Role of miR-34c microRNA in the late steps of spermatogenesis

MiR-663a Stimulates Proliferation and Suppresses Early Apoptosis of Human Spermatogonial Stem Cells by Targeting NFIX and Regulating Cell Cycle

Human spermatogonial stem cells (SSCs) could have significant applications in reproductive medicine and regenerative medicine because of their great plasticity. The fate determinations of human SSCs are mediated by epigenetic factors. However, nothing is known about the regulation of non-coding RNA on human SSCs. Here we have explored for the first time the expression, function, and target of miR-663a in human SSCs. MiR-663a was upregulated in human spermatogonia compared with pachytene spermatocytes, as indicated by microRNA microarray and real-time PCR. CCK-8 and 5-Ethynyl-2′-deoxyuridine (EDU) assays revealed that miR-663a stimulated cell proliferation and DNA synthesis of human SSCs. Annexin V and propidium iodide (PI) staining and flow cytometry demonstrated that miR-663a inhibited early and late apoptosis of human SSCs. Furthermore, NFIX was predicted and verified as a direct target of miR-663a. NFIX silencing led to an enhancement of cell proliferation and DNA synthesis and a reduction of the early apoptosis of human SSCs. NFIX silencing neutralized the influence of miR-663a inhibitor on the proliferation and apoptosis of human SSCs. Finally, both miR-663a mimics and NFIX silencing upregulated the levels of cell cycle regulators, including Cyclin A2, Cyclin B1, and Cyclin E1, whereas miR-663a inhibitor had an adverse effect. Knockdown of Cyclin A2, Cyclin B1, and Cyclin E1 led to the decrease in the proliferation of human SSCs. Collectively, miR-663a has been identified as the first microRNA that promotes the proliferation and DNA synthesis and suppresses the early apoptosis of human SSCs by targeting NFIX via cell cycle regulators Cyclin A2, Cyclin B1, and Cyclin E1. This study thus provides novel insights into the molecular mechanisms underlying human spermatogenesis, and it could offer novel targets for treating male infertility and other human diseases.

Identification and characterisation of microRNAs and Piwi-interacting RNAs in cockerels' spermatozoa by Solexa sequencing

1. There has been substantial research focused on the roles of microRNAs (miRNAs) and Piwi-interacting RNAs (piRNAs) derived from mammalian spermatozoa; however, comparatively little is known about the role of spermatozoa-derived miRNAs and piRNAs within breeding cockerels' spermatozoa. 2. A small RNA library of cockerels' spermatozoa was constructed using Illumina high-throughput sequencing technology. Unique sequences with lengths of 18-26 nucleotides were mapped to miRBase 21.0 and unique sequences with lengths of 25-37 nucleotides were mapped to a piRNA database. A total of 1311 miRNAs and 2448 potential piRNAs were identified. Based on stem-loop qRT-PCR, 8 miRNAs were validated. 3. Potential target genes of the abundant miRNAs were predicted, and further Kyoto Encyclopedia of Genes and Genomes database (KEGG) and Gene Ontology (GO) analyses were performed, which revealed that some candidate miRNAs were involved in the spermatogenesis process, spermatozoa epigenetic programming and further embryonic development. 5. GO and KEGG analyses based on mapping genes of expressed piRNAs were performed, which revealed that spermatozoal piRNAs could play important regulatory roles in embryonic development of offspring. 6. The search for endogenous spermatozoa miRNAs and piRNAs will contribute to a preliminary database for functional and molecular mechanistic studies in embryonic development and spermatozoa epigenetic programming.

Identification and characterization of microRNAs in the pituitary of pubescent goats

BACKGROUND

Puberty is the period during a female mammal's life when it enters estrus and ovulates for the first time; this indicates that a mammal is capable of reproduction. The onset of puberty is a complex and tightly coordinated biological event; it has been reported that microRNAs (miRNAs) are involved in regulating the initiation of puberty.

METHODS

We performed miRNA sequencing on pituitary tissue from prepubescent and pubescent goats to investigate differences in miRNA expression during the onset of puberty in female goats. The target genes of these miRNAs were evaluated by GO enrichment and KEGG pathway analysis to identify critical pathways regulated by these miRNAs during puberty in goats. Finally, we selected four known miRNA and one novel miRNAs to evaluate expression patterns in two samples via qRT-PCR to validate the RNA-seq data.

RESULTS

In this study, 476 miRNAs were detected in goat pituitary tissue; 13 of these were specifically expressed in the pituitary of prepubescent goats, and 17 were unique to the pituitary of pubescent goats. Additionally, 73 novel miRNAs were predicted in these two libraries. 20 differentially expressed miRNAs were identified in this study. KEGG pathway enrichment analysis revealed that the differentially expressed miRNA target genes were enriched in pathways related to ovary development during puberty, including the GABAergic synapse, oxytocin signaling pathway, the cAMP signaling pathway, progesterone-mediated oocyte maturation. In this study, differential miRNA expression in the pituitary tissue of prepubescent and pubescent goats were identified and characterized.

CONCLUSION

These results provide important information regarding the potential regulation of the onset of goat puberty by miRNAs, and contribute to the elucidation of miRNA regulated processes during maturation and reproduction.

An miR-200 Cluster on Chromosome 23 Regulates Sperm Motility in Zebrafish

Besides its well-documented roles in cell proliferation, apoptosis, and carcinogenesis, the function of the p53-microRNA axis has been recently revealed in the reproductive system. Recent studies indicated that miR-200 family members are dysregulated in nonobstructive azoospermia patients, whereas their functions remain poorly documented. The aim of this study was to investigate the function of the miR-200 family on zebrafish testis development and sperm activity. There was no substantial difference in testis morphology and histology between wild-type (WT) and knockout zebrafish with deletion of miR-200 cluster on chromosome 6 (chr6-miR-200-KO) or on chromosome 23 (chr23-miR-200-KO). Interestingly, compared with WT zebrafish, the chr6-miR-200-KO zebrafish had no difference on sperm motility, whereas chr23-miR-200-KO zebrafish showed significantly improved sperm motility. Consistently, ectopic expression of miR-429a, miR-200a, and miR-200b, which are located in the miR-200 cluster on chromosome 23, significantly reduced motility traits of sperm. Several sperm motility-related genes, such as amh, wt1a, and srd5a2b have been confirmed as direct targets of miR-200s on chr23. 17α-ethynylestradiol (EE2) exposure resulted in upregulated expression of p53 and miR-429a in testis and impairment of sperm motility. Strikingly, in p53 mutant zebrafish testis, the expression levels of miR-200s on chr23 were significantly reduced and accompanied by a stimulation of sperm motility. Moreover, the upregulation of miR-429a associated with EE2 treatment was abolished in testis with p53 mutation. And the impairment of sperm activity by EE2 treatment was also eliminated when p53 was mutated. Together, our results reveal that miR-200 cluster on chromosome 23 controls sperm motility in a p53-dependent manner.

