Stop-gain mutations in UBAP1 cause pure autosomal-dominant spastic paraplegia
Stop-gain mutations in UBAP1 cause pure autosomal-dominant spastic paraplegia
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UBAP1 的停止突变导致纯常染色体显性痉挛性截瘫
DOI：
10.1093/brain/awz158
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发表时间：
2019-08-01
期刊：
影响因子：
14.5
通讯作者：
Chen, Wan-Jin
中科院分区：
文献类型：
--
作者：
Lin, Xiang;Su, Hui-Zhen;Chen, Wan-Jin
遗传性痉挛性截瘫是指由皮质脊髓束退变引起的一组异质性神经退行性疾病。遗传性痉挛截瘫患者的临床特征表现为进行性痉挛、过度反射和肌肉无力。在这里，为了扩大先前未知的遗传性痉挛截瘫致病基因和亚型的越来越广泛的库，我们对来自两个无关的中国家系的6名患者和2名非患者进行了完整的外显子测序，这些患者患有常染色体显性遗传性痉挛截瘫，并且在已知的遗传性痉挛截瘫相关基因中缺乏突变。外显子序列分析显示，与痉挛截瘫共分离的泛素相关蛋白1(UBAP1)基因存在两个停增突变：c.247_248insGTGAATTC(p.I83Sfs*11)和c.526G4T(p.E176*)。我们还在另外38个常染色体显性遗传性痉挛性截瘫中国家系的两个无关家系中发现了两个UBAP1移码突变：c.324_325delCA(p.H108Qfs*10)和c.425_426delAG(p.K143Sfs*15)。主要的疾病表现为单纯的以肢体痉挛为主的截瘫。在体内，斑马鱼中Ubap1的下调会导致组织形态异常，抑制运动神经元的生长，降低运动量，缩短寿命。UBAP1被掺入转运复合体I所需的内体分选复合体中，并与泛素结合在内体分选中发挥作用。患者来源的截断形式(S)的UBAP1在HeLa细胞和野生型小鼠皮质神经元培养中引起内小体异常聚集、显著的内小体增大和泛素化蛋白的细胞质积累。对来自转基因Ubap1(FLOX)小鼠的培养的皮质神经元进行的生化和免疫细胞化学实验证实，UBAP1的干扰导致早期内体加工和泛素化蛋白质分选的失调。值得注意的是，Ubap1的缺失促进了神经退行性变，这可能是由细胞凋亡介导的。我们的研究提供了遗传和生化证据，证明UBAP1基因突变可导致纯常染色体显性遗传性痉挛性截瘫。
Hereditary spastic paraplegias refer to a heterogeneous group of neurodegenerative disorders resulting from degeneration of the corticospinal tract. Clinical characterization of patients with hereditary spastic paraplegias represents progressive spasticity, exaggerated reflexes and muscular weakness. Here, to expand on the increasingly broad pools of previously unknown hereditary spastic paraplegia causative genes and subtypes, we performed whole exome sequencing for six affected and two unaffected individuals from two unrelated Chinese families with an autosomal dominant hereditary spastic paraplegia and lacking mutations in known hereditary spastic paraplegia implicated genes. The exome sequencing revealed two stop-gain mutations, c.247_248insGTGAATTC (p.I83Sfs*11) and c.526G4T (p.E176*), in the ubiquitin-associated protein 1 (UBAP1) gene, which co-segregated with the spastic paraplegia. We also identified two UBAP1 frameshift mutations, c.324_325delCA (p.H108Qfs*10) and c.425_426delAG (p.K143Sfs*15), in two unrelated families from an additional 38 Chinese pedigrees with autosomal dominant hereditary spastic paraplegias and lacking mutations in known causative genes. The primary disease presentation was a pure lower limb predominant spastic paraplegia. In vivo downregulation of Ubap1 in zebrafish causes abnormal organismal morphology, inhibited motor neuron outgrowth, decreased mobility, and shorter lifespan. UBAP1 is incorporated into endosomal sorting complexes required for transport complex I and binds ubiquitin to function in endosome sorting. Patient-derived truncated form(s) of UBAP1 cause aberrant endosome clustering, pronounced endosome enlargement, and cytoplasmic accumulation of ubiquitinated proteins in HeLa cells and wild-type mouse cortical neuron cultures. Biochemical and immunocytochemical experiments in cultured cortical neurons derived from transgenic Ubap1(flox) mice confirmed that disruption of UBAP1 leads to dysregulation of both early endosome processing and ubiquitinated protein sorting. Strikingly, deletion of Ubap1 promotes neurodegeneration, potentially mediated by apoptosis. Our study provides genetic and biochemical evidence that mutations in UBAP1 can cause pure autosomal dominant spastic paraplegia.