Biology subjects

Thermes, V.

Publications and source records attributed to Thermes, V..

7 recordsLinked to original sources

bioRxiv2026

miR-202 drives medaka fertility by targeting antagonistic Yap-dependent transcriptional regulators tead3b and vgll4b in a sex-dependent manner

How miRNAs can sometimes drive major organism-level phenotypes by targeting a single gene and by triggering limited changes in mRNA levels remains poorly understood, especially in vertebrates. In medaka, the knockout of miR-202-5p, a gonad-specific miRNA in vertebrates, leads to impaired male and female fertility, including drastically reduced egg production and low developmental success. Here we show that miR-202-5p drives gamete formation by targeting antagonist Yap-dependent transcriptional regulators tead3b and vgll4b in a sex-dependent manner. Disruption of the miR-202-5p binding site in the 3UTR of tead3b, but not vgll4b, results in a significant decrease in female fertility. In contrast, disrupting miR-202-5p target site in the 3UTR of vgll4b, but not tead3b, results in impaired male fertility. In females, 3D ovary imaging and RNA-seq analysis of isolated ovarian follicles revealed that disrupting miR-202-5p binding to the 3 UTR of tead3b results in a polycystic ovarian syndrome (PCOS)-like phenotype and the expression of many PCOS-associated marker, including androgen signaling and estrogen metabolism genes. In males, disrupting miR-202-5p binding to the 3UTR of vgll4b triggers severe phenotypes, including reduced sperm motility and abnormal testicular development. No effects on sex ratio were observed, indicating that miR-202-5p drives gamete formation by regulating mechanisms acting down-stream of the sex-determining cascade. The analysis of miR-202-5p target sites in 3 UTRs suggests long-term conservation of antagonistic TEAD and VGLL targeting across vertebrate species, including mammals. Together, our results show that miR-202-5p drives fertility by leveraging antagonistic Yap-dependent transcriptional regulators in a sex dependent manner.

genetics↗

bioRxiv2026

Identification of miR-187 as a modulator of early oogenesis and female fecundity in medaka

MicroRNAs (miRNAs) are known regulators of ovarian function in vertebrates, yet their physiological roles in fish reproduction remain poorly understood. Here, we identified miR-187 as one of the most ovarian-enriched miRNAs in medaka (Oryzias latipes) and we uncovered its function in vivo using CRISPR/Cas9-mediated gene inactivation. miR-187-3p is expressed in oocytes and granulosa cells in the ovary, and in discrete brain areas. Its loss-of-function leads to a significant reduction in female fecundity. High-resolution 3D imaging of whole ovaries revealed that mir-187 mutants accumulate early stage I follicles and show reduced progression to later stages, indicating a defect in early follicle recruitment and growth. Transcriptomic profiling of mutant ovaries revealed extensive gene-expression remodeling, including downregulation of key regulators of steroidogenesis, Wnt/{beta}-catenin signaling, and TGF-{beta} pathways, and upregulation of genes associated with early follicle activation and immature somatic cell states. Using an expression-based target-prediction pipeline, we identified several putative miR-187-3p targets, including nr6a1a (gcnf) and dpagt1, two genes previously implicated in oocyte differentiation and female fertility in mammals. Together, our results demonstrate that miR-187 acts as a previously unrecognized regulator of early folliculogenesis and female reproductive capacity in medaka, expanding the repertoire of miRNAs with essential in vivo roles in teleost oogenesis and female fecundity. AUTHOR SUMMARYSuccessful fish reproduction depends on the continuous production of oocytes within the ovary. This process depends on the coordinated development of germ cells and the supporting somatic cells. Although microRNAs (miRNAs) are known to post-transcriptionally regulate gene expression, their physiological roles in the fish ovary and female reproduction remain poorly understood. In this study, we used the medaka to investigate the function of miR-187, a miRNA strongly enriched in the ovary. By generating a CRISPR/Cas9 knockout line, we showed that females lacking miR-187 produce fewer eggs and display defects in early follicle development. Using whole-ovary 3D imaging, we found that mutant females accumulate early follicles that fail to progress through normal growth stages. Transcriptomic analyses revealed broad gene-expression changes affecting pathways involved in follicle activation, somatic cell maturation, and ovarian signaling. Our results demonstrate that miR-187 is a previously unrecognized regulator of early folliculogenesis and female fecundity in medaka. This work expands the landscape of miRNA-mediated regulation in the ovary and highlights the importance of post-transcriptional mechanisms in controlling reproductive success in teleosts. Grant supportThe DYNAMO project (French National Research Agency, ANR-18-CE20-0004). The OVOPAUSE project (French National Research Agency, ANR-22-CE45-00017-02). The IMMO project (INRAE Metaprogramme DIGIT-BIO).