Comparative Profiling of MicroRNAs Reveals the Underlying Toxicological Mechanism in Mice Testis Following Carbon Ion Radiation

This study investigated the toxicity of heavy ion radiation to mice testis by microRNA (miRNA) sequencing and bioinformatics analyses. Testicular indices and histology were measured following enterocoelia irradiation with a 2 Gy carbon ion beam, with the testes exhibiting the most serious injuries at 4 weeks after carbon ion radiation (CIR) exposure. Illumina sequencing technology was used to sequence small RNA libraries of the control and irradiated groups at 4 weeks after CIR. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses implicated differential miRNAs in the regulation of target genes involved in metabolism, development, and reproduction. Here, 8 miRNAs, including miR-34c-5p, miR-138, and 6 let-7 miRNA family members previously reported in testis after radiation, were analyzed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) to validate miRNA sequencing data. The differentially expressed miRNAs described here provided a novel perspective for the role of miRNAs in testis toxicity following CIR.

Integrated analysis miRNA and mRNA profiling in patients with severe oligozoospermia reveals miR-34c-3p downregulates PLCXD3 expression

Our previous research suggested that an integrated analysis of microRNA (miRNA) and messenger RNA (mRNA) expression is helpful to explore miRNA-mRNA interactions and to uncover the molecular mechanisms of male infertility. In this study, microarrays were used to compare the differences in the miRNA and mRNA expression profiles in the testicular tissues of severe oligozoospermia (SO) patients with obstructive azoospermia (OA) controls with normal spermatogenesis. Four miRNAs (miR-1246, miR-375, miR-410, and miR-758) and six mRNAs (SLC1A3, PRKAR2B, HYDIN, WDR65, PRDX1, and ADATMS5) were selected to validate the microarray data using quantitative real-time PCR. Using statistical calculations and bioinformatics predictions, we identified 33 differentially expressed miRNAs and 1,239 differentially expressed mRNAs, among which one potential miRNA-target gene pair, miR-34c-3p and PLCXD3 (Phosphatidylinositol-Specific Phospholipase C, X Domain Containing 3), was identified. Immunohistochemical analysis indicated that PLCXD3 was located within the germ cells of the mouse and human testis. Moreover, we found that miR-34c-3p was able to decrease PLCXD3 expression in mouse (GC-1 and TM4) and human (NCM460) cell lines, presumably indicating the possibility that miR-34c-3p acts as an intracellular mediator in germinal lineage differentiation. Notably, we reported the expression of the PLCXD3 protein in a man with normal spermatogenesis and the lack of the PLCXD3 protein in a man with SO. Therefore, the identified miRNA and mRNA may represent a potentially novel molecular regulatory network and therapeutic targets for the study or treatment of SO, which might provide a better understanding of the molecular basis of spermatogenesis dysfunction.

Regulatory Functions of MicroRNAs in Male Reproductive Health: A New Approach to Understanding Male Infertility

MicroRNAs (miRNAs) are a novel class of small noncoding RNAs (ncRNAs) that play critical roles in regulation of gene expression, especially at posttranscriptional level. Over the past decade, the degree to which miRNAs are involved in male infertility has become clear. They are expressed in a cell- or phase-specific manner during spermatogenesis and play crucial role in male reproductive health. Therefore, dysregulation of miRNAs in testicular cells can be considered as a molecular basis for reproductive failure and male infertility. The abnormal expression pattern of miRNAs can be transmitted to the offspring via assisted reproductive techniques (ART) and results in the birth of children with a higher risk of infertility, congenital abnormalities, and morbidity. This review expounds on the miRNAs reported to play essential roles in somatic cells development, germ cells differentiation, steroidogenesis, normal spermatogenesis, sperm maturation, and male infertility, as well as emphasizes their importance as minimally invasive biomarkers of male infertility.

miR-34a Regulates Sperm Motility in Zebrafish

Increasing attention has been focused on the role of microRNAs in post-transcription regulation during spermatogenesis. Recently, the miR-34 family has been shown to be involved in the spermatogenesis, but the clear function of the miR-34 family in spermatogenesis is still obscure. Here we analyzed the function of miR-34a, a member of the miR-34 family, during spermatogenesis using miR-34a knockout zebrafish generated by the clustered regularly interspaced short palindromic repeats/associated protein 9 (CRISPR/Cas9) system. miR-34a knockout zebrafish showed no obvious defects on testis morphology and sperm quantity. However, we found a significant increase in progressive sperm motility that is one of the pivotal factors influencing in vitro fertilization rates, in the knockout zebrafish. Moreover, breeding experiments showed that, when miR-34a-knockout male zebrafish mated with the wide-type females, they had a higher fertilization rate than did the wide-type males. Glycogen synthase kinase-3a (gsk3a), a potential sperm motility regulatory gene was predicted to be targeted by miR-34a, which was further supported by luciferase reporter assays, since a significant decrease of luciferase activity was detected upon ectopic overexpression of miR-34a. Our findings suggest that miR-34a downregulates gsk3a by targeting its 3' untranslated region, and miR-34a/gsk3a interaction modulates sperm motility in zebrafish. This study will help in understanding in the role of the miR-34 family during spermatogenesis and will set paths for further studies.

miR‐31 Regulates Spermatogonial Stem Cells Meiosis via Targeting Stra8

Stra8 (stimulated by retinoic acid gene 8) is a specific gene that is expressed in mammalian germ cells during transition from mitosis to meiosis and plays a key role in the initiation of meiosis in mammals and birds. So, the evaluation of the Stra8 pathway in cSSCs may provide a deeper insight into mammalian spermatogenesis. miRNA was also an important regulating factor for meiosis of SSCs. However, there is currently no data indicating that miRNA regulate the meiosis of SSCs via Stra8. Here, we predicted the prospective miRNA targeting to Stra8 using the online Bioinformatics database‐Targetscan, and performed an analysis of the dual‐luciferase recombinant vector, pGL3‐CMV‐LUC‐MCS‐Stra8‐3′UTR. miR‐31 mimics (miR‐31m), miR‐31 inhibitors (miR‐31i), Control (NC, scrambled oligonucleotides transfection) were transfected into cSSCs; Stra8 and miRNA were analyzed by RT‐qPCR, immunofluorescence, and Western blot. The detection of haploid was conducted by flow cytometry. The results showed that miR‐31 regulates meiosis of cSSCs via targeting Stra8 in vitro and in vivo. Our study identifies a new regulatory pathway that miR‐31 targets Stra8 and inhibits spermatogenesis. J. Cell. Biochem. 118: 4844–4853, 2017. © 2017 Wiley Periodicals, Inc.

Cellular and molecular characterization of gametogenic progression in ex vivo cultured prepuberal mouse testes

BACKGROUND

Recently, an effective testis culture method using a gas-liquid interphase, capable of differentiate male germ cells from neonatal spermatogonia to spermatozoa has been developed. Nevertheless, this methodology needs deep analyses that allow future experimental approaches in basic, pathologic and/or reprotoxicologic studies. Because of this, we characterized at cellular and molecular levels the entire in vitro spermatogenic progression, in order to understand and evaluate the characteristics that define the spermatogenic process in ex vivo cultured testes compared to the in vivo development.

METHODS

Testicular explants of CD1 mice aged 6 and 10 days post-partum were respectively cultured during 55 and 89 days. Cytological and molecular approaches were performed, analyzing germ cell proportion at different time culture points, meiotic markers immunodetecting synaptonemal complex protein SYCP3 by immunocytochemistry and the relative expression of different marker genes along the differentiation process by Reverse Transcription - quantitative Polymerase Chain Reaction. In addition, microRNA and piwi-interactingRNA profiles were also evaluated by Next Generation Sequencing and bioinformatic approaches.

