Detecting positive darwinian selection in brain-expressed genes during human evolution

• Published in: Chinese science bulletin 2007-02, Vol.52 (3), p.324-335
• Main Authors: Qi, XueBin, Yang, Su, Zheng, HongKun, Wang, YinQiu, Liao, ChengHong, Liu, Ying, Chen, XiaoHua, Shi, Hong, Yu, XiaoJing, Lin, Alice A., Cavalli-Sforza, Luca L., Wang, Jun, Su, Bing
• Format: Article
• Language: English
• Subjects: Pan troglodytes; Primates; 人科动物; 人类进化; 人脑表达基因; 正向选择; 达尔文学说; 适应性进化
• ISSN: 1001-6538; 1861-9541
• DOI: 10.1007/s11434-007-0062-y

To understand the genetic basis that underlies the phenotypic divergence between human end non- human primates, we screened e total of 7176 protein-coding genes expressed in the human brain end compared them with the chimpanzee orthologs to identify genes that show evidence of rapid evolution in the human lineage. Our results showed that the nonsynonymous/synonymous substitution （Ka/Ka） ratio for genes expressed in the brain of human end chimpanzee is 0.3854, suggesting that the brain-expressed genes ere under functional constraint. The X-linked human brein-exprsseed genes evolved more rapidly than eutosomel ones. We further dissected the molecular evolutionary patterns of 34 candidate genes by sequencing representative primate species to identify lineage-specific adaptive evolution. Fifteen out of the 34 candidate genes showed evidence of positive Darwinian selection in human end/or chimpanzee lineages. These genes ere predicted to play diverse functional roles in embryonic development, spermetogenesis and male fertility, signal trensduction, sensory nociception, end neural function. This study together with others demonstrated the usefulness end power of phylogenetic comparison of multiple closely related species in detecting lineage-specific adaptive evolution, and the identification of the positively selected brain-expressed genes may add new knowledge to the understanding of molecular mechanism of human origin.