title: Characterization of the avian Trojan gene family reveals contrasting evolutionary constraints.
abstract: "Trojan" is a leukocyte-specific, cell surface protein originally identified in the chicken. Its molecular function has been hypothesized to be related to anti-apoptosis and the proliferation of immune cells. The Trojan gene has been localized onto the Z sex chromosome. The adjacent two genes also show significant homology to Trojan, suggesting the existence of a novel gene/protein family. Here, we characterize this Trojan family, identify homologues in other species and predict evolutionary constraints on these genes. The two Trojan-related proteins in chicken were predicted as a receptor-type tyrosine phosphatase and a transmembrane protein, bearing a cytoplasmic immuno-receptor tyrosine-based activation motif. We identified the Trojan gene family in ten other bird species and found related genes in three reptiles and a fish species. The phylogenetic analysis of the homologues revealed a gradual diversification among the family members. Evolutionary analyzes of the avian genes predicted that the extracellular regions of the proteins have been subjected to positive selection. Such selection was possibly a response to evolving interacting partners or to pathogen challenges. We also observed an almost complete lack of intracellular positively selected sites, suggesting a conserved signaling mechanism of the molecules. Therefore, the contrasting patterns of selection likely correlate with the interaction and signaling potential of the molecules.
authors: Institute of Diagnostics, Department of Medical Microbiology and Immunology, University of Oulu, Oulu, Finland; Nordlab Oulu, Oulu University Hospital, Oulu, Finland; Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland.
authors: Petar
authors: P
authors: Petrov
authors: Institute of Diagnostics, Department of Medical Microbiology and Immunology, University of Oulu, Oulu, Finland; Nordlab Oulu, Oulu University Hospital, Oulu, Finland; Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland.
authors: Riikka
authors: R
authors: Syrjänen
authors: Division of Genetics and Genomics, The Roslin Institute and R(D)SVS, University of Edinburgh, Roslin, United Kingdom.
authors: Jacqueline
authors: J
authors: Smith
authors: Division of Genetics and Genomics, The Roslin Institute and R(D)SVS, University of Edinburgh, Roslin, United Kingdom.
authors: Maria Weronika
authors: MW
authors: Gutowska
authors: Institute of Diagnostics, Department of Medical Microbiology and Immunology, University of Oulu, Oulu, Finland; Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland.
authors: Tatsuya
authors: T
authors: Uchida
authors: Institute of Diagnostics, Department of Medical Microbiology and Immunology, University of Oulu, Oulu, Finland; Nordlab Oulu, Oulu University Hospital, Oulu, Finland; Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland.
authors: Olli
authors: O
authors: Vainio
authors: Division of Genetics and Genomics, The Roslin Institute and R(D)SVS, University of Edinburgh, Roslin, United Kingdom.
authors: David W
authors: DW
authors: Burt
mesh_terms: D000818:Animals; D002645:Chickens / Q000235:genetics*; D003593:Cytoplasm / Q000378:metabolism; D019143:Evolution, Molecular; D005110:Extracellular Space / Q000378:metabolism; D023281:Genomics; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D012641:Selection, Genetic; D012689:Sequence Homology, Nucleic Acid
chemical_list: D008565:Membrane Proteins