TDP-43 Cytoplasmic Translocation in the Skin Fibroblasts of ALS Patients (original) (raw)
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Acta Neuropathologica Communications, 2015
Amyotrophic lateral sclerosis (ALS) is an adult-onset disease characterized by the selective degeneration of motor neurons in the brain and spinal cord progressively leading to paralysis and death. Current diagnosis of ALS is based on clinical assessment of related symptoms. The clinical manifestations observed in ALS appear relatively late in the disease course after degeneration of a significant number of motor neurons. As a result, the identification and development of disease-modifying therapies is difficult. Therefore, novel strategies for early diagnosis of neurodegeneration, to monitor disease progression and to assess response to existing and future treatments are urgently needed. Factually, many neurological disorders, including ALS, are accompanied by skin changes that often precede the onset of neurological symptoms. Aiming to generate an innovative human-based model to facilitate the identification of predictive biomarkers associated with the disease, we developed a unique ALS tissue-engineered skin model (ALS-TES) derived from patient's own cells. The ALS-TES presents a number of striking features including altered epidermal differentiation, abnormal dermo-epidermal junction, delamination, keratinocyte infiltration, collagen disorganization and cytoplasmic TDP-43 inclusions. Remarkably, these abnormal skin defects, uniquely seen in the ALS-derived skins, were detected in pre-symtomatic C9orf72-linked ALS patients carrying the GGGGCC DNA repeat expansion. Consequently, our ALS skin model could represent a renewable source of human tissue, quickly and easily accessible to better understand the physiopathological mechanisms underlying this disease, to facilitate the identification of disease-specific biomarkers, and to develop innovative tools for early diagnosis and disease monitoring.
Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques, 2015
Amyotrophic lateral sclerosis (ALS) is an adult-onset disease characterized by the selective degeneration of motor neurons in the brain and spinal cord resulting in progressive paralysis and death. Current diagnosis of ALS is based on clinical assessment of related symptoms, which appear only late in the disease course after degeneration of a significant number of motor neurons. As a result, the identification and development of disease-modifying therapies is difficult, making ALS an incurable disease. Novel strategies for early diagnosis of ALS, to monitor disease progression and to assess response to existing and future treatments are urgently needed.Many neurological disorders, including ALS, are accompanied by skin changes that often precede the onset of neurological symptoms. We have developed a unique ALS tissue-engineered skin model (ALS-TES), derived from the cells of ALS patients, in order to study the earliest stages of ALS-related skin pathology. For each participant, two...
ALS skin fibroblasts reveal oxidative stress and ERK1/2-mediated cytoplasmic localization of TDP-43
Cellular Signalling, 2020
The main hallmark of many forms of familiar and sporadic amyotrophic lateral sclerosis (ALS) is a reduction in nuclear TDP-43 protein and its inclusion in cytoplasmic aggregates in motor neurons. In order to understand which cellular and molecular mechanisms underlie the mislocalization of TDP-43, we examined human skin fibroblasts from two individuals with familial ALS, both with mutations in TDP-43, and two individuals with sporadic ALS, both without TDP-43 mutations or mutations in other ALS related genes. We found that all ALS fibroblasts had a partially cytoplasmic localization of TDP-43 and had reduced cell metabolism as compared to fibroblasts from apparently healthy individuals. ALS fibroblasts showed an increase in global protein synthesis and an increase in 4E-BP1 and rpS6 phosphorylation, which is indicative of mTORC1 activity. We also observed a decrease in glutathione (GSH), which suggests that oxidative stress is elevated in ALS. ERK1/2 activity regulated the extent of oxidative stress and the localization of TDP-43 in the cytoplasm in all ALS fibroblasts. Lastly, ALS fibroblasts showed reduced stress granule formation in response to H 2 O 2 stress. In conclusion, these findings identify specific cellular and molecular defects in ALS fibroblasts, thus providing insight into potential mechanisms that may also occur in degenerating motor neurons.
Acta Neuropathologica, 2011
TDP-43, encoded by TARDBP, is a ubiquitously expressed, primarily nuclear protein. In recent years, TDP-43 has been identified as the major pathological protein in ALS due to its mislocalisation in the cytoplasm of motor neurons of patients with and without TARDBP mutations and expression in forms that do not match its predicted molecular weight. In this study, the TDP-43 profile was investigated using western immunoblot analysis in whole lysates, nuclei and cytoplasm of circulating lymphomonocytes from 16 ALS patients, 4 with (ALS/ TDP?) and 12 without (ALS/TDP-) TARDBP mutations in the protein C-terminal domain, and thirteen age-matched, healthy donors (controls). Three disease-unaffected first-degree relatives of an ALS/TDP? patient were also included: one carried the parent mutation (Rel/TDP?) whereas the other two did not (Rel/TDP-). In all ALS patients, relatives and controls, TDP-43 retained the predicted molecular weight in whole cell lysates and nuclei, but in the cytoplasm its molecular weight was slightly smaller than expected. In quantitative terms, TDP-43 was expressed at approximately the same levels in whole cell lysates of ALS patients, relatives and controls. In contrast, TDP-43 accumulated in the cytoplasm with concomitant nuclear depletion in all ALS/TDP? patients, in about 50% of ALS/TDP-patients and in the Rel/ TDP? subject compared to the controls. In the remaining ALS/TDP-patients and in the two Rel/TDP-subjects, TDP-43 matched the control levels in both subcellular compartments. Were these findings further confirmed, circulating lymphomonocytes could be informative of TDP-43 mislocalisation in nervous tissue and used as a biomarker for future disease risk.
