盘点2018年渐冻症（ALS）十大研究进展

一.   《Nature medicine》和《Cell》：C9orf72致病新机制被揭示—多聚GR二肽重复扩增损害蛋白翻译和应激颗粒动力学，而应激颗粒还具有破坏核质运输过程的负面作用。最后，神经元形成的多聚GA异常聚集体可以募集蛋白酶体。

这项研究揭示了C9orf72引起ALS/FTD的机制。C9orf72重复扩增引起蛋白翻译障碍和慢性应激，而应激颗粒的形成可以募集蛋白酶体，并破坏核质运输。

摘要：The major genetic cause of frontotemporaldementia (FTD) and amyotrophic lateral sclerosis (ALS) is a C9orf72 G4C2 repeat expansion1,2. Proposed mechanisms by which the expansioncauses c9FTD/ALS include toxicity from repeat-containing RNA and from dipeptiderepeat proteins translated from these transcripts. To investigate thecontribution of poly(GR) dipeptide repeat proteins to c9FTD/ALS pathogenesis ina mammalian in vivo model, we generated mice that expressed GFP-(GR)100 in the brain. GFP-(GR)100 mice developed age-dependent neurodegeneration, brain atrophy, and motor and memory deficits throughthe accumulation of diffuse, cytoplasmic poly(GR). Poly(GR) co-localized withribosomal subunits and the translation initiation factor eIF3η in GFP-(GR)100 mice and, of importance, in c9FTD/ALS patients.Combined with the differential expression of ribosome-associated genes inGFP-(GR)100 mice, these findings demonstratepoly(GR)-mediated ribosomal distress. Indeed, poly(GR) inhibited canonical andnon-canonical protein translation in HEK293T cells, and also induced theformation of stress granules and delayed their disassembly. These data suggestthat poly(GR) contributes to c9FTD/ALS by impairing protein translation andstress granule dynamics, consequently causing chronic cellular stress andpreventing cells from mounting an effective stress response. Decreasingpoly(GR) and/or interrupting interactions between poly(GR) and ribosomal andstress granule-associated proteins may thus represent potential therapeuticstrategies to restore homeostasis.

参考文献：

1.Poly(GR) impairs protein translation and stress granule dynamics inC9orf72-associated frontotemporal dementia and amyotrophic lateral sclerosis. NatMed. 2018 Aug;24(8):1136-1142.

2.Stress Granule Assembly Disrupts Nucleocytoplasmic Transport. Cell. 2018 May3;173(4):958-971.e17.

3.In Situ Structure of Neuronal C9orf72 Poly-GA Aggregates Reveals ProteasomeRecruitment. Cell. 2018 Feb 8;172(4):696-705.e12.

4.Context-Dependent and Disease-Specific Diversity in Protein Interactions withinStress Granules. Cell. 2018 Jan 25;172(3):590-604.

二.   《Cell》：TBK-1致病机制被发现—TBK1抑制发育和衰老过程中RIPK-1引起的凋亡和炎症反应。

TBK1突变引起ALS和FTD。这项研究揭示了TBK1缺陷可导致ALS/FTD的所有关键特征，包括：神经炎症、TDP-43沉积、轴突变性、神经元丢失和行为学缺陷。

摘要：Aging is a major risk factor for both genetic andsporadic neurodegenerative disorders. However, it is unclear how aginginteracts with genetic predispositions to promote neurodegeneration. Here, weinvestigate how partial loss of function of TBK1, a major genetic cause foramyotrophic lateral sclerosis (ALS) and frontotemporal dementia(FTD) comorbidity, leads to age-dependent neurodegeneration. We show thatTBK1 is an endogenous inhibitor of RIPK1 and the embryonic lethality of Tbk1-/- miceis dependent on RIPK1 kinase activity. In aging human brains, anotherendogenous RIPK1 inhibitor, TAK1, exhibits a marked decrease in expression. Weshow that in Tbk1+/- mice, the reduced myeloid TAK1 expressionpromotes all the key hallmarks of ALS/FTD, including neuroinflammation, TDP-43aggregation, axonal degeneration, neuronal loss, and behavior deficits, whichare blocked upon inhibition of RIPK1. Thus, aging facilitates RIPK1 activationby reducing TAK1 expression, which cooperates with genetic risk factors to promotethe onset of ALS/FTD.

参考文献：TBK1Suppresses RIPK1-Driven Apoptosis and Inflammation during Development and inAging. Cell. 2018 Sep 6;174(6):1477-1491.e19.

