title: Murine male germ cell apoptosis induced by busulfan treatment correlates with loss of c-kit-expression in a Fas/FasL- and p53-independent manner.
abstract: Male germ cell apoptosis has been extensively explored in rodents. In contrast, very little is known about the susceptibility of developing germ cells to apoptosis in response to busulfan treatment. Spontaneous apoptosis of germ cells is rarely observed in the adult mouse testis, but under the experimental conditions described here, busulfan-treated mice exhibited a marked increase in apoptosis and a decrease in testis weight. TdT-mediated dUTP-X nicked end labeling analysis indicates that at one week following busulfan treatment, apoptosis was confined mainly to spermatogonia, with lesser effects on spermatocytes. The percentage of apoptosis-positive tubules and the apoptotic cell index increased in a time-dependent manner. An immediate effect was observed in spermatogonia within one week of treatment, and in the following week, secondary effects were observed in spermatocytes. RT-PCR analysis showed that expression of the spermatogonia-specific markers c-kit and Stra 8 was reduced but that Gli I gene expression remained constant, which is indicative of primary apoptosis of differentiating type A spermatogonia. Three and four weeks after busulfan treatment, RAD51 and FasL expression decreased to nearly undetectable levels, indicating that meiotic spermatocytes and post-meiotic cells, respectively, were lost. The period of germ cell depletion did not coincide with increased p53 or Fas/FasL expression in the busulfan-treated testis, although p110Rb phosphorylation and PCNA expression were inhibited. These data suggest that increased depletion of male germ cells in the busulfan-treated mouse is mediated by loss of c-kit/SCF signaling but not by p53- or Fas/FasL-dependent mechanisms. Spermatogonial stem cells may be protected from cell death by modulating cell cycle signaling such that E2F-dependent protein expression, which is critical for G1 phase progression, is inhibited.
authors.affiliation: Division of Applied Life Science, College of Agriculture and Life Science, Gyeongsang National University, Jin-ju, GyeongNam 660-701, South Korea.
authors.forename: Yun-Jung
authors.initials: YJ
authors.lastname: Choi
authors.forename: Do-Won
authors.initials: DW
authors.lastname: Ok
authors.forename: Dueg-Nam
authors.initials: DN
authors.lastname: Kwon
authors.forename: Jong-Il
authors.initials: JI
authors.lastname: Chung
authors.forename: Heung-Cheol
authors.initials: HC
authors.lastname: Kim
authors.forename: Sung-Moon
authors.initials: SM
authors.lastname: Yeo
authors.forename: Teoan
authors.initials: T
authors.lastname: Kim
authors.forename: Han-Geuk
authors.initials: HG
authors.lastname: Seo
authors.forename: Jin-Hoi
authors.initials: JH
authors.lastname: Kim
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000477:Alkylating Agents / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D015415:Biomarkers; D002066:Busulfan / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D053222:Fas Ligand Protein; D018507:Gene Expression Regulation, Developmental; D005854:Germ Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D006801:Humans; D020287:In Situ Nick-End Labeling; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009929:Organ Size; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics / Q000378:metabolism*; D051135:Rad51 Recombinase; D016160:Retinoblastoma Protein / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D013737:Testis / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D019014:fas Receptor / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000477:Alkylating Agents; D015415:Biomarkers; D004268:DNA-Binding Proteins; C505661:FASLG protein, human; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D018809:Proliferating Cell Nuclear Antigen; D011506:Proteins; D016160:Retinoblastoma Protein; C102019:Stra8 protein, mouse; D016159:Tumor Suppressor Protein p53; D019014:fas Receptor; D019009:Proto-Oncogene Proteins c-kit; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; C495154:Rad51 protein, mouse; D002066:Busulfan