Murine follicular development requires oocyte DICER, but not DROSHA

Divergent composition and transposon-silencing activity of small RNAs in mammalian oocytes

BACKGROUND

Small RNAs are essential for germ cell development and fertilization. However, fundamental questions remain, such as the level of conservation in small RNA composition between species and whether small RNAs control transposable elements in mammalian oocytes.

RESULTS

Here, we use high-throughput sequencing to profile small RNAs and poly(A)-bearing long RNAs in oocytes of 12 representative vertebrate species (including 11 mammals). The results show that miRNAs are generally expressed in the oocytes of each representative species (although at low levels), whereas endo-siRNAs are specific to mice. Notably, piRNAs are predominant in oocytes of all species (except mice) and vary widely in length. We find PIWIL3-associated piRNAs are widespread in mammals and generally lack 3'-2'-O-methylation. Additionally, sequence identity is low between homologous piRNAs in different species, even among those present in syntenic piRNA clusters. Despite the species-specific divergence, piRNAs retain the capacity to silence younger TE subfamilies in oocytes.

CONCLUSIONS

Collectively, our findings illustrate a high level of diversity in the small RNA populations of mammalian oocytes. Furthermore, we identify sequence features related to conserved roles of small RNAs in silencing TEs, providing a large-scale reference for future in-depth study of small RNA functions in oocytes.

Bovine models for human ovarian diseases

During early embryonic development, late fetal growth, puberty, adult reproductive years, and advanced aging, bovine and human ovaries closely share molecular pathways and hormonal signaling mechanisms. Other similarities between these species include the size of ovaries, length of gestation, ovarian follicular and luteal dynamics, and pathophysiology of ovarian diseases. As an economically important agriculture species, cattle are a foundational species in fertility research with decades of groundwork using physiologic, genetic, and therapeutic experimental techniques. Many technologies used in modern reproductive medicine, such as ovulation induction using hormonal therapy, were first used in cows before human trials. Human ovarian diseases with naturally occurring bovine correlates include premature ovary insufficiency (POI), polycystic ovarian syndrome (PCOS), and sex-cord stromal tumors (SCSTs). This article presents an overview of bovine ovary research related to causes of infertility, ovarian diseases, diagnostics, and therapeutics, emphasizing where the bovine model can offer advantages over other lab animals for translational applications.

Non-Coding RNAs: lncRNAs, miRNAs, and piRNAs in Sexual Development

Non-coding RNAs (ncRNAs) are a group of RNAs that do not encode functional proteins, including long non-coding RNAs (lncRNAs), microRNAs (miRNAs), PIWI-interacting RNAs (piRNAs), and short interfering RNAs (siRNAs). In the last 2 decades an effort has been made to uncover the role of ncRNAs during development and disease, and nowadays it is clear that these molecules have a regulatory function in many of the developmental and physiological processes where they have been studied. In this review, we provide an overview of the role of ncRNAs during gonad determination and development, focusing mainly on mammals, although we also provide information from other species, in particular when there is not much information on the function of particular types of ncRNAs during mammalian sexual development.

The emerging role of microRNAs in fish ovary: A mini review

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression primarily at the post-transcriptional levels. It is now well established that miRNAs are crucial regulators of many developmental and physiological processes, including reproduction. In teleosts, expression profiling studies have shown that miRNAs are expressed in the fish ovary and their levels are regulated during follicle development and by hormones. Using CRISPR/Cas9 mediated gene knockout strategies, several recent studies have provided strong evidence that miR-202 and miR-200s on chromosome 23 play critical roles in regulating ovarian development, oogenesis, and ovulation. In this mini review, we provide a brief overview of canonical miRNA biogenesis and functions; summarize miRNAs that are expressed in fish ovary; and discuss the emerging role of miRNAs in regulating fish ovarian functions.

Emerging roles for noncoding RNAs in female sex steroids and reproductive disease

The "central dogma" of molecular biology, that is, that DNA blueprints encode messenger RNAs which are destined for translation into protein, has been challenged in recent decades. In actuality, a significant portion of the genome encodes transcripts that are transcribed into functional RNA. These noncoding RNAs (ncRNAs), which are not transcribed into protein, play critical roles in a wide variety of biological processes. A growing body of evidence derived from mouse models and human data demonstrates that ncRNAs are dysregulated in various reproductive pathologies, and that their expression is essential for female gametogenesis and fertility. Yet in many instances it is unclear how dysregulation of ncRNA expression leads to a disease process. In this review, we highlight new observations regarding the roles of ncRNAs in the pathogenesis of disordered female steroid hormone production and disease, with an emphasis on long noncoding RNAs (lncRNAs) and microRNAs (miRNAs). We will focus our discussion in the context of three ovarian disorders which are characterized in part by altered steroid hormone biology - diminished ovarian reserve, premature ovarian insufficiency, and polycystic ovary syndrome. We will also discuss the limitations and challenges faced in studying noncoding RNAs and sex steroid hormone production. An enhanced understanding of the role of ncRNAs in sex hormone regulatory networks is essential in order to advance the development of potential diagnostic markers and therapeutic targets for diseases, including those in reproductive health. Our deepened understanding of ncRNAs has the potential to uncover new applications and therapies; however, in many cases, the next steps will involve distinguishing critical ncRNAs from those which are merely changing in response to a particular disease state, or which are altogether unrelated to disease pathophysiology.

Dicing the Disease with Dicer: The Implications of Dicer Ribonuclease in Human Pathologies

Gene expression dictates fundamental cellular processes and its de-regulation leads to pathological conditions. A key contributor to the fine-tuning of gene expression is Dicer, an RNA-binding protein (RBPs) that forms complexes and affects transcription by acting at the post-transcriptional level via the targeting of mRNAs by Dicer-produced small non-coding RNAs. This review aims to present the contribution of Dicer protein in a wide spectrum of human pathological conditions, including cancer, neurological, autoimmune, reproductive and cardiovascular diseases, as well as viral infections. Germline mutations of Dicer have been linked to Dicer1 syndrome, a rare genetic disorder that predisposes to the development of both benign and malignant tumors, but the exact correlation of Dicer protein expression within the different cancer types is unclear, and there are contradictions in the data. Downregulation of Dicer is related to Geographic atrophy (GA), a severe eye-disease that is a leading cause of blindness in industrialized countries, as well as to psychiatric and neurological diseases such as depression and Parkinson's disease, respectively. Both loss and upregulation of Dicer protein expression is implicated in severe autoimmune disorders, including psoriasis, ankylosing spondylitis, rheumatoid arthritis, multiple sclerosis and autoimmune thyroid diseases. Loss of Dicer contributes to cardiovascular diseases and causes defective germ cell differentiation and reproductive system abnormalities in both sexes. Dicer can also act as a strong antiviral with a crucial role in RNA-based antiviral immunity. In conclusion, Dicer is an essential enzyme for the maintenance of physiology due to its pivotal role in several cellular processes, and its loss or aberrant expression contributes to the development of severe human diseases. Further exploitation is required for the development of novel, more effective Dicer-based diagnostic and therapeutic strategies, with the goal of new clinical benefits and better quality of life for patients.

Using bioinformatics and metabolomics to identify altered granulosa cells in patients with diminished ovarian reserve

Background

During fertility treatment, diminished ovarian reserve (DOR) is a challenge that can seriously affect a patient's reproductive potential. However, the pathogenesis of DOR is still unclear and its treatment options are limited. This study aimed to explore DOR's molecular mechanisms.

Methods

We used R software to analyze the mRNA microarray dataset E-MTAB-391 downloaded from ArrayExpress, screen for differentially expressed genes (DEGs), and perform functional enrichment analyses. We also constructed the protein-protein interaction (PPI) and miRNA-mRNA networks. Ovarian granulosa cells (GCs) from women with DOR and the control group were collected to perform untargeted metabolomics analyses. Additionally, small molecule drugs were identified using the Connectivity Map database.

Results

We ultimately identified 138 DEGs. Our gene ontology (GO) analysis indicated that DEGs were mainly enriched in cytokine and steroid biosynthetic processes. According to the Kyoto Encyclopedia of Genes and Genomes (KEGG), the DEGs were mainly enriched in the AGE (advanced glycation end-product)-RAGE (receptor for AGE) signaling pathway in diabetic complications and steroid biosynthesis. In the PPI network, we determined that JUN, EGR1, HMGCR, ATF3, and SQLE were hub genes that may be involved in steroid biosynthesis and inflammation. miRNAs also played a role in DOR development by regulating target genes. We validated the differences in steroid metabolism across GCs using liquid chromatography-tandem mass spectrometry (LC-MS/MS). We selected 31 small molecules with potentially positive or negative influences on DOR development.

Conclusion

We found that steroidogenesis and inflammation played critical roles in DOR development, and our results provide promising insights for predicting and treating DOR.

Epigenetic Modifications due to Environment, Ageing, Nutrition, and Endocrine Disrupting Chemicals and Their Effects on the Endocrine System

The epigenome of an individual can be altered by endogenous hormones, environment, age, diet, and exposure to endocrine disrupting chemicals (EDCs), and the effects of these modifications can be seen across generations. Epigenetic modifications to the genome can alter the phenotype of the individual without altering the DNA sequence itself. Epigenetic modifications include DNA methylation, histone modification, and aberrant microRNA (miRNA) expression; they begin during germ cell development and embryogenesis and continue until death. Hormone modulation occurs during the ageing process due to epigenetic modifications. Maternal overnutrition or undernutrition can affect the epigenome of the fetus, and the effects can be seen throughout life. Furthermore, maternal care during the childhood of the offspring can lead to different phenotypes seen in adulthood. Diseases controlled by the endocrine system, such as obesity and diabetes, as well as infertility in females can be associated with epigenetic changes. Not only can these phenotypes be seen in F1, but also some chemical effects can be passed through the germline and have effects transgenerationally, and the phenotypes are seen in F3. The following literature review expands upon these topics and discusses the state of the science related to epigenetic effects of age, diet, and EDCs on the endocrine system.

MicroRNA Biogenesis Machinery Is Dysregulated in the Endometrium of Infertile Women Suggesting a Role in Receptivity and Infertility

MicroRNAs (miRs) regulate endometrial function and their dysregulation could underlie unexplained infertility in women. Ribonucleases including DICER and DROSHA, and the proteins, ARGONAUTE 1 (AGO 1) and 2 (AGO 2) regulate the biogenesis/maturation of miRs. We aimed to elucidate the expression and localization of miR biogenesis machinery components during the human menstrual cycle and compare their levels in endometrium from women with normal fertility and primary unexplained infertility. miR biogenesis components were measured by quantitative-RT-PCR and immunohistochemistry. In the endometrium of women with normal fertility, DROSHA immunolocalized maximally to the epithelium during the early and mid-secretory phases compared with the proliferative and late-secretory phases. Stromal DICER immunostaining intensity was higher in the late-secretory phase compared with all other phases in fertile women. DROSHA mRNA was reduced in the mid-secretory-infertile whole endometrial tissue (has all cells of the tissue), and primary epithelial and stromal cells while no differences were found in DICER, AGO1, and AGO2 mRNA. In the luminal epithelium, DROSHA staining intensity was reduced in early and mid-secretory-infertile while DICER staining was reduced in the early secretory-infertile compared with their respective fertile groups. DICER and DROSHA were dynamically regulated across the menstrual cycle and reduced levels during receptivity phase could underlie implantation failure/infertility.

The small non-coding RNA profile of mouse oocytes is modified during aging

Oocytes are reliant on messenger RNA (mRNA) stores to support their survival and integrity during a protracted period of transcriptional dormancy as they await ovulation. Oocytes are, however, known to experience an age-associated alteration in mRNA transcript abundance, a phenomenon that contributes to reduced developmental potential. Here we have investigated whether the expression profile of small non-protein-coding RNAs (sRNAs) is similarly altered in aged mouse oocytes. The application of high throughput sequencing revealed substantial changes to the global sRNA profile of germinal vesicle stage oocytes from young (4-6 weeks) and aged mice (14-16 months). Among these, 160 endogenous small-interfering RNAs (endo-siRNAs) and 10 microRNAs (miRNAs) were determined to differentially accumulate within young and aged oocytes. Further, we revealed decreased expression of two members of the kinesin protein family, Kifc1 and Kifc5b, in aged oocytes; family members selectively targeted for expression regulation by endo-siRNAs of elevated abundance. The implications of reduced Kifc1 and Kifc5b expression were explored using complementary siRNA-mediated knockdown and pharmacological inhibition strategies, both of which led to increased rates of aneuploidy in otherwise healthy young oocytes. Collectively, our data raise the prospect that altered sRNA abundance, specifically endo-siRNA abundance, could influence the quality of the aged oocyte.

