Department of Biomolecular Chemistry, University of Wisconsin-Madison School of Medicine and Public Health, 440 Henry Mall, Madison, WI 53706, USA.
Department of Chemistry and Biochemistry, Institute of Molecular Biophysics, Florida State University, 91 Chieftan Way, Tallahassee, FL 32306, USA.
Cell Rep. 2018 Aug 28;24(9):2248-2260. doi: 10.1016/j.celrep.2018.07.081.
Length-dependent axonopathy of the corticospinal tract causes lower limb spasticity and is characteristic of several neurological disorders, including hereditary spastic paraplegia (HSP) and amyotrophic lateral sclerosis. Mutations in Trk-fused gene (TFG) have been implicated in both diseases, but the pathomechanisms by which these alterations cause neuropathy remain unclear. Here, we biochemically and genetically define the impact of a mutation within the TFG coiled-coil domain, which underlies early-onset forms of HSP. We find that the TFG (p.R106C) mutation alters compaction of TFG ring complexes, which play a critical role in the export of cargoes from the endoplasmic reticulum (ER). Using CRISPR-mediated genome editing, we engineered human stem cells that express the mutant form of TFG at endogenous levels and identified specific defects in secretion from the ER and axon fasciculation following neuronal differentiation. Together, our data highlight a key role for TFG-mediated protein transport in the pathogenesis of HSP.
皮质脊髓束的轴突变性与长度相关，导致下肢痉挛，是几种神经疾病的特征，包括遗传性痉挛性截瘫（HSP）和肌萎缩侧索硬化症。Trk-fused 基因（TFG）的突变与这两种疾病都有关，但这些改变导致神经病变的病理机制尚不清楚。在这里，我们从生物化学和遗传学的角度定义了 TFG 卷曲螺旋域内突变的影响，该突变是 HSP 早发型的基础。我们发现，TFG（p.R106C）突变改变了 TFG 环复合物的紧凑性，而 TFG 环复合物在货物从内质网（ER）中的输出中起着关键作用。使用 CRISPR 介导的基因组编辑，我们构建了表达内源性突变 TFG 的人类干细胞，并在神经元分化后发现 ER 分泌和轴突聚集出现特定缺陷。总之，我们的数据强调了 TFG 介导的蛋白质运输在 HSP 发病机制中的关键作用。