developmental biology↗

bioRxiv2025

Circulating microRNAs reveal egg-brain crosstalk and a brain-specific microRNA linked to the onset of the next reproductive cycle in iteroparous salmonids

Mechanisms regulating the transition between two consecutive reproductive cycles are complex and remain poorly understood, mostly because they involve a dialog between the ovary and the central nervous system that is difficult to disentangle. In rainbow trout (Oncorhynchus mykiss), an iteroparous species spawning every year, removal of the eggs from the body cavity was used as a switch to trigger the onset of the next reproductive cycle. Changes in circulating miRNAs (c-miRNAs) levels in blood plasma and ovarian fluid were then monitored over time. Upon removal of the eggs from the body cavity we observed the dramatic down regulation of the blood plasma levels of a single c-miRNA (miR-139-5p) that is predominantly expressed in the brain. In contrast, very distinct c-miRNAs profiles were observed in blood plasma when eggs are retained in the body cavity. Among plasma c-miRNAs showing dynamic changes with egg retention, miR-135c is strongly expressed in the brain and pituitary, while miR-457a is predominant in the postovulatory ovary. In addition, egg retention in the body cavity triggers a dramatic drop in ovarian fluid levels of miR-202-5p, a miRNA known to regulate egg production in fish. Our observations reveal that the transition between two successive reproductive cycles involves a crosstalk between the eggs and the central system and that a single miRNA, miR-139, predominantly expressed in the brain, is associated with the onset of the next reproductive cycle. We identified possible miR-139-5p functional targets in rainbow trout and other iteroparous species that have been lost in semelparous salmonids. Our results offer new research perspectives to better understand the mechanisms triggering the next reproductive cycle in iteroparous fish species, including post-transcriptional regulations by miR-139 in the brain.

physiology↗

bioRxiv2023

Looking for a needle in a haystack: de novo phenotypic target identification reveals Hippo pathway-mediated miR-202 regulation of egg production

Understanding microRNA (miRNA) functions has been hampered by major difficulties in identifying their biological target(s). Currently, the main limitation is the lack of a suitable strategy to identify biologically relevant targets among a high number of putative targets. Here we provide a proof of concept of successful de novo (i.e., without prior knowledge of its identity) miRNA phenotypic target (i.e., target whose de-repression contributes to the phenotypic outcomes) identification from RNA-seq data. Using the medaka mir-202 knock-out (KO) model in which inactivation leads to a major organism-level reproductive phenotype, including reduced egg production, we introduced novel criteria including limited fold-change in KO and low interindividual variability in gene expression to reduce the list of 2,853 putative targets to a short list of 5. We selected tead3b, a member of the evolutionarily-conserved Hippo pathway, known to regulate ovarian functions, due to its remarkably strong and evolutionarily conserved binding affinity for miR-202-5p. Deleting the miR-202-5p binding site in the 3 UTR of tead3b, but not of other Hippo pathway members sav1 and vgll4b, triggered a reduced egg production phenotype. This is one of the few successful examples of de novo functional assignment of a miRNA phenotypic target in vivo in vertebrates.