Endo-siRNAs repress expression of SINE1B during in vitro maturation of porcine oocyte

Approximately 40% of mammalian genome is made of transposable elements (TEs), and during specific biological processes, such as gametogenesis, they may be activated by global demethylation, so strict silencing mechanism is indispensable for genomic stability. Here, we performed small RNA-seq on Dicer1 knockdown (KD) oocytes in pig, and observed short interspersed nuclear elements 1B (SINE1B) derived endogenous small interfering RNAs (endo-siRNAs), termed SINE1B-siRNAs, were significantly decreased and their biogenesis was dependent on Dicer1 and transcript of SINE1B. Furthermore, by injection of mimics and inhibitors of the SINE1B-siRNAs into germinal vesicle-stage (GV-stage) oocytes, we found the maturation rate was significantly decreased by SINE1B-siRNAs, indicating the SINE1B-siRNAs are indispensible for in vitro maturation (IVM) of porcine oocyte. To figure out the mechanism, we checked the expression pattern and DNA methylation status of SINE1B during IVM of porcine oocytes, and demonstrated the SINE1B-siRNAs could repress SINE1B expression induced by hypomethylation at a post-transcriptional level. Our results suggest that during gametogenesis when the erasure of DNA methylation occurs, endo-siRNAs act as a chronic response to limit retrotransposon activation.

DICER1 regulates antibacterial function of epididymis by modulating transcription of β-defensins

DICER1 is a key enzyme responsible for the maturation of microRNAs. Recent evidences suggested that DICER1 and microRNAs expressed in epididymis were involved in the control of male fertility. However, the exact mechanism remains to be elucidated. Here, we created a mouse line by targeted disruption of Dicer1 gene in the principal cells of distal caput epididymis. Our data indicated that a set of β-defensin genes were downregulated by DICER1 rather than by microRNAs. Moreover, DICER1 was significantly enriched in the promoter of β-defensin gene and controlled transcription. Besides, the antibacterial ability of the adult epididymis significantly declined upon Dicer1 deletion both in vitro and in vivo. And a higher incidence of reproductive defect was observed in middle-aged Dicer1-/- males. These results suggest that DICER1 plays an important role in transcription of β-defensin genes, which are associated with the natural antibacterial properties in a microRNA-independent manner, and further impacts the male fertility.

Oxidative stress modulates the expression of apoptosis-associated microRNAs in bovine granulosa cells in vitro

Despite its essential role in ovulation, oxidative stress (OS) has been found to be cytotoxic to cells, while microRNAs (miRNAs) are known as a major regulator of genes involved in cellular defense against cytotoxicity. However, a functional link between OS and miRNA expression changes in granulosa cells (GCs) remains to be investigated. Here, we investigate the OS modulation of apoptosis-associated miRNAs and their biological relevance in bovine GCs. Following the evaluation of cell viability, accumulation of reactive oxygen species (ROS), cytotoxicity and mitochondrial activity, we used a ready-to-use miRNA PCR array to identify differentially regulated miRNAs. The results showed that exposure to 150 μM H₂O₂ for 4 h creates remarkable signs of OS in GCs characterized by more than 50% loss of cell viability, higher nuclear factor erythroid 2-related factor 2 (NRF2) nuclear translocation, significantly (p < 0.05) higher abundance of antioxidant genes, significantly (p < 0.001) higher accumulation of ROS, lower mitochondrial activity and a higher (p < 0.001) number of apoptotic nuclei compared to that of the control group. miRNA expression analysis revealed that a total of 69 miRNAs were differentially regulated in which 47 and 22 miRNAs were up- and downregulated, respectively, in stressed GCs. By applying the 2-fold and p < 0.05 criteria, we found 16 miRNAs were upregulated and 10 miRNAs were downregulated. Target prediction revealed that up- and downregulated miRNAs potentially targeted a total of 6210 and 3575 genes, respectively. Pathway analysis showed that upregulated miRNAs are targeting the genes involved mostly in cell survival, intracellular communication and homeostasis, cellular migration and growth control and disease pathways. Our results showed that OS modulates the expression of apoptosis-associated miRNAs that might have effects on cellular or molecular damages.

Identification of microRNAs in granulosa cells from patients with different levels of ovarian reserve function and the potential regulatory function of miR-23a in granulosa cell apoptosis

This study aimed to determine the microRNA (miRNA) profiles in granulosa cells (GCs) from the follicular fluid (FF) of patients with varying levels of ovarian reserve function. We included 45 women undergoing in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) treatment. After collecting GCs from each patient, total RNA was extracted from 12 samples. Using Illumina/deep-sequencing technology, we analyzed the small RNAs in each group. Using the R package, we identified the differentially expressed (DE) miRNAs among patients with varying levels of ovarian reserve function. We identified 20 conserved and 3 novel miRNAs that were upregulated in the poor ovarian response (POR) group and 30 conserved miRNAs and 1 novel miRNA that were upregulated in the polycystic ovary syndrome (PCOS) group. Bioinformatics analysis revealed complementary pairing between miR-23a and the 3'-untranslated region (UTR) of the Sirt1 mRNA. miR-23a can regulate SIRT1 protein expression at the posttranscriptional level in GCs. Overexpressing miR-23a can inhibit the expression of SIRT1, decrease the stimulatory effect of SIRT1 on the ERK1/2 pathway, inhibit the expression of p-ERK1/2, and increase apoptosis in GCs. Previous studies confirmed that miR-23a targets SIRT1 and promotes apoptosis in GCs by inhibiting the ERK1/2 signaling pathway. This study provides a novel perspective regarding the role of miRNAs in the regulation of human GC apoptosis in vitro.

