Project description:Female gamete production relies on coordinated molecular and cellular processes that occur in the ovary throughout oogenesis. In fish, as in other vertebrates, these processes have been extensively studied both in terms of endocrine/paracrine regulation and protein expression and activity. The role of small non-coding RNAs in the regulation of animal reproduction remains however largely unknown and poorly investigated, despite a growing interest for the importance of miRNAs in a wide variety of biological processes. Here, we analyzed the role of miR-202, a miRNA predominantly expressed in male and female gonads in several vertebrate species. We studied its expression in the medaka ovary and generated a mutant line (using CRISPR/Cas9 genome editing) to determine its importance for reproductive success with special interest for egg production. Our results show that miR-202-5p is the most abundant mature form of the miRNA and that it is expressed in granulosa cells and in the unfertilized egg. The knock out (KO) of mir-202 gene resulted in a strong phenotype both in terms of number and quality of eggs produced. Mutant females exhibited either no egg production or produced a dramatically reduced number of eggs that could not be fertilized, ultimately leading to no reproductive success. We quantified the size distribution of the oocytes in the ovary of KO females and performed a large-scale transcriptomic analysis approach to identified dysregulated molecular pathways. Together, cellular and molecular analyses indicate that the lack of miR-202 impairs the early steps of oogenesis/folliculogenesis and decreases the number of large (i.e. vitellogenic) follicles, ultimately leading to dramatically reduced female fecundity. This study sheds new light on the regulatory mechanisms that control the early steps of follicular development, including possible targets of miR-202-5p, and provides the first in vivo functional evidence that a gonad-predominant microRNA may have a major role in female reproduction.

Project description:The anabolic androgen 17M-NM-2-trenbolone (TB) can cause masculinization and reduce fecundity of fish. However, the underlying mechanisms of various biological pathways including metabolism, biosynthesis etc. are largely unknown. Here, we evaluated the effects of TB using the medaka DNA microarray representing 36,398 genes. Larval medaka, Oryzias latipes, (within 24 hrs posthatch) were exposed to TB at various concentrations (2, 6, 20, 60, 100, 200 ng/L) for up to 7 days. Dose-response relationships in gene expression levels of the categorized genes were analyzed using the cumulative chisquared method. Microarray analyses of the TB-exposed larvae showed that 117 and 32 genes were determined as up and down-regulated genes, respectively. The most significant GO term for biological process identified within this gene list was lipid metabolic process, which contained 26 genes in up-regulated genes. In this category, M-bM-^@M-^\cholesterol biosynthetic processM-bM-^@M-^] was highlighted as an important subcategory with 15 genes, including hydroxymethylglutaryl-CoA synthase cytoplasmic, squalene monooxygenase, lanosterol synthase etc. RT-PCR measurements in these genes were consistent with the microarray results in the direction and magnitude of these changes in gene expression. On the other hands, in the category of M-bM-^@M-^\sexual differentiation and developmentM-bM-^@M-^], genes related to hypothalamic-pituitary-gonadal (HPG) axis were not affected by TB treatment except for one gene encoded to cytochrome P450 19A1. Genes related to oogenesis, such as choriogenins and vitellogenins were weakly down regulated at 2-200 ng/L of TB. Our findings demonstrate that genes encoding cholesterol synthesis pathway via the mevalonate pathway were controlled by TB in larval medaka. TB concentrations used were 0 (control), 2, 6, 20, 60, 100 and 200 ng/L for 7 days of exposure. Each TB treatment had 90 larval medaka for each chamber. At day 7 of the exposures, triplicate samples (30 larvae/sample) from each chamber respectively were collected, flash-frozen in liquid nitrogen, and stored in liquid nitrogen until RNA extraction.

Project description:Potential miR-202 targets were identified using a targetome-wide RIP-based microarray. HeLa cells were transfected with either a miR-202 mimic or a scrambled single-stranded RNA negative control. RNA was isolated from total cell lysate prior to IP and from antibody-immobilized Protein G agarose beads-RNP complexes (post-IP). Ribonucleoprotein IP was performed using the RIP-Assay kit for microRNA (MBL) according to the protocol described by the manufacturer. Briefly, anti-EIF2C2/Ago2 monoclonal antibody (Novus Biologicals, LLC) was incubated with Protein G plus agarose beads (Pierce) at 4M-BM-0C overnight to prepare antibody-immobilized beads. 20 million cells were harvested and washed four times with ice-cold DEPC-treated PBS. The cell pellet was lysed with 500 M-NM-<l of lysis buffer and the supernatant was incubated with Protein G agarose beads without antibody to reduce nonspecific adsorption. The cell lysate was then transferred into a tube containing antibody-immobilized Protein G agarose beads and incubated for 3 hours at 4M-BM-0C. Genome-wide expression levels were analyzed in total RNA samples from total cell lysate and antibody-immobilized Protein G agarose beads-RNP complexes from cells transfected with miR-202 mimic or negative control using the Agilent 44K 60-mer human whole-genome microarray. Signal hybridization and scans were performed by MOGene, LC (St Louis, MO) (run in biological duplicate). The normalized signal intensities of probes from RNP-bead complexes (post-IP fraction) were divided by the signal intensities from total cell lysate (pre-IP fraction) in miR-202 mimic-transfected cells. Transcripts were identified as members of the global miRNA targetome if they exhibited an enrichment fold change > 2.0. From this list, post-IP to pre-IP signal intensity ratios in miR-202 mimic-transfected cells were divided by post-IP to pre-IP signal intensity ratios in NC cells. Transcripts exhibiting normalized signal ratios of > 1.5 were considered to be bound with miR-202 in the RNA-induced silencing complex (RISC), and therefore potential direct miR-202 targets.

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The microARN-202 (miR-202) controls female fecundity by regulating oogenesis in medaka

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