scholarly journals Cortical hyperexcitability drives dying forward ALS symptoms and pathology in mice

2021 ◽  
Author(s):  
Mouna Haidar ◽  
Aida Viden ◽  
Brittany Cuic ◽  
Taide Wang ◽  
Marius Rosier ◽  
...  
Keyword(s):  
Motor Neurons ◽  
Corticospinal Tract ◽  
Neuromuscular Junctions ◽  
Dna Binding Protein ◽  
Spinal Motor Neurons ◽  
Spinal Motor ◽  
Cortical Hyperexcitability ◽  
The Central Nervous System ◽  
Lateral Sclerosis ◽  
Intrinsic Feature

Amyotrophic lateral sclerosis (ALS) is a progressive fatal disorder caused by degeneration of motor neurons in the cortex and spinal cord. The origin of ALS in the central nervous system is unclear, however cortical hyperexcitability appears as an early and intrinsic feature of ALS and has been linked to degeneration of spinal motor neurons via a dying-forward mechanism. Here, we implement chemogenetics to validate the dying forward hypothesis of ALS in mice. We show that chronic hyperexcitability of corticomotoneurons induced by excitatory chemogenetics results in motor symptoms and core neuropathological hallmarks of ALS, including corticomotoneuron loss, corticospinal tract degeneration and reactive gliosis. Importantly, corticomotoneuron loss was sufficient to drive degeneration of spinal motor neurons and neuromuscular junctions (NMJs), associated with cytoplasmic TAR DNA binding protein 43 (TDP-43) pathology. These findings establish a cortical origin of ALS mediated by neuronal hyperexcitability, consistent with a dying forward mechanism of neurodegeneration.

scholarly journals Pathologic Thr175 tau phosphorylation in CTE and CTE with ALS

Neurology ◽  
2018 ◽  
Vol 90 (5) ◽  
pp. e380-e387 ◽  
Author(s):  
Alexander J. Moszczynski ◽  
Wendy Strong ◽  
Kathy Xu ◽  
Ann McKee ◽  
Arthur Brown ◽  
...  
Keyword(s):  
Motor Neurons ◽  
Hippocampal Neurons ◽  
Glycogen Synthase ◽  
Chronic Traumatic Encephalopathy ◽  
Spinal Cord Tissue ◽  
Tau Pathology ◽  
Spinal Motor Neurons ◽  
Spinal Motor ◽  
Pathologic Features ◽  
Lateral Sclerosis

ObjectiveTo investigate whether chronic traumatic encephalopathy (CTE) and CTE with amyotrophic lateral sclerosis (CTE-ALS) exhibit features previously observed in other tauopathies of pathologic phosphorylation of microtubule-associated protein tau at Thr175 (pThr175 tau) and Thr231 (pThr231 tau), and glycogen synthase kinase–3β (GSK3β) activation, and whether these pathologic features are a consequence of traumatic brain injury (TBI).MethodsTau isoform expression was assayed by western blot in 6 stage III CTE cases. We also used immunohistochemistry to analyze 5 cases each of CTE, CTE-ALS, and 5 controls for expression of activated GSK3β, pThr175 tau, pThr231 tau, and oligomerized tau within spinal cord tissue and hippocampus. Using a rat model of moderate TBI, we assessed tau pathology and phospho-GSK3β expression at 3 months postinjury.ResultsCTE and CTE-ALS are characterized by the presence of all 6 tau isoforms in both soluble and insoluble tau isolates. Activated GSK3β, pThr175 tau, pThr231 tau, and oligomerized tau protein expression was observed in hippocampal neurons and spinal motor neurons. We observed tau neuronal pathology (fibrillar inclusions and axonal damage) and increased levels of pThr175 tau and activated GSK3β in moderate TBI rats.ConclusionsPathologic phosphorylation of tau at Thr175 and Thr231 and activation of GSK3β are features of the tauopathy of CTE and CTE-ALS. These features can be replicated in an animal model of moderate TBI.

scholarly journals A Commentary on TDP-43 and DNA Damage Response in Amyotrophic Lateral Sclerosis

2019 ◽  
Vol 13 ◽  
pp. 117906951988016 ◽  
Author(s):  
Joy Mitra ◽  
Muralidhar L Hegde
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Amyotrophic Lateral Sclerosis ◽  
Dna Damage Response ◽  
Motor Neurons ◽  
Dsb Repair ◽  
Spinal Motor Neurons ◽  
Spinal Motor ◽  
Damage Response ◽  
Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating, motor neuron degenerative disease without any cure. About 95% of the ALS patients feature abnormalities in the RNA/DNA-binding protein, TDP-43, involving its nucleo-cytoplasmic mislocalization in spinal motor neurons. How TDP-43 pathology triggers neuronal apoptosis remains unclear. In a recent study, we reported for the first time that TDP-43 participates in the DNA damage response (DDR) in neurons, and its nuclear clearance in spinal motor neurons caused DNA double-strand break (DSB) repair defects in ALS. We documented that TDP-43 was a key component of the non-homologous end joining (NHEJ) pathway of DSB repair, which is likely the major pathway for repair of DSBs in post-mitotic neurons. We have also uncovered molecular insights into the role of TDP-43 in DSB repair and showed that TDP-43 acts as a scaffold in recruiting the XRCC4/DNA Ligase 4 complex at DSB damage sites and thus regulates a critical rate-limiting function in DSB repair. Significant DSB accumulation in the genomes of TDP-43-depleted, human neural stem cell-derived motor neurons as well as in ALS patient spinal cords with TDP-43 pathology, strongly supported a TDP-43 involvement in genome maintenance and toxicity-induced genome repair defects in ALS. In this commentary, we highlight our findings that have uncovered a link between TDP-43 pathology and impaired DNA repair and suggest potential possibilities for DNA repair-targeted therapies for TDP-43-ALS.

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