RESULTS

The method promoted and maintained the spermatogenic process during 89 days. At a cytological level we detected spermatogenic development delays of cultured explants compared to the natural in vivo process. The expression of different spermatogenic stages gene markers correlated with the proportion of different cell types detected in the cytological preparations.

CONCLUSIONS

In vitro progression analysis of the different spermatogenic cell types, from both 6.5 dpp and 10.5 dpp testes explants, has revealed a relative delay in relation to in vivo process. The expression of the genes studied as biomarkers correlates with the cytologically and functional detected progression and differential expression identified in vivo. After a first analysis of deep sequencing data it has been observed that as long as cultures progress, the proportion of microRNAs declined respect to piwi-interactingRNAs levels that increased, showing a similar propensity than which happens in in vivo spermatogenesis. Our study allows to improve and potentially to control the ex vivo spermatogenesis development, opening new perspectives in the reproductive biology fields including male fertility.

The roles of microRNAs and siRNAs in mammalian spermatogenesis

MicroRNAs and siRNAs, both of which are AGO-bound small RNAs, are essential for mammalian spermatogenesis. Although their precise germline roles remain largely uncharacterized, recent discoveries suggest that they function in mechanisms beyond microRNA-mediated post-transcriptional control, playing roles in DNA repair and transcriptional regulation within the nucleus. Here, we discuss the latest findings regarding roles for AGO proteins and their associated small RNAs in the male germline. We integrate genetic, clinical and genomics data, and draw upon findings from non-mammalian models, to examine potential roles for AGO-bound small RNAs during spermatogenesis. Finally, we evaluate the emerging and differing roles for AGOs and AGO-bound small RNAs in the male and female germlines, suggesting potential reasons for these sexual dimorphisms.

Summary: This Review article summarizes the latest findings regarding roles for AGO proteins and their associated small RNAs in the male germline, with a particular focus on spermatogenesis.

MicroRNA-150 regulates steroidogenesis of mouse testicular Leydig cells by targeting STAR

Leydig cells are essential for male reproductive development throughout life. Production of androgens as well as intermediate steroids is tightly regulated. Although microRNAs (miRNAs) are suggested to play important roles in spermatogenesis, little is currently known regarding the regulation of steroidogenesis by miRNAs in Leydig cells. Here, we found that miR-150 was predominantly expressed in Leydig cells within mouse testis. Therefore, we determined steroidogenesis of the Leydig cells in which miR-150 was knocked down or overexpressed using miR-150 antagomir and agomir, respectively. Compared with negative control group, a significant increase of STAR expression was observed in miR-150 antagomir-treated Leydig cells. Conversely, STAR expression was significantly reduced in miR-150 agomir-transfected Leydig cells. Production of sex-steroid precursors and testosterone of Leydig cells was also negatively controlled by miR-150. We further identified Star as a target of miR-150 using luciferase reporter assay. Finally, we confirmed that miR-150 was necessary for steroidogenesis and spermatogenesis in vivo via intratesticular injection of miR-150 antagomir or agomir. Taken together, our studies suggest that miR-150 negatively regulates the expression of STAR and steroidogenesis of Leydig cells in mice.

MicroRNAs downregulated following immune activation of rat testis

PROBLEM

Little is known about how infection and the response to inflammation affect the microRNA (miRNA) profile of the male reproductive tract. We hypothesized that expression of inflammatory-related miRNAs would be altered following immune activation of rat testis.

METHOD OF STUDY

Testis total RNA was purified from Sprague-Dawley rats 3 or 6 hours after receiving a 5 mg/kg intraperitoneal injection of bacterial lipopolysaccharide (LPS) and examined by qPCR using an 84-panel miRNA array.

RESULTS

Five inflammatory-related miRNAs showed a greater than twofold downregulation (P<.05) in the 3-hour group (rno-let-7f-5p, rno-miR-200c-3p, rno-miR-23a-3p, rno-miR-23b-3p, rno-miR-98-5p) and five from the 6-hour group (rno-miR-17-5p, rno-miR-19a-3p, rno-miR-34a-5p, rno-miR-34c-5p, rno-miR-449a-5p).

CONCLUSION

Review of the literature has revealed that these miRNAs also play important roles in the maintenance of fertility, formation and elimination of cancer, and development of the male reproductive tract. Further study will lead to a greater understanding of male reproductive immunology and related health issues.

Class II phosphoinositide 3-kinase C2β regulates a novel signaling pathway involved in breast cancer progression

It is now well established that the enzymes phosphoinositide 3-kinases (PI3Ks) have a key role in the development and progression of many cancer types and indeed PI3Ks inhibitors are currently being tested in clinical trials. Although eight distinct PI3K isoforms exist, grouped into three classes, most of the evidence currently available are focused on one specific isoform with very little known about the potential role of the other members of this family in cancer. Here we demonstrate that the class II enzyme PI3K-C2β is overexpressed in several human breast cancer cell lines and in human breast cancer specimens. Our data indicate that PI3K-C2β regulates breast cancer cell growth in vitro and in vivo and that PI3K-C2β expression in breast tissues is correlated with the proliferative status of the tumor. Specifically we show that downregulation of PI3K-C2β in breast cancer cell lines reduces colony formation, induces cell cycle arrest and inhibits tumor growth, in particular in an estrogen-dependent in vivo xenograft. Investigation of the mechanism of the PI3K-C2β-dependent regulation of cell cycle progression and cell growth revealed that PI3K-C2β regulates cyclin B1 protein levels through modulation of microRNA miR-449a levels. Our data further demonstrate that downregulation of PI3K-C2β inhibits breast cancer cell invasion in vitro and breast cancer metastasis in vivo. Consistent with this, PI3K-C2β is highly expressed in lymph-nodes metastases compared to matching primary tumors. These data demonstrate that PI3K-C2β plays a pivotal role in breast cancer progression and in metastasis development. Our data indicate that PI3K-C2β may represent a key molecular switch that regulates a rate-limiting step in breast tumor progression and therefore it may be targeted to limit breast cancer spread.

miRNA-34c inhibits myoblasts proliferation by targeting YY1

miRNAs are increasingly being implicated as key regulators of cell proliferation, apoptosis, and differentiation. miRNA-34c appears to play a crucial role in cancer pathogenesis wherein it exerts its effect as a tumor suppressor. However, the role of miR-34c in myoblast proliferation remains poorly understood. Here, we found that overexpression miR-34c inhibited myoblasts proliferation by reducing the protein and mRNA expression of cell cycle genes. In contrast, blocking the function of miR-34c promoted myoblasts proliferation and increased the protein and mRNA expression of cell cycle genes. Moreover, miR-34c directly targeted YY1 and inhibited its expression. Similar to overexpression miR-34c, knockdown of YY1 by siRNA suppressed myoblasts proliferation. Our study provides novel evidence for a role of miR-34c in inhibiting myoblasts proliferation by repressing YY1. Thus, miR-34c has the potential to be used to enhance skeletal muscle development and regeneration.

