Nuclear pore destruction and loss of nuclear TDP-43 in FUS mutation-related amyotrophic lateral sclerosis motor neurons

Negative features of sporadic amyotrophic lateral sclerosis: Motor neurons of Onuf's nucleus survive in ADAR2-conditional knockout mice

Patients with amyotrophic lateral sclerosis (ALS) do not develop oculomotor disturbances and vesicorectal dysfunction until end-stage disease owing to the survival of certain motor neurons (MNs), including oculomotor neurons and MNs within Onuf's nucleus. In sporadic ALS, adenosine deaminase acting on RNA 2 (ADAR2)-mediated editing of GluA2 mRNA at the Q/R site is compromised in lower MNs. We previously developed genetically modified mice with a conditional knockout of ADAR2 in cholinergic neurons (ADAR2flox/flox/VAChT-Cre, Fast; AR2). These mice displayed slow and progressive lower motor neuron death with TAR DNA-binding protein 43 (TDP-43) pathology, attributable to insufficient editing at the GluA2 Q/R site due to ADAR2 deficiency. MN death was more common in fast-fatigable MNs owing to differential vulnerability under conditions of ADAR2 deficiency. Although facial and hypoglossal nerves were impaired in AR2 mice, cell death did not occur within the oculomotor nerve nucleus, as observed in patients with sporadic ALS. Since the basis for avoiding cystorectal damage in ALS is unknown, we compared the features of Onuf's nucleus MNs in 12-month-old AR2 mice with those in age-matched wild-type mice. Although the number of MNs was not significantly lower in AR2 mice, the neurons exhibited a shrunken morphology and TDP-43 pathology. Onuf's nucleus MNs could survive in an ADAR2-deficient state and mainly included fast fatigue-resistant (FR) and slow (S) MNs. In summary, FR and S MNs show increased resilience to ADAR2 deficiency, potentially participating in an important neuronal death avoidance mechanism in ALS.

TDP-43 CSF Concentrations Increase Exponentially with Age in Metropolitan Mexico City Young Urbanites Highly Exposed to PM2.5 and Ultrafine Particles and Historically Showing Alzheimer and Parkinson's Hallmarks. Brain TDP-43 Pathology in MMC Residents Is Associated with High Cisternal CSF TDP-43 Concentrations

Environmental exposures to fine particulate matter (PM2.5) and ultrafine particle matter (UFPM) are associated with overlapping Alzheimer’s, Parkinson’s and TAR DNA-binding protein 43 (TDP-43) hallmark protein pathologies in young Metropolitan Mexico City (MMC) urbanites. We measured CSF concentrations of TDP-43 in 194 urban residents, including 92 MMC children aged 10.2 ± 4.7 y exposed to PM2.5 levels above the USEPA annual standard and to high UFPM and 26 low pollution controls (11.5 ± 4.4 y); 43 MMC adults (42.3 ± 15.9 y) and 14 low pollution adult controls (33.1 ± 12.0 y); and 19 amyotrophic lateral sclerosis (ALS) patients (52.4 ± 14.1 y). TDP-43 neuropathology and cisternal CSF data from 20 subjects—15 MMC (41.1 ± 18.9 y) and 5 low pollution controls (46 ± 16.01 y)—were included. CSF TDP-43 exponentially increased with age (p < 0.0001) and it was higher for MMC residents. TDP-43 cisternal CSF levels of 572 ± 208 pg/mL in 6/15 MMC autopsy cases forecasted TDP-43 in the olfactory bulb, medulla and pons, reticular formation and motor nuclei neurons. A 16 y old with TDP-43 cisternal levels of 1030 pg/mL exhibited TDP-43 pathology and all 15 MMC autopsy cases exhibited AD and PD hallmarks. Overlapping TDP-43, AD and PD pathologies start in childhood in urbanites with high exposures to PM2.5 and UFPM. Early, sustained exposures to PM air pollution represent a high risk for developing brains and MMC UFPM emissions sources ought to be clearly identified, regulated, monitored and controlled. Prevention of deadly neurologic diseases associated with air pollution ought to be a public health priority and preventive medicine is key.

Nuclear Pore Dysfunction in Neurodegeneration

The nuclear pore complex (NPC) is a large multimeric structure that is interspersed throughout the membrane of the nucleus and consists of at least 33 protein components. Individual components cooperate within the nuclear pore to facilitate selective passage of materials between the nucleus and cytoplasm while simultaneously performing pore-independent roles throughout the cell. NPC dysfunction is a hallmark of neurodegenerative disorders including Alzheimer's disease, Huntington's disease, and amyotrophic lateral sclerosis (ALS). NPC components can become mislocalized or altered in expression in neurodegeneration. These alterations in NPC structure are often detrimental to the neuronal function and ultimately lead to neuronal loss. This review highlights the importance of nucleocytoplasmic transport and NPC integrity and how dysfunction of such may contribute to neurodegeneration.