In a phase 1–2 dose-escalation trial involving adults with ALS due to SOD1 mutations who received intrathecal tofersen (an antisense oligonucleotide) or placebo, the levels of mutant SOD1 in the CSF were 33 percentage points lower in the highest-dose tofersen group than in the placebo group.
In this manuscript, we detail the creation and possible uses of a new website that illustrates microRNA expression by cell type in the central nervous system. Similar databases for protein-coding genes have achieved widespread use, however no comparable tool for microRNA expression existed before this. We believe this new resource will serve as a valuable tool for researchers moving forward in microRNA research and enable the generation of previously unexplored hypotheses. This work was a collaboration between our group and the lab of Dr. Joseph Dougherty in the Departments of Genetics and Psychiatry at Washington University.
In this manuscript, we describe the development of a new tool called “AAV calling cards” for measuring enhancer and transcription factor (TF)-mediated regulation in the mouse brain. It offers novel advantages over other methodologies, including the ability to probe epigenetic profiles in specific, targeted cellular populations and to record and integrate transient TF binding events over time. AAV calling cards will now enable unique studies in the areas of neurodevelopment and neurodegeneration. This work was a collaboration between our group and two labs in the Department of Genetics at Washington University, those of Dr. Robi Mitra and Dr. Joseph Dougherty.
Mutations in superoxide dismutase 1 (SOD1) are responsible for 20% of familial ALS. Given the gain of toxic function in this dominantly inherited disease, lowering SOD1 mRNA and protein is predicted to provide therapeutic benefit. We have developed next-generation SOD1 ASOs that more potently reduce SOD1 mRNA and protein and extend survival in SOD1G93A mice. These results define a highly potent, new SOD1 ASO ready for human clinical trial and suggest that at least some components of muscle response can be reversed by therapy.
We recently demonstrated that microRNA-218 (miR-218) is greatly enriched in motor neurons and is released extracellularly in amyotrophic lateral sclerosis model rats. To determine if the released, motor neuron-derived miR-218 may have a functional role in amyotrophic lateral sclerosis, we examined the effect of miR-218 on neighbouring astrocytes. Surprisingly, we found that extracellular, motor neuron-derived miR-218 can be taken up by astrocytes and is sufficient to downregulate an important glutamate transporter in astrocytes [excitatory amino acid transporter 2 (EAAT2)]. The effect of miR-218 on astrocytes extends beyond EAAT2 since miR-218 binding sites are enriched in mRNAs translationally downregulated in amyotrophic lateral sclerosis astrocytes. Inhibiting miR-218 with antisense oligonucleotides in amyotrophic lateral sclerosis model mice mitigates the loss of EAAT2 and other miR-218-mediated changes, providing an important in vivo demonstration of the relevance of microRNA-mediated communication between neurons and astrocytes. These data define a novel mechanism in neurodegeneration whereby microRNAs derived from dying neurons can directly modify the glial phenotype and cause astrocyte dysfunction.
Multiple neurodegenerative diseases are characterized by single-protein dysfunction and aggregation. Antisense oligonucleotides (ASOs) are small sequences of DNA able to target RNA transcripts, resulting in reduced or modified protein expression. ASOs hold considerable promise for neurodegenerative disease therapies as evidenced by SMA and ALS human clinical trial successes, and preclinical efforts in other CNS disorders continue to progress.
Motor neurons are the cell type that is selectively lost in ALS. To develop tools to understand and monitor ALS disease progression, Mariah Hoye of Dr. Miller’s group identified factors that were specifically expressed in motor neurons only. These factors, called microRNAs (or miRNAs), may help researchers understand why motor neurons, and not other cell types, are selectively lost in ALS. One of the motor neuron enriched miRNAs was detected in spinal tap biofluid from an ALS rat model and its levels changed as disease progressed. These data suggest that miR-218 could be a clinically useful marker of disease status. Furthermore, Hoye found that rats treated with an ALS therapy had restored levels of the motor neuron marker, suggesting that miR-218 is a motor neuron specific and drug responsive marker for ALS rodents.
Aