A Novel TFG Mutation in a Korean Family with α‐Synucleinopathy and Amyotrophic Lateral Sclerosis

• Published in: Movement disorders Vol. 37; no. 2; pp. 384 - 391
• Main Authors: Yoo, Dallah, Lee, Wonjae, Lee, Seung‐Jae, Sung, Jung‐Joon, Jeon, Gye Sun, Ban, Jae‐Jun, Shin, Chaewon, Kim, Jungho, Kim, Hyo Sun, Ahn, Tae‐Beom
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.02.2022; Wiley Subscription Services, Inc
• Subjects: Amyotrophic lateral sclerosis; Amyotrophic Lateral Sclerosis - genetics; Atrophy; Basal ganglia; Brain diseases; Cell viability; Central nervous system diseases; Dopamine transporter; Electromyography; Endoplasmic reticulum; Genotypes; HeLa Cells; Humans; Movement disorders; Mutation; Nerve conduction; Neurodegeneration; Neurodegenerative diseases; Parkinson's disease; parkinsonism; Pathogenicity; Phenotypes; Protein transport; Proteins - genetics; Republic of Korea; Synuclein; Synucleinopathies; Tropomyosin; tropomyosin‐receptor kinase fused gene (TFG); Republic of Korea; parkinsonism; tropomyosin-receptor kinase fused gene (TFG); amyotrophic lateral sclerosis; endoplasmic reticulum
• ISSN: 0885-3185; 1531-8257
• DOI: 10.1002/mds.28857

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. © 2021 International Parkinson and Movement Disorder Society