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.

New roles for Dicer in the nucleolus and its relevance to cancer

The nucleolus is a distinct compartment of the nucleus responsible for ribosome biogenesis. Mis-regulation of nucleolar functions and of the cellular translation machinery has been associated with disease, in particular with many types of cancer. Indeed, many tumor suppressors (p53, Rb, PTEN, PICT1, BRCA1) and proto-oncogenes (MYC, NPM) play a direct role in the nucleolus, and interact with the RNA polymerase I transcription machinery and the nucleolar stress response. We have identified Dicer and the RNA interference pathway as having an essential role in the nucleolus of quiescent Schizosaccharomyces pombe cells, distinct from pericentromeric silencing, by controlling RNA polymerase I release. We propose that this novel function is evolutionarily conserved and may contribute to the tumorigenic pre-disposition of DICER1 mutations in mammals.

Role of microRNAs in premature ovarian insufficiency

Premature ovarian insufficiency (POI) is a typical disorder of amenorrhea lasting for a minimum of 4 months. The typical characteristics comprised of declined estrogen and raised serum concentrations of follicle-stimulating hormone (FSH) in women <40-year-old, primarily originating from iatrogenic factors, karyotypic abnormalities, and genetic factors. However, the etiology of POI remains unknown in approximately 90% of cases. POI could lead to infertility, osteoporosis, cardiovascular disorder, and cognitive dysfunction. MicroRNAs (miRNAs) are a class of endogenous noncoding RNAs (ncRNAs) that can mediate post-translational silencing of the genes involved in the regulation of proliferation, differentiation, apoptosis, development, tumorigenesis, and hematopoiesis. Recently, the regulatory functions of miRNAs in the development of POI have been the topic of intensive research. The present review addresses the association of miRNAs' machinery genes (Dicer, Drosha, and XPO5) with POI and the miRNA expression profiles in the plasma of patients with POI. In addition, several specific miRNAs (miR-23a, miR-27a, miR-22-3p, miR-146a, miR-196a, miR-290-295, miR-423, and miR-608) related to POI are also examined in order to highlight the issues that deserve further investigation. A thorough understanding of the exact regulatory roles of miRNAs is imperative to gain novel insights into the etiology of idiopathic POI and offer new research directions in the field.

Switches in Dicer Activity During Oogenesis and Early Development

Dicer is a versatile protein regulating diverse biological processes via the production of multiple classes of small regulatory RNAs, including microRNAs (miRNAs) and small interfering RNAs (siRNAs). In this chapter, we will discuss roles for Dicer in driving temporal changes in activity of individual small RNA classes to support oogenesis and early embryogenesis. Genetic strategies that perturb particular functions of Dicer family proteins, such as ablation of individual Dicer paralogs or their binding partners as well as introduction of point mutations to individual domains, allowed the dissection of Dicer functions in diverse small RNA pathways. Evolutionary conservation and divergence of the mechanisms highlight the importance of Dicer versatility in supporting rapid changes in gene expression during oogenesis and early development. Furthermore, we will discuss potential roles of Dicer in transgenerational inheritance of small RNA-mediated gene regulation.

Epigenetics: A key paradigm in reproductive health

It is well established that there is a heritable element of susceptibility to chronic human ailments, yet there is compelling evidence that some components of such heritability are transmitted through non-genetic factors. Due to the complexity of reproductive processes, identifying the inheritance patterns of these factors is not easy. But little doubt exists that besides the genomic backbone, a range of epigenetic cues affect our genetic programme. The inter-generational transmission of epigenetic marks is believed to operate via four principal means that dramatically differ in their information content: DNA methylation, histone modifications, microRNAs and nucleosome positioning. These epigenetic signatures influence the cellular machinery through positive and negative feedback mechanisms either alone or interactively. Understanding how these mechanisms work to activate or deactivate parts of our genetic programme not only on a day-to-day basis but also over generations is an important area of reproductive health research.

