel, Italy, Germany and Spain. The team was co-led by Lander of the Broad Institute, Richard Wilson of the Washington University School of Medicine and Robert Waterston of the University of Washington in Seattle.
The work is funded in part by the National Human Genome Research Institute of the National Institutes of Health.