title: The nuclear import factor importin α4 can protect against oxidative stress.
abstract: The importin (IMP) superfamily of nuclear transport proteins is essential to key developmental pathways, including in the murine testis where expression of the 6 distinct IMPα proteins is highly dynamic. Present predominantly from the spermatocyte stage onwards, IMPα4 is unique in showing a striking nuclear localization, a property we previously found to be linked to maintenance of pluripotency in embryonic stem cells and to the cellular stress response in cultured cells. Here we examine the role of IMPα4 in vivo for the first time using a novel transgenic mouse model in which we overexpress an IMPα4-EGFP fusion protein from the protamine 1 promoter to recapitulate endogenous testicular germ cell IMPα4 expression in spermatids. IMPα4 overexpression did not affect overall fertility, testis morphology/weight or spermatogenic progression under normal conditions, but conferred significantly (>30%) increased resistance to oxidative stress specifically in the spermatid subpopulation expressing the transgene. Consistent with a cell-specific role for IMPα4 in protecting against oxidative stress, haploid germ cells from IMPα4 null mice were significantly (c. 30%) less resistant to oxidative stress than wild type controls. These results from two unique and complementary mouse models demonstrate a novel protective role for IMPα4 in stress responses specifically within haploid male germline cells, with implications for male fertility and genetic integrity.
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University, Australia.
authors.forename: Julia C
authors.initials: JC
authors.lastname: Young
authors.forename: Jennifer D
authors.initials: JD
authors.lastname: Ly-Huynh
authors.forename: Helen
authors.initials: H
authors.lastname: Lescesen
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Miyamoto
authors.forename: Cate
authors.initials: C
authors.lastname: Browne
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Yoneda
authors.forename: Peter
authors.initials: P
authors.lastname: Koopman
authors.forename: Kate L
authors.initials: KL
authors.lastname: Loveland
authors.forename: David A
authors.initials: DA
authors.lastname: Jans
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000235:genetics*; D000818:Animals; D015139:Blotting, Southern; D015153:Blotting, Western; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000235:genetics* / Q000378:metabolism; D049109:Cell Proliferation; D004247:DNA / Q000235:genetics; D005298:Fertility; D005434:Flow Cytometry; D005854:Germ Cells / Q000166:cytology / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D018384:Oxidative Stress; D011401:Promoter Regions, Genetic / Q000235:genetics; D011479:Protamines / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013087:Spermatids / Q000166:cytology / Q000378:metabolism*; D013091:Spermatogenesis; D013737:Testis / Q000166:cytology / Q000378:metabolism*; D028901:alpha Karyopherins / Q000502:physiology*
chemical_list: C106306:KPNA3 protein, human; C082073:PRM1 protein, human; D011479:Protamines; D011993:Recombinant Fusion Proteins; D028901:alpha Karyopherins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D004247:DNA
keywords: Importin/karyopherin; Nuclear transport; Oxidative stress; Spermatogenesis