Downregulation of microRNA‑34b is responsible for the elevation of blood pressure in spontaneously hypertensive rats

The present study aimed to identify the microRNA (miRNA) responsible for the development of primary hypertension, and examine the downstream signaling pathway, which mediates the effect of the miRNA. Reverse transcription‑quantitative polymerase chain reaction analysis was performed to identify which miRNA may be involved in the pathogenesis of hypertension. In silico analysis and a luciferase assay were used to validate the target of the selected miRNA, and miRNA mimics and small interfering (si)RNA of the target were transfected into smooth muscle cells to examine its effect on the biological activity of the cells. miR‑34b was found to be upregulated in spontaneously hypertensive rats (SHRs), compared with Wistar Kyoto (WKY) rats. Therefore, the present study used online miRNA target prediction tools to predict the candidate target genes of miR‑34b in the database, and consequently identified cyclin G1 (CCNG1) and cyclin‑dependent kinase 6 (CDK6) as its possible target genes. CDK6 subsequently identified to be the direct target gene of miR‑34b using a luciferase reporter assay in vascular smooth muscle cells (VSMCs). The present study also established the possible negative regulatory association between miR‑34b and CDK6 via investigating the mRNA and protein expression levels of CDK6 and CCNG1 in VSMCs collected from the SHRs and WKY rats, respectively. To investigate the signaling pathways between miR‑34b and CDK6, the mRNA and protein expression levels of CDK6, and the proliferation rates were compared in VSMCs transfected with CDK6 siRNA or miR‑34b mimics, the results of which indicated that the miR‑34b mimics exerted the same effects on the expression of CDK6 and cell proliferation as CDK6 siRNA. The negative regulatory association between miR‑34b and its target, CDK6, was confirmed, which may offer potential as a novel therapeutic target in the treatment of hypertension.

Functional changes in mRNA expression and alternative pre-mRNA splicing associated with the effects of nutrition on apoptosis and spermatogenesis in the adult testis

Background

The effects of nutrition on testis mass in the sexually mature male have long been known, however, the cellular and molecular processes of the testis response to nutrition was not fully understood.

Methods

We tested whether the defects in spermatogenesis and increases in germ cell apoptosis in the testis that are induced by under-nutrition are associated with changes in mRNA expression and pre-mRNA alternative splicing using groups of 8 male sheep fed for a 10% increase or 10% decrease in body mass over 65 days.

Results

We identified 2,243 mRNAs, including TP53 and Claudin 11, that were differentially expressed in testis from underfed and well-fed sheep (FDR < 0.1), and found that their expression changed in parallel with variations in germ cell numbers, testis size, and spermatogenesis. Furthermore, pairs of 269 mRNAs and 48 miRNAs were identified on the basis of target prediction. The regulatory effect of miRNAs on mRNA expression, in combination with functional analysis, suggests that these miRNAs are involved in abnormal reproductive morphology, apoptosis and male infertility. Nutrition did not affect the total number of alternative splicing events, but affected 206 alternative splicing events. A total of 159 genes, including CREM, SPATA6, and DDX4, were differentially spliced between dietary treatments, with functions related to RNA splicing and spermatogenesis. In addition, three gene modules were positively correlated with spermatogenesis-related phenotypic traits and negatively related to apoptosis-related phenotypic traits. Among these gene modules, seven (CFLAR, PTPRC, F2R, MAP3K1, EPHA7, APP, BCAP31) were also differentially expressed between nutritional treatments, indicating their potential as markers of spermatogenesis or apoptosis.

Conclusions

Our findings on significant changes in mRNAs and pre-mRNA alternative splicing under-nutrition suggest that they may partly explain the disruption of spermatogenesis and the increase germ cell apoptosis. However, more research is required to verify their causal effects in regulating spermatogenesis and germ cell apoptosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3385-8) contains supplementary material, which is available to authorized users.

Transcriptome profiling of the developing male germ line identifies the miR-29 family as a global regulator during meiosis

MicroRNAs are essential for spermatogenesis. However, the stage-specific requirements for particular miRNAs in the male mammalian germ line remain largely uncharacterized. The miR-34 family is, to date, the only miRNA proven to be necessary for the production of sperm in mammals, though its germline roles are poorly understood. Here, we generate and analyze paired small RNA and mRNA profiles across different stages of germline development in male mice, focusing on time points shortly before and during meiotic prophase I. We show that in addition to miR-34, miR-29 also mediates widespread repression of mRNA targets during meiotic prophase I in the male mouse germline. Furthermore, we demonstrate that predicted miR-29 target mRNAs in meiotic cells are largely distinct from those of miR-34, indicating that miR-29 performs a regulatory function independent of miR-34. Prior to this work, no germline role has been attributed to miR-29. To begin to understand roles for miR-29 in the germ line, we identify targets of miR-29 undergoing post transcriptional downregulation during meiotic prophase I, which likely correspond to the direct targets of miR-29. Interestingly, candidate direct targets of miR-29 are enriched in transcripts encoding extracellular matrix components. Our results implicate the miR-29 family as an important regulatory factor during male meiosis.

The beagle dog MicroRNA tissue atlas: identifying translatable biomarkers of organ toxicity

Background

MicroRNAs (miRNA) are varied in length, under 25 nucleotides, single-stranded noncoding RNA that regulate post-transcriptional gene expression via translational repression or mRNA degradation. Elevated levels of miRNAs can be detected in systemic circulation after tissue injury, suggesting that miRNAs are released following cellular damage. Because of their remarkable stability, ease of detection in biofluids, and tissue specific expression patterns, miRNAs have the potential to be specific biomarkers of organ injury. The identification of miRNA biomarkers requires a systematic approach: 1) determine the miRNA tissue expression profiles within a mammalian species via next generation sequencing; 2) identify enriched and/or specific miRNA expression within organs of toxicologic interest, and 3) in vivo validation with tissue-specific toxicants. While miRNA tissue expression has been reported in rodents and humans, little data exists on miRNA tissue expression in the dog, a relevant toxicology species. The generation and evaluation of the first dog miRNA tissue atlas is described here.

Results

Analysis of 16 tissues from five male beagle dogs identified 106 tissue enriched miRNAs, 60 of which were highly enriched in a single organ, and thus may serve as biomarkers of organ injury. A proof of concept study in dogs dosed with hepatotoxicants evaluated a qPCR panel of 15 tissue enriched miRNAs specific to liver, heart, skeletal muscle, pancreas, testes, and brain. Dogs with elevated serum levels of miR-122 and miR-885 had a correlative increase of alanine aminotransferase, and microscopic analysis confirmed liver damage. Other non-liver enriched miRNAs included in the screening panel were unaffected. Eli Lilly authors created a complimentary Sprague Dawely rat miRNA tissue atlas and demonstrated increased pancreas enriched miRNA levels in circulation, following caerulein administration in rat and dog.

Conclusion

The dog miRNA tissue atlas provides a resource for biomarker discovery and can be further mined with refinement of dog genome annotation. The 60 highly enriched tissue miRNAs identified within the dog miRNA tissue atlas could serve as diagnostic biomarkers and will require further validation by in vivo correlation to histopathology. Once validated, these tissue enriched miRNAs could be combined into a powerful qPCR screening panel to identify organ toxicity during early drug development.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2958-x) contains supplementary material, which is available to authorized users.

