Genetic analysis of the cystatin C gene in familial and sporadic ALS patients

Filtered Cerebrospinal Fluid From Patients With Amyotrophic Lateral Sclerosis Displays an Altered Proteome and Affects Motor Phenotype in a Mouse Model

INTRODUCTION

Cerebrospinal fluid (CSF) has been implicated in amyotrophic lateral sclerosis (ALS) due to its ability to spread inflammatory proteins throughout the nervous system. We hypothesized that filtration of the CSF could remove pathogenic proteins and prevent them from altering motor phenotypes in a mouse model.

METHODS

We filtered the CSF from 11 ALS patients via 100 kilodaltons (kD) molecular weight cut-off filters. We used mass spectrometry-based discovery proteomics workflows to compare protein abundances before and after filtration. To test the effects of CSF filtration on motor function, we injected groups of mice with saline, filtered ALS-CSF, or unfiltered ALS-CSF (n=12 per group) and assessed motor function via pole descent and open field tests.

RESULTS

We identified proteins implicated in ALS pathogenesis and showed that these were removed in significant amounts in our workflow. Key filtered proteins included complement proteins, chitinases, serine protease inhibitors, and neuro-inflammatory proteins such as amyloid precursor protein, chromogranin A, and glial fibrillary acidic protein. Compared to the filtered ALS-CSF mice, unfiltered ALS-CSF mice took longer to descend a pole (10 days post-injection, 11.14 seconds vs 14.25 seconds, p = 0.02) and explored less on an open field (one day post-injection, 21.81 m vs 16.83 m, p = 0.0004).

CONCLUSIONS

We demonstrated the ability to filter proteins from the CSF of ALS patients and identified potentially pathologic proteins that were reduced in quantity. Additionally, we demonstrated the ability of unfiltered ALS-CSF to induce motor deficits in mice on the pole descent and open field tests and showed that filtration could prevent this deficit. Given the lack of effective treatments for ALS, this could be a novel solution for patients suffering from this deadly and irreversible condition.

Proteinopathies as Hallmarks of Impaired Gene Expression, Proteostasis and Mitochondrial Function in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal adult-onset neurodegenerative disease characterized by progressive degeneration of upper and lower motor neurons. As with the majority of neurodegenerative diseases, the pathological hallmarks of ALS involve proteinopathies which lead to the formation of various polyubiquitylated protein aggregates in neurons and glia. ALS is a highly heterogeneous disease, with both familial and sporadic forms arising from the convergence of multiple disease mechanisms, many of which remain elusive. There has been considerable research effort invested into exploring these disease mechanisms and in recent years dysregulation of RNA metabolism and mitochondrial function have emerged as of crucial importance to the onset and development of ALS proteinopathies. Widespread alterations of the RNA metabolism and post-translational processing of proteins lead to the disruption of multiple biological pathways. Abnormal mitochondrial structure, impaired ATP production, dysregulation of energy metabolism and calcium homeostasis as well as apoptosis have been implicated in the neurodegenerative process. Dysfunctional mitochondria further accumulate in ALS motor neurons and reflect a wider failure of cellular quality control systems, including mitophagy and other autophagic processes. Here, we review the evidence for RNA and mitochondrial dysfunction as some of the earliest critical pathophysiological events leading to the development of ALS proteinopathies, explore their relative pathological contributions and their points of convergence with other key disease mechanisms. This review will focus primarily on mutations in genes causing four major types of ALS (C9ORF72, SOD1, TARDBP/TDP-43, and FUS) and in protein homeostasis genes (SQSTM1, OPTN, VCP, and UBQLN2) as well as sporadic forms of the disease. Finally, we will look to the future of ALS research and how an improved understanding of central mechanisms underpinning proteinopathies might inform research directions and have implications for the development of novel therapeutic approaches.

A Japanese ALS6 family with mutation R521C in the FUS/TLS gene: a clinical, pathological and genetic report

Here we report a Japanese family with amyotrophic lateral sclerosis (ALS) characterized by very rapid progression, high penetrance and an autosomal dominant mode of inheritance. The phenotype includes atrophy of sternocleidomastoideus muscles, bulbar involvement, weakness of neck muscles and proximal muscle atrophy. These clinical symptoms are reminiscent of myopathy. All patients examined had similar clinical symptoms, age at onset and disease duration. The proband was found to have mutation R521C in the FUS/TLS gene, and was diagnosed as having ALS6. Autopsy material was available from the mother of the proband and FUS-immunoreactive neuronal and glial cytoplasmic inclusions were observed in the anterior horn of the spinal cord. While atrophy and weakness of the sternocleidomastoideus muscle is not emphasized in previous reports, this symptom may be a clinical hallmark of ALS6.

