Rationale & hypothesis: ALS is a devastating progressive neurodegenerative condition, which results in death. TARDBP encoded protein, TDP-43, has been implicated in both the sporadic and familial ALS cases. Animal models of TDP-43 have been inconclusive and the role of TDP-43 in ALS remains an enigma to date. Fibroblasts obtained from the patients carrying mutations in TARDBP gene provide a vital tool in investigation of TDP-43 due to physiological levels of TDP-43.
Methodology: Immunocytochemistry was performed on three lines of control and three different TDP-43 mutant fibroblast lines (M337V, G287V, A321V) and confocal microscopy was performed to identify general TDP-43, phosphorylated TDP-43 and anti p62 (to identify ubiquitin) localisations. Fibroblasts were also subjected to 0.5 mM arsenite and the stress response was assessed using markers of stress granules such as TIAR and HUR. Recovery after stress was also assessed.
Findings/conclusion: In keeping with findings in ALS postmortem material, relative clearing of nuclear TDP-43 was noted in mutant TDP-43 fibroblasts (p < 0.001). TDP-43 fibroblasts also showed accumulation of p62 positive aggregates (p < 0.0003), and phosphorylated TDP-43 accumulation (p < 0.001) compared to controls, suggesting that mutant TDP-43 fibroblasts share some characteristics of the surviving motor neurons from both sALS and fALS. Following exogenic stress endogenous TDP-43 localised to HUR positive stress granules (p < 0.01), formation of stress granules and their recovery were significantly impaired in mTDP-43 cases (p < 0.01) suggesting that dysfunction of TDP-43 dysregulates handling of exogenic stress. We suggest that this may contribute to premature degeneration of motor neurons expressing mutant TDP-43 in ALS patients. Fibroblasts also form a robust and an economical platform to study TDP-43 related neurodegeneration.
I have obtained patient and Institutional Review Board (IRB) approval and local ethics committee approval.
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© 2015 Published by Elsevier Inc.
