Cloning, Characterization, and Localization of Mouse and Human SPO11

Saccharomyces cerevisiae strains harboring a nonreciprocal, bridgeinduced translocation (BIT) between chromosomes VIII and XV exhibited an abnormal phenotype comprising elongated buds and multibudded, unevenly nucleated pseudohyphae. In these cells, we found evidence of molecular effects elicited by the translocation event and specific for its particular genomic location. Expression of genes flanking both translocation breakpoints increased up to five times, correlating with an increased RNA polymerase II binding to their promoters and with their histone acetylation pattern. Microarray data, CHEF, and quantitative PCR confirmed the data on the dosage of genes present on the chromosomal regions involved in the translocation, indicating that telomeric fragments were either duplicated or integrated mostly on chromosome XI. FACS analysis revealed that the majority of translocant cells were blocked in G1 phase and a few of them in G2. Some cells showed a posttranslational decrease of cyclin B1, in agreement with elongated buds diagnostic of a G2/M phase arrest. The actin1 protein was in some cases modified, possibly explaining the abnormal morphology of the cells. Together with the decrease in Rad53p and the lack of its phosphorylation, these results indicate that these cells have undergone adaptation after checkpointmediated G2/M arrest after chromosome translocation. These BIT translocants could serve as model systems to understand further the cellular and molecular effects of chromosome translocation and provide fundamental information on its etiology of neoplastic transformation in mammals.DNA integration ͉ yeast ͉ genome expression ͉ genome dynamics ͉ transcription

Section: Discussionmentioning

confidence: 97%

Cellular and molecular effects of nonreciprocal chromosome translocations in Saccharomyces cerevisiae

Nikitin

Tosato²,

Zavec³

et al. 2008

“…SSCs share molecular markers with undifferentiated spermatogonia (13)(14)(15)(16)(17), and these markers were expressed at significantly higher levels at 1 wk after birth in the testes of WT mice than in cKO mice. However, molecular markers for differentiated spermatogonia (18)(19)(20)(21)(22) were present at significantly higher levels at 1 wk after birth in cKO mice than in WT mice. In addition, germ cells containing the ZBTB16 marker for SSCs and undifferentiated spermatogonia (15) were detected by immunohistochemistry in 2-wk-old WT mice, but rarely in cKO males, and some of their tubules lack proliferating germ cells.…”

Section: Discussionmentioning

confidence: 99%

“…SSCs also share molecular markers with undifferentiated spermatogonia, including Nanos2, Gfra1, Zbtb16, Bcl6b, and THY1 (13)(14)(15)(16)(17). In addition, differentiating spermatogonia have characteristic molecular markers, including Ngn3, Nanos3, Spo11, and KIT (18)(19)(20)(21)(22). These molecular markers have been proven to be valuable tools for monitoring the presence or absence of different populations of spermatogonia.…”

mentioning

confidence: 99%

Targeting theGdnfGene in peritubular myoid cells disrupts undifferentiated spermatogonial cell development

Chen

Willis

Eddy

2016

157

128

Spermatogonial stem cells (SSCs) are a subpopulation of undifferentiated spermatogonia located in a niche at the base of the seminiferous epithelium delimited by Sertoli cells and peritubular myoid (PM) cells. SSCs self-renew or differentiate into spermatogonia that proliferate to give rise to spermatocytes and maintain spermatogenesis. Glial cell line-derived neurotrophic factor (GDNF) is essential for this process. Sertoli cells produce GDNF and other growth factors and are commonly thought to be responsible for regulating SSC development, but limited attention has been paid to the role of PM cells in this process. A conditional knockout (cKO) of the androgen receptor gene in PM cells resulted in male infertility. We found that testosterone (T) induces GDNF expression in mouse PM cells in vitro and neonatal spermatogonia (including SSCs) co-cultured with T-treated PM cells were able to colonize testes of germ cell-depleted mice after transplantation. This strongly suggested that T-regulated production of GDNF by PM cells is required for spermatogonial development, but PM cells might produce other factors in vitro that are responsible. In this study, we tested the hypothesis that production of GDNF by PM cells is essential for spermatogonial development by generating mice with a cKO of the Gdnf gene in PM cells. The cKO males sired up to two litters but became infertile due to collapse of spermatogenesis and loss of undifferentiated spermatogonia. These studies show for the first time, to our knowledge, that the production of GDNF by PM cells is essential for undifferentiated spermatogonial cell development in vivo.spermatogonial stem cell | stem cell niche | male fertility | spermatogenesis | conditional gene targeting T he seminiferous epithelium is separated by tight junctions between Sertoli cells into a luminal compartment containing spermatocytes and spermatids and a basal compartment containing spermatogonial stem cells (SSCs) and spermatogonia. The basal compartment is bounded above and on the sides by Sertoli cells and below by the basement membrane of the seminiferous tubule and a layer of peritubular myoid (PM) cells. SSCs are thought to reside in a microenvironmental niche in the basal compartment, where extrinsic cues influence their decision to either self-renew or enter the pathway of spermatogonial development (1, 2). They are a minor fraction of the undifferentiated spermatogonia in the basal compartment. The other undifferentiated spermatogonia (progenitors) give rise to differentiating spermatogonia that proliferate mitotically to progress on a developmental pathway toward becoming spermatocytes (3, 4). Our current understanding of the progression of SSCs to differentiating spermatogonia comes mainly from cell kinetic studies, germ cell transplantation assays, and the use of molecular markers that identify different populations of spermatogonia.The leading model for spermatogonial development specifies that when SSCs divide, they either self-renew by becoming two type A-single (A s ) spermato...