ROLE OF FREE AND EXOSOMAL TDP-43 AS A DIAGNOSTIC TOOL IN NEURODEGENERATIVE DISEASES
Alzheimer's & Dementia, 2014
and other neurological diseases (7). However, other studies have even reported elevated levels of TDP-43 in blood from ALS patients (8 -11). Therefore, the source of TDP-43 in blood and CSF in particular deserves attention. We analysed paired CSF and serum samples of FTLD, ALS and controls for the presence and concentration of TDP-43 by means of immunoblotting in each pair of CSF serum samples. These CSF/blood ratios were compared with the CSF/blood ratios of proteins of similar molecular weight in the Felgenhauer blot according to their hydrodynamic radius in order to determine whether TDP-43 is mainly blood-derived (12,13). To investigate additional sources of TDP-43, we also looked at purifi ed exosomes from CSF. TDP-43 was also investigated using 2D-immunoblotting and targeted mass spectrometry .
TDP-43 and Cytoskeletal Proteins in ALS
Molecular Neurobiology, 2017
Amyotrophic lateral sclerosis (ALS) represents a rapidly progressing neurodegenerative disease and is characterized by a degeneration of motor neurons. Motor neurons are particularly susceptible to selective and early degeneration because of their extended axon length and their dependency on the cytoskeleton for its stability, signaling, and axonal transport. The motor neuron cytoskeleton comprises actin filaments, neurofilaments like peripherin, and microtubules. The Transactivating Response Region (TAR) DNA Binding Protein (TDP-43) forms characteristic cytoplasmic aggregates in motor neurons of ALS patients, and at least in part, the pathogenesis of ALS seems to be driven by toxic pTDP-43 aggregates in cytoplasm, which lead to a diminished axon formation and reduced axon length. Diminished axon formation and reduced axon length suggest an interaction of TDP-43 with the cytoskeleton of motor neurons. TDP-43 interacts with several cytoskeletal components, e.g., the microtubuleassociated protein 1B (MAP1B) or the neurofilament light chain (NFL) through direct binding to its RNA. From a clinical perspective, cytoskeletal biomarkers like phosphorylated neurofilament heavy chain (pNFH) and NFL are already clinically used in ALS patients to predict survival, disease progression, and duration. Thus, in this review, we focus on the interaction of TDP-43 with the different cytoskeleton components such as actin filaments, neurofilaments, and microtubules as well as their associated proteins as one aspect in the complex pathogenesis of ALS.
Pathological TDP-43 in parkinsonism–dementia complex and amyotrophic lateral sclerosis of Guam
Acta Neuropathologica, 2007
Pathological TDP-43 is the major disease protein in frontotemporal lobar degeneration characterized by ubiquitin inclusions (FTLD-U) with/without motor neuron disease (MND) and in amyotrophic lateral sclerosis (ALS). As Guamanian parkinsonism-dementia complex (PDC) or Guamanian ALS (G-PDC or G-ALS) of the Chamorro population may present clinically similar to FTLD-U and ALS, TDP-43 pathology may be present in the G-PDC and G-ALS. Thus, we examined cortical or spinal cord samples from 54 Guamanian subjects for evidence of TDP-43 pathology. In addition to cortical neuro-Wbrillary and glial tau pathology, G-PDC was associated with cortical TDP-43 positive dystrophic neurites and neuronal and glial inclusions in gray and/or white matter. Biochemical analyses showed the presence of FTLD-U-like insoluble TDP-43 in G-PDC, but not in Guam controls (G-C). Spinal cord pathology of G-PDC or G-ALS was characterized by tau positive tangles as well as TDP-43 positive inclusions in lower motor neurons and glial cells. G-C had variable tau and negligible TDP-43 pathology.
Neurology and Clinical Neuroscience, 2013
C9ORF72 and the 43 kDa TAR DNA-binding protein are key molecules in the development of TDP-43 pathology in amyotrophic lateral sclerosis (ALS). The hexanucleotide repeat expansion in C9ORF72 also leads to frontotemporal lobar degeneration, whereas mutation of TARDBP mainly causes ALS, indicating that TDP-43 plays a more fundamental role in the development of ALS. In tissues affected with ALS, TDP-43 is dislocated from the nucleus, forms cytoplasmic inclusions, and is phosphorylated and truncated. Accumulating evidence suggests that the disappearance of TDP-43 from the nucleus precedes inclusion formation, indicating that its disappearance from the nucleus is crucial in the development of TDP-43 pathology. Alterations in the quality and quantity of TDP-43 might result in the disappearance of TDP-43 from the nucleus. Regarding quality, phosphorylation and truncation of TDP-43 is not necessary for its disappearance from the nucleus or for inclusion formation. Although it has been speculated that studies of TDP-43 harboring ALS-associated mutations are useful for understanding the molecular pathogenesis of sporadic ALS, the functional and biochemical differences between mutated and wild-type TDP-43 remain unclear. Regarding quantity, an increased amount of TDP-43 is an attractive hypothesis as it has been shown that increased amounts of TDP-43 are toxic. Moreover, several reports have suggested that increased levels of TDP-43 are found in sporadic ALS as well as in ALS with TDP-43 mutations. However, these findings remain controversial. Increased understanding of the mechanisms responsible for regulating TDP-43 will provide a basis for determining the molecular pathogenesis of ALS.