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1.
In mice, the juvenile spermatogonial depletion (jsd) mutation results in a single wave of spermatogenesis followed by failure of type A spermatogonial stem cells to repopulate the testis, rendering male animals sterile. It is not clear whether the defect in jsd resides in a failure of the somatic component to support spermatogenesis or in a failure that is intrinsic to the mutant's germ cells. To determine if the jsd intratesticular environment is capable of supporting spermatogenesis, germ cell transplantation experiments were performed in which C57BL/6 ROSA germ cells were transplanted into jsd recipients. To determine if jsd spermatogonia are able to develop in a permissive seminiferous environment, jsd germ cells were transplanted into W/W(v) and busulfan-treated C57BL/6 animals. The data demonstrate that up to 7 mo after transplantation of normal germ cells, jsd seminiferous tubules are capable of supporting spermatogenesis. In contrast, when jsd germ cells were transplanted into busulfan-treated C57BL/6 testis, or into testis of W/W(v) mice, no jsd-derived spermatogenesis was observed. The data support the hypothesis that the jsd phenotype is due to a defect in the germ cells themselves, and not in the intratubular environment.  相似文献   

2.
Spermatogenesis is dependent primarily on testosterone action on the Sertoli cells, but the molecular mechanisms have not been identified. Attempts to identify testosterone-regulated target genes in Sertoli cells have used microarray analysis of gene expression in mice lacking the androgen receptor (AR) in Sertoli cells (SCARKO) and wild-type mice, but the analyses have been complicated both by alteration of germ cell composition of the testis when pubertal or adult mice were used and by differences in Sertoli-cell gene expression from the expression in adults when prepubertal mice were used. To overcome these limitations and identify AR-regulated genes in adult Sertoli cells, we compared gene expression in adult jsd (Utp14b jsd/jsd, juvenile spermatogonial depletion) mouse testes and with that in SCARKO-jsd mouse testes, since their cellular compositions are essentially identical, consisting of only type A spermatogonia and somatic cells. Microarray analysis identified 157 genes as downregulated and 197 genes as upregulated in the SCARKO-jsd mice compared to jsd mice. Some of the AR-regulated genes identified in the previous studies, including Rhox5, Drd4, and Fhod3, were also AR regulated in the jsd testes, but others, such as proteases and components of junctional complexes, were not AR regulated in our model. Surprisingly, a set of germ cell–specific genes preferentially expressed in differentiated spermatogonia and meiotic cells, including Meig1, Sycp3, and Ddx4, were all upregulated about 2-fold in SCARKO-jsd testes. AR-regulated genes in Sertoli cells must therefore be involved in the regulation of spermatogonial differentiation, although there was no significant differentiation to spermatocytes in SCARKO-jsd mice. Further gene ontogeny analysis revealed sets of genes whose changes in expression may be involved in the dislocation of Sertoli cell nuclei in SCARKO-jsd testes.  相似文献   

3.
4.
Using subtractive hybridization and polymerase chain reaction, we developed a differential cloning system, the fragmented cDNA subtraction method, that requires only small amounts of materials. The cloning system was used to isolate several cDNA fragments expressed more abundantly in the premeiotic day 3 post-natal mouse testis than in the adult mouse testis. The isolated cDNA fragments included cDNA encoding the murine cyclin D2. Northern blot and in situ hybridization analyses revealed that, during testis development, cyclin D2 expression was most abundant in the neonatal proliferating Sertoli cells. Those type A spermatogonia that were thought to divide mitotically also expressed cyclin D2 mRNA. Other spermatogenic cells, such as mitotically arrested gonocytes in neonatal testis and meiotically dividing germ cells in adult testis as well as adult Sertoli cells, were negative for the cyclin D2 signal. Adult W/W v mutant mice lacking germ cells expressed cyclin D2 mRNA in terminally differentiated Sertoli cells. Elimination of germ cells other than the undifferentiated type A spermatogonia by treating wild-type mice with an anti-c- kit monoclonal antibody did not result in the expression of cyclin D2 in Sertoli cells. These results demonstrate that there are lineage- and developmental-specific expression patterns of cyclin D2 mRNA during mouse testis development. At the same time, it is suggested that primitive type A spermatogonia affect the cyclin D2 expression of Sertoli cells.  相似文献   

