Research Resources: Comparative MicroRNA Profiles in Human Corona Radiata Cells and Cumulus Oophorus Cells Detected by Next-Generation Small RNA Sequencing. Tong XH 2014 et al.
During folliculogenesis, cumulus cells surrounding the oocyte differentiate into corona radiata cells (CRCs) and cumulus oophorus cells (COCs), which are involved in gonadal steroidogenesis and the development of germ cells. Several studies suggested that microRNAs (miRNAs) play an important regulatory role at the post-transcriptional level in cumulus cells. However, comparative miRNA profiles and associated processes in human CRCs and COCs have not been reported before. In this study, miRNA profiles were obtained from CRCs and COCs using next generation sequencing in women undergoing controlled ovarian stimulation for IVF. A total of 785 and 799 annotated miRNAs were identified in CRCs and COCs, while high expression levels of six novel miRNAs were detected both in CRCs and in COCs. In addition, different expression patterns in CRCs and COCs were detected in 72 annotated miRNAs. To confirm the miRNA profile in COCs and CRCs, quantitative real-time PCR was used to validate the expression of annotated miRNAs, differentially expressed miRNAs, and novel miRNAs. The miRNAs in the let-7 family were found to be involved in the regulation of a broad range of biological processes in both cumulus cell populations, which was accompanied by a large amount of miRNA editing. Bioinformatics analysis showed that amino acid and energy metabolism were targeted significantly by miRNAs that were differentially expressed between CRCs and COCs. Our work extends the current knowledge of the regulatory role of miRNAs and their targeted pathways in folliculogenesis, and provides novel candidates for molecular biomarkers in the research of female infertility.
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General function
RNA processing
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Cellular localization
Cytoplasmic
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Ovarian function
Follicle development, Follicle atresia
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Expression and Preliminary Functional Profiling of the let-7 Family during Porcine Ovary Follicle Atresia. Cao R et al. (2015) Most follicles in the mammalian ovary undergo atresia. Granulosa cell apoptosis is a hallmark of follicle atresia. Our previous study using a microRNA (miRNA) microarray showed that the let-7 microRNA family was differentially expressed during follicular atresia. However, whether the let-7 miRNA family members are related to porcine (Sus scrofa) ovary follicular apoptosis is unclear. In the current study, real-time quantitative polymerase chain reaction showed that the expression levels of let-7 family members in follicles and granulosa cells were similar to our microarray data, in which miRNAs let-7a, let-7b, let-7c, and let-7i were significantly decreased in early atretic and progressively atretic porcine ovary follicles compared with healthy follicles, while let-7g was highly expressed during follicle atresia. Furthermore, flow cytometric analysis and Hoechst33342 staining demonstrated that let-7g increased the apoptotic rate of cultured granulosa cells. In addition, let-7 target genes were predicted and annotated by TargetScan, PicTar, gene ontology and Kyoto encyclopedia of genes and genomes pathways. Our data provide new insight into the association between the let-7 miRNA family in granulosa cell programmed death.//////////////////
Expression regulated by
FSH
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A network of miRNAs expressed in the ovary are regulated by FSH. Yao N et al. The process of folliculogenesis requires a tightly regulated series of gene expression that are a pre-requisite to the development of ovarian follicle. Among these genes, follicle-stimulating hormone (FSH) is notable for its dual role in development of follicles as well as proliferation and differentiation of granulosa cells. The post-transcriptional expression of these genes is under the control of microRNAs (miRNAs), a class of small, endogenous RNAs that negatively impact gene expression. This study was carried out to determine the role of several miRNAs including mir-143, let-7a, mir-125b, let-7b, let-7c, mir-21 in follicular development in the mouse. The expression of these RNAs was very low in primordial follicles but these became readily detectable in the granulosa cells of primary, secondary and antral follicles. We show that this expression of some miRNAs (mir-143, let-7a, mir-15b) is under negative control of FSH. Together, these findings suggest that FSH regulates folliculogenesis by a novel pathway of miRNAs.
Ovarian localization
Granulosa
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MicroRNA transcriptome in the newborn mouse ovaries determined by massive parallel sequencing. Ahn HW et al. Small noncoding RNAs, such as microRNAs (miRNAs) are involved in diverse biological processes including organ development and tissue differentiation. Global disruption of miRNA biogenesis in Dicer knockout mice disrupts early embryogenesis and primordial germ cell formation. However, the role of miRNAs in early folliculogenesis is poorly understood. In order to identify a full transcriptome set of small RNAs expressed in the newborn ovary, we extracted small RNA fraction from mouse newborn ovary tissues and subjected it to massive parallel sequencing using the Genome Analyzer from Illumina. Massive sequencing produced 4,655,992 reads of 33 bp each representing a total of 154 Mbp of sequence data. The Pash alignment algorithm mapped 50.13% of the reads to the mouse genome. Sequence reads were clustered based on overlapping mapping coordinates and intersected with known miRNAs, snoRNAs, piRNA clusters, and repetitive genomic regions. 25.2% of the reads mapped to known miRNAs, 25.5% to genomic repeats, 3.5% to piRNAs, and 0.18% to snoRNAs. 398 known miRNA species were among the sequenced small RNAs, and 118 isomiR sequences that are not in the miRBase database. Let-7 family was the most abundantly expressed miRNA and mmu-mir-672, mmu-mir-322, mmu-mir-503 and mmu-mir-465 family are the most abundant X-linked miRNA detected. X-linked mmu-mir-503, mmu-mir-672 and mmu-mir-465 family showed preferential expression in testes and ovaries. We also identified 4 novel miRNAs that are preferentially expressed in gonads. Gonadal selective miRNAs may play important roles in ovarian development, folliculogenesis, and female fertility.