Many cell lines commonly used for biological studies have been found to harbor exogenous agents such as the human tumor viruses Epstein-Barr virus (EBV) and human papillomavirus. Nevertheless, broad-based, unbiased approaches to globally assess the presence of ectopic organisms within cell model systems have not previously been available. We reasoned that high-throughput sequencing should provide unparalleled insights into the microbiomes of tissue culture cell systems. Here we have used our RNA-seq analysis pipeline, PARSES (Pipeline for Analysis of RNA-Seq Exogenous Sequences), to investigate the presence of ectopic organisms within two EBV-positive B-cell lines commonly used by EBV researchers. Sequencing data sets from both the Akata and JY B-cell lines were found to contain reads for EBV, and the JY data set was found to also contain reads from the murine leukemia virus (MuLV). Further investigation revealed that MuLV transcription in JY cells is highly active. We also identified a number of MuLV alternative splicing events, and we uncovered evidence of APOBEC3G (apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G)-dependent DNA editing. Finally, reverse transcription-PCR analysis showed the presence of MuLV in three other human B-cell lines (DG75, Ramos, and P3HR1 Cl.13) commonly used by investigators in the Epstein-Barr virus field. We believe that a thorough examination of tissue culture microbiomes using RNA-seq/PARSES-like approaches is critical for the appropriate utilization of these systems in biological studies.

SUMMARY

Homeostatic synaptic plasticity is important for maintaining stability of neuronal function, but heterogeneous expression mechanisms suggest that distinct facets of neuronal activity may shape the manner in which compensatory synaptic changes are implemented. Here, we demonstrate that local presynaptic activity gates a retrograde form of homeostatic plasticity induced by blockade of AMPA receptors (AMPARs) in cultured hippocampal neurons. We show that AMPAR blockade produces rapid (< 3 hrs) protein synthesis-dependent increases in both presynaptic and postsynaptic function, and that the induction of presynaptic, but not postsynaptic, changes requires coincident local activity in presynaptic terminals. This “state-dependent” modulation of presynaptic function requires postsynaptic release of brain-derived neurotrophic factor (BDNF) as a retrograde messenger, which is locally synthesized in dendrites in response to AMPAR blockade. Taken together, our results reveal a local cross-talk between active presynaptic terminals and postsynaptic signaling that dictates the manner by which homeostatic plasticity is implemented at synapses.

Respiratory muscle involvement is a recognised, but often late, complication of amyotrophic lateral sclerosis (ALS). The clinical features and prognosis of 21 patients with respiratory onset ALS are reported here. On a retrospective chart review, it was found that 2.7% of patients with ALS presenting to a tertiary care specialty clinic have respiratory symptoms as their first clinical symptom of ALS. Only 14% of these individuals presented acutely and required emergency intubation. The mean survival time of the total group from symptom onset to death or permanent ventilation was 27.0 (14.9) months, which was not significantly different from the survival time in patients with bulbar onset ALS. Non‐invasive positive pressure ventilation (NIPPV) significantly improved survival compared with those who did not use NIPPV. This study suggests that ALS with respiratory onset does not necessarily follow a rapidly progressive course.

OBJECTIVE

To discuss the epidemiology, pathogenesis, diagnosis, expected course, prognosis, and treatment of amyotrophic lateral sclerosis (ALS), a degenerative disorder of the nervous system associated with progressive weakness.

QUALITY OF EVIDENCE

PubMed and the Cochrane Database of Systematic Reviews were searched using the MeSH headings “amyotrophic lateral sclerosis,” “therapy,” “epidemiology,” and “etiology.” Articles containing the best available evidence were reviewed. Most provided level II and III evidence. There were some level I drug trials.

MAIN MESSAGE

Amyotrophic lateral sclerosis is associated with progressive dysarthria, dysphagia, and weakness in the extremities. Diagnosis is based on physical examination, electrophysiology, and excluding other confounding conditions. There is no cure for this devastating disorder. Certain treatments, however, can improve survival and quality of life.

CONCLUSION

Because ALS is a complex disease, care of ALS patients is best provided at multidisciplinary clinics that specialize in managing patients with this disorder.

Expanded glutamine repeats of the ataxin-2 (ATXN2) protein cause spinocerebellar ataxia type 2 (SCA2), a rare neurodegenerative disorder. More recent studies have suggested that expanded ATXN2 repeats are a genetic risk factor for amyotrophic lateral sclerosis (ALS) via an RNA-dependent interaction with TDP-43. Given the phenotypic diversity observed in SCA2 patients, we set out to determine the polymorphic nature of the ATXN2 repeat length across a spectrum of neurodegenerative disorders. In this study, we genotyped the ATXN2 repeat in 3919 neurodegenerative disease patients and 4877 healthy controls and performed logistic regression analysis to determine the association of repeat length with the risk of disease. We confirmed the presence of a significantly higher number of expanded ATXN2 repeat carriers in ALS patients compared with healthy controls (OR = 5.57; P= 0.001; repeat length >30 units). Furthermore, we observed significant association of expanded ATXN2 repeats with the development of progressive supranuclear palsy (OR = 5.83; P= 0.004; repeat length >30 units). Although expanded repeat carriers were also identified in frontotemporal lobar degeneration, Alzheimer's and Parkinson's disease patients, these were not significantly more frequent than in controls. Of note, our study identified a number of healthy control individuals who harbor expanded repeat alleles (31–33 units), which suggests caution should be taken when attributing specific disease phenotypes to these repeat lengths. In conclusion, our findings confirm the role of ATXN2 as an important risk factor for ALS and support the hypothesis that expanded ATXN2 repeats may predispose to other neurodegenerative diseases, including progressive supranuclear palsy.

