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Master thesis

Identification et caractérisation de petits ARN non codants exprimés dans l'ovaire et potentiellement impliqués dans l'ovogenèse chez le médaka

Abstract : Oogenesis refers to the cellular processes that take place within the ovary and result in the formation of female gametes in each reproductive cycle in fish. The regulation of this cellular process has long been studied from a genetic point of view, revealing a large number of genes coding for proteins involved in endocrine regulation or in intracellular signaling pathways. The non-coding portion of the genome has been set aside for a long time as secondary to the coding portion of the genome. It is now known that "non-coding" genes can play a major role in the regulation of various biological processes. Among these "non-coding" genes are microRNA and piRNA genes whose active forms are short sequences of 18-32 nucleotides. These two classes of small non-coding RNAs (ncRNAs) are considered to be regulators of gene expression and chromatin structure. While these small ncRNAs are now widely studied, their involvement in the control of oogenesis remains poorly documented. In this study, we set out to investigate the involvement of miRNAs and piRNAs during oogenesis in the medaka model fish (Oryzias latipes). First, we looked for small ncRNAs expressed specifically or predominantly in the ovary, using a high-throughput sequencing approach (small RNAseq). We identified 3 predominantly ovarian miRNAs (miR-202, miR-187 and miR-7552b) and 42 piRNAs with specific ovarian expression, unrelated to transposable elements and genome protection. We hypothesized that these predominantly ovarian ncRNAs could be involved in the regulation of ovarian gene expression and as such play an important role in ovogenesis. In a second step, we performed a functional analysis of one of the above-mentioned candidates, miR-202, by gene inactivation (KO CRISPR). The gonadal expression of miR-202 is by far the strongest among the ncRNAs identified and is localized in granulosa cells. Moreover, miR-202 has already been demonstrated in the gonads of many other vertebrate species. In the absence of miR-202, we have observed a strong decrease in fertility as well as a defect in the development of the adult ovary leading to a strong decrease in fertility. To conclude, we have been able to provide here a detailed repertoire of small ovarian ncRNAs potentially involved in fertility in the medaka and demonstrate the essential role of one of them in oogenesis. This work contributes to our knowledge of the molecular networks underlying reproductive capacity in fish.
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Master thesis
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https://hal-ephe.archives-ouvertes.fr/hal-03127948
Contributor : Stéphanie Gay Connect in order to contact the contributor
Submitted on : Monday, February 1, 2021 - 7:04:30 PM
Last modification on : Wednesday, November 17, 2021 - 12:31:58 PM
Long-term archiving on: : Sunday, May 2, 2021 - 7:54:06 PM

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Stéphanie Gay, Violette Thermes, Sophie Couve, Julien Bobe. Identification et caractérisation de petits ARN non codants exprimés dans l'ovaire et potentiellement impliqués dans l'ovogenèse chez le médaka. Sciences du Vivant [q-bio]. 2020. ⟨hal-03127948⟩

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