Differences in the expression of microRNAs and their predicted gene targets between cauda epididymal and ejaculated boar sperm

Mammalian spermatozoa gradually mature and acquire fertility during the transition from the testis to the caput and cauda epididymis, after which they are stored at the tail of the epididymis and the ampulla of vas deferens. During ejaculation, mixing of spermatozoa with the secretions of accessory sex glands leads to their dilution and changes in their function. Although remarkable progress has been made toward the understanding of changes in spermatozoa biochemistry and function before and after ejaculation, it is unknown whether microRNAs (miRNAs) are involved in regulating the function of spermatozoa during the transition between the cauda epididymis and ejaculation. In this study, 48 miRNAs were selected for analysis on the basis of their potential involvement in spermatogenesis, sperm maturation, and quality parameters markers. The differential expression levels of these 48 miRNAs between the caudal epididymis and fresh ejaculates of boar spermatozoa were determined. We found that 15 miRNAs were significantly differentially expressed (eight downregulated and seven upregulated) between boar cauda epididymal and fresh spermatozoa. Five miRNAs hypothesized to be involved in sperm apoptosis were further tested to demonstrate their influence over the expression of their target mRNAs using quantitative reverse-transcription polymerase chain reaction. Together, our findings suggest that these differentially expressed miRNAs are associated with the functional regulation of spermatozoa between cauda epididymis and ejaculation.

Genome-wide differential expression of genes and small RNAs in testis of two different porcine breeds and at two different ages

Some documented evidences proved small RNAs (sRNA) and targeted genes are involved in mammalian testicular development and spermatogenesis. However, the detailed molecular regulation mechanisms of them remain largely unknown so far. In this study, we obtained a total of 10,716 mRNAs, 67 miRNAs and 16,953 piRNAs which were differentially expressed between LC and LW pig breeds or between the two sexual maturity stages. Of which, we identified 16 miRNAs and 28 targeted genes possibly related to spermatogenesis; 14 miRNA and 18 targeted genes probably associated with cell adhesion related testis development. We also annotated 579 piRNAs which could potentially regulate cell death, nucleosome organization and other basic biology process, which implied that those piRNAs might be involved in sexual maturation difference. The integrated network analysis results suggested that some differentially expressed genes were involved in spermatogenesis through the ECM-receptor interaction, focal adhesion, Wnt and PI3K-Akt signaling pathways, some particular miRNAs have the negative regulation roles and some special piRNAs have the positive and negative regulation roles in testicular development. Our data provide novel insights into the molecular expression and regulation similarities and diversities of spermatogenesis and testicular development in different pig breeds at different stages of sexual maturity.

MicroRNA-224 regulates self-renewal of mouse spermatogonial stem cells via targeting DMRT1

MicroRNAs (miRs) play a key role in the control of gene expression in a wide array of tissue systems, where their functions include the regulation of self-renewal, cellular differentiation, proliferation and apoptosis. However, the function and mechanisms of individual miRs in regulating spermatogonial stem cell (SSC) homeostasis remain unclear. In the present study, we report for the first time that miR-224 is highly expressed in mouse SSCs. Functional assays using miRNA mimics and inhibitors reveal that miR-224 is essential for differentiation of SSCs. Mechanistically, miR-224 promotes differentiation of SSCs via targeting doublesex and Mab-3-related transcription factor 1 (DMRT1). Moreover, WNT/β-catenin signalling pathway is involved in miR-224-mediated regulation of SSCs self-renewal. We further demonstrate that miR-224 overexpression increases the expression of GFRα1 and PLZF, accompanied by the down-regulation of DMRT1 in mouse testes. Our findings provide novel insights into molecular mechanisms regulating differentiation of SSCs and may have important implications for regulating male reproduction.

MicroRNA profiles in a monkey testicular injury model induced by testicular hyperthermia

To characterize microRNAs (miRNAs) involved in testicular toxicity in cynomolgus monkeys, miRNA profiles were investigated using next‐generation sequencing (NGS), microarray and reverse transcription‐quantitative real‐time‐PCR (RT‐qPCR) methods. First, to identify organ‐specific miRNAs, we compared the expression levels of miRNAs in the testes to those in representative organs (liver, heart, kidney, lung, spleen and small intestine) obtained from naïve mature male and female monkeys (n = 2/sex) using NGS analysis. Consequently, miR‐34c‐5p, miR‐202‐5p, miR‐449a and miR‐508‐3p were identified to be testicular‐specific miRNAs in cynomolgus monkeys. Next, we investigated miRNA profiles after testicular–hyperthermia (TH) treatment to determine which miRNAs are involved in testicular injury. In this experiment, mature male monkeys were divided into groups with or without TH‐treatment (n = 3/group) by immersion of the testes in a water bath at 43 °C for 30 min for 5 consecutive days. As a result, TH treatment induced testicular injury in all animals, which was characterized by decreased numbers of spermatocytes and spermatids. In a microarray analysis of the testis, 11 up‐regulated (>2.0 fold) and 13 down‐regulated (<0.5 fold) miRNAs were detected compared with those in the control animals. Interestingly, down‐regulated miRNAs included two testicular‐specific miRNAs, miR‐34c‐5p and miR‐449a, indicating their potential use as biomarkers for testicular toxicity. Furthermore, RT‐qPCR analysis revealed decreased expression levels of testicular miR‐34b‐5p and miR‐34c‐5p, which are enriched in meiotic cells, reflecting the decrease in pachytene spermatocytes and spermatids after TH treatment. These results provide valuable insights into the mechanism of testicular toxicity and potential translational biomarkers for testicular toxicity. Copyright © 2016 The Authors. Journal of Applied Toxicology published by John Wiley & Sons Ltd.

In this study, we identified 4 testicular‐specific miRNAs, miR‐34c‐5p, miR‐202‐5p, miR‐449a, and miR‐508‐3p based on next‐generation sequencing of miRNAs from representative organs obtained from naïve mature cynomolgus monkeys. Next, miRNAs were profiled in a model of testicular injury induced by testicular hyperthermia. Microarray and PCR analyses revealed down‐regulation of miR‐34c‐5p in the testis, which is enriched in meiotic cells, reflecting decreased numbers of pachytene spermatocytes and spermatids by the treatment.

The role of epigenetics in idiopathic male infertility

Infertility is a complex disorder with multiple genetic and environmental causes. Although some specific mutations have been identified, other factors responsible for sperm defects remain largely unknown. Despite considerable efforts to identify the pathophysiology of the disease, we cannot explain the underlying mechanisms of approximately half of infertility cases. This study reviews current data on epigenetic regulation and idiopathic male infertility. Recent data have shown an association between epigenetic modifications and idiopathic infertility. In this regard, epigenetics has emerged as one of the promising research areas in understanding male infertility. Many studies have indicated that epigenetic modifications, including DNA methylation in imprinted and developmental genes, histone tail modifications and short non-coding RNAs in spermatozoa may have a role in idiopathic male infertility.

