title: Adaptive evolution of SCML1 in primates, a gene involved in male reproduction.
abstract: BACKGROUND
  Genes involved in male reproduction are often the targets of natural and/or sexual selection. SCML1 is a recently identified X-linked gene with preferential expression in testis. To test whether SCML1 is the target of selection in primates, we sequenced and compared the coding region of SCML1 in major primate lineages, and we observed the signature of positive selection in primates.
  
  
  RESULTS
  We analyzed the molecular evolutionary pattern of SCML1 in diverse primate species, and we observed a strong signature of adaptive evolution which is caused by Darwinian positive selection. When compared with the paralogous genes (SCML2 and SCMH1) of the same family, SCML1 evolved rapidly in primates, which is consistent with the proposed adaptive evolution, suggesting functional modification after gene duplication. Gene expression analysis in rhesus macaques shows that during male sexual maturation, there is a significant expression change in testis, implying that SCML1 likely plays a role in testis development and spermatogenesis. The immunohistochemical data indicates that SCML1 is preferentially expressed in germ stem cells of testis, therefore likely involved in spermatogenesis.
  
  
  CONCLUSIONS
  The adaptive evolution of SCML1 in primates provides a new case in understanding the evolutionary process of genes involved in primate male reproduction.
authors.affiliation: State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, PR China. haihuiwu2002@gmail.com
authors.forename: Hai-hui
authors.initials: HH
authors.lastname: Wu
authors.forename: Bing
authors.initials: B
authors.lastname: Su
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics; D019143:Evolution, Molecular; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D010179:Pancreas / Q000378:metabolism; D010802:Phylogeny; D063146:Polycomb-Group Proteins; D011323:Primates / Q000235:genetics*; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics*; D012098:Reproduction / Q000235:genetics*; D012641:Selection, Genetic; D016415:Sequence Alignment; D012741:Sexual Maturation / Q000235:genetics; D013737:Testis / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D063146:Polycomb-Group Proteins; D012097:Repressor Proteins; C112628:SCML1 protein, human