With the development of RNA-seq technology, tens of thousands of circular RNAs (circRNAs), a novel class of RNAs, have been identified. However, little is known about circRNA formation and biogenesis in hepatocellular carcinoma (HCC). We performed ribosomal-depleted RNA-seq profiling of HCC and para-carcinoma tissues and analyzed the expression of a hotspot circRNA derived from the 3'UTR of the stearoyl-CoA desaturase (SCD) gene, termed SCD-circRNA 2. It was significantly upregulated in HCC and correlated with poor patient prognosis. Moreover, we observed that the production of SCD-circRNA 2 was dynamically regulated by RNA-binding protein 3 (RBM3). RBM3 overexpression was indicative of a short recurrence-free survival and poor overall survival for HCC patients. Furthermore, by modulating the RBM3 or SCD-circRNA 2 levels, we found that RBM3 promoted the HCC cell proliferation in a SCD-circRNA 2 dependent manner. Herein, we report that RBM3 is crucial for the SCD-circRNA 2 formation in HCC cells, which not only provides mechanistic insights into cancer-related circRNA dysregulation but also establishes RBM3 as an oncogene with both therapeutic potential and prognostic value. FUND: This work was supported by the National Key Research and Development Program of China (2016YFC1302303), the National Natural Science Foundation of China (Grant No. 81672345 and 81,402,269). The funders did not have any roles in study design, data collection, data analysis, interpretation, writing of the report.

Multifunctional N6-methyladenosine (m6A) has been revealed to be an important epigenetic component in various physiological and pathological processes, but its role in female ovarian aging remains unclear. Thus, we demonstrated m6A demethylase FTO downregulation and the ensuing increased m6A in granulosa cells (GCs) of human aged ovaries, while FTO-knockdown GCs showed faster aging-related phenotypes mediated. Using the m6A-RNA-sequence technique (m6A-seq), increased m6A was found in the FOS-mRNA-3′UTR, which is suggested to be an erasing target of FTO that slows the degradation of FOS-mRNA to upregulate FOS expression in GCs, eventually resulting in GC-mediated ovarian aging. FTO acts as a senescence-retarding protein via m6A, and FOS knockdown significantly alleviates the aging of FTO-knockdown GCs. Altogether, the abovementioned results indicate that FTO in GCs retards FOS-dependent ovarian aging, which is a potential diagnostic and therapeutic target against ovarian aging and age-related reproductive diseases.

Rationale: Hepatocellular carcinoma (HCC) is a highly heterogeneous and malignant disease with the complex immune microenvironment, which ultimately influence clinic outcomes of patients. However, the spatial expression patterns of diverse immune cells among tumor microenvironment remain to be further deciphered.

Without intervention, a considerable proportion of patients with metabolism‐associated fatty liver disease (MAFLD) will progress from simple steatosis to metabolism‐associated steatohepatitis (MASH), liver fibrosis, and even hepatocellular carcinoma. However, the molecular mechanisms that control progressive MAFLD have yet to be fully determined. Here, we unraveled that the expression of the N6-methyladenosine (m6A) methyltransferase METTL14 is remarkably downregulated in the livers of both patients and several murine models of MAFLD, whereas hepatocyte-specific depletion of this methyltransferase aggravated lipid accumulation, liver injury, and fibrosis. Conversely, hepatic Mettl14 overexpression alleviated the above pathophysiological changes in mice fed on a high-fat diet (HFD). Notably, in vivo and in vitro mechanistic studies indicated that METTL14 downregulation decreased the level of GLS2 by affecting the translation efficiency mediated by YTHDF1 in an m6A-depedent manner, which might help to form an oxidative stress microenvironment and accordingly recruit Cx3cr1⁺Ccr2⁺ monocyte-derived macrophages (Mo-macs). In detail, Cx3cr1⁺Ccr2⁺ Mo-macs can be categorized into M1-like macrophages and S100A4-positive macrophages and then further activate hepatic stellate cells (HSCs) to promote liver fibrosis. Further experiments revealed that CX3CR1 can activate the transcription of S100A4 via CX3CR1/MyD88/NF-κB signaling pathway in Cx3cr1⁺Ccr2⁺ Mo-macs. Restoration of METTL14 or GLS2, or interfering with this signal transduction pathway such as inhibiting MyD88 could ameliorate liver injuries and fibrosis. Taken together, these findings indicate potential therapies for the treatment of MAFLD progression.