5.
Mutations in the dominant-white spotting (W; c-kit) and stem cell factor (Sl; SCF) genes, which encode the transmembrane tyrosine kinase receptor and its ligand, respectively, affect both the proliferation and differentiation of many types of stem cells. Almost all homozygous W or Sl mutant mice are sterile because of the lack of differentiated germ cells or spermatogonial stem cells. To characterize spermatogenesis in c-kit/SCF mutants and to understand the role of c-kit signal transduction in spermatogonial stem cells, the existence, proliferation, and differentiation of spermatogonia were examined in the W/Wv mutant mouse testis. In the present study, some of the W/Wv mutant testes completely lacked spermatogonia, and many of the remaining testes contained only a few spermatogonia. Examination of the proliferative activity of the W/Wv mutant spermatogonia by transplantation of enhanced green fluorescent protein (eGFP)-labeled W/Wv spermatogonia into the seminiferous tubules of normal SCF (W/Wv) or SCF mutant (Sl/Sld) mice demonstrated that the W/Wv spermatogonia had the ability to settle and proliferate, but not to differentiate, in the recipient seminiferous tubules. Although the germ cells in the adult W/Wv testis were c-kit-receptor protein-negative undifferentiated type A spermatogonia, the juvenile germ cells were able to differentiate into spermatogonia that expressed the c-kit-receptor protein. Furthermore, differentiated germ cells with the c-kit-receptor protein on the cell surface could be induced by GnRH antagonist treatment, even in the adult W/Wv testis. These results indicate that all the spermatogonial stem cell characteristics of settlement, proliferation, and differentiation can be demonstrated without stimulating the c-kit-receptor signal. The c-kit/SCF signal transduction system appears to be necessary for the maintenance and proliferation of differentiated c-kit receptor-positive spermatogonia but not for the initial step of spermatogonial cell differentiation.  相似文献   

6.
Adult C57BL/6J male mice homozygous for the mutant gene, juvenile spermatogonial depletion (jsd/jsd), show azoosper4ia and testes reduced to one-third normal size, but are otherwise phenotypically normal. In contrast, adult jsd/jsd females are fully fertile. This feature facilitated mapping the jsd gene to the centromeric end of chromosome 1; the gene order is jsd-Isocitrate dehydrogenase-1 (Idh-1)-Peptidase-3 (Pep-3). Analysis of testicular histology from jsd/jsd mice aged 3-10 wk revealed that these mutant mice experience one wave of spermatogenesis, but fail to continue mitotic proliferation of type A spermatogonial cells at the basement membrane. As a consequence, histological sections of testes from mutant mice aged 8-52 wk showed tubules populated by modest numbers of Sertoli cells, with only an occasional spermatogonial cell. Some sperm with normal morphology and motility were observed in epididymides of 6.5- but not in 8-wk or older mutants. Treatment with retinol failed to alter the loss of spermatogenesis in jsd/jsd mice. Analyses of serum hormones of jsd/jsd males showed that testosterone levels were normal at all ages--a finding corroborated by normal seminal vesicle and vas deferens weights, whereas serum follicle-stimulating hormone levels were significantly elevated in mutant mice from 4 to 20 wk of age. We hypothesize the jsd/jsd male may be deficient in proliferative signals from Sertoli cells that are needed for spermatogenesis.  相似文献   

7.
Dynamin 2 and dynamin 3 are highly expressed in testis. However, their functions in the tissue remain unclear. Considering that dynamin 1, neuron-specific isoform of dynamin, plays a pivotal role in endocytosis, functions of dynamin 2 and dynamin 3 in testis must be essential. Cellular expression and subcellular localization of dynamin 2 and dynamin 3 in testis were investigated. Dynamin 2 and dynamin 3 were highly expressed in germ cells and Sertoli cells, constituents of seminiferous tubules. By immunofluorescence it was revealed that dynamin 2 colocalizes with clathrin both at the plasmamembrane and at Golgi in a cell line of Sertoli cells. Immunoreactivity for dynamin 3, on the other hand, appeared as finer puncta, which did not colocalize with clathrin, suggesting that these two dynamins have distinct functions in Sertoli cells. In the klotho deficient mouse testis, which demonstrates disorder in spermatogenesis, expression of dynamin 2 and dynamin 3 was drastically reduced indicating possible association of these proteins with spermatogenesis.  相似文献   

