Dallah Yoo1, Wonjae Lee2,3, Seung-Jae Lee2, Jung-Joon Sung4, Gye Sun Jeon4,5, Jae-Jun Ban4,5, Chaewon Shin6, Jungho Kim7, Hyo Sun Kim7, Tae-Beom Ahn1. 1. Department of Neurology, Kyung Hee University Hospital, Kyung Hee University College of Medicine, Seoul, Republic of Korea. 2. Department of Biomedical Sciences, Neuroscience Research Institute, and Department of Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea. 3. Neuramedy Co., Ltd, Seoul, Republic of Korea. 4. Department of Neurology, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Republic of Korea. 5. Biomedical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea. 6. Department of Neurology, Neuroscience Center, Chungnam National University Sejong Hospital, Chungnam National University College of Medicine, Sejong-si, Republic of Korea. 7. Laboratory of Molecular and Cellular Biology, Department of Life Science, Sogang University, Seoul, Republic of Korea.
Abstract
BACKGROUND: Tropomyosin-receptor kinase fused gene (TFG) functions as a regulator of intracellular protein packaging and trafficking at the endoplasmic reticulum exit sites. TFG has recently been proposed as a cause of multisystem proteinopathy. OBJECTIVES: Here, we describe a Korean family presenting with Parkinson's disease or amyotrophic lateral sclerosis caused by a novel variant of TFG (c.1148 G > A, p.Arg383His). METHODS: We collected clinical, genetic, dopamine transporter imaging, nerve conduction, and electromyography data from the seven subjects. To verify the pathogenicity of the R383H variant, we studied cell viability and the abnormal aggregation of α-synuclein and TAR DNA-binding protein 43 (TDP-43) in HeLa cells expressing R383H-TFG. RESULTS: The clinical phenotypes of the R383H-TFG mutation varied; of the five family members, one had Parkinson's disease, three had subclinical parkinsonism, and one (the proband) had amyotrophic lateral sclerosis. The individual with multiple system atrophy was the proband's paternal cousin, but the TFG genotype was not confirmed due to unavailability of samples. Our in vitro studies showed that R383H-TFG overexpression impaired cell viability. In cells co-expressing R383H-TFG and α-synuclein, insoluble α-synuclein aggregates increased in concentration and were secreted from the cells and co-localized with R383H-TFG. The levels of cytoplasmic insoluble aggregates of TDP-43 increased in HeLa cells expressing R383H-TFG and co-localized with R383H-TFG. CONCLUSIONS: Clinical and in vitro studies have supported the pathogenic role of the novel TFG mutation in α-synucleinopathy and TDP-43 proteinopathy. These findings expand the phenotypic spectrum of TFG and suggest a pivotal role of endoplasmic reticulum dysfunction during neurodegeneration.
BACKGROUND: Tropomyosin-receptor kinase fused gene (TFG) functions as a regulator of intracellular protein packaging and trafficking at the endoplasmic reticulum exit sites. TFG has recently been proposed as a cause of multisystem proteinopathy. OBJECTIVES: Here, we describe a Korean family presenting with Parkinson's disease or amyotrophic lateral sclerosis caused by a novel variant of TFG (c.1148 G > A, p.Arg383His). METHODS: We collected clinical, genetic, dopamine transporter imaging, nerve conduction, and electromyography data from the seven subjects. To verify the pathogenicity of the R383H variant, we studied cell viability and the abnormal aggregation of α-synuclein and TAR DNA-binding protein 43 (TDP-43) in HeLa cells expressing R383H-TFG. RESULTS: The clinical phenotypes of the R383H-TFG mutation varied; of the five family members, one had Parkinson's disease, three had subclinical parkinsonism, and one (the proband) had amyotrophic lateral sclerosis. The individual with multiple system atrophy was the proband's paternal cousin, but the TFG genotype was not confirmed due to unavailability of samples. Our in vitro studies showed that R383H-TFG overexpression impaired cell viability. In cells co-expressing R383H-TFG and α-synuclein, insoluble α-synuclein aggregates increased in concentration and were secreted from the cells and co-localized with R383H-TFG. The levels of cytoplasmic insoluble aggregates of TDP-43 increased in HeLa cells expressing R383H-TFG and co-localized with R383H-TFG. CONCLUSIONS: Clinical and in vitro studies have supported the pathogenic role of the novel TFG mutation in α-synucleinopathy and TDP-43 proteinopathy. These findings expand the phenotypic spectrum of TFG and suggest a pivotal role of endoplasmic reticulum dysfunction during neurodegeneration.
Authors: Jennifer L Peotter; Iryna Pustova; Molly M Lettman; Shalini Shatadal; Mazdak M Bradberry; Allison D Winter-Reed; Maya Charan; Erin E Sharkey; James R Alvin; Alyssa M Bren; Annika K Oie; Edwin R Chapman; M Shahriar Salamat; Anjon Audhya Journal: Proc Natl Acad Sci U S A Date: 2022-09-26 Impact factor: 12.779