The role of N6-methyladenosine (m6A) in eye diseases

ω-3PUFAs Inhibit Hypoxia-Induced Retinal Neovascularization via Regulating Microglial Pyroptosis through METTL14-Mediated m6A Modification of IFNB1 mRNA

Retinal neovascular disease is the leading reason of vision impairment in all ages. Here, we figured out the function and mechanism of omega-3 polyunsaturated fatty acids (ω-3PUFAs) in hypoxia-induced retinal neovascularization by focusing on microglial pyroptosis. Microglia BV-2 cells were given ω-3PUFAs treatment and co-cultured with mouse retinal microvascular endothelial cells (MRMECs) under hypoxia. Tube formation assay, transwell assay and wound healing assay were utilized to monitor the MRMEC angiogenesis. Cell counting kit-8, western blot, lactate dehydrogenase assay, and enzyme-linked immunosorbent assay were used to assess pyroptosis of BV-2 cells. RNA sequencing and methylated RNA immunoprecipitation-polymerase chain reaction were utilized to identify the target gene of methyltransferase-like 14 (METTL14) and its N6-methyladenosine (m6A) level in BV-2 cells. BV-2 cells prominently enhanced MRMEC angiogenesis under hypoxia, but this effect was abolished after ω-3PUFAs treatment. ω-3PUFAs inhibited pyroptosis in hypoxia-induced BV-2 cells, and BV-2 cell pyroptosis boosted angiogenesis of MRMECs. Additionally, ω-3PUFAs markedly augment the expression of MELLL14 in BV-2 cells, and METTL14 knockdown promoted BV-2 cell pyroptosis and BV-2 cell-mediated angiogenesis in MEMECs. Mechanistically, interferon beta 1 (IFNB1) was a target of METTL14, and METTL14 silencing increased the mRNA expression and decreased the m6A modification of IFNB1 in BV-2 cells. Our results uncovered that ω-3PUFAs diminished hypoxia-induced retinal neovascularization through controlling microglial pyroptosis via METTL14-mediated m6A modification. This study offers a novel potential target for the treatment of retinal neovascular diseases.

IGF2BP2 Maintains Retinal Pigment Epithelium Homeostasis by Stabilizing PAX6 and OTX2

Purpose

N6-methyladenosine (m6A) methylation is a chemical modification that occurs on RNA molecules, where the hydrogen atom of adenine (A) nucleotides is replaced by a methyl group, forming N6-methyladenosine. This modification is a dynamic and reversible process that plays a crucial role in regulating various biological processes, including RNA stability, transport, translation, and degradation. Currently, there is a lack of research on the role of m6A modifications in maintaining the characteristics of RPE cells. m6A readers play a crucial role in executing the functions of m6A modifications, which prompted our investigation into their regulatory roles in the RPE.

Methods

Phagocytosis assays, immunofluorescence staining, flow cytometry experiments, β-galactosidase staining, and RNA sequencing (RNA-seq) were conducted to assess the functional and cellular characteristics changes in retinal pigment epithelium (RPE) cells following short-hairpin RNA-mediated knockdown of insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2). RNA-seq and ultraviolet crosslinking immunoprecipitation with high-throughput sequencing (HITS-CLIP) were employed to identify the target genes regulated by IGF2BP2. adeno-associated virus (AAV) subretinal injection was performed in 6- to 8-week-old C57 mice to reduce IGF2BP2 expression in the RPE, and the impact of IGF2BP2 knockdown on mouse visual function was assessed using immunofluorescence, quantitative real-time PCR, optical coherence tomography, and electroretinography.

Results

IGF2BP2 was found to have a pronounced effect on RPE phagocytosis. Subsequent in-depth exploration revealed that IGF2BP2 modulates the mRNA stability of PAX6 and OTX2, and the loss of IGF2BP2 induces inflammatory and aging phenotypes in RPE cells. IGF2BP2 knockdown impaired RPE function, leading to retinal dysfunction in vivo.

Conclusions

Our data suggest a crucial role of IGF2BP2 as an m6A reader in maintaining RPE homeostasis by regulating the stability of PAX6 and OTX2, making it a potential target for preventing the occurrence of retinal diseases related to RPE malfunction.

Comprehensive landscape of RNA N6-methyladenosine modification in lens epithelial cells from normal and diabetic cataract

To gain more insight into the mechanism of cataract formation from the perspective of epigenetics in the diabetic population, lens epithelium from diabetic cataract patients and health individuals were collected separately and analyzed for N6-methyladenosine (m6A)-modified RNA using methylated RNA immunoprecipitation sequencing (MeRIP-Seq). Subsequently, differential expression analysis was performed on m6A-regulated messenger RNA (mRNA), circular RNA (circRNA), and long non-coding RNA (lncRNA), followed by functional annotation using the Gene Ontology (GO) database. Furthermore, analysis of single-cell data of lens complemented the intrinsic association and cellular heterogeneity of cataract and m6A regulators. In this study, both the global expression levels and peak intensity of m6A-tagged RNAs were increased in patients with diabetic cataract. And we noted multiple core enzymes were upregulated in the diabetic cataract (DC) samples. Besides, single-cell RNA sequencing analysis of the lens revealed the heterogeneous expression of RNA m6A regulators across different cell types, and we noted that the early fiber cell cluster was also closely associated with the onset of cataract and m6A modification. The results comprehensively revealed the dynamic modification landscape of m6A on mRNA, circRNA, and lncRNA, which might provide valuable resources for future studies of the pathogenesis of DCs.