MiR-202 controls female fecundity by regulating medaka oogenesis

Abstract

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.

The Role of MicroRNAs in Mammalian Fertility: From Gametogenesis to Embryo Implantation

“…Interestingly, in vitro functional study of miR-130b showed the involvement of this miRNA in oocyte maturation by regulating the SMAD5 and MSK1genes [44]. Similarly, other studies have shown the role of miR-318 [45], miR-202 [46] and let-7, miR-278 [47], miR-378 [48] and miR-125a-3p [49] during oogenesis.…”

Heterogenic Origin of Micro RNAs in Atlantic Salmon (Salmo salar) Seminal Plasma

“…In the present study, miR-202-5p localized to both germ and somatic lineages in juvenile testes and ovaries of Atlantic salmon and was highly abundant in somatic supporting cells in mature testes ( Figure 5 and Figure S5). In medaka, miR-202-5p is abundant in unfertilized oocytes and in the follicular cells of the ovary, and is essential for the regulation of oogenesis [38]. Together, these results suggest a conserved role of miR-202-5p in reproductive processes in teleost gonad development during gamete maturation, and indicate supporting somatic cell origin of miR-202-5p in a mature gonad.…”

Circular RNA profiling in the oocyte and cumulus cells reveals thatcircARMC4is essential for porcine oocyte maturation

“…This potential interplay between circRNA and miRNA could provide a reference for elucidating regulatory mechanisms of these DECs in oocyte meiotic maturation. Indeed, recent studies have shown that maternal miRNA participates in regulating oocyte maturation and early embryo development in several species, including pigs (Wright et al, 2016), medaka (Gay et al, 2018), and C.elegans (Minogue et al, 2018). Specifically, miRNA-7 was found to inhibit epidermal growth factor receptor (EGFR) expression in human cancer cells (Webster et al, 2009) and EGFR signaling is required for cumulus cell expansion and oocyte maturation (Prochazka et al, 2017), suggesting that miRNA-7 may negatively regulate oocyte maturation.…”

“…This may be due to the imperfectness of in vitro culture conditions currently used that cannot achieve the optimal maturational outcomes, and there is inadequate information regarding the unique molecular mechanisms of porcine oocyte meiotic maturation (Sun and Nagai, 2003; Prather et al, 2009). It is known that oocyte maturation is intricately regulated by cumulus cell or oocyte itself derived non-coding RNAs, such as microRNA (miRNA) (Dallaire and Simard, 2016; Wright et al, 2016; Li et al, 2017b; Gay et al, 2018; Minogue et al, 2018), endogenous small interference RNA (siRNA) (Suh et al, 2010) and long non-coding RNA (lncRNA) (Taylor et al, 2015). Recently, circular RNA (circRNA) has received increasing attention in multiple biological research fields.…”