Le Weidong, Wang Panpan, Al-Nusaif Murad, Zhang Jun, Yang Huijia, Yang Yuting, Kim Kunhyok, Li Song, Liu Cong, Cai Huaibin
The First Affiliated Hospital Of Dalian Medical University.
First Affiliated Hospital of Dalian Medical University.
Res Sq. 2023 May 18:rs.3.rs-2901370. doi: 10.21203/rs.3.rs-2901370/v1.
Although mutations have been linked to -propeller protein-associated neurodegeneration (BPAN), the precise molecular and cellular mechanisms behind this disease remain elusive. This study aims to shed light on the effects of WDR45-deficiency on neurodegeneration, specifically axonal degeneration, within the midbrain dopaminergic (DAergic) system. By examining pathological and molecular alterations, we hope to better understand the disease process.
To investigate the effects of WDR45 dysfunction on mouse behaviors and DAergic neurons, we developed a mouse model in which WDR45 was conditionally knocked out in midbrain DAergic neurons (). Through a longitudinal study, we assessed alterations in mouse behavior using open field, rotarod, Y-maze, and 3-chamber social approach tests. To examine the pathological changes in DAergic neuron soma and axons, we utilized a combination of immunofluorescence staining and transmission electron microscopy. Additionally, we performed proteomic analyses of the striatum to identify the molecules and processes involved in striatal pathology.
Our study of mice revealed a range of deficits, including impaired motor function, emotional instability, and memory loss, coinciding with the profound loss of midbrain DAergic neurons. Prior to neuronal loss, we observed massive axonal enlargements in both the dorsal and ventral striatum. These enlargements were characterized by the accumulation of extensively fragmented tubular endoplasmic reticulum (ER), a hallmark of axonal degeneration. Additionally, we found that mice exhibited disrupted autophagic flux. Proteomic analysis of the striatum in these mice showed that many differentially expressed proteins (DEPs) were enriched in amino acid, lipid, and tricarboxylic acid metabolisms. Of note, we observed significant alterations in the expression of genes encoding DEPs that regulate phospholipids catabolic and biosynthetic processes, such as lysophosphatidylcholine acyltransferase 1, ethanolamine-phosphate phospho-lyase, and abhydrolase domain containing 4, N-acyl phospholipase B. These findings suggest a possible link between phospholipid metabolism and striatal axon degeneration.
In this study, we have uncovered the molecular mechanisms underlying the contribution of WDR45-deficiency to axonal degeneration, revealing intricate relationships between tubular ER dysfunction, phospholipid metabolism, BPAN and other neurodegenerative diseases. These findings significantly advance our understanding of the fundamental molecular mechanisms driving neurodegeneration and may provide a foundation for developing novel, mechanistically-based therapeutic interventions.
尽管突变已与β-螺旋桨蛋白相关神经退行性变（BPAN）相关联，但该疾病背后确切的分子和细胞机制仍不清楚。本研究旨在阐明WDR45缺陷对中脑多巴胺能（DAergic）系统内神经退行性变，特别是轴突变性的影响。通过检查病理和分子改变，我们希望更好地了解疾病过程。
为了研究WDR45功能障碍对小鼠行为和DAergic神经元的影响，我们构建了一种小鼠模型，其中WDR45在中脑DAergic神经元中被条件性敲除（）。通过纵向研究，我们使用旷场试验、转棒试验、Y迷宫试验和三室社交接近试验评估小鼠行为的改变。为了检查DAergic神经元胞体和轴突的病理变化，我们结合使用免疫荧光染色和透射电子显微镜。此外，我们对纹状体进行了蛋白质组学分析，以确定参与纹状体病理的分子和过程。
我们对小鼠的研究揭示了一系列缺陷，包括运动功能受损、情绪不稳定和记忆丧失，这与中脑DAergic神经元的大量丧失一致。在神经元丧失之前，我们在背侧和腹侧纹状体中均观察到大量轴突肿胀。这些肿胀的特征是广泛碎片化的管状内质网（ER）的积累，这是轴突变性的一个标志。此外，我们发现小鼠表现出自噬通量破坏。对这些小鼠纹状体的蛋白质组学分析表明，许多差异表达蛋白（DEP）在氨基酸、脂质和三羧酸代谢中富集。值得注意的是，我们观察到编码调节磷脂分解代谢和生物合成过程的DEP的基因表达有显著改变，如溶血磷脂酰胆碱酰基转移酶1、乙醇胺磷酸磷酸裂解酶和含水解酶结构域4、N-酰基磷脂酶B。这些发现表明磷脂代谢与纹状体轴突变性之间可能存在联系。
在本研究中，我们揭示了WDR45缺陷导致轴突变性的分子机制，揭示了管状内质网功能障碍、磷脂代谢、BPAN和其他神经退行性疾病之间的复杂关系。这些发现显著推进了我们对驱动神经退行性变的基本分子机制的理解，并可能为开发基于机制的新型治疗干预措施提供基础。
