Transcriptomes of ATG7 Knockout Microglia

Multiple Sclerosis (MS) is a leading cause of incurable progressive disability in young adults caused by inflammation in the central nervous system (CNS) that triggers demyelination, glial cell dysfunction and irreversible neuro-axonal damage1. While considerable progress has been made in treating early inflammatory relapsing-remitting MS, the mechanisms underpinning the progressive stage remain largely unknown. The capacity of microglia, the CNS-resident phagocytes, to clear tissue debris is essential for both maintaining and restoring CNS homeostasis2,3 and this capacity diminishes with age4-6. Age strongly associates with the risk of developing progressive MS7,8. Herein we demonstrate that the recovery from inflammation is dependent on the ability of microglia to clear tissue debris and that blocking this process leads to development of progressive disease in a murine model of MS. Microglia-specific deletion of the general autophagy regulator Atg7, but not the canonical macroautophagy protein Ulk1, led to increased intracellular accumulation of phagocytosed myelin. This further associated with the alteration of the microglial phenotype towards that previously described in other neurodegenerative diseases2,3,9. Moreover, Atg7 deficient microglia showed striking similarities with microglia from aged wild type mice, which also demonstrated accumulation of myelin debris and inability to recover from MS-like disease. In contrast, the induction of autophagy using the disaccharide Trehalose in aged mice led to functional myelin clearance and remission from MS-like disease. Our results demonstrate that a non-canonical form of autophagy in microglia is responsible for myelin clearance and that impairment of this pathway markedly changes microglial phenotype and prevents recovery from MS-like disease. Importantly, we show that using a disaccharide ubiquitously found in plant-derived foods to boost autophagy in cells in which this process is naturally diminished can be utilized for therapeutic purposes.Project was run on 4 lanes with a 10M sequencing depth

多发性硬化症（Multiple Sclerosis, MS）是青年群体中无法治愈的进行性残疾的主要诱因，其病因是中枢神经系统（central nervous system, CNS）的炎症反应，该炎症会诱发脱髓鞘、胶质细胞功能障碍以及不可逆的神经轴突损伤¹。尽管在早期炎症性复发缓解型多发性硬化症的治疗上已取得显著进展，但驱动疾病进展阶段的分子机制仍未完全阐明。小胶质细胞（microglia）作为中枢神经系统驻留的吞噬细胞，其清除组织碎屑的能力对维持和恢复中枢神经系统稳态至关重要²,³，而该能力会随年龄增长而衰退⁴⁻⁶。年龄与进展型多发性硬化症的发病风险密切相关⁷,⁸。本研究证实，炎症消退依赖于小胶质细胞清除组织碎屑的能力，而阻断该过程会在多发性硬化症小鼠模型中诱发疾病进展。特异性敲除小胶质细胞中的通用自噬（autophagy）调节因子Atg7，而非经典巨自噬（macroautophagy）蛋白Ulk1，会导致吞噬的髓鞘在细胞内的积累量显著增加。这进一步伴随小胶质细胞表型的改变，该表型与此前在其他神经退行性疾病中报道的一致²,³,⁹。此外，Atg7缺陷型小胶质细胞与老年野生型小鼠的小胶质细胞表现出显著相似性，后者同样存在髓鞘碎屑积累以及无法从类多发性硬化症中恢复的表型。与之相反，在老年小鼠中使用二糖海藻糖（Trehalose）诱导自噬，可实现有效的髓鞘清除并使类多发性硬化症得到缓解。本研究结果证实，小胶质细胞中存在一种非经典自噬途径，该途径负责髓鞘的清除；而该途径的受损会显著改变小胶质细胞表型，并阻碍类多发性硬化症的恢复。重要的是，本研究表明，利用一种广泛存在于植物源性食物中的二糖，可在自噬功能自然衰退的细胞中增强自噬活性，这一策略可用于治疗相关疾病。本项目采用4个泳道进行测序，测序深度为10M。