title: The evolution, regulation, and function of placenta-specific genes.
abstract: A number of placenta-specific genes (e.g., Tpbp, Plac1, Syncytin, and retrotransposon-associated genes such as Peg10, Rtl1, Endothelin B receptor, Insl4, Leptin, Midline1, and Pleiotrophin), enhancer elements (e.g., glycoprotein hormone alpha-subunit) and gene isoforms (e.g., 3betaHSD, Cyp19), as well as placenta-specific members of gene families (e.g., Gcm1, Mash2, Rhox, Esx1, Cathepsin, PAG, TKDP, Psg, Siglec) have been identified. This review summarizes their evolution, regulation, and biochemical functions and discusses their significance for placental development and function. Strikingly, the number of unique, truly placenta-specific genes that have been discovered to date is very small. The vast majority of placenta-specific gene products have resulted from one of three mechanisms: evolution of placenta-specific promoters, evolution of large gene families with several placenta-specific members, or adoption of functions associated with endogenous retroviruses and retroelements. Interestingly, nearly all the examples of placenta-specific genes that have been discovered to date are not present in all placental mammals.
authors.affiliation: Department of Comparative Biology & Experimental Medicine, Faculty of Veterinary Medicine, and the Graduate Program in Biochemistry & Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada. srawn@ucalgary.ca
authors.forename: Saara M
authors.initials: SM
authors.lastname: Rawn
authors.forename: James C
authors.initials: JC
authors.lastname: Cross
mesh_terms: D000818:Animals; D020077:Endogenous Retroviruses / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006728:Hormones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007136:Immunoglobulins / Q000235:genetics / Q000378:metabolism; D005810:Multigene Family; D010920:Placenta / Q000033:anatomy & histology / Q000502:physiology*; D011247:Pregnancy; D018626:Retroelements; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D006728:Hormones; D007136:Immunoglobulins; D018626:Retroelements; D014157:Transcription Factors