Non-cell-autonomous effect of human SOD1 G37R astrocytes on motor neurons derived from human embryonic stem cells

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by motor neuron death. ALS can be induced by mutations in the superoxide dismutase 1 gene (SOD1). Evidence for the non-cell-autonomous nature of ALS emerged from the observation that wild-type glial cells extended the survival of SOD1 mutant motor neurons in chimeric mice. To uncover the contribution of astrocytes to human motor neuron degeneration, we cocultured hESC-derived motor neurons with human primary astrocytes expressing mutated SOD1. We detected a selective motor neuron toxicity that was correlated with increased inflammatory response in SOD1-mutated astrocytes. Furthermore, we present evidence that astrocytes can activate NOX2 to produce superoxide and that effect can be reversed by antioxidants. We show that NOX2 inhibitor, apocynin, can prevent the loss of motor neurons caused by SOD1-mutated astrocytes. These results provide an assay for drug screening using a human ALS in vitro astrocyte-based cell model.

Characteristics associated with participation in DNA banking: The National Registry of Veterans with ALS

OBJECTIVE

Characteristics that may influence participation in DNA banks are not well defined. The purpose of this study was to examine characteristics associated with participation in a DNA bank among veterans diagnosed with Amyotrophic Lateral Sclerosis (ALS).

METHODS

Veterans who screened eligible for the National Registry of Veterans with ALS were initially contacted about the DNA Bank via telephone and then mailed a consent form. Registry participants were then categorized as consented for the DNA bank, actively refused, or passively refused (consent form not returned after >3 months and multiple reminders). The associations of consent status with age, gender, race, military branch, years of military service, VA health system use, and ALS Functional Rating Scale (ALSFRS) scores were examined.

RESULTS

Registry participants (N=1020) were 98% male, 9.5% non-white, and the mean age was 64.1 years. 61.1% of participants were current VA health system users, and the branches of service were: Army (46.1%), Navy (22.1%), Air Force (23.2%), and Marines (8.3%). A total of 14.7% of Registry participants refused DNA banking (9.4% active refusal, 5.3% passive refusal). Results from multivariable models indicated participants who were non-White, VA users, or had lower ALSFRS scores (reflecting poorer function) had higher odds of refusal. Race and VA use were associated with active refusal, while age and ALSFRS score were associated with passive refusal.

CONCLUSION

Although the overall refusal rate for DNA banking was relatively low, we still found important differences in consent by race, VA use, and functional status in this cohort of veterans with ALS. Because differential participation in DNA banking may influence generalizability, further efforts are needed to understand and intervene to reduce these differences.

Altered distribution and levels of cathepsinD and cystatins in amyotrophic lateral sclerosis transgenic mice: Possible roles in motor neuron survival

In amyotrophic lateral sclerosis (ALS) there is a selective degeneration of motor neurons leading to muscle paralysis and death. The mechanism underlying cell demise in ALS is not fully understood, but involves the activation of different proteolytic enzymes, including the caspase family of cysteine proteases. We have here studied whether other proteases, such as the cathepsins, residing in lysosomes, and the cathepsin inhibitors, cystatinB and -C are changed in ALS. The expression and protein levels of the cathepsinB, -L and -D all increased in the spinal cord in ALS mice, carrying the mutant copper/zinc superoxide dismutase (SOD1) gene. At the cellular level, cathepsinB and -L were present in ventral motor neurons in controls, but in the ALS mice cathepsinB was also expressed by glial fibrillary acidic protein (GFAP) positive astrocytes. The distribution of the aspartic protease, cathepsinD also changed in ALS with a loss of the lysosomal staining in motor neurons. Inhibition of caspases by means of X-chromosome-linked inhibitor of apoptosis protein (XIAP) overexpression did not inhibit cleavage of cathepsinD in ALS mice, suggesting a caspase-independent pathway. Expression of cystatinB and -C increased slightly in the ALS spinal cords. Immunostaining showed that in ALS, cystatinC was present in motor neurons and in GFAP positive astrocytes. CystatinB that is a neuroprotective factor decreased in motor neurons in ALS but was expressed by activated microglial cells. The observed changes in the levels and distributions of cathepsinD and cystatinB and-C indicate a role of these proteins in the degeneration of motor neurons in ALS.