title: Impaired spermatogenesis and fertility in mice carrying a mutation in the Spink2 gene expressed predominantly in testes.
abstract: Spermatogenesis is a complex process involving an intrinsic genetic program composed of germ cell-specific and -predominant genes. In this study, we investigated the mouse Spink2 (serine protease inhibitor Kazal-type 2) gene, which belongs to the SPINK family of proteins characterized by the presence of a Kazal-type serine protease inhibitor-pancreatic secretory trypsin inhibitor domain. We showed that recombinant mouse SPINK2 has trypsin-inhibitory activity. Distribution analyses revealed that Spink2 is transcribed strongly in the testis and weakly in the epididymis, but is not detected in other mouse tissues. Expression of Spink2 is specific to germ cells in the testis and is first evident at the pachytene spermatocyte stage. Immunoblot analyses demonstrated that SPINK2 protein is present in male germ cells at all developmental stages, including in testicular spermatogenic cells, testicular sperm, and mature sperm. To elucidate the functional role of SPINK2 in vivo, we generated mutant mice with diminished levels of SPINK2 using a gene trap mutagenesis approach. Mutant male mice exhibit significantly impaired fertility; further phenotypic analyses revealed that testicular integrity is disrupted, resulting in a reduction in sperm number. Moreover, we found that testes from mutant mice exhibit abnormal spermatogenesis and germ cell apoptosis accompanied by elevated serine protease activity. Our studies thus provide the first demonstration that SPINK2 is required for maintaining normal spermatogenesis and potentially regulates serine protease-mediated apoptosis in male germ cells.
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea.
authors.forename: Boyeon
authors.initials: B
authors.lastname: Lee
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea.
authors.forename: Inju
authors.initials: I
authors.lastname: Park
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea.
authors.forename: Sora
authors.initials: S
authors.lastname: Jin
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea.
authors.forename: Heejin
authors.initials: H
authors.lastname: Choi
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea.
authors.forename: Jun Tae
authors.initials: JT
authors.lastname: Kwon
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea.
authors.forename: Jihye
authors.initials: J
authors.lastname: Kim
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea.
authors.forename: Juri
authors.initials: J
authors.lastname: Jeong
authors.affiliation: Department of Life Science, The Catholic University of Korea, Bucheon 420-743, Korea, and.
authors.forename: Byung-Nam
authors.initials: BN
authors.lastname: Cho
authors.affiliation: Gamete Biology Section, Laboratory of Reproductive and Developmental Toxicology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709.
authors.forename: Edward M
authors.initials: EM
authors.lastname: Eddy
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea,. Electronic address: choch@gist.ac.kr.
authors.forename: Chunghee
authors.initials: C
authors.lastname: Cho
mesh_terms: D000818:Animals; D017209:Apoptosis; D005298:Fertility / Q000502:physiology*; D006023:Glycoproteins / Q000096:biosynthesis* / Q000235:genetics; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D008817:Mice, Mutant Strains; D016296:Mutagenesis; D009928:Organ Specificity / Q000502:physiology; D000074162:Serine Peptidase Inhibitors, Kazal Type; D015843:Serpins / Q000096:biosynthesis* / Q000235:genetics; D013091:Spermatogenesis / Q000502:physiology*; D013094:Spermatozoa / Q000166:cytology / Q000378:metabolism*; D013737:Testis / Q000166:cytology / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology*
chemical_list: D006023:Glycoproteins; C561771:SPINK2 protein, mouse; D000074162:Serine Peptidase Inhibitors, Kazal Type; D015843:Serpins