MicroRNA profiling in ethylene glycol monomethyl ether-induced monkey testicular toxicity model

To establish and characterize ethylene glycol monomethyl ether (EGME)-induced testicular toxicity model in cynomolgus monkeys, EGME at 0 or 300 mg/kg was administered orally to sexually mature male cynomolgus monkeys (n = 3/group) for 4 consecutive days. Circulating and testicular microRNA (miRNA) profiles in this model were investigated using miRNA microarray or real-time quantitative reverse transcription-PCR methods. EGME at 300 mg/kg induced testicular toxicity in all the monkeys, which was characterized histopathologically by decreases in pachytene spermatocytes and round spermatids, without any severe changes in general conditions or clinical pathology. In microarray analysis, 16 down-regulated and 347 up-regulated miRNAs were detected in the testis, and 326 down-regulated but no up-regulated miRNAs were detected in plasma. Interestingly, miR-1228 and miR-2861 were identified as abundant miRNAs in plasma and the testis of control animals, associated presumably with apoptosis and cell differentiation, respectively, and were prominently increased in the testis of EGME-treated animals, reflecting the recovery from EGME-induced testicular damages via stimulating cell proliferation and differentiation of sperm. Furthermore, down-regulation of miR-34b-5p and miR-449a, which are enriched in meiotic cells like pachytene spermatocytes, was obvious in the testis, suggesting that these spermatogenic cells were damaged by the EGME treatment. In conclusion, EGME-induced testicular toxicity in cynomolgus monkeys was shown, and this model would be useful for investigating the mechanism of EGME-induced testicular toxicity and identifying testicular biomarkers. Additionally, testicular miR-34b-5p and miR-449a were suggested to be involved in damage of pachytene spermatocytes.

Non-coding RNA in Spermatogenesis and Epididymal Maturation

Testicular germ and somatic cells express many classes of small ncRNAs, including Dicer-independent PIWI-interacting RNAs, Dicer-dependent miRNAs, and endogenous small interfering RNA. Several studies have identified ncRNAs that are highly, exclusively, or preferentially expressed in the testis and epididymis in specific germ and somatic cell types. Temporal and spatial expression of proteins is a key requirement of successful spermatogenesis and large-scale gene transcription occurs in two key stages, just prior to transcriptional quiescence in meiosis and then during spermiogenesis just prior to nuclear silencing in elongating spermatids. More than 60 % of these transcripts are then stockpiled for subsequent translation. In this capacity ncRNAs may act to interpret and transduce cellular signals to either maintain the undifferentiated stem cell population and/or drive cell differentiation during spermatogenesis and epididymal maturation. The assignation of specific roles to the majority of ncRNA species implicated as having a role in spermatogenesis and epididymal function will underpin fundamental understanding of normal and disease states in humans such as infertility and the development of germ cell tumours.

Small non-coding RNAs and their associated proteins in spermatogenesis

The importance of the gene regulation roles of small non-coding RNAs and their protein partners is of increasing focus. In this paper, we reviewed three main small RNA species which appear to affect spermatogenesis. MicroRNAs (miRNAs) are single stand RNAs derived from transcripts containing stem-loops and hairpins which target corresponding mRNAs and affect their stability or translation. Many miRNA species have been found to be related to normal male germ cell development. The biogenesis of piRNAs is still largely unknown but several models have been proposed. Some piRNAs and PIWIs target transposable elements and it is these that may be active in regulating translation or stem cell maintenance. endo-siRNAs may also participate in sperm development. Some possible interactions between different kinds of small RNAs have even been suggested. We also show that male germ granules are seen to have a close relationship with a considerable number of mRNAs and small RNAs. Those special structures may also participate in sperm development.

Altered miRNA Signature of Developing Germ-cells in Infertile Patients Relates to the Severity of Spermatogenic Failure and Persists in Spermatozoa

The aim of this study was to assess the cellular miRNA expression behaviour in testes with spermatogenic failure (SpF). We performed a high-throughput screen of 623 mature miRNAs by a quantitative RT-qPCR-based approach in histologically well-defined testicular samples with spermatogenic disruption at different germ-cell stages, which revealed altered patterns of miRNA expression. We focussed on the differentially expressed miRNAs whose expression correlated with the number of testicular mature germ-cells and described the combined expression values of a panel of three miRNAs (miR-449a, miR-34c-5p and miR-122) as a predictive test for the presence of mature germ-cells in testicular biopsy. Additionally, we determined decreased cellular miRNA content in developing germ-cells of SpF testis; this was more noticeable the earlier the stage of germ-cell differentiation was affected by maturation failure. Furthermore, we showed that the miRNA expression profile in mature sperm from mild SpF patients was widely altered. Our results suggest that the cellular miRNA content of developed germ-cells depends heavily on the efficacy of the spermatogenic process. What is more, spermatozoa that have fulfilled the differentiation process still retain the dysregulated miRNA pattern observed in the developing SpF germ-cells. This altered miRNA molecular signature may have functional implications for the male gamete.

Bioimaging of microRNA34c in a single sperm using a molecular beacon

The VisuFect-conjugated molecular beacon was developed for non-invasive visualization of microRNA34c in a living single mouse sperm.

DICER Regulates the Formation and Maintenance of Cell-Cell Junctions in the Mouse Seminiferous Epithelium

The endonuclease DICER that processes micro-RNAs and small interfering RNAs is essential for normal spermatogenesis and male fertility. We previously showed that the deletion of Dicer1 gene in postnatal spermatogonia in mice using Ngn3 promoter-driven Cre expression caused severe defects in the morphogenesis of haploid spermatid to mature spermatozoon, including problems in cell polarization and nuclear elongation. In this study, we further analyzed the same mouse model and revealed that absence of functional DICER in differentiating male germ cells induces disorganization of the cell-cell junctions in the seminiferous epithelium. We detected discontinuous and irregular apical ectoplasmic specializations between elongating spermatids and Sertoli cells. The defective anchoring of spermatids to Sertoli cells caused a premature release of spermatids into the lumen. Our findings may help also explain the abnormal elongation process of remaining spermatids because these junctions and the correct positioning of germ cells in the epithelium are critically important for the progression of spermiogenesis. Interestingly, cell adhesion-related genes were generally upregulated in Dicer1 knockout germ cells. Claudin 5 ( Cldn5 ) was among the most upregulated genes and we show that the polarized localization of CLAUDIN5 in the apical ectoplasmic specializations was lost in Dicer1 knockout spermatids. Our results suggest that DICER-dependent pathways control the formation and organization of cell-cell junctions in the seminiferous epithelium via the regulation of cell adhesion-related genes.

MiR-122 partly mediates the ochratoxin A-induced GC-2 cell apoptosis

Ochratoxin A (OTA) is a mycotoxin which has been shown to be nephrotoxic, hepatotoxic, and immunotoxic to animals, and mainly exists in the mildew grain. MicroRNAs (miRNAs) regulate a wide variety of cellular processes. However, the toxic effects of OTA on the germ cell and whether miRNAs mediate the effects of OTA-induced GC-2 cell apoptosis are still not clear. In the present study, OTA treatment resulted in a dose-dependent increase apoptosis in GC-2 cells. MiR-122 was increased in the OTA-treated GC-2 cells. It showed that Bcl-w was down-regulated after OTA treatment, and caspase-3 was obviously activated. Cyclin G1 (CCNG1) was significantly decreased, and inversely the expression of p53 was increased. Inhibition of miR-122 partly relieved the OTA-induced GC-2 cell apoptosis. These results indicate that OTA induces GC-2 cell apoptosis by causing the increase of caspase-3 activity and that miR-122 partly mediates the OTA-induced cell apoptosis.

