Regulation of Spermatogonial Stem Cells by MicroRNAs.
Bibliographic record
Abstract
MicroRNAs (miRNAs) have recently been identified as a new class of short single-stranded endogenous RNA molecules (~22 nt in length). Although miRNAs were first discovered in Caenorhabditis elegans in 1993, it was only 10 years ago that they were identified in mammals. MiRNAs are highly conserved across species and it has been estimated that miRNAs may regulate up to 30% of all genes in the human genome. MiRNAs have critical functions in many diverse biological processes, including the regulation of stemness, cell proliferation, differentiation, and apoptosis. The miRNA 17-92 cluster has been suggested to play important roles in regulating renewal and/or differentiation of stem cells, including in ES cells and in other adult stem cells. However, the function of miRNAs in regulating spermatogonial stem cells (SSCs) is still unknown. In this study, we explored the expression, the role, and the targets of the miRNA 17-92 cluster in SSCs, specifically miRNA-20, miRNA-106a, and miRNA-93. Real-time PCR and fluorescent in situ hybridization revealed that miRNA-20 and miRNA-106a were abundantly expressed in mouse SSCs (GFRA1+ spermatogonia), whereas their expression decreased significantly in the differentiated c-kit+ spermatogonia, suggesting that miRNA-20 and miRNA-106a play a role in regulating renewal of the SSCs. MiRNA-93 was significantly lower in the SSCs compared to the differentiated spermatogonia, suggesting that miRNA-93 regulates differentiation. Using miRNA microarrays, we identified a list of miRNAs that were enriched in the SSCs compared to non-stem cells, e.g., Let-7G and Let-7I. To identify cell phenotype and genes regulated by a particular miRNA, we used mimics to miRNA-20, miRNA-106a, and miRNA-93, both in vitro and in vivo. The miRNA mimics are chemically synthesized RNA designed to mimic individual endogenous mature miRNAs. The mimics enter the miRNA-processing pathway and are treated identical to their endogenous counterpart. Semi-quantitative RT-PCR demonstrated that miRNA-20 and miRNA-106a mimics increased expression of PCNA and Plzf mRNA in the SSCs. In contrast, miRNA-20 and miRNA-106a inhibitors induced the expression of c-kit mRNA. These results further suggest that miRNA-20 and miRNA-106a may be involved in renewal of SSCs. Using software prediction and an in vitro study, we demonstrated that Stat3 is a target of miRNA-20 and miRNA-106a. We next examined the role of these miRNAs in vivo using mimics transfected into the GFRA1+ SSCs. These miRNA-transfected stem cells were then transplanted into seminiferous tubules of sterile busulfan treated mice. The miRNA-20 and miRNA-106a mimics increased significantly the number of SSCs in the testes of the busulfan treated mice, compared to controls, when analyzed by immunohistochemistry after 60 days. Our study provides novel insights into the endogenous small RNA molecules that regulate SSCs and has important implications on offering new therapeutic targets for the treatment of male infertility as well as a novel approach for the treatment of male contraception. (platform)
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".