Background

Middle cerebral artery occlusion (MCAo) in mice results in a brain infarct, the volume of which depends on the length of occlusion. Following permanent occlusion, neuropathological changes – including a robust glial inflammatory response – also occur downstream of the infarct in the spinal cord.

Methods

We have performed short, transient MCAo in mice to induce penumbral damage spanning the motor cortex. A 30 minute MCAo using a poly-L-lysine-coated intraluminal suture introduced through a common carotid artery incision was performed in 17 female C57BL/6 mice. Five sham-operated mice received common carotid artery ligation without insertion of the suture. Neurobehavioural assessments were performed during occlusion, immediately following reperfusion, and at 24 and 72 hours post-reperfusion. Routine histological and immunohistochemical studies were performed at 24 and 72 hours.

Results

In 11 of the surviving 16 mice subjected to MCAo, we observed a focal, subcortical necrotic lesion and a reproducible, diffuse cortical lesion with accompanying upper motor neuron involvement. This was associated with contralateral ventral spinal cord microglial priming without significant reactive astrocytosis or lower motor neuron degeneration.

Conclusion

The advantages to this method are that it yields a reproducible cortical lesion, the extent of which is predictable using behavioural testing during the period of ischemia, with upper motor neuron involvement and downstream priming, but not full activation, of microglia in the lumbar spinal cord. In addition, survival is excellent following the 30 minutes of occlusion, rendering this a novel and useful model for examining the effects of microglial priming in the spinal motor neuron pool.

Under normal conditions, the proline-directed serine/threonine residues of neurofilament tail-domain repeats are exclusively phosphorylated in axons. In pathological conditions such as amyotrophic lateral sclerosis (ALS), motor neurons contain abnormal perikaryal accumulations of phosphorylated neurofilament proteins. The precise mechanisms for this compartment-specific phosphorylation of neurofilaments are not completely understood. Although localization of kinases and phosphatases is certainly implicated, another possibility involves Pin1 modulation of phosphorylation of the proline-directed serine/threonine residues. Pin1, a prolyl isomerase, selectively binds to phosphorylated proline-directed serine/threonine residues in target proteins and isomerizes cis isomers to more stable trans configurations. In this study we show that Pin1 associates with phosphorylated neurofilament-H (p-NF-H) in neurons and is colocalized in ALS-affected spinal cord neuronal inclusions. To mimic the pathology of neurodegeneration, we studied glutamate-stressed neurons that displayed increased p-NF-H in perikaryal accumulations that colocalized with Pin1 and led to cell death. Both effects were reduced upon inhibition of Pin1 activity by the use of an inhibitor juglone and down-regulating Pin1 levels through the use of Pin1 small interfering RNA. Thus, isomerization of lys-ser-pro repeat residues that are abundant in NF-H tail domains by Pin1 can regulate NF-H phosphorylation, which suggests that Pin1 inhibition may be an attractive therapeutic target to reduce pathological accumulations of p-NF-H.

Peripherin, a neuronal intermediate filament (nIF) protein found associated with pathological aggregates in motor neurons of patients with amyotrophic lateral sclerosis (ALS) and of transgenic mice overexpressing mutant superoxide dismutase-1 (SOD1G37R), induces the selective degeneration of motor neurons when overexpressed in transgenic mice. Mouse peripherin is unique compared with other nIF proteins in that three peripherin isoforms are generated by alternative splicing. Here, the properties of the peripherin splice variants Per 58, Per 56, and Per 61 have been investigated in transfected cell lines, in primary motor neurons, and in transgenic mice overexpressing peripherin or overexpressing SOD1G37R. Of the three isoforms, Per 61 proved to be distinctly neurotoxic, being assembly incompetent and inducing degeneration of motor neurons in culture. Using isoform-specific antibodies, Per 61 expression was detected in motor neurons of SOD1G37R transgenic mice but not of control or peripherin transgenic mice. The Per 61 antibody also selectively labeled motor neurons and axonal spheroids in two cases of familial ALS and immunoprecipitated a higher molecular mass peripherin species from disease tissue. This evidence suggests that expression of neurotoxic splice variants of peripherin may contribute to the neurodegenerative mechanism in ALS.

Background

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal motor neuron disease, and protein aggregation has been proposed as a possible pathogenetic mechanism. However, the aggregate protein constituents are poorly characterized so knowledge on the role of aggregation in pathogenesis is limited.

Methodology/Principal Findings

We carried out a proteomic analysis of the protein composition of the insoluble fraction, as a model of protein aggregates, from familial ALS (fALS) mouse model at different disease stages. We identified several proteins enriched in the detergent-insoluble fraction already at a preclinical stage, including intermediate filaments, chaperones and mitochondrial proteins. Aconitase, HSC70 and cyclophilin A were also significantly enriched in the insoluble fraction of spinal cords of ALS patients. Moreover, we found that the majority of proteins in mice and HSP90 in patients were tyrosine-nitrated. We therefore investigated the role of nitrative stress in aggregate formation in fALS-like murine motor neuron-neuroblastoma (NSC-34) cell lines. By inhibiting nitric oxide synthesis the amount of insoluble proteins, particularly aconitase, HSC70, cyclophilin A and SOD1 can be substantially reduced.

Conclusion/Significance

Analysis of the insoluble fractions from cellular/mouse models and human tissues revealed novel aggregation-prone proteins and suggests that nitrative stress contribute to protein aggregate formation in ALS.