Bruce Lefroy Centre for Genetic Health Research, Murdoch Childrens Research Institute, Melbourne, VIC 3052, Australia; Department of Paediatrics, University of Melbourne, Melbourne, VIC 3052, Australia.
Bruce Lefroy Centre for Genetic Health Research, Murdoch Childrens Research Institute, Melbourne, VIC 3052, Australia.
Am J Hum Genet. 2014 Dec 4;95(6):729-35. doi: 10.1016/j.ajhg.2014.10.015. Epub 2014 Nov 26.
Advances in understanding the etiology of Parkinson disease have been driven by the identification of causative mutations in families. Genetic analysis of an Australian family with three males displaying clinical features of early-onset parkinsonism and intellectual disability identified a ∼45 kb deletion resulting in the complete loss of RAB39B. We subsequently identified a missense mutation (c.503C>A [p.Thr168Lys]) in RAB39B in an unrelated Wisconsin kindred affected by a similar clinical phenotype. In silico and in vitro studies demonstrated that the mutation destabilized the protein, consistent with loss of function. In vitro small-hairpin-RNA-mediated knockdown of Rab39b resulted in a reduction in the density of α-synuclein immunoreactive puncta in dendritic processes of cultured neurons. In addition, in multiple cell models, we demonstrated that knockdown of Rab39b was associated with reduced steady-state levels of α-synuclein. Post mortem studies demonstrated that loss of RAB39B resulted in pathologically confirmed Parkinson disease. There was extensive dopaminergic neuron loss in the substantia nigra and widespread classic Lewy body pathology. Additional pathological features included cortical Lewy bodies, brain iron accumulation, tau immunoreactivity, and axonal spheroids. Overall, we have shown that loss-of-function mutations in RAB39B cause intellectual disability and pathologically confirmed early-onset Parkinson disease. The loss of RAB39B results in dysregulation of α-synuclein homeostasis and a spectrum of neuropathological features that implicate RAB39B in the pathogenesis of Parkinson disease and potentially other neurodegenerative disorders.
对帕金森病病因的认识的进展得益于在家族中发现了致病突变。对一个澳大利亚家族的遗传分析，该家族有三名男性表现出早发性帕金森病和智力残疾的临床特征，发现了一个约 45 kb 的缺失，导致 RAB39B 完全丢失。随后，我们在一个无关联的威斯康星州家族中发现了 RAB39B 的错义突变（c.503C>A [p.Thr168Lys]），该家族受到类似临床表型的影响。计算机模拟和体外研究表明，该突变使蛋白质不稳定，符合功能丧失。体外短发夹 RNA 介导的 Rab39b 敲低导致培养神经元树突突中的 α-突触核蛋白免疫反应性斑点密度降低。此外，在多种细胞模型中，我们证明 Rab39b 的敲低与 α-突触核蛋白的稳态水平降低有关。尸检研究表明 RAB39B 的缺失导致帕金森病的病理证实。黑质中有大量多巴胺能神经元丧失，广泛存在经典的路易体病理学。其他病理特征包括皮质路易体、脑铁积累、tau 免疫反应性和轴突球体。总的来说，我们已经表明 RAB39B 的功能丧失突变导致智力残疾和病理证实的早发性帕金森病。RAB39B 的缺失导致 α-突触核蛋白的动态平衡失调，并出现一系列神经病理学特征，表明 RAB39B 参与了帕金森病的发病机制，可能还参与了其他神经退行性疾病的发病机制。