三.   《Cell》：FUS突变引起液相稳态异常从而引起FUS入核运输障碍和FUS细胞内聚集。

这两项研究的主要发现是揭示了ALS/FTD中FUS细胞内聚集的主要机制。入核受体和FUS结合之后可以抑制FUS的相分离进而促进FUS的入核转运，但是FUS的核定位序列突变后会减弱入核受体的伴侣蛋白活性，促进FUS的相分离和应激颗粒的形成。

摘要：Cytoplasmic FUS aggregates are a pathologicalhallmark in a subset of patients with frontotemporal dementia (FTD) or amyotrophic lateral sclerosis (ALS). A key step that isdisrupted in these patients is nuclear import of FUS mediated by the importreceptor Transportin/Karyopherin-β2. In ALS-FUS patients, this is caused bymutations in the nuclear localization signal (NLS) of FUS that weakenTransportin binding. In FTD-FUS patients, Transportin is aggregated, and post-translationalarginine methylation, which regulates the FUS-Transportin interaction, is lost.Here, we show that Transportin and arginine methylation have a crucial functionbeyond nuclear import-namely to suppress RGG/RG-driven phase separation andstress granule association of FUS. ALS-associated FUS-NLS mutations weaken thechaperone activity of Transportin and loss of FUS arginine methylation, as seenin FTD-FUS, promote phase separation, and stress granule partitioning of FUS.Our findings reveal two regulatory mechanisms of liquid-phase homeostasis thatare disrupted in FUS-associated neurodegeneration.

参考文献：

1.Phase Separation of FUS Is Suppressed by Its Nuclear Import Receptor andArginine Methylation. Cell. 2018 Apr 19;173(3):706-719.e13.

2.Nuclear Import Receptor Inhibits Phase Separation of FUS through Binding toMultiple Sites. Cell. 2018 Apr 19;173(3):693-705.e22.

四.   《Nature medicine》：C9orf72与自噬相关—C9orf72的单倍剂量不足引起ALS/FTD神经变性。

这项研究发现C9orf72能够和内体相互作用，并促进囊泡转运和溶酶体生物合成。一旦C9orf72重复扩增之后就会引起兴奋性毒性和毒性二肽重复扩增蛋白的清除障碍。因此，增加C9orf72水平或者增强其功能可以改善ALS/FTD神经变性。

摘要：An intronic GGGGCC repeat expansion in C9ORF72 isthe most common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia(FTD), but the pathogenic mechanism of this repeat remains unclear. Using humaninduced motor neurons (iMNs), we found that repeat-expanded C9ORF72 washaploinsufficient in ALS. We found that C9ORF72 interacted with endosomes andwas required for normal vesicle trafficking and lysosomal biogenesis in motorneurons. Repeat expansion reduced C9ORF72 expression, triggeringneurodegeneration through two mechanisms: accumulation of glutamate receptors,leading to excitotoxicity, and impaired clearance of neurotoxic dipeptiderepeat proteins derived from the repeat expansion. Thus, cooperativity betweengain- and loss-of-function mechanisms led to neurodegeneration. RestoringC9ORF72 levels or augmenting its function with constitutively active RAB5 orchemical modulators of RAB5 effectors rescued patient neuron survival and ameliorated neurodegenerativeprocesses in both gain- and loss-of-function C9ORF72 mouse models. Thus,modulating vesicle trafficking was able to rescue neurodegeneration caused bythe C9ORF72 repeat expansion. Coupled with rare mutations in ALS2, FIG4,CHMP2B, OPTN and SQSTM1, our results reveal mechanistic convergence on vesicletrafficking in ALS and FTD.

参考文献：Haploinsufficiencyleads to neurodegeneration in C9ORF72 ALS/FTD human induced motor neurons. NatMed. 2018 Mar;24(3):313-325.

 五.   《Sci Transl Med》：靶向SOD1的人源性抗体改善ALS小鼠模型的运动症状。

这项研究的意义就在于发现了靶向SOD1的人源性抗体可以和异常折叠的SOD1结合，并可延长ALS小鼠模型的寿命长达2个月。

摘要：Mutations in the gene encoding superoxidedismutase 1 (SOD1) lead to misfolding and aggregation of SOD1 and cause familialamyotrophic lateral sclerosis (FALS). However, the implications ofwild-type SOD1 misfolding in sporadic forms of ALS (SALS) remain unclear. Byscreening human memory B cells from a large cohort of healthy elderly subjects,we generated a recombinant human monoclonal antibody (α-miSOD1) thatselectively bound to misfolded SOD1, but not to physiological SOD1 dimers. Onpostmortem spinal cord sections from 121 patients with ALS, α-miSOD1 antibodyidentified misfolded SOD1 in a majority of cases, regardless of their SOD1genotype. In contrast, the α-miSOD1 antibody did not bind to its epitope inmost of the 41 postmortem spinal cord sections from non-neurological control(NNC) patients. In transgenic mice overexpressing disease-causing human SOD1G37R orSOD1G93A mutations, treatment with the α-miSOD1 antibodydelayed the onset of motor symptoms, extended survival by up to 2 months, andreduced aggregation of misfolded SOD1 and motor neuron degeneration. These effects were obtainedwhether α-miSOD1 antibody treatment was administered by direct braininfusion or peripheral administration. Theseresults support the further development of α-miSOD1 antibody as a candidatetreatment for ALS involving misfolding of SOD1.

