Shunli Zhao

N6-methyladenosine (m6A) is an important epitranscriptomic mark with high abundance in the brain. Recently, it has been found to be involved in the regulation of memory formation and mammalian cortical neurogenesis. However, while it is now established that m6A methylation occurs in a spatially restricted manner, its functions in specific brain regions still await elucidation. We identify widespread and dynamic RNA m6A methylation in the developing mouse cerebellum and further uncover distinct features of continuous and temporal-specific m6A methylation across the four postnatal developmental processes. Temporal-specific m6A peaks from P7 to P60 exhibit remarkable changes in their distribution patterns along the mRNA transcripts. We also show spatiotemporal-specific expression of m6A writers METTL3, METTL14, and WTAP and erasers ALKBH5 and FTO in the mouse cerebellum. Ectopic expression of METTL3 mediated by lentivirus infection leads to disorganized structure of both Purkinje and glial cells. In addition, under hypobaric hypoxia exposure, Alkbh5-deletion causes abnormal cell proliferation and differentiation in the cerebellum through disturbing the balance of RNA m6A methylation in different cell fate determination genes. Notably, nuclear export of the hypermethylated RNAs is enhanced in the cerebellum of Alkbh5-deficient mice exposed to hypobaric hypoxia. Together, our findings provide strong evidence that RNA m6A methylation is controlled in a precise spatiotemporal manner and participates in the regulation of postnatal development of the mouse cerebellum.

N 6 -methyladenosine (m 6 A) is the most abundant epitranscriptomic mark found on mRNA and has important roles in various physiological processes. Despite the relatively high m 6 A levels in the brain, its potential functions in the brain remain largely unexplored. We performed a transcriptome-wide methylation analysis using the mouse brain to depict its region-specific methylation profile. RNA methylation levels in mouse cerebellum are generally higher than those in the cerebral cortex. Heterogeneity of RNA methylation exists across different brain regions and different types of neural cells including the mRNAs to be methylated, their methylation levels and methylation site selection. Common and region-specific methylation have different preferences for methylation site selection and thereby different impacts on their biological functions. In addition, high methylation levels of fragile X mental retardation protein (FMRP) target mRNAs suggest that m 6 A methylation is likely to be used for selective recognition of target mRNAs by FMRP in the synapse. Overall, we provide a region-specific map of RNA m 6 A methylation and characterize the distinct features of specific and common methylation in mouse cerebellum and cerebral cortex. Our results imply that RNA m 6 A methylation is a newly identified element in the region-specific gene regulatory network in the mouse brain.

BACKGROUND: Gastric cancer (GC) is a malignant tumour originating from the gastric mucosa epithelium that seriously threatens human health. DCLK1, miR-15b and lncRNA SNHG1 play potential roles in the occurrence of GC, but the mechanism remains unclear. METHODS: Gene expression of DCLK1, miR-15b and lncRNA SNHG1 was investigated by qRT-PCR. Protein expression was detected by Western blotting. Migration and invasion of gastric cancer cells was tested by a Transwell assay and wound healing assay. Cell proliferation was measured by an MTT assay. Finally, the correctness of the prediction results was confirmed by a dual-luciferase reporter assay. RESULTS: The expression of DCLK1, Notch1, and SNHG1 was increased in GC tissues, while the expression of miR-15b was decreased. Overexpression of lncRNA SNHG1 promoted the expression of DCLK1 and Nothc1 in GC cells. Moreover, miR-15b targeted DCLK1 to regulate Notch1 expression and inhibited the EMT process in GC cells. SNHG1 enhanced the effects of DCLK1/Notch1 on the EMT process through regulating miR-15b expression. CONCLUSION: SNHG1 enhances the EMT process in GC cells through DCLK1-mediated Notch1 pathway, which can be a potential target for treating GC.

BACKGROUND: Recently research reported that miR-185-3p could serve as an independent prognosis factor in gastric cancer (GC). However, the functional role and underlying mechanism of miR-185-3p in GC and epithelial-mesenchymal transition (EMT) progression remains largely elusive. METHODS: Quantitative real-time polymerase chain reaction (qRT-PCR) was carried out to analyze the expression of miR-185-3p and cathepsin D in patient-derived GC samples and various GC cell lines. Scratch assay and Transwell assay were used to evaluate the migration ability. The influence of miR-185-3p on the cell cycle distribution and cell apoptosis was evaluated using flow cytometry. Western blotting assay was performed to detect the expression of EMT associated proteins and the activity of PI3K/Akt signaling pathway. Furthermore, the interaction between miR-185-3p and cathepsin D was explored by dual-luciferase reporter assay. RESULTS: Our data revealed that miR-185-3p was down-regulated, while cathepsin D was up-regulated in both patient-derived GC samples and GC cells. Apart from inducing apoptosis, overexpression of miR-185-3p also inhibited EMT process and migration of GC cells. Mechanically, we firstly verified that miR-185-3p directly targeted the cathepsin D. Furthermore, miR-185-3p exerted its function on EMT process and migration via inhibiting cathepsin D to mediated PI3K/Akt signaling pathway. CONCLUSIONS: Our findings suggested that miR-185-3p targeted cathepsin D inhibiting EMT process via PI3K/Akt signaling, which may serve as a potential prognosis factor and therapeutic target to reduce the malignancy of GCs.