Production of offspring from a germline stem cell line derived from prepubertal ovaries of germline reporter mice

STUDY HYPOTHESIS

We investigated whether DEAD-box polypeptide 4 (DDX4) positive cells from post-natal ovaries of germline lineage reporter mice can be isolated based on endogenously expressed fluorescent proteins and used to establish a cell line for producing offspring.

STUDY FINDING

DDX4-positive cells from post-natal ovaries of germline lineage reporter mice can be isolated and used to establish a cell line for producing offspring.

WHAT IS KNOWN ALREADY

In recent years, female germline stem cells (FGSCs) have been isolated from the ovaries of post-natal mice by magnetic-activated cell sorting or fluorescence-activated cell sorting (FACS) relying on an antibody against DDX4. However, whether DDX4-positive cells from post-natal ovaries of germline lineage reporter mice can be established without using an antibody, as well as a cell line established for producing offspring, remains unknown.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

To obtain the expected offspring (Ddx4-Cre;mT/mG mice), Ddx4-Cre mice were crossed with mT/mG mice. In the ovaries of Ddx4-Cre;mT/mG mice, germ cells were destined to express enhanced green fluorescent protein (EGFP) while somatic cells still express tandem dimer Tomato (tdTomato). Therefore, the germ cells could be clearly distinguished from somatic cells by fluorescent proteins. Then, we investigated the pattern of fluorescent cells in the ovaries of 21-day-old Ddx4-Cre;mT/mG mice under a fluorescent microscope. Germ cells were sorted by FACS without using antibody and used to establish a FGSC line. The FGSC line was analyzed by DDX4 immunostaining, Edu (5-ethynyl-2'-deoxyuridine) labeling, and RT-PCR for germ cell markers. Finally, the physiological function of the FGSC line was examined by transplanting FGSCs into the ovaries of sterilized recipients and subsequent mating.

MAIN RESULTS AND THE ROLE OF CHANCE

Firstly, we have successfully isolated FGSCs from the ovaries of 21-day-old Ddx4-Cre;mT/mG mice based on endogenously expressed fluorescent proteins. FACS was used to separate the cells and 2.3% of all viable cells was EGFP-positive germ cells. Subsequently, a FGSC line was established that was doubly positive for DDX4 immunostaining and Edu labeling. The mRNA expression of several germ cell markers in this cell line, such as Ddx4, Deleted in azoospermia-like (Dazl), B lymphocyte-induced maturation protein-1 (Blimp1), Stella and Fragilis, was detected. Lastly, the FGSC line was proven to be functional under physiological conditions, as offspring were produced after transplanting FGSCs into ovaries of sterilized recipients and a subsequent mating.

LIMITATIONS, REASONS FOR CAUTION

The molecular mechanisms of proliferation and differentiation of FGSCs in vivo and in vitro still need to be elucidated.

WIDER IMPLICATIONS OF THE FINDINGS

Our results confirm that DDX4-positive cells can be separated from post-natal mouse ovaries and used to establish cell lines that are functional in producing offspring, and provide further evidence for the existence of post-natal FGSCs in mammals. The Ddx4-Cre;mT/mG mouse strain is an ideal model for the isolation, characterization and propagation of FGSCs and is a useful tool for fully elucidating the molecular mechanisms of proliferation and differentiation of FGSCs in vivo and in vitro.

LARGE SCALE DATA

none.

STUDY FUNDING AND COMPETING INTERESTS

This work was supported by National Basic Research Program of China (2013CB967401) and the National Nature Science Foundation of China (81370675, 81200472 and 81421061). The authors declare no competing interests.

Sperm-borne miRNAs and endo-siRNAs are important for fertilization and preimplantation embryonic development

Although it is believed that mammalian sperm carry small noncoding RNAs (sncRNAs) into oocytes during fertilization, it remains unknown whether these sperm-borne sncRNAs truly have any function during fertilization and preimplantation embryonic development. Germline-specific Dicer and Drosha conditional knockout (cKO) mice produce gametes (i.e. sperm and oocytes) partially deficient in miRNAs and/or endo-siRNAs, thus providing a unique opportunity for testing whether normal sperm (paternal) or oocyte (maternal) miRNA and endo-siRNA contents are required for fertilization and preimplantation development. Using the outcome of intracytoplasmic sperm injection (ICSI) as a readout, we found that sperm with altered miRNA and endo-siRNA profiles could fertilize wild-type (WT) eggs, but embryos derived from these partially sncRNA-deficient sperm displayed a significant reduction in developmental potential, which could be rescued by injecting WT sperm-derived total or small RNAs into ICSI embryos. Disrupted maternal transcript turnover and failure in early zygotic gene activation appeared to associate with the aberrant miRNA profiles in Dicer and Drosha cKO spermatozoa. Overall, our data support a crucial function of paternal miRNAs and/or endo-siRNAs in the control of the transcriptomic homeostasis in fertilized eggs, zygotes and two-cell embryos. Given that supplementation of sperm RNAs enhances both the developmental potential of preimplantation embryos and the live birth rate, it might represent a novel means to improve the success rate of assisted reproductive technologies in fertility clinics.