参考文献：Ahuman-derived antibody targets misfolded SOD1 and ameliorates motor symptoms inmouse models of amyotrophic lateral sclerosis. Sci Transl Med. 2018 Dec5;10(470).

 六.   《Nature》：TDP-43新来源—肌肉再生过程中TDP-43和RNA形成淀粉样肌颗粒可能是TDP-43异常聚集体的来源。

这篇文章的价值在于揭示了TDP-43聚集体的来源。无论是在ALS还是包涵体肌病中都存在TDP-43聚集体，但其来源却不清楚。这篇文章发现了在肌肉再生过程中，TDP-43可以和RNA结合形成淀粉样肌颗粒以促进肌节蛋白的合成。但在肌肉发育成熟后，TDP-43形成的肌颗粒就会消失。因此，这些肌颗粒的增加或者清除下降可能是TDP-43产生的原因。

摘要：A dominant histopathological feature inneuromuscular diseases, including amyotrophic lateral sclerosis and inclusion body myopathy, iscytoplasmic aggregation of the RNA-binding protein TDP-43. Although raremutations in TARDBP-the gene that encodes TDP-43-that lead to proteinmisfolding often cause protein aggregation, most patients do not have any mutationsin TARDBP. Therefore, aggregates of wild-type TDP-43 arise in most patients byan unknown mechanism. Here we show that TDP-43 is an essential protein fornormal skeletal muscle formation that unexpectedly forms cytoplasmic,amyloid-like oligomeric assemblies, which we call myo-granules, duringregeneration of skeletal muscle in mice and humans. Myo-granules bind to mRNAsthat encode sarcomeric proteins and are cleared as myofibres mature. Althoughmyo-granules occur during normal skeletal-muscle regeneration, myo-granules canseed TDP-43 amyloid fibrils in vitro and are increased in a mouse model ofinclusion body myopathy. Therefore, increased assembly or decreased clearanceof functionally normal myo-granules could be the source of cytoplasmic TDP-43 aggregatesthat commonly occur in neuromuscular disease.

参考文献：TDP-43and RNA form amyloid-like myo-granules in regenerating muscle. Nature. 2018Nov;563(7732):508-513.

七.   《Nature medicine》：ALS新药研发突破—通过iPSC模型，研究人员发现了改善多种ALS病理表型的药物。

摘要：Amyotrophic lateral sclerosis (ALS) is aheterogeneous motor neuron disease for which no effective treatment isavailable, despite decades of research into SOD1-mutant familial ALS (FALS).The majority of ALS patients have no familial history, making the modeling ofsporadic ALS (SALS) essential to the development of ALS therapeutics. However,as mutations underlying ALS pathogenesis have not yet been identified, itremains difficult to establish useful models of SALS. Using induced pluripotentstem cell (iPSC) technology to generate stem anddifferentiated cells retaining the patients' full genetic information, we haveestablished a large number of in vitro cellular models of SALS. These modelsshowed phenotypic differences in their pattern of neuronal degeneration, typesof abnormal protein aggregates, celldeath mechanisms,and onset and progression of these phenotypes in vitro among cases. Wetherefore developed a system for case clustering capable of subdividing these heterogeneousSALS models by their in vitro characteristics. We further evaluatedmultiple-phenotype rescue of these subclassified SALS models using agentsselected from non-SOD1 FALS models, and identified ropinirole as a potentialtherapeutic candidate. Integration of the datasets acquired in this studypermitted the visualization of molecular pathologies shared across a wide rangeof SALS models.

参考文献：Modelingsporadic ALS in iPSC-derived motor neurons identifies a potential therapeuticagent. Nat Med. 2018 Oct;24(10):1579-1589.

八.   《Neuron》：FUS突变通过抑制轴突内蛋白质合成进而推动疾病的进展。

这项研究发现了FUS突变引起的神经毒性主要包括抑制轴突内蛋白翻译、引起突触功能障碍、加剧年龄相关的运动和认知恶化，但并不会引起胞质内异常聚集、细胞核定位异常和FUS结合的pre-mRNA的错乱剪接。

摘要：Through the generation of humanized FUS miceexpressing full-length human FUS, we identify that when expressed at nearendogenous murine FUS levels, both wild-type and ALS-causing and frontotemporaldementia (FTD)-causing mutations complement the essential function(s) of murineFUS. Replacement of murine FUS with mutant, but not wild-type, human FUS causesstress-mediated induction of chaperones, decreased expression of ion channelsand transporters essential for synaptic function, and reduced synaptic activitywithout loss of nuclear FUS or its cytoplasmic aggregation. Most strikingly,accumulation of mutant human FUS is shown to activate an integrated stressresponse and to inhibit local, intra-axonal protein synthesis in hippocampalneurons and sciatic nerves. Collectively, our evidence demonstrates that humanALS/FTD-linked mutations in FUS induce a gain of toxicity that includesstress-mediated suppression in intra-axonal translation, synaptic dysfunction,and progressive age-dependent motor and cognitive disease without cytoplasmicaggregation, altered nuclear localization, or aberrant splicing of FUS-boundpre-mRNAs. VIDEO ABSTRACT.