8.
Spermatogonial stem cells are required for the initiation of spermatogenesis and the continuous production of sperm. In addition, they can acquire pluripotency and differentiate into derivatives of the three embryonic germ layers when cultured in the appropriate conditions. Therefore, understanding the signaling pathways that lead to self-renewal or differentiation of these cells is of paramount importance for the treatment of infertility, the development of male contraceptives, the treatment of testicular cancers, and ultimately for tissue regeneration. In this report, we studied some of the signaling pathways triggered by glial cell line-derived neurotrophic factor (GDNF), a component of the spermatogonial stem cell niche produced by the somatic Sertoli cells. As model systems, we used primary cultures of mouse spermatogonial stem cells, a mouse spermatogonial stem cell line and freshly isolated testicular tubules. We report here that GDNF promotes spermatogonial stem cell proliferation through activation of members of the Src kinase family, and that these kinases exert their action through a PI3K/Akt-dependent pathway to up-regulate N-myc expression. Thus, to proliferate, spermatogonial stem cells activate mechanisms that are similar to the processes observed in brain stem cells and lung progenitors.  相似文献   

9.
Male mice that are homozygous for the juvenile spermatogonial depletion (jsd) mutation in the Utp14b gene undergo several waves of spermatogenesis. However, spermatogonial differentiation ceases and in adults, spermatogonia are the only germ cells that remain. To understand further the blockage in spermatogonial differentiation in Utp14b(jsd) mutant mice, we correlated the rate and severity of spermatogonial depletion and the restoration of spermatogenesis following the suppression of testosterone or elevation of testicular temperature with the genetic background. Testes from Utp14b(jsd) mutant mice on B6, C3H, and mixed C3H-B6-129 (HB129) genetic backgrounds all showed steady decreases in the numbers of normal spermatogonia between 8 wk and 20 wk of age. The percentages of tubules with differentiating germ cells were higher and the spermatogonia were more advanced in C3H- background than in B6- or HB129-background Utp14b(jsd) mice. Genetic crosses showed that the source of the Y chromosome was a major factor in determining the severity of spermatogonial depletion in Utp14b(jsd) mutant mice. When Utp14b(jsd) mutants were subjected to total androgen ablation or unilateral cryptorchidization, spermatogenic development recovered markedly in the C3H and HB129 background but showed less recovery in the B6-background mice. The differences noted between the strains in terms of the severity of spermatogonial depletion were not dependent upon testosterone level or scrotal temperature but correlated with the magnitudes of the effects of elevated temperature on normal and Utp14b(jsd) mutant spermatogenic cells. Thus, the abilities of germ cells in certain strains to survive elevated temperatures may be related to their abilities to maintain some degree of differentiation potential after the Utp14b(jsd) gene is mutated.  相似文献   

10.
Ubiquitin carboxyl-terminal hydrolase 1 (UCH-L1) can be detected in mouse testicular germ cells, mainly spermatogonia and somatic Sertoli cells, but its physiological role is unknown. We show that transgenic (Tg) mice overexpressing EF1alpha promoter-driven UCH-L1 in the testis are sterile due to a block during spermatogenesis at an early stage (pachytene) of meiosis. Interestingly, almost all spermatogonia and Sertoli cells expressing excess UCH-L1, but little PCNA (proliferating cell nuclear antigen), showed no morphological signs of apoptosis or TUNEL-positive staining. Rather, germ cell apoptosis was mainly detected in primary spermatocytes having weak or negative UCH-L1 expression but strong PCNA expression. These data suggest that overexpression of UCH-L1 affects spermatogenesis during meiosis and, in particular, induces apoptosis in primary spermatocytes. In addition to results of caspases-3 upregulation and Bcl-2 downregulation, excess UCH-L1 influenced the distribution of PCNA, suggesting a specific role for UCH-L1 in the processes of mitotic proliferation and differentiation of spermatogonial stem cells during spermatogenesis.  相似文献   

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