Humam-chimpanzee comparison

Despite the close evolutionary relationship and striking genetic similarity between humans and chimpanzees, there are remarkable differences in anatomy, behavior, and disease susceptibility in the two species. One step towards understanding the biological basis of these phenotypic differences is to characterize quantitative differences in levels of expression of genes in humans and chimpanzees. To contribute to such analysis, we compared gene expression patterns in lymphoblastoid cell lines between nine unrelated humans and ten unrelated chimpanzees by using human cDNA microarrays. Hybridizations to arrays containing 43,233 features produced high quality data for 22,879 cDNA clones, representing 20,266 Unigenes. We observed statistically significant differences in transcript levels for 32% of these genes (P < 0.05, Student t test), with about 200 cDNAs showing differences of more than 2-fold (lower bounds of 95% confidence interval). Among these are genes involved in cell surface glycosylation and responses to toxins and viruses. Examination of functional annotations for the differentially expressed genes revealed lower expression of “cell cycle” and “energy pathways” genes, and higher expression of “chemokines”, “26S proteasome” and “cell motility” genes in chimpanzee samples. These genes and pathways could underlie some of the phenotypic differences between humans and chimpanzees.

This work was carried out in collaboration with Jie Zhang, a former postdoc at the Myers' lab.