シンポジウム
45 分子機能から紐解くALS病態の新たな側面：ALS/FTLD分子病態の再考
45 Rethinking molecular mechanism of ALS/FTLD
座長：石垣 診祐（名古屋大学大学院医学系研究科）・築地 仁美（名古屋市立大学 大学院薬学研究科） |
|---|
| 2022年7月1日 9:00～9:20 沖縄コンベンションセンター 会議場B1 第3会場
2S03m-01
FUSの機能から再考するFTLDの病態
Redefinition of FTLD based on FUS function
*石垣 診祐(1)
1. 名古屋大学大学院医学系研究科
*Shinsuke Ishigaki(1)
1. Nagoya University Graduate School of Medicine
Keyword: FTLD, ALS, FUS, tau
The frontotemporal lobar degeneration (FTLD) spectrum includes FTLD, amyotrophic lateral sclerosis (ALS), progressive supranuclear palsy (PSP), and cortico-basal degeneration (CBD). TDP-43 and FUS are causative for ALS and FTLD, which collectively comprise a continuous disease spectrum of multisystem proteinopathies. On the other hand, 4-repeat (4R)-tau predominant aggregations are associated with PSP and CBD, while 3-repeat (3R)-tau accumulates in Pick disease (PiD). Using a mouse model, we reported that FUS regulates alternative splicing of tau proteins in coordination with Splicing factor, proline- and glutamine-rich (SFPQ). Under normal conditions, the two proteins form a high-molecular-weight complex in the nucleus. Disease-associated mutations in FUS gene, however, disrupt formation of the complex resulting in unregulated alternative splicing of tau, a disproportional increase in the 4R-tau/3R-tau ratio, and eventually neurodegeneration. In addition, neuropathological study revealed spatial dissociation of SFPQ and FUS in the neuronal nuclei of ALS/FTLD-FUS, ALS/FTLD-TDP, PSP, and CBD. Immunohistochemical imaging showed clear dissociation in hippocampal granule cells and Betz cells with statistically supported quantitative analysis of the hippocampal granule cells. Immunoprecipitation studies showed limited FUS-based SFPQ precipitation in the cases with ALS/FTLD and PSP. Thus, impaired interactions between FUS and SFPQ constitute a common pathogenic mechanism across FTLD spectrum diseases other than protein aggregation. Based on these findings, we are developing therapeutics to modify conformation of FUS and SFPQ as well as biomarkers which can visualize behavioral alterations caused by FUS dysfunction. | | 2022年7月1日 9:20～9:45 沖縄コンベンションセンター 会議場B1 第3会場
2S03m-02
Glial TDP-43 function in ALS/FTD
*Shuo-Chien Ling(1)
1. National University of Singapore
Keyword: ALS, FTD, TDP-43, glia
Common genetic loci and pathological signatures have unified two seemingly different adult-onset neurodegenerative diseases, amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), which affect predominantly the motor system and cognition, respectively. In particular, mutations in TDP-43 are causal for both diseases coupled with the pathological TDP-43 inclusions present in the neurons and glia indicate that TDP-43 dysfunctions in these cells trigger ALS and FTD pathogenesis. Furthermore, TDP-43 aggregates, collectively known as TDP-43 proteinopathies, are common in aging human brains and in other neurodegenerative diseases, such as Alzheimer’s disease (AD), underscoring the critical role of TDP-43 in brain health and diseases.
