@misc{oai:ir.soken.ac.jp:00001043,
 author = {齋藤, 憲二 and サイトウ, ケンジ and SAITO, Kenji},
 month = {2016-02-17, 2016-02-17},
 note = {Continuation of spermatogenic process throughout life relies on a proper<br />regulation of self-renewal and differentiation of spermatogonial stem cells which is<br />present in a special cellular organization called a niche. In spite of biological<br />significance of the spermatogonial stem cells, little is known about their behavior and<br />properties because of a lack of model system to approach the stem cell maintenance<br /> and differentiation in several organisms. <br />　　In this study, I show the presence of subpopulations in zebrafish type A<br />spermatogonia which is classically considered homogeneous pepulation varying in<br />size, location pattern and cell cycle phase. Morphological analysis showed two types<br />of type A sperrnatogonia that are focalized distant from basement membranes (termed<br />type A<small>dt</small>) and close to basement membranes (A<small>cl</small>). The thymidine analogue <br />5-bromo-2'-deoxyuridine (BrdU) incorporation experiments showed that duration of <br />cell cycle of the type A<small>cl</small> spermatogonia was longer than that of the.type A<small>dt</small> <br />spermatogonia. Tracing label-retaining cells (LRCs), after 4 weeks of chase, I <br />observed occasionally BrdU-positive type A<small>cl</small> spermatogonia. Immunohistochemical<br /> analysis using antibody against zebrafish homologue of Synthetic lethal mutant of <br />dpb11-1 (zSld5) which is able to distinguish between the guiescent cells and the <br />proliferation cells showed that type A<small>cl</small> spermatogonia could be divided into two<br />subpopulations. One population is zSld5-positive type A<small>cl</small> spermatogonia and the other <br />is zSld5-negative type A<small>cl</small> spermatogonia In addition, many LRCs are contained in a<br />latter population. All the results suggest that type zSld5-negative type A<small>cl</small> spermatogonia <br />are most undifferentiated type A spermatogonia. <br />　　It is generally known that spermatogonial stem cells have ability to restore <br />spermatogenesis when a testis was damaged by a drug or irradiation. To elucidate the<br />characterization of type A spermatogonia, I examined the effect of cytotoxic reagent <br />busulfan on male germ cells. As a result, only type A<small>cl</small> spermatogonia survived after <br />treatment of busulfan, and then recovered spermatogenesis. The morphological <br />observation suggests that type A<small>cl</small> spermatogonia are the most resistant cell population <br />against busulfan in the zebrafish testis. Detailed analysis revealed that the number of <br />zSld5-positive type type A<small>cl</small> spermatogonia increased transiently after busulfan treatment, while the number of type zSld5-negative type A<small>cl</small> spermatogonia relatively stabilized. These results suggest that both zSld5-negative and zSld5-positive type A<small>cl</small> spermatogonia would posses a feature of spermatogonial stem cells, like a actual stem cell and a potential stem cell, respectively. <br />　　Furthermore, I developed the <i>in vitro</i> culture condition for supporting the maintenance and proliferation of type A spermatogonia by the use of Sertoli feeder ZtA6-6 cells for 1 month or so. <br />　　This study represents the first step towards further understanding the character of spermatogonial stem cells and molecular mechanisms to maintain the undifferentaition status in teleosts., application/pdf, 総研大甲第1161号},
 title = {Characterization of type A spermatogonia and development of the culture system in zebrafish},
 year = {}
}