Alpha-synucleinopathies are a group of progressive neurodegenerative disorders, characterized by intracellular deposits of aggregated α-synuclein (αS). The clinical heterogeneity of these diseases is thought to be attributed to conformers (or strains) of αS but the contribution of inclusions in various cell types is unclear. The aim of the present work was to study αS conformers among different transgenic (TG) mouse models of α-synucleinopathies. To this end, four different TG mouse models were studied (Prnp-h[A53T]αS; Thy1-h[A53T]αS; Thy1-h[A30P]αS; Thy1-mαS) that overexpress human or murine αS and differed in their age-of-symptom onset and subsequent disease progression. Postmortem analysis of end-stage brains revealed robust neuronal αS pathology as evidenced by accumulation of αS serine 129 (p-αS) phosphorylation in the brainstem of all four TG mouse lines. Overall appearance of the pathology was similar and only modest differences were observed among additionally affected brain regions. To study αS conformers in these mice, we used pentameric formyl thiophene acetic acid (pFTAA), a fluorescent dye with amyloid conformation-dependent spectral properties. Unexpectedly, besides the neuronal αS pathology, we also found abundant pFTAA-positive inclusions in microglia of all four TG mouse lines. These microglial inclusions were also positive for Thioflavin S and showed immunoreactivity with antibodies recognizing the N-terminus of αS, but were largely p-αS-negative. In all four lines, spectral pFTAA analysis revealed conformational differences between microglia and neuronal inclusions but not among the different mouse models. Concomitant with neuronal lesions, microglial inclusions were already present at presymptomatic stages and could also be induced by seeded αS aggregation. Although nature and significance of microglial inclusions for human α-synucleinopathies remain to be clarified, the previously overlooked abundance of microglial inclusions in TG mouse models of α-synucleinopathy bears importance for mechanistic and preclinical-translational studies.

中文翻译：

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与神经元病变不同的α-突触核蛋白病转基因小鼠模型中突出的小神经胶质包裹体。

α-突触核蛋白病是一组进行性神经退行性疾病，其特征是聚集的α-突触核蛋白（αS）在细胞内沉积。这些疾病的临床异质性被认为是由于αS的构象异构体（或菌株）引起的，但尚不清楚内含物在各种细胞类型中的作用。本工作的目的是研究α-突触核蛋白病的不同转基因（TG）小鼠模型之间的αS构象异构体。为此，研究了四种过度表达人或鼠类αS且其差异的TG小鼠模型（Prnp-h [A53T]αS; Thy1-h [A53T]αS; Thy1-h [A30P]αS;Thy1-mαS）症状年龄发作和随后的疾病进展。末期大脑的事后分析显示，健壮的神经元αS病理表现为所有四只TG小鼠系的脑干中αS丝氨酸129（p-αS）磷酸化的积累所证明。病理的整体外观是相似的，并且在另外受影响的大脑区域之间仅观察到适度的差异。为了研究这些小鼠中的αS构象异构体，我们使用了五聚体甲酰基噻吩乙酸（pFTAA），一种具有淀粉样构象依赖性光谱特性的荧光染料。出乎意料的是，除了神经元αS病理学，我们还在所有四个TG小鼠系的小胶质细胞中发现了大量pFTAA阳性包涵体。这些小神经胶质包涵体也对硫黄素S呈阳性，并显示与识别αSN末端的抗体的免疫反应性，但大部分为p-αS阴性。在所有四行中 光谱pFTAA分析揭示了小胶质细胞和神经元内含物之间的构象差异，但在不同的小鼠模型之间没有。与神经元病变相伴，在症状发生前阶段已经存在小胶质细胞包涵体，也可能由种子αS聚集诱导。尽管小胶质细胞包涵体对人α-突触核蛋白病的性质和意义仍有待澄清，但先前被忽视的TG-α-突触神经病小鼠模型中的小胶质囊内含物丰富对机械和临床前翻译研究具有重要意义。