genomics↗

bioRxiv2021

Deciphering sex-specific miRNAs as heat-recorders in zebrafish

MicroRNAs (miRNAs) are important post-transcriptional regulators of gene expression in a wide variety of physiological processes, including those related to the reproductive system. Although in the last decade a plethora of miRNAs has been reported, the miRNA alterations occurred by environmental cues and their biological functions have not yet been elucidated. With the aim to identify epigenetic regulations mediated by miRNAs in the gonads in a climate change scenario, zebrafish (Danio rerio) were subjected to high temperatures during sex differentiation (18-32 days post fertilization, dpf), a treatment that results in male-skewed sex ratios. Once the fish reached adulthood (90 dpf), ovaries and testes were sequenced by high-throughput technologies. About 101 million high-quality reads were obtained from gonadal samples. Analyses of the expression levels of the miRNAs identified a total of 23 and 1 differentially expressed (DE) miRNAs in ovaries and testes, respectively, two months after the heat treatment. Most of the identified miRNAs were involved in human sex-related cancer. After retrieving 3 UTR regions, ~400 predicted targets of the 24 DE miRNAs were obtained, some with reproduction-related functions. Their synteny in the zebrafish genome was, for more than half of them, in the chromosomes 7, 2, 4, 3 and 11 in the ovaries, chromosome 4 being the place where the predicted sex-associated-region (sar) is localized in wild zebrafish. Further, spatial localization in the gonads of two selected miRNAs (miR-122-5p and miR-146-5p) showed exclusive expression in the ovarian germ cells. The present study expands the catalog of sex-specific miRNAs and deciphers, for the first time, thermosensitive miRNAs in the zebrafish gonads that might be used as potential epimarkers to predict environmental past events.

genomics↗

bioRxiv2020

C-Eci: A Cubic-Eci Combined Clearing Method For 3D Follicular Content Analysis In The Fish Ovary

Deciphering mechanisms of oocyte development in female fishes still remains challenging and a comprehensive overview of this process at the level of the organ is still needed. The recent development optical tissue clearing methods have tremendously boosted the 3D imaging of large size biological samples that are naturally opaque. However, no attempt of clearing on fish ovary that accumulates extremely high concentration of lipids within oocytes has been reported to date. To face with this ovarian-specific challenge, we combined two existing clearing methods, the non-toxic solvent-based Eci method for efficient clearing and the CUBIC method to enhance lipid removal and reduce non-specific staining. The methyl green fluorescent dye was used to stain nuclei and delineate follicles. Using this procedure (named C-Eci), ovaries of both medaka and trout could be imaged in 3D and all follicles analyzed. To our knowledge this is the first procedure elaborated for clearing and imaging fish ovary in 3D. The C-Eci methods thus provides an interesting tool for getting precise quantitative data on follicular content in fish ovary and promises to be useful for further morphological studies. SummaryA modified ethyl-cinnamate-based clearing method allows solving fish ovary-specific challenges for 3D imaging, including high lipid-contents, and analyzing the ovarian follicular content in medaka and trout.

developmental biology↗

bioRxiv2018

MicroRNA-202 (miR-202) controls female fecundity by regulating medaka oogenesis

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 engineering) to determine its importance for reproductive success with special interest for egg production. Our results show that miR-202-5p is the biologically active form of the miRNA and that it is expressed in granulosa cells and in the unfertilized egg. The knock out (KO) of miR-202 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 drastically 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 genome-wide transcriptomic analysis approach to identified dysregulated molecular pathways. Together, cellular and molecular analyses indicate that 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 and provides the first in vivo functional evidence that an ovarian-predominant microRNA may have a major role in female reproduction.\n\nAuthor summaryThe role of small non-coding RNAs in the regulation of animal reproduction remains 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 gonads in vertebrate. We studied its expression in the medaka ovary and knocked out the miR-202 genes to study its importance for reproductive success. We showed that the lack of miR-202 results in the sterility of both females and males. In particular, it lead to a drastic reduction of both the number and the quality of eggs produced by females. Mutant females exhibited either no egg production or produced a drastically reduced number of eggs that could not be fertilized, ultimately leading to no reproductive success. Quantitative histological and molecular analyses indicated that miR-202 KO impairs oocyte development and is also associated with the dysregulation of many genes that are critical for reproduction. This study sheds new light on the regulatory mechanisms that control oogenesis and provides the first in vivo functional evidence that an ovarian-predominant microRNA may have a major role in female reproduction.

genetics↗