“…Homologous recombination in meiosis is required for proper chromosome segregation and generation of genetic diversity (22). In budding yeast, SPO11 plays a major role in the initiation of meiotic recombination (23) by catalyzing the formation of DSBs via a topoisomerase-like transesterase activity (24).…”

mentioning

confidence: 99%

The Arabidopsis AtRAD51 gene is dispensable for vegetative development but required for meiosis

Chen

Markmann-Mulisch

et al. 2004

264

328

The maintenance of genome integrity and the generation of biological diversity are important biological processes, and both involve homologous recombination. In yeast and animals, homologous recombination requires the function of the RAD51 recombinase. In vertebrates, RAD51 seems to have acquired additional functions in the maintenance of genome integrity, and rad51 mutations cause lethality, but it is not clear how widely these functions are conserved among eukaryotes. We report here a loss-of-function mutant in the Arabidopsis homolog of RAD51, AtRAD51. The atrad51-1 mutant exhibits normal vegetative and flower development and has no detectable abnormality in mitosis. Therefore, AtRAD51 is not necessary under normal conditions for genome integrity. In contrast, atrad51-1 is completely sterile and defective in male and female meioses. During mutant prophase I, chromosomes fail to synapse and become extensively fragmented. Chromosome fragmentation is suppressed by atspo11-1, indicating that AtRAD51 functions downstream of AtSPO11-1. Therefore, AtRAD51 likely plays a crucial role in the repair of DNA doublestranded breaks generated by AtSPO11-1. These results suggest that RAD51 function is essential for chromosome pairing and synapsis at early stages in meiosis in Arabidopsis. Furthermore, major aspects of meiotic recombination seem to be conserved between yeast and plants, especially the fact that chromosome pairing and synapsis depend on the function of SPO11 and RAD51.H omologous recombination and DNA-damage repair are fundamental biological processes found in all life forms. Homologous recombination plays a major role in both maintaining genome stability (DNA-damage repair) and the generation of genetic variability. Defects in DNA-damage repair generally lead to genome instability and are increasingly found to be associated with cancer in mammals. The active surveillance mechanisms that can recognize and precisely repair DNA damage to prevent the accumulation of errors are meanwhile thought to be intimately involved in the prevention of cancer and the delaying of aging (1, 2). Genes playing critical roles in homologous recombination are important for these processes.Homologous recombination has been intensively studied in budding yeast Saccharomyces cerevisiae, and a number of genes have been identified that function in this process. Some of these genes, including RAD51, were identified based on the hypersensitivity of their mutants to radiation (3). RAD51 and another yeast gene, DMC1, share significant sequence homology with the bacterial recA gene (4). Similar to the bacterial RecA protein, the yeast RAD51 protein acts in homology searching, DNA pairing, and strand exchange (5), activities important for both DNAdamage repair and meiosis. RAD51 homologs have been found in all eukaryotic organisms thus far and are well studied in the vertebrates human, mouse, and chicken. In contrast to yeast, the loss of RAD51 function is lethal in both chicken DT40 and mouse cells (4). These RAD51-deficient cells arrest dur...