Identification of MicroRNAs in Zebrafish Spermatozoa

MicroRNAs (miRNAs) participate in almost all biological processes. Plenty of evidences show that some testis- or spermatozoa-specific miRNAs play crucial roles in the process of gonad and germ cell development. In this study, the spermatozoa miRNA profiles were investigated through a combination of illumina deep sequencing and bioinformatics analysis in zebrafish. Deep sequencing of small RNAs yielded 11,820,680 clean reads. By mapping to the zebrafish genome, we identified 400 novel and 204 known miRNAs that could be grouped into 104 families. Furthermore, we selected the six highest expressions of known miRNAs to detect their expression patterns in different tissues by stem-loop quantitative real-time polymerase chain reaction. We found that among the six miRNAs, dre-miR-202-5p displayed specific and high expression in zebrafish spermatozoa and testis. Fluorescence in situ hybridization analysis indicated that dre-miR-202-5p was predominantly expressed in all kind of germ cells at different spermatogenetic stages, including spermatogonia and spermatozoa, but barely expressed in the germ cells in the ovary. This sex-biased expression pattern suggests that dre-miR-202-5p might be related to spermatogenesis and the functioning of spermatozoa. The identification of miRNAs in zebrafish spermatozoa and germ cells offers new insights into the spermatogenesis and spermatozoa in the teleost and other vertebrates.

Differential Expression of miR-34c and Its Predicted Target Genes in Testicular Tissue at Different Development Stages of Swine

To verified the target genes of miR-34c, bioinformatics software was used to predict the targets of miR-34c. Three possible target genes of miR-34c related to spermatogenesis and male reproductive development: zinc finger protein 148 (ZNF148), kruppel-like factor 4 (KLF4), and platelet-derived growth factor receptor alpha (PDGFRA) were predicted. Then, the expression of miR-34c and its target genes were detected in swine testicular tissue at different developmental stages by quantitative polymerase chain reaction. The results suggested that the expression of PDGFRA has the highest negative correlation with miR-34c. Then immunohistochemical staining was done to observe the morphology of swine testicular tissue at 2-days and 3, 4, 5-months of age, which indicated that PDGFRA was mainly expressed in the support cells near the basement membrane during the early development stages of testicular tissue, but that the expression of PDGFRA was gradually reduced in later stages. Therefore, western blot analyzed that the highest expression of PDGFRA was generated in 2-days old testicular tissues and the expression levels reduced at 3 and 4-months old, which correlated with the results of immunohistochemical staining. In conclusion, PDGFRA is a target gene of miR-34c.

The microRNA signature of mouse spermatozoa is substantially modified during epididymal maturation

In recent years considerable effort has been devoted to understanding the epigenetic control of sperm development, leading to an increased appreciation of the importance of RNA interference pathways, and in particular miRNAs, as key regulators of spermatogenesis and epididymal maturation. It has also been shown that sperm are endowed with an impressive array of miRNA that have been implicated in various aspects of fertilization and embryo development. However, to date there have been no reports on whether the sperm miRNA signature is static or whether it is influenced by their prolonged maturation within the male reproductive tract. To investigate this phenomenon, we employed next-generation sequencing to systematically profile the miRNA signature of maturing mouse spermatozoa. In so doing we have provided the first evidence for the posttesticular modification of the sperm miRNA profile under normal physiological conditions. Such modifications include the apparent loss and acquisition of an impressive cohort of some 113 and 115 miRNAs, respectively, between the proximal and distal epididymal segments. Interestingly, the majority of these changes occur late in maturation and include the uptake of novel miRNA species in addition to a significant increase in many miRNAs natively expressed in immature sperm. Because sperm are not capable of de novo transcription, these findings identify the epididymis as an important site in establishing the sperm epigenome with the potential to influence the peri-conceptual environment of the female reproductive tract, contribute to the inheritance of acquired characteristics, and/or alter the developmental trajectory of the resulting offspring.

Expression of Flotilin-2 and Acrosome Biogenesis Are Regulated by MiR-124 during Spermatogenesis

MicroRNAs (miRNAs) are a class of short non-coding RNA molecules, which diversely regulate gene expression in organisms. Although the regulatory role of these small RNA molecules has been recently explored in animal spermatogenesis, the role of miR-124 in male germ cells is poorly defined. In our previous study, flotillin-2 was investigated as a novel Golgi-related protein involved in sperm acrosome biogenesis. The current study was designed to analyze the contribution of miR-124 in the regulation of flotillin-2 expression during mouse acrosome biogenesis. Luciferase assays revealed the target effects of miR-124 on flotillin-2 expression. Following intratesticular injection of miR-124 in 3-week-old male mice, quantitative real-time RT-PCR and western blot analysis were employed to confirm the function of miR-124 in regulating flotillin-2 after 48 hours. Sperm abnormalities were assessed 3 weeks later by ordinary optical microscopy, the acrosome abnormalities were also assessed by PNA staining and transmission electron microscopy. The results showed the proportion of sperm acrosome abnormalities was significantly higher than that of the control group. The expression of flotillin-2 and caveolin-1 was significantly downregulated during acrosome biogenesis. These results indicated that miR-124 could potentially play a role in caveolin-independent vesicle trafficking and modulation of flotillin-2 expression in mouse acrosome biogenesis.

Next Generation Sequencing Analysis Reveals Segmental Patterns of microRNA Expression in Mouse Epididymal Epithelial Cells

The functional maturation of mammalian spermatozoa is accomplished as the cells descend through the highly specialized microenvironment of the epididymis. This dynamic environment is, in turn, created by the combined secretory and absorptive activity of the surrounding epithelium and displays an extraordinary level of regionalization. Although the regulatory network responsible for spatial coordination of epididymal function remains unclear, recent evidence has highlighted a novel role for the RNA interference pathway. Indeed, as noncanonical regulators of gene expression, small noncoding RNAs have emerged as key elements of the circuitry involved in regulating epididymal function and hence sperm maturation. Herein we have employed next generation sequencing technology to profile the genome-wide miRNA signatures of mouse epididymal cells and characterize segmental patterns of expression. An impressive profile of some 370 miRNAs were detected in the mouse epididymis, with a subset of these specifically identified within the epithelial cells that line the tubule (218). A majority of the latter miRNAs (75%) were detected at equivalent levels along the entire length of the mouse epididymis. We did however identify a small cohort of miRNAs that displayed highly regionalized patterns of expression, including miR-204-5p and miR-196b-5p, which were down- and up-regulated by approximately 39- and 45-fold between the caput/caudal regions, respectively. In addition we identified 79 miRNAs (representing ~ 21% of all miRNAs) as displaying conserved expression within all regions of the mouse, rat and human epididymal tissue. These included 8/14 members of let-7 family of miRNAs that have been widely implicated in the control of androgen signaling and the repression of cell proliferation and oncogenic pathways. Overall these data provide novel insights into the sophistication of the miRNA network that regulates the function of the male reproductive tract.

