title: PIWIL1 Is Expressed in the Canine Testis, Increases with Sexual Maturity, and Binds Small RNAs.
abstract: Spermatogenesis is a highly regulated process leading to the development of functional spermatozoa through meiotic division and subsequent maturation. Recent studies have suggested that a novel class of Argonaute proteins, known as the PIWI clade, plays important roles in multiple stages of spermatogenesis. PIWI proteins bind specific small noncoding RNAs, called PIWI-interacting RNAs (piRNAs). These piRNAs guide the PIWI-piRNA complex to retrotransposon targets that become expressed during meiosis. Retrotransposons are subsequently silenced, either through PIWI "slicer" activity or through PIWI-directed methylation of the retrotransposon locus. Most mammalian studies have employed mouse models where sterility follows PIWI inactivation. The goal of this study was to characterize canine PIWIL1 to determine whether expression pattern and functional characteristics support a similar function in that species. Canine PIWIL1 cDNA is a 2.6-kb transcript that encodes an 861-amino acid protein showing high homology to other mammalian PIWIL1 proteins and containing features consistent with PIWI family members (PAZ, PIWI domains). Analysis of PIWIL1 protein and transcript levels revealed that PIWIL1 expression is limited to the testes and is associated with sexual maturity, with mature dogs showing higher levels of PIWIL1 expression. Immunohistochemistry demonstrated expression primarily in seminiferous tubules and confirmed higher levels of PIWIL1 in mature dogs. Functional characterization by RNA immunoprecipitation demonstrated that canine PIWIL1 binds short RNAs consistent in size with piRNAs (27-32 nucleotides). Together, these studies represent the first characterization of a PIWI protein in the dog and suggest that it is a functional piRNA-binding protein most highly expressed in the mature testes.
authors.affiliation: Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada.
authors.forename: Leanne
authors.initials: L
authors.lastname: Stalker
authors.affiliation: Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada.
authors.forename: Stewart J
authors.initials: SJ
authors.lastname: Russell
authors.affiliation: Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada.
authors.forename: Carmon
authors.initials: C
authors.lastname: Co
authors.affiliation: Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Foster
authors.affiliation: Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada jlamarre@uoguelph.ca.
authors.forename: Jonathan
authors.initials: J
authors.lastname: LaMarre
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D060565:Argonaute Proteins / Q000378:metabolism*; D003001:Cloning, Molecular; D004285:Dogs; D015870:Gene Expression; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D020733:RNA, Small Cytoplasmic / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D016601:RNA-Binding Proteins / Q000378:metabolism; D012671:Seminiferous Tubules / Q000378:metabolism; D012741:Sexual Maturation / Q000502:physiology*; D013737:Testis / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: D060565:Argonaute Proteins; D020733:RNA, Small Cytoplasmic; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins
keywords: PIWI; canine reproduction; piRNA; spermatogenesis; testis