Comparing primate genomes is an approach that can help scientists understand the genetic basis of the physical and biochemical traits that distinguish primate species. James Sikela and colleagues, for example, collected DNA from humans, chimpanzees, bonobos, gorillas, and orangutans to identify variations in the number of copies of individual genes among the different species. Their work is published in this month’s issue of the open-access journal, PLoS Biology.
Overall, Sikela and colleagues found more than 1,000 genes with changes in copy number in specific primate lineages. All the great ape species showed more increases than decreases in gene copy numbers, but humans showed the highest number of genes with increased copy numbers, at 134, and many of these duplicated human genes are implicated in brain structure and function.
Because some of these gene changes were unique to each of the species examined, they will likely account for some of the physiological and morphological characteristics that are unique to each species. One cluster of genes that amplified only in humans was mapped to a genomic area that appears prone to instability in human, chimp, bonobo, and gorilla. This region has undergone modifications in each of the other descendent primate species, suggesting an evolutionary role. In humans, gene mutations in this region are also associated with the inherited disorder spinal muscular atrophy. This fact, along with the observation that there are human-specific gene duplications in this region, suggests a link between genome instability, disease processes, and evolutionary adaptation.
The research paper is available at the Public Library of Science - abstract is below:
Given that gene duplication is a major driving force of evolutionary change and the key mechanism underlying the emergence of new genes and biological processes, this study sought to use a novel genome-wide approach to identify genes that have undergone lineage-specific duplications or contractions among several hominoid lineages. Interspecies cDNA array-based comparative genomic hybridization was used to individually compare copy number variation for 39,711 cDNAs, representing 29,619 human genes, across five hominoid species, including human. We identified 1,005 genes, either as isolated genes or in clusters positionally biased toward rearrangement-prone genomic regions, that produced relative hybridization signals unique to one or more of the hominoid lineages. Measured as a function of the evolutionary age of each lineage, genes showing copy number expansions were most pronounced in human (134) and include a number of genes thought to be involved in the structure and function of the brain. This work represents, to our knowledge, the first genome-wide gene-based survey of gene duplication across hominoid species. The genes identified here likely represent a significant majority of the major gene copy number changes that have occurred over the past 15 million years of human and great ape evolution and are likely to underlie some of the key phenotypic characteristics that distinguish these species.