MicroRNA-34c expression in donor cells influences the early development of somatic cell nuclear transfer bovine embryos

The essence of the reprogramming activity of somatic cell nuclear transfer (SCNT) embryos is to produce normal fertilized embryos. However, reprogramming of somatic cells is not as efficient as the reprogramming of sperm. In this report, we describe the effect of an inducible, specific miR-34 microRNA expression in donor cells that enables a similar level of sperm:transgene expression on the early development of SCNT embryos. Our results showed that donor cells with doxycycline (dox)-induced miR-34c expression for the preparation of SCNT embryos resulted in altered developmental rates, histone modification (H3K9ac and H3K4me3), and extent of apoptosis. The cleavage rate and blastocyst formation of the induced nuclear transfer (NT) group were significantly increased. The immunofluorescence signal of H3K9ac in embryos in the induced NT group significantly increased in two-cell- and eight-cell-stage embryos; that of H3K4me3 increased significantly in eight-cell-stage embryos. Although significant differences in staining signals of apoptosis were not detected between groups, lower apoptosis levels were observed in the induced NT group. In conclusion, miR-34c expression induced by dox treatment enhances the developmental potential of SCNT embryos, modifies the epigenetic status, and changes blastocyst quality.

miR-34 and p53: New Insights into a Complex Functional Relationship

miR-34, a tumor suppressor miRNA family transcriptionally activated by p53, is considered a critical mediator of p53 function. However, knockout of the mouse miR-34 family has little or no effect on the p53 response. The relative contribution of different miR-34 family members to p53 function or how much p53 relies on miR-34 in human cells is unclear. Here we show that miR-34a has a complex effect on the p53 response in human cells. In HCT116 cells miR-34a overexpression enhances p53 transcriptional activity, but the closely related family members, miR-34b and miR-34c, even when over-expressed, have little effect. Both TP53 itself and MDM4, a strong p53 transactivation inhibitor, are direct targets of miR-34a. The genes regulated by miR-34a also include four other post-translational inhibitors of p53. miR-34a overexpression leads to variable effects on p53 levels in p53-sufficient human cancer cell lines. In HCT116, miR-34a overexpression increases p53 protein levels and stability. About a quarter of all mRNAs that participate in the human p53 network bind to biotinylated miR-34a, suggesting that many are direct miR-34a targets. However, only about a fifth of the mRNAs that bind to miR-34a also bind to miR-34b or miR-34c. Two human cell lines knocked out for miR-34a have unimpaired p53-mediated responses to genotoxic stress, like mouse cells. The complex positive and negative effects of miR-34 on the p53 network suggest that rather than simply promoting the p53 response, miR-34a might act at a systems level to stabilize the robustness of the p53 response to genotoxic stress.

The small RNA content of human sperm reveals pseudogene-derived piRNAs complementary to protein-coding genes

At the end of mammalian sperm development, sperm cells expel most of their cytoplasm and dispose of the majority of their RNA. Yet, hundreds of RNA molecules remain in mature sperm. The biological significance of the vast majority of these molecules is unclear. To better understand the processes that generate sperm small RNAs and what roles they may have, we sequenced and characterized the small RNA content of sperm samples from two human fertile individuals. We detected 182 microRNAs, some of which are highly abundant. The most abundant microRNA in sperm is miR-1246 with predicted targets among sperm-specific genes. The most abundant class of small noncoding RNAs in sperm are PIWI-interacting RNAs (piRNAs). Surprisingly, we found that human sperm cells contain piRNAs processed from pseudogenes. Clusters of piRNAs from human testes contain pseudogenes transcribed in the antisense strand and processed into small RNAs. Several human protein-coding genes contain antisense predicted targets of pseudogene-derived piRNAs in the male germline and these piRNAs are still found in mature sperm. Our study provides the most extensive data set and annotation of human sperm small RNAs to date and is a resource for further functional studies on the roles of sperm small RNAs. In addition, we propose that some of the pseudogene-derived human piRNAs may regulate expression of their parent gene in the male germline.

Roles of small RNAs in the effects of nutrition on apoptosis and spermatogenesis in the adult testis

We tested whether reductions in spermatozoal quality induced by under-nutrition are associated with increased germ cell apoptosis and disrupted spermatogenesis, and whether these effects are mediated by small RNAs. Groups of 8 male sheep were fed for a 10% increase or 10% decrease in body mass over 65 days. Underfeeding increased the number of apoptotic germ cells (P < 0.05) and increased the expression of apoptosis-related genes (P < 0.05) in testicular tissue. We identified 44 miRNAs and 35 putative piRNAs that were differentially expressed in well-fed and underfed males (FDR < 0.05). Some were related to reproductive system development, apoptosis (miRNAs), and sperm production and quality (piRNAs). Novel-miR-144 (miR-98), was found to target three apoptotic genes (TP53, CASP3, FASL). The proportion of miRNAs as a total of small RNAs was greater in well-fed males than in underfed males (P < 0.05) and was correlated (r = 0.8, P < 0.05) with the proportion of piRNAs in well-fed and underfed males. In conclusion, the reductions in spermatozoal quality induced by under-nutrition are caused, at least partly, by disruptions to Sertoli cell function and increased germ cell apoptosis, mediated by changes in the expression of miRNAs and piRNAs.

Confrontation, Consolidation, and Recognition: The Oocyte's Perspective on the Incoming Sperm

From the oocyte's perspective, the incoming sperm poses a significant challenge. Despite (usually) arising from a male of the same species, the sperm is a "foreign" body that may carry with it additional, undesirable factors such as transposable elements (mainly retroposons) into the egg. These factors can arise either during spermatogenesis or while the sperm is moving through the epididymis or the female genital tract. Furthermore, in addition to the paternal genome, the sperm also carries its own complex repertoire of RNAs into the egg that includes mRNAs, lncRNAs, and sncRNAs. Last, the paternal genome itself is efficiently packaged into a protamine (nucleo-toroid) and histone (nucleosome)-based chromatin scaffold within which much of the RNA is embedded. Taken together, the sperm delivers a far more complex package to the egg than was originally thought. Understanding this complexity, at both the compositional and structural level, depends largely on investigating sperm chromatin from both the genomic (DNA packaging) and epigenomic (RNA carriage and extant histone modifications) perspectives. Why this complexity has arisen and its likely purpose requires us to look more closely at what happens in the oocyte when the sperm gains entry and the processes that then take place preparing the paternal (and maternal) genomes for syngamy.

MicroRNAs and DNA methylation as epigenetic regulators of mitosis, meiosis and spermiogenesis

Spermatogenesis is composed of three distinctive phases, which include self-renewal of spermatogonia via mitosis, spermatocytes undergoing meiosis I/II and post-meiotic development of haploid spermatids via spermiogenesis. Spermatogenesis also involves condensation of chromatin in the spermatid head before transformation of spermatids to spermatozoa. Epigenetic regulation refers to changes of heritably cellular and physiological traits not caused by modifications in the DNA sequences of the chromatin such as mutations. Major advances have been made in the epigenetic regulation of spermatogenesis. In this review, we address the roles and mechanisms of epigenetic regulators, with a focus on the role of microRNAs and DNA methylation during mitosis, meiosis and spermiogenesis. We also highlight issues that deserve attention for further investigation on the epigenetic regulation of spermatogenesis. More importantly, a thorough understanding of the epigenetic regulation in spermatogenesis will provide insightful information into the etiology of some unexplained infertility, offering new approaches for the treatment of male infertility.