Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01655, USA; Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01655, USA.
Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01655, USA.
Neurobiol Dis. 2021 Jul;155:105368. doi: 10.1016/j.nbd.2021.105368. Epub 2021 Apr 20.
Parkinson's disease (PD) is the most common form of neurodegenerative movement disorder, associated with profound loss of dopaminergic neurons from the basal ganglia. Though loss of dopaminergic neuron cell bodies from the substantia nigra pars compacta is a well-studied feature, atrophy and loss of their axons within the nigrostriatal tract is also emerging as an early event in disease progression. Genes that drive the Wallerian degeneration, like Sterile alpha and toll/interleukin-1 receptor motif containing (Sarm1), are excellent candidates for driving this axon degeneration, given similarities in the morphology of axon degeneration after axotomy and in PD. In the present study we assessed whether Sarm1 contributes to loss of dopaminergic projections in mouse models of PD. In Sarm1 deficient mice, we observed a significant delay in the degeneration of severed dopaminergic axons distal to a 6-OHDA lesion of the medial forebrain bundle (MFB) in the nigrostriatal tract, and an accompanying rescue of morphological, biochemical and behavioural phenotypes. However, we observed no difference compared to controls when striatal terminals were lesioned with 6-OHDA to induce a dying back form of neurodegeneration. Likewise, when PD phenotypes were induced using AAV-induced alpha-synuclein overexpression, we observed similar modest loss of dopaminergic terminals in Sarm1 knockouts and controls. Our data argues that axon degeneration after MFB lesion is Sarm1-dependent, but that other models for PD do not require Sarm1, or that Sarm1 acts with other redundant genetic pathways. This work adds to a growing body of evidence indicating Sarm1 contributes to some, but not all types of neurodegeneration, and supports the notion that while axon degeneration in many context appears morphologically similar, a diversity of axon degeneration programs exist.
帕金森病（PD）是最常见的神经退行性运动障碍，与基底神经节中多巴胺能神经元的大量丧失有关。虽然黑质致密部多巴胺能神经元细胞体的丢失是一个研究得很好的特征，但黑质纹状体束内其轴突的萎缩和丢失也正在成为疾病进展的早期事件。像 Sarm1 这样驱动沃勒氏变性的基因，由于轴突切断后轴突变性的形态与 PD 相似，是驱动这种轴突变性的极好候选基因。在本研究中，我们评估了 Sarm1 是否有助于 PD 小鼠模型中多巴胺能投射的丧失。在 Sarm1 缺陷小鼠中，我们观察到中脑导水管周围灰质束（MFB）6-OHDA 损伤后切断的多巴胺能轴突的变性明显延迟，并且形态、生化和行为表型得到挽救。然而，当用 6-OHDA 损伤纹状体终末以诱导退行性神经变性时，与对照组相比，我们没有观察到差异。同样，当使用 AAV 诱导的α-突触核蛋白过表达诱导 PD 表型时，我们观察到 Sarm1 敲除小鼠和对照组中多巴胺能终末的类似适度丧失。我们的数据表明，MFB 损伤后的轴突变性依赖于 Sarm1，但其他 PD 模型不需要 Sarm1，或者 Sarm1 与其他冗余的遗传途径一起作用。这项工作增加了越来越多的证据，表明 Sarm1 有助于一些，但不是所有类型的神经退行性变，并支持这样一种观点，即在许多情况下，虽然轴突变性在形态上看起来相似，但存在多种轴突变性程序。