参考文献：ALS/FTD-LinkedMutation in FUS Suppresses Intra-axonal Protein Synthesis and Drives DiseaseWithout Nuclear Loss-of-Function of FUS. Neuron. 2018 Nov 21;100(4):816-830.e7.

九.   《Ann Neurol》：干细胞治疗新突破—自体骨髓来源间充质干细胞治疗ALS初见疗效。

这是一个II期临床研究。主要发现是自体骨髓来源间充质干细胞可以降低ALSFRS-R分数，而且治疗效果可以维持到注射后6个月。研究人员认为其机制可能是间充质干细胞的抗炎症作用增加。

摘要：

OBJECTIVE:

Toassess the safety and efficacy of 2 repeated intrathecal injections ofautologous bone marrow-derived mesenchymal stem cells (BM-MSCs) in amyotrophiclateral sclerosis (ALS).

METHODS:

Ina phase 2 randomized controlled trial (NCT01363401), 64 participants with ALSwere randomly assigned treatments (1:1) of riluzole alone (control group, n =31) or combined with 2 BM-MSC injections (MSC group, n = 33). Safety wasassessed based on the occurrence of adverse events. The primary efficacyoutcome was changes in Amyotrophic Lateral Sclerosis Functional RatingScale-Revised (ALSFRS-R) score from baseline to 4 and 6 months postinjection.Post hoc analysis includes investigation of cerebrospinal fluid biomarkers andlong-term survival analysis.

RESULTS:

Safetyrating showed no groupwise difference with absence of serious treatment-relatedadverse events. Mean changes in ALSFRS-R scores from baseline to 4 and 6 monthspostinjection were reduced in the MSC group compared with the control group (4months: 2.98, 95% confidence interval [CI] = 1.48-4.47, p < 0.001; 6 months:3.38, 95% CI = 1.23-5.54, p = 0.003). The MSC group showed decreasedproinflammatory and increased anti-inflammatory cytokines. In good responders,transforming growth factor β1 significantly showed inverse correlation withmonocyte chemoattractant protein-1. There was no significant difference inlong-term survival between groups.

INTERPRETATION:

Repeatedintrathecal injections of BM-MSCs demonstrated a possible clinical benefitlasting at least 6 months, with safety, in ALS patients. A plausible actionmechanism is that BM-MSCs mediate switching from pro- to anti-inflammatoryconditions. A future randomized, double-blind, large-scale phase 3 clinicaltrial with additional BM-MSC treatments is required to evaluate long-termefficacy and safety. Ann Neurol 2018;84:361-373.

参考文献：RepeatedIntrathecal Mesenchymal Stem Cells for Amyotrophic Lateral Sclerosis. AnnNeurol. 2018 Sep;84(3):361-373.

十.   《Nature neuroscience》：TDP-43损害核孔复合体并破坏核质运输过程。

这项研究发现TDP-43可以引起核孔蛋白和转运因子的错误定位，从而破坏核孔复合体的完整和核质运输过程。

摘要：Thecytoplasmic mislocalization and aggregation of TAR DNA-binding protein-43(TDP-43) is a common histopathological hallmark of theamyotrophic lateral sclerosis and frontotemporal dementia diseasespectrum (ALS/FTD). However, the composition of aggregates and theircontribution to the disease process remain unknown. Here we usedproximity-dependent biotin identification (BioID) to interrogate theinteractome of detergent-insoluble TDP-43 aggregates and found them enrichedfor components of the nuclear pore complex and nucleocytoplasmic transportmachinery. Aggregated and disease-linked mutant TDP-43 triggered thesequestration and/or mislocalization of nucleoporins and transport factors, andinterfered with nuclear protein import and RNA export in mouse primary corticalneurons, human fibroblasts and induced pluripotent stem cell-derived neurons. Nuclear pore pathology ispresent in brain tissue in cases of sporadic ALS and thoseinvolving genetic mutations in TARDBP and C9orf72. Our data strongly implicateTDP-43-mediated nucleocytoplasmic transport defects as a common diseasemechanism in ALS/FTD.

参考文献：TDP-43pathology disrupts nuclear pore complexes and nucleocytoplasmic transport inALS/FTD. Nat Neurosci. 2018 Feb;21(2):228-239.