A survey of DICER1 hotspot mutations in ovarian and testicular sex cord-stromal tumors

Sertoli-Leydig cell tumors are characterized by the presence of somatic DICER1 hotspot mutations. In this study, we sought to define the association between DICER1 hotspot mutations and different morphologic subtypes of ovarian Sertoli-Leydig cell tumors. Furthermore, we aimed to assess whether DICER1 hotspot mutations occur in other ovarian sex cord-stromal tumors, testicular sex cord-stromal tumors, or other female genital tract tumors with rhabdomyosarcomatous differentiation. We subjected a series of ovarian Sertoli-Leydig cell tumors (n=32), Sertoli cell tumors (n=5) and gynandroblastomas (n=5), testicular sex cord-stromal tumors (n=15) and a diverse group of female genital tract tumors with rhabdomyosarcomatous morphology (n=10) to DICER1 hotspot mutation analysis using Sanger sequencing. We also tested two gynandroblastomas for the presence of FOXL2 hotspot mutations (p.C134W; c.402C>G). Twenty of 32 (63%) Sertoli-Leydig cell tumors harbored a DICER1 hotspot mutation, of which 80% had the p.E1705K mutation. No association was found between DICER1 mutation status and the presence of heterologous or retiform differentiation in Sertoli-Leydig cell tumors. DICER1 mutations were found at similar frequencies in gynandroblastoma (2/5; 40%) and ovarian Sertoli cell tumors (5/8; 63%; P>0.1), and all mutated tumors harbored a p.E1705K mutation. DICER1 hotspot mutations were also identified in a single cervical rhabdomyosarcoma and in the rhabdomyosarcomatous component of a uterine carcinosarcoma. No DICER1 mutations were detected in testicular sex cord-stromal tumors. Two DICER1 wild-type gynandroblastomas harbored a p.C134W FOXL2 hotspot mutation in both tumor components. In this study we confirmed that DICER1 hotspot mutations occur in over half of ovarian Sertoli-Leydig cell tumors, and are unrelated to tumor differentiation. We also widened the spectrum of ovarian sex cord-stromal tumors with sertoliform differentiation, in which DICER1 mutations are known to occur, to include Sertoli cell tumors and gynandroblastomas. Our results suggest that DICER1 mutations may not have a role in testicular sex cord-stromal tumorigenesis.

MicroRNA in ovarian function

The mammalian ovary is a dynamic organ. The coordination of follicle recruitment, selection, and ovulation and the timely development and regression of the corpus luteum are essential for a functional ovary and fertility. Deregulation of any of these processes results in ovarian dysfunction and potential infertility. MicroRNA (miRNA) are short noncoding RNA that regulate developmental processes and time-sensitive functions. The expression of miRNA in the ovary varies with cell type, function, and stage of the estrous cycle. miRNA are involved in the formation of primordial follicles, follicular recruitment and selection, follicular atresia, oocyte-cumulus cell interaction, granulosal cell function, and luteinization. miRNA are differentially expressed in luteal cells at the various stages of the estrous cycle and during maternal recognition of pregnancy, suggesting a role in luteal development, maintenance, and regression. An understanding of the patterns of expression and functions of miRNA in the ovary will lead to novel therapeutics to treat ovarian dysfunction and improve fertility and, potentially, to the development of better contraceptives.

Does adipose tissue-derived stem cell therapy improve graft quality in freshly grafted ovaries?

BACKGROUND

A major concern in ovarian transplants is substantial follicle loss during the initial period of hypoxia. Adipose tissue-derived stem cells (ASCs) have been employed to improve angiogenesis when injected into ischemic tissue. This study evaluated the safety and efficacy of adipose tissue-derived stem cells (ASCs) therapy in the freshly grafted ovaries 30 days after injection.

