NCBI Summary:
microRNAs (miRNAs) are short (20-24 nt) non-coding RNAs that are involved in post-transcriptional regulation of gene expression in multicellular organisms by affecting both the stability and translation of mRNAs. miRNAs are transcribed by RNA polymerase II as part of capped and polyadenylated primary transcripts (pri-miRNAs) that can be either protein-coding or non-coding. The primary transcript is cleaved by the Drosha ribonuclease III enzyme to produce an approximately 70-nt stem-loop precursor miRNA (pre-miRNA), which is further cleaved by the cytoplasmic Dicer ribonuclease to generate the mature miRNA and antisense miRNA star (miRNA*) products. The mature miRNA is incorporated into a RNA-induced silencing complex (RISC), which recognizes target mRNAs through imperfect base pairing with the miRNA and most commonly results in translational inhibition or destabilization of the target mRNA. The RefSeq represents the predicted microRNA stem-loop. [provided by RefSeq, Sep 2009]
General function
Cell proliferation, RNA processing
Comment
Cellular localization
Secreted
Comment
Ovarian function
Steroid metabolism, Early embryo development
Comment
Association of miRNA - 320 expression level and its target gene endothelin-1 with the susceptibility and clinical features of polycystic ovary syndrome. Rashad NM et al. (2019) Polycystic ovary syndrome (PCOS) is a common reproductive endocrine disorder characterized by obesity, hyperandrogenism, and insulin resistance (IR). MicroRNAs (miRNAs) are small noncoding RNA associated with ovarian follicle development and female fertility. The objective of this study was to investigate the role of miRNA- 320 and its target gene endothelin-1 (ET-1) as a noninvasive biomarker of PCOS and to evaluate its possible relationship with IR as well as clinic-morphological features of PCOS. Case-control study enrolled 60 patients with PCOS and 40 control group. We subdivided our PCOS women according to homeostasis model assessments of insulin resistance (HOMA-IR) to PCOS women with and without IR.ET-1 levels were measured by ELISA. We estimated the serum expression level of miRNA- 320 by real-time polymerase chain reaction. Our results revealed that serum miR-320 expression level was lower in PCOS patients compared to controls, in particular, PCOS women with IR. Moreover, it was negatively correlated to its target gene; ET-I as well as fasting serum insulin (FSI), HOMA-IR, PCOS phenotype; hirsutism score, ovarian volume and antral follicle count (AFC). In the PCOS group, linear regression analysis revealed that only hirsutism and HOMA-IR was the main predictor of expression levels of miRNA - 320 among other clinical and laboratory biomarkers of PCOS. The sensitivity and specificity of serum miR-320 expression levels in diagnosis PCOS was 80, and 97.5% respectively. The Expression serum levels of miR-320 were lower in PCOS compared to control and it could be a noninvasive diagnostic biomarker of PCOS.//////////////////
MicroRNA‑320a inhibition decreases insulin‑induced KGN cell proliferation and apoptosis by targeting PCGF1. Yang L et al. (2017) MicroRNAs (miRNAs) are widely involved in regulation of cellular processes of polycystic ovary syndrome (PCOS). However, the function of miR‑320a in PCOS remains unclear. The present study aimed to explore the effect of miR‑320a on PCOS cell proliferation and apoptosis following treatment with insulin, and to clarify the underlying mechanism. PCOS tissues and corresponding normal tissues were collected from 16 female patients with PCOS. KGN cells were pre‑treated with insulin, and KGN cells were transfected with ASO‑miR‑320a, miR‑320a mimics and polycomb group ring finger 1 (PCGF1) overexpression plasmids. Expressions of miR‑320a and PCGF1 were detected using the reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). Dual‑Luciferase reporter assays were performed to investigate the target gene of miR‑320a. MTS, colony formation and flow cytometry assays were performed to determine cell viability, colony formation, and apoptosis, respectively. Furthermore, mRNA and protein expression levels of B‑cell lymphoma 2 apoptosis regulator (Bcl‑2) and Bcl‑2 associated protein X apoptosis regulator (Bax) were examined using RT‑qPCR and western blotting. The results demonstrated that miR‑320a expression was significantly increased in PCOS tissues compared with normal tissues. Moreover, miR‑320a was upregulated in insulin‑induced cells in a dose‑dependent manner. Inhibition of miR‑320a suppressed insulin‑induced cell viability and colony formation, and promoted apoptosis. Luciferase reporter assays demonstrated that PCGF1 was a target of miR‑320a. Additionally, PCGF1 overexpression inhibited cell viability and colony formation and promoted apoptosis. Additionally, the mRNA and protein levels of Bcl‑2 were inhibited by miR‑320a suppression and PCGF1 overexpression, while Bax expression was promoted by them in insulin‑induced cells. The results of the present study demonstrated that miR‑320a inhibition decreased insulin‑induced KGN cell proliferation and apoptosis by targeting PCGF1. These data indicated that miR‑320a may serve as a potential diagnostic biomarker for PCOS.//////////////////
Transactivation of miR-320 by miR-383 regulates granulosa cell functions by targeting E2F1 and SF-1* Yin M 2014 et al.
