RNA m6A dynamic modification mediated by nucleus-localized FTO is involved in follicular reserve.

In eukaryotic organisms, the most common internal modification of messenger RNA (mRNA) is N6-methyladenosine (m6A). This modification can be dynamically and reversibly controlled by specific enzymes known as m6A writers and erasers. The fat-mass and obesity-associated protein (FTO) catalyzes RNA demethylation and plays a critical role in various physiological and pathological processes. Our research identified dynamic alterations in both m6A and FTO during the assembly of primordial follicles, with an inverse relationship observed for m6A levels and nuclear-localized FTO expression. Application of Fto small interfering RNA (siRNA) altered the expression of genes related to cell proliferation, hormone regulation, and cell chemotaxis, and affected RNA alternative splicing. Overexpression of the full-length Fto gene led to changes in m6A levels, alternative splicing of Cdk5, cell proliferation, cell cycle progression, and proportion of primordial follicles. Conversely, overexpression of Fto lacking a nuclear localization signal (NLS) did not significantly alter m6A levels or primordial follicle assembly. These findings suggest that FTO, localized in the nucleus but not in the cytoplasm, regulates RNA m6A demethylation and plays a role in cell proliferation, cell cycle progression, and primordial follicle assembly. These results highlight the potential of m6A and its eraser FTO as possible biomarkers and therapeutic targets.

Di (2-ethylhexyl) Phthalate Exposure Impairs the microRNAs Expression Profile During Primordial Follicle Assembly.

This research was performed to estimate the potential effects of Di (2-ethylhexyl) phthalate (DEHP) on changes of ovarian miRNA expression profile during mouse primordial follicle assembly using miRNAs-seq analysis. The ovaries of newborn mice were collected and in vitro cultured with different concentration of DEHP for 72 h. Then they were prepared for miRNAs-seq analysis. The results indicated that DEHP exposure altered ovarian miRNA expression profile of newborn mice. Eighteen differentially expressed miRNAs were screened after 100 µM DEHP exposure. The target mRNAs of differentially expressed miRNAs were predicted and further analyzed through gene ontology (GO) enrichment analysis and pathway enrichment analysis. Our results showed that the differentially expressed miRNAs from DEHP exposure can regulate ovarian development by targeting mRNAs involved in MAPK, mTOR, FoxO signaling pathways. Three miRNAs of miR-32-5p, miR-19a-3p, and miR-141-3p were randomly selected from the differentially expressed miRNAs to quantify their expression level by miRNA qRT-PCR. The results of qRT-PCR and miRNA-seq were consistent. Considering one of its target gene PTEN of miR-19a-3p and the decreased level of pAKT and increased Bax/Bcl-2 under DEHP exposure, we speculated that the altered expression of miR-19a-3p by DEHP exposure affected mouse primordial follicle assembly via PI3K/AKT1/mTOR signaling pathway. Epigenetic changes are one of the most important targets of toxicant exposure. The effects of DEHP exposure on microRNA (one of the epigenetic regulators) expression profile were uncovered to enrich the research on relationship of epigenetics and toxicant exposure.