METHODS

Rat ASCs (rASCs) obtained from transgenic rats expressing green fluorescent protein (GFP)-(5 × 10(4) cells/ovary) were injected in topic (intact) or freshly grafted ovaries of 30 twelve-week-old adult female Wistar rats. The whole ovary was grafted in the retroperitoneum without vascular anastomosis, immediately after oophorectomy. Vaginal smears were performed daily to assess the resumption of the estrous cycle. Estradiol levels, grafts morphology and follicular viability and density were analyzed. Immunohistochemistry assays were conducted to identify and quantify rASC-GFP(+), VEGF tissue expression, apoptosis (cleaved caspase-3 and TUNEL), and cell proliferation (Ki-67). Quantitative gene expression (qPCR) for VEGF-A, Bcl2, EGF and TGF-β1 was evaluated using RT-PCR and a double labeling immunofluorescence assay for GFP and Von Willebrand Factor (VWF) was performed.

RESULTS

Grafted ovaries treated with rASC-GFP(+) exhibited earlier resumption of the estrous phase (p < 0.05), increased VEGF-A expression (11-fold in grafted ovaries and 5-fold in topic ovaries vs. control) and an increased number of blood vessels (p < 0.05) in ovarian tissue without leading to apoptosis or cellular proliferation (p > 0.05). Estradiol levels were similar among groups (p > 0.05). rASC-GFP(+) were observed in similar quantities in the topic and grafted ovaries (p > 0.05), and double-labeling for GFP and vWF was observed in both injected groups.

CONCLUSION

rASC therapy in autologous freshly ovarian grafts could be feasible and safe, induces earlier resumption of the estrous phase and enhances blood vessels in rats. This pilot study may be useful in the future for new researches on frozen-thawed ovarian tissue.

Pervasive Genotypic Mosaicism in Founder Mice Derived from Genome Editing through Pronuclear Injection

Genome editing technologies, especially the Cas9/CRISPR system, have revolutionized biomedical research over the past several years. Generation of novel alleles has been simplified to unprecedented levels, allowing for rapid expansion of available genetic tool kits for researchers. However, the issue of genotypic mosaicism has become evident, making stringent analyses of the penetrance of genome-edited alleles essential. Here, we report that founder mice, derived from pronuclear injection of ZFNs or a mix of guidance RNAs and Cas9 mRNAs, display consistent genotypic mosaicism for both deletion and insertion alleles. To identify founders with greater possibility of transmitting the mutant allele through the germline, we developed an effective germline genotyping method. The awareness of the inherent genotypic mosaicism issue with genome editing will allow for a more efficient implementation of the technologies, and the germline genotyping method will save valuable time and resources.

Breeding scheme and maternal small RNAs affect the efficiency of transgenerational inheritance of a paramutation in mice

Paramutations result from interactions between two alleles at a single locus, whereby one induces a heritable change in the other. Although common in plants, paramutations are rarely studied in animals. Here, we report a new paramutation mouse model, in which the paramutant allele was induced by an insertional mutation and displayed the "white-tail-tip" (WTT) phenotype. The paramutation phenotype could be transmitted across multiple generations, and the breeding scheme (intercrossing vs. outcrossing) drastically affected the transmission efficiency. Paternal (i.e., sperm-borne) RNAs isolated from paramutant mice could induce the paramutation phenotype, which, however, failed to be transmitted to subsequent generations. Maternal miRNAs and piRNAs appeared to have an inhibitory effect on the efficiency of germline transmission of the paramutation. This paramutation mouse model represents an important tool for dissecting the underlying mechanism, which should be applicable to the phenomenon of epigenetic transgenerational inheritance (ETI) in general. Mechanistic insights of ETI will help us understand how organisms establish new heritable epigenetic states during development, or in times of environmental or nutritional stress.

Involvement of miRNAs and Cell-Secreted Vesicles in Mammalian Ovarian Antral Follicle Development

Ovarian follicular development is a controlled series of events culminating with an ovulatory or atretic follicle. MicroRNAs (miRNAs) are small noncoding RNAs involved in translational regulation of genes in different developmental processes. Deletion of Dicer in mice ovaries demonstrated the importance of miRNAs in reproduction, which led to infertility. The miRNAs were thought to act only within host cells; however, these molecules are also present in cell-secreted vesicles. These vesicles are present in body fluids such as milk, serum, and ovarian follicular fluid. Vesicles are secreted in extracellular fluids and travel from donor to target cells, mediating transfer of bioactive material. Herein we discuss the role of hormonal-regulated miRNAs within different ovarian follicular cells as well as cell-secreted vesicles participation in mammalian ovarian follicular fluid. Furthermore, we discuss the possibility of miRNAs transference mediated by cell-secreted vesicles present in ovarian follicular fluid, increasing the versatility of miRNA functions during antral follicle development.