TDP-43 is ubiquitously expressed. Curiously, pathological TDP-43 also can be found in neurons, glia and other peripheral systems. Two key questions: the physiological functions of TDP-43 in different cell types, and whether the loss of TDP-43 in distinct glia contribute to ALS/FTD pathogenesis, remain unresolved. To this end, we systematically analyzed mice with TDP-43 deleted in distinct glia, including oligodendrocytes, Schwann cells and astrocytes. We uncovered that (1) TDP-43 is indispensable for oligodendrocyte survival and myelination by regulating cholesterol metabolism, (2) TDP-43 is required for maximize conduction velocity by maintaining paranodal assembly in Schwann cells, and (3) TDP-43 maintains the protective status of astrocytes. Loss of TDP-43 function in each of the distinct glia results in motor deficits without apparent damage to motor neurons. These results highlight that TDP-43 participate in different physiological role in distinct glia, and TDP-43 dysfunction in different glia may be an integral part of ALS pathogenesis. | | 2022年7月1日 9:45～10:05 沖縄コンベンションセンター 会議場B1 第3会場
2S03m-03
Abnormal distribution and function of the survival of motor neuron (SMN) protein in ALS
*Hitomi Tsuiji(1)
1. Grad Sch Pharmaceut Sci, Nagoya City Univ, Nagoya, Japan
Keyword: ALS, motor neuron disease, spliceosome, RNA granules
A G4C2 repeat expansion in the C9ORF72 gene is the most common genetic cause of amyotrophic lateral sclerosis (ALS), a devastating motor neuron disease. In the neurons of ALS patients, dipeptide repeat proteins (DPR) including poly(glycine-arginine) and poly(proline-arginine) are produced from the G4C2 repeats by an unconventional form of translation, which are thought to be toxic to cells. GEM bodies are nuclear structures that harbor survival of motor neuron (SMN) protein. They are essential for spliceosome integrity and we previously discovered that they are lost in the motor neurons of ALS patients. Here we show that DPR accumulation interferes with GEM formation and proper SMN localization in HeLa cells and in iPSC-derived motor neurons from an ALS patient. Accumulation of poly(glycine-arginine) markedly reduced the number of GEM bodies and caused the formation of aberrant cytoplasmic RNA granules that sequestered SMN. Another arginine-rich DPR, poly(proline-arginine) did not alter GEM formation but significantly impaired the disassembly of stress granules. Taken together, DPRs produced from the C9orf72 mutation impair GEM formation and proper SMN localization. Our findings might help to provide a mechanism to explain the abnormal RNA splicing seen in motor neurons of C9orf72-ALS patients. | | 2022年7月1日 10:05～10:30 沖縄コンベンションセンター 会議場B1 第3会場
2S03m-04
Investigation of pathogenic TDP-43 oligomers in neurodegenerative diseases
*Yun-Ru Ruby Chen(1)
1. Genomics Research Center, Academia Sinica, Taiwan
Keyword: a
TDP-43 is an RNA binding protein normally resided in the nucleus. Since 2006, TDP-43 inclusions are found in brain and/or spinal cord tissue of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar dementia (FTLD) patients. The inclusions were also found in nearly 57% Alzheimer’s disease (AD) patients who present faster disease progression and greater brain atrophy1. In 2014, we found that recombinant full-length human TDP-43 forms toxic spherical oligomers and perturbs amyloid-β (Aβ) fibrillization2. We generated TDP-43 oligomer-specific antibody, TDP-O, and identified the species in FTLD patients by immunostaining and immunoprecipitation. In this talk, I will first present our study to investigate the role of TDP-43 in AD. We identified the interaction of TDP-43 and Aβ and examined the effect of TDP-43 in Aβ fibrillization and in AD mouse models. We also showed that TDP-43 oligomers mostly colocalized with intraneuronal Aβ in the brain of AD patients. Together, we demonstrated that TDP-43 inhibits Aβ fibrillization through its Aβ interaction and exacerbates AD pathology3. In addition, I will discuss our latest results on the therapeutic and diagnostic potential of TDP-43 oligomer-specific monoclonal antibody for ALS. | | 2022年7月1日 10:30～11:00 沖縄コンベンションセンター 会議場B1 第3会場
2S03m-05
TDP-43 represses cryptic exon inclusion in FTD/ALS gene UNC13A
*Aaron D Gitler(1)
1. Stanford University
Keyword: TDP-43, UNC13A, cryptic splicing, ALS/FTD
A hallmark pathological feature of neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) is the depletion of RNA-binding protein TDP-43 from the nucleus of neurons in the brain and spinal cord. A major function of TDP-43 is as a repressor of cryptic exon inclusion during RNA splicing. Single nucleotide polymorphisms (SNPs) in UNC13A are among the strongest genome-wide association study (GWAS) hits associated with FTD/ALS in humans, but how those variants increase risk for disease is unknown. Here we show that TDP-43 represses a cryptic exon splicing event in UNC13A. Loss of TDP-43 from the nucleus in human brain, neuronal cell lines, and iPSC-derived motor neurons resulted in the inclusion of a cryptic exon in UNC13A mRNA and reduced UNC13A protein expression. Remarkably, the top variants associated with FTD/ALS risk in humans are located in the cryptic exon harboring intron itself and we show that they increase UNC13A cryptic exon splicing in the face of TDP-43 dysfunction. Together, our data provide a direct functional link between one of the strongest genetic risk factors for FTD/ALS (UNC13Agenetic variants) and loss of TDP-43 function. | | | |
|
|
