title: Impaired spermatogenic ability of testicular germ cells in mice deficient in the LIM-kinase 2 gene.
abstract: LIM-Kinase (LIMK), including LIMK1 and LIMK2, is the only known catalytic protein among LIM-family molecules. It is well known that LIMK phosphorylates and inactivates cofilin, an actin-depolymerizing factor regulating actin reorganization, while in vivo functions have remained to be elucidated. In the present study, we generated Limk2 gene-deficient mice in which three LIMK2 isoforms were disrupted in a Cre-mediated fashion. Impaired cofilin phosphorylation was clearly observed in Limk2-/- fibroblasts stimulated with bradykinin or lysophosphatidic acid, thereby suggesting that Cdc42 or Rho-dependent LIMK activation did not occur. However, Limk2-/- mice did not exhibit embryonic lethality or any phenotypic abnormalities in postnatal growth and development, except for spermatogenesis in the testis. The testes of Limk2-/- mice were smaller in size and partial degeneration of spermatogenic cells in the seminiferous tubules was apparent in association with increased apoptosis. In addition, the viability of Limk2-/- spermatogenic cells, when cultured under stressed conditions, was diminished. Furthermore, the potential for germ cells to differentiate in a regenerative state was severely impaired in Limk2-/- testis. Experimental hyperthermia induced impairment of ADF/cofilin phosphorylation and the formation of intranuclear cofilin inclusions in mutant germ cells. Based on these findings, we propose that LIMK2, especially the testis-specific isoform tLIMK2, plays an important role in proper progression of spermatogenesis by regulation of cofilin activity and/or localization in germ cells.
authors.affiliation: Division of Molecular Regenerative Medicine, Course of Advanced Medicine B7, Osaka University Graduate School of Medicine, Suita, Osaka, 565-0871, Japan.
authors.forename: Hisaaki
authors.initials: H
authors.lastname: Takahashi
authors.forename: Uichi
authors.initials: U
authors.lastname: Koshimizu
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Miyazaki
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Nakamura
mesh_terms: D051339:Actin Depolymerizing Factors; D000818:Animals; D017209:Apoptosis; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured / Q000473:pathology; D003456:Cryptorchidism / Q000473:pathology; D051345:Destrin; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation; D018390:Gene Targeting; D006358:Hot Temperature; D007248:Infertility, Male / Q000235:genetics*; D054461:Lim Kinases; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008840:Microfilament Proteins / Q000378:metabolism; D020033:Protein Isoforms / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D011494:Protein Kinases / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D011499:Protein Processing, Post-Translational; D013091:Spermatogenesis / Q000235:genetics*; D013094:Spermatozoa / Q000378:metabolism / Q000473:pathology*; D013737:Testis / Q000473:pathology*; D020764:cdc42 GTP-Binding Protein / Q000502:physiology
chemical_list: D051339:Actin Depolymerizing Factors; D051345:Destrin; C495825:Dstn protein, mouse; D008840:Microfilament Proteins; D020033:Protein Isoforms; D011494:Protein Kinases; D054461:Lim Kinases; C095325:Limk2 protein, mouse; D020764:cdc42 GTP-Binding Protein