Our previous studies have shown that miR-320 is one of the most down-regulated miRNAs in mouse ovarian granulosa cells (GCs) after TGF-1 treatment. However, the underlying mechanisms of miR-320 involved in GC function during follicular development remain unknown. In this study, we found that PMSG treatment resulted in the suppression of miR-320 expression in a time-dependent manner. miR-320 was mainly expressed in GCs and oocytes of mouse ovarian follicles in follicular development. Overexpression of miR-320 inhibited estradiol (E2) synthesis and proliferation of GCs through targeting E2F1 and SF-1. E2F1/SF-1 mediated miR-320-induced suppression of GC proliferation and of GC steroidogenesis. FSH down-regulated the expression of miR-320 and regulated the function of miR-320 in mouse GCs. miR-383 promoted the expression of miR-320 and enhanced miR-320-mediated suppression of GC proliferation. Injection of miR-320 into the ovaries of mice partially promoted the production of testosterone and progesterone, but inhibited E2 release in vivo. Moreover, the expression of miR-320 and miR-383 was up-regulated in the follicular fluid of polycystic ovarian syndrome (PCOS) patients, while the expression of E2F1 and SF-1 was down-regulated in GCs. These data demonstrated that miR-320 regulates the proliferation and steroid production by targeting E2F1 and SF-1 in the follicular development. Understanding the regulation of miRNA biogenesis and function in the follicular development will potentiate the usefulness of miRNA in the treatment of reproduction and some steroid-related disorders.
/////////////////////////
Expression regulated by
Comment
Ovarian localization
Oocyte, Cumulus, Granulosa, Follicular Fluid
Comment
MiRNA-320 in the human follicular fluid is associated with embryo quality in vivo and affects mouse embryonic development in vitro. Feng R et al. (2015) Previous work from our laboratory demonstrated the existence of miRNAs in human follicular fluid. In the current study, we have sought to identify miRNAs that might affect oocyte/embryo quality in patients undergoing intracytoplasmic sperm injection and to investigate their roles in in vitro fertilization outcomes in mouse oocytes. 53 samples were classified as Group 1 (high quality) if the day-3 embryos had seven and more cells or as Group 2 (low quality) if the embryos had six and fewer cells. TaqMan Human microRNAs cards and qRT-PCR were performed to verify differently expressed miRNAs. The function of the corresponding miRNA was investigated in mouse oocytes by injecting them with miRNA-inhibitor oligonucleotides. We found that hsa-miR-320a and hsa-miR-197 had significantly higher expression levels in the Group 1 follicular fluids than in Group 2 (p = 0.0073 and p = 0.008, respectively). Knockdown of mmu-miR-320 in mouse oocytes strongly decreased the proportions of MII oocytes that developed into two-cell and blastocyst stage embryos (p = 0.0048 and p = 0.0069, respectively). Wnt signaling pathway components had abnormal expression level in miR-320 inhibitor-injected oocytes. This study provides the first evidence that miRNAs in human follicular fluid are indicative of and can influence embryo quality.//////////////////
MicroRNAs: new candidates for the regulation of the human cumulus-oocyte complex. Assou S 2013 et al.
STUDY QUESTION
What is the expression pattern of microRNAs (miRNAs) in human cumulus-oocyte complexes (COCs)?
SUMMARY ANSWER
Several miRNAs are enriched in cumulus cells (CCs) or oocytes, and are predicted to target genes involved in biological functions of the COC.
