title: Stage-specific Importin13 activity influences meiosis of germ cells in the mouse.
abstract: Importin-mediated transport of cargoes is known to be a key mechanism for nucleo-cytoplasmic trafficking of molecules. Ipo13, which is a member of Importin-beta gene family, encodes two transcripts by utilizing different transcription start sites. In the mouse, the full-length transcript (L-Ipo13) is expressed in the primordial germ cells in the embryo and is later expressed predominantly at the pachytene phase of meiosis in both male and female germ cells. The shorter transcript (TS-Ipo13) is only expressed in the germ cells in the adult testis. Activity of L-Ipo13, but not TS-Ipo13, mediates the nuclear accumulation of ubiquitin-conjugating enzyme 9 (UBC9), a cargo of human IPO13. This finding is consistent with the progressive accumulation of UBC9 in the nucleus of the meiotic germ cells after the onset of L-Ipo13 expression. Following siRNA knockdown of IPO13 activity in the fetal ovary, fewer germ cells are found to progress to the late-pachytene stage of meiosis and nuclear accumulation of UBC9 is reduced. Our findings strongly implicate a stage-specific role of IPO13 in nuclear-cytoplasmic translocation of cargoes that accompanies meiotic differentiation of the mouse germ cells.
authors.affiliation: Embryology Unit, Children's Medical Research Institute, Locked Bag 23, Wentworthville, NSW, 2145, Australia.
authors.forename: Yasuka L
authors.initials: YL
authors.lastname: Yamaguchi
authors.forename: Satomi S
authors.initials: SS
authors.lastname: Tanaka
authors.forename: Kunio
authors.initials: K
authors.lastname: Yasuda
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Matsui
authors.forename: Patrick P L
authors.initials: PP
authors.lastname: Tam
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005854:Germ Cells / Q000378:metabolism*; D028884:Karyopherins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D008540:Meiosis; D051379:Mice; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism; D000098843:Ubiquitin-Conjugating Enzyme UBC9
chemical_list: D028884:Karyopherins; C514744:importin 13 protein, mouse; D044763:Ubiquitin-Conjugating Enzymes; D000098843:Ubiquitin-Conjugating Enzyme UBC9