title: Mouse Tudor Repeat-1 (MTR-1) is a novel component of chromatoid bodies/nuages in male germ cells and forms a complex with snRNPs.
abstract: Characteristic ribonucleoprotein-rich granules, called nuages, are present in the cytoplasm of germ-line cells in many species. In mice, nuages are prominent in postnatal meiotic spermatocytes and postmeiotic round spermatids, and are often called chromatoid bodies at the stages. We have isolated Mouse tudor repeat-1 (Mtr-1) which encodes a MYND domain and four copies of the tudor domain. Multiple tudor domains are a characteristic of the TUDOR protein, a component of Drosophila nuages. Mtr-1 is expressed in germ-line cells and is most abundant in fetal prospermatogonia and postnatal primary spermatocytes. The MTR-1 protein is present in the cytoplasm of prospermatogonia, spermatocytes, and round spermatids, and predominantly localizes to chromatoid bodies. We show that (1) an assembled form of small nuclear ribonucleoproteins (snRNPs), which usually function as spliceosomal complexes in the nucleus, accumulate in chromatoid bodies, and form a complex with MTR-1, (2) when expressed in cultured cells, MTR-1 forms discernible granules that co-localize with snRNPs in the cell plasm during cell division, and (3) the deletion of multiple tudor domains in MTR-1 abolishes the formation of such granules. These results suggest that MTR-1, which would provide novel insights into evolutionary comparison of nuages, functions in assembling snRNPs into cytoplasmic granules in germ cells.
authors.affiliation: Department of Development and Differentiation, Institute for Frontier Medical Sciences, Kyoto University, Kyoto 606-8507, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Chuma
authors.forename: Masateru
authors.initials: M
authors.lastname: Hiyoshi
authors.forename: Akitsugu
authors.initials: A
authors.lastname: Yamamoto
authors.forename: Mihoko
authors.initials: M
authors.lastname: Hosokawa
authors.forename: Kazufumi
authors.initials: K
authors.lastname: Takamune
authors.forename: Norio
authors.initials: N
authors.lastname: Nakatsuji
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018797:Cell Cycle Proteins; D002455:Cell Division; D003594:Cytoplasmic Granules / Q000378:metabolism / Q000648:ultrastructure; D018076:DNA, Complementary / Q000235:genetics; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D008297:Male; D051379:Mice; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017411:Ribonucleoproteins, Small Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013087:Spermatids / Q000378:metabolism; D013090:Spermatocytes / Q000378:metabolism; D013093:Spermatogonia / Q000378:metabolism; D013094:Spermatozoa / Q000378:metabolism* / Q000648:ultrastructure; D014162:Transfection
chemical_list: D018797:Cell Cycle Proteins; D018076:DNA, Complementary; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D017411:Ribonucleoproteins, Small Nuclear; C488681:Tdrd1 protein, mouse