Effects of m 6 A methylation of MAT2A mRNA regulated by METTL16 on learning and memory, hippocampal synaptic plasticity and Aβ1-42 in 5×FAD mice

Sha Li ^1* Huan Chen ¹ Fangzhen Guo ¹ Yan Zhao ¹ WEI LIU ¹ Bingyv Chen ¹ Chang Wang ¹ Lining Huang ² Sufang Jiang ² Xiaowei Ma ³ Huiling Ren ⁴ Huixian Cui ¹

• ¹ Hebei Medical University, Shijiazhuang, China
• ² Second Hospital of Hebei Medical University, Shijiazhuang, Hebei Province, China
• ³ The First hospital of Hebei Medical University, Shijiazhuang, Hebei Province, China
• ⁴ Third Hospital of Hebei Medical University, Shijiazhuang, Hebei Province, China

Background: Alzheimer's disease (AD) is a common neurodegenerative disorder affecting older adults, characterized by progressive cognitive decline and pathological features such as amyloid plaque deposition, neuronal loss, and synaptic reduction. RNA N6-methyladenosine (m 6 A) methylation is prevalent in the brain and is intricately linked to synaptic plasticity, learning, and memory in AD. However, the precise mechanisms underlying these associations remain elusive.Methods: This study employed the overexpression of methyltransferase-like protein 16 (METTL16), or overexpression of methionine adenosyltransferase 2A (MAT2A), or a combination of METTL16 overexpression with MAT2A knockdown to explore the influence of METTL16 on the regulation of MAT2A in cognitive function, hippocampal synaptic plasticity, and amyloid-beta (Aβ1-42) metabolism in 5×FAD mice.Results: Our findings indicated a reduction in m 6 A methylation levels and the expression of METTL16 and MAT2A in the hippocampus of 5×FAD mice.Overexpression of METTL16 led to an increase in overall m 6 A methylation levels, Furthermore, overexpression of either METTL16 or MAT2A enhanced learning and memory in 5×FAD mice, elevated the expression levels of postsynaptic density 95 (PSD95) and synaptophysin (Syp), increased dendritic spine density, and decreased the accumulation of Aβ1-42 in the hippocampus. In the hippocampus of 5×FAD mice, METTL16 was found to upregulate both the protein and mRNA levels of MAT2A, as well as enhance MAT2A mRNA m 6 A methylation levels. Concurrent, overexpression of METTL16 and knockdown of MAT2A in the hippocampus resulted in impaired learning and memory in 5×FAD mice, alongside a reduction in synaptic protein expression and dendritic spine density, and an increase in Aβ1-42 accumulation.The present study demonstrated that METTL16 enhances learning and memory in 5×FAD mice by regulating MAT2A mRNA m 6 A methylation, which leads to increased expression levels of PSD95 and Syp, greater dendritic spine density, and reduced Aβ1-42 accumulation in the hippocampus. These findings reveal a novel approach for investigating the pathophysiological role of METTL16 in AD and offer new insights for developing of potential therapeutic targets for AD.