WHAT IS KNOWN ALREADY
The transcriptional profiles of human MII oocytes and the surrounding CCs are known. However, very limited data are available about post-transcriptional regulators, such as miRNAs. This is the first study focussing on the identification and quantification of small RNAs, including miRNAs, in human oocytes and CCs using a deep-sequencing approach.
STUDY DESIGN, SIZE, DURATION
MII oocytes and CCs were collected from women who underwent IVF.
PARTICIPANTS/MATERIALS, SETTING, METHODS
Using the Illumina/deep-sequencing technology, we analyzed the small RNAome of pooled MII oocytes (n = 24) and CC samples (n = 20). The mRNA targets of CC and MII oocyte miRNAs were identified using in silico prediction algorithms. Using oligonucleotide microarrays, genome-wide gene expression was studied in oocytes (10 pools of 19 ? 3 oocytes/each) and 10 individual CC samples. TaqMan miRNA assays were used to confirm the sequencing results in independent pools of MII oocytes (3 pools of 8 ? 3 oocytes/each) and CC samples (3 pools of 7 ? 3 CCs/each). The functional role of one miRNA, MIR23a, was assessed in primary cultures of human CCs.
MAIN RESULTS AND THE ROLE OF CHANCE
Deep sequencing of small RNAs yielded more than 1 million raw reads. By mapping reads with a single location to the human genome, known miRNAs that were abundant in MII oocytes (MIR184, MIR100 and MIR10A) or CCs (MIR29a, MIR30d, MIR21, MIR93, MIR320a, MIR125a and the LET7 family) were identified. Predicted target genes of the oocyte miRNAs were associated with the regulation of transcription and cell cycle, whereas genes targeted by CC miRNAs were involved in extracellular matrix and apoptosis. Comparison of the predicted miRNA target genes and mRNA microarray data resulted in a list of 224 target genes that were differentially expressed in MII oocytes and CCs, including PTGS2, CTGF and BMPR1B that are important for cumulus-oocyte communication. Functional analysis using primary CC cultures revealed that BCL2 and CYP19A1 mRNA levels were decreased upon MIR23a overexpression.
LIMITATIONS, REASONS FOR CAUTION
Only known miRNAs were investigated in the present study on COCs. Moreover, the source of the material is MII oocytes that failed to fertilize.
WIDER IMPLICATIONS OF THE FINDINGS
The present findings suggest that miRNA could play a role in the regulation of the oocyte and CC crosstalk.
STUDY FUNDING/COMPETING INTEREST(S)
This work was partially supported by a grant from Ferring Pharmaceuticals. The authors of the study have no conflict of interest to report.
TRIAL REGISTRATION NUMBER
Not applicable.
/////////////////////////
Identification of microRNAs in human follicular fluid: characterization of microRNAs that govern steroidogenesis in vitro and are associated with polycystic ovary syndrome in vivo. Sang Q et al. Context:Human follicular fluid is a combination of proteins, metabolites, and ionic compounds that is indicative of the general state of follicular metabolism and is associated with maturation and quality of oocytes. Deviations in these components are often associated with reproductive diseases. There has been no report of microRNAs (miRNAs) in human follicular fluids.Objective:We hypothesized that human follicular fluid may contain miRNAs. We sought to identify cell-free miRNAs in human follicular fluid and to investigate these miRNAs's function in vitro and any roles they play in polycystic ovary syndrome.Design:Genome-wide deep sequencing and TaqMan miRNA arrays were used to identify miRNAs, and the roles of the highly expressed miRNAs in steroidogenesis were investigated in KGN cells. Quantification of candidate miRNAs in follicular fluids of PCOS and controls was performed using TaqMan miRNA assays.Results:We identified miRNAs in microvesicles and the supernatant of human follicular fluid. Bioinformatics analysis showed that the most highly expressed miRNAs targeted genes associated with reproductive, endocrine, and metabolic processes. We found that miR-132, miR-320, miR-520c-3p, miR-24, and miR-222 regulate estradiol concentrations and that miR-24, miR-193b, and miR-483-5p regulate progesterone concentrations. Finally, we showed that miR-132 and miR-320 are expressed at significantly lower levels in the follicular fluid of polycystic ovary patients than in healthy controls (p =0.005, p =0.0098, respectively)Conclusion:These results demonstrate that there are numerous miRNAs in human follicular fluids, some of which play important roles in steroidogenesis and PCOS. This study substantially revises our understanding of the content of human follicular fluid and lays the foundation for the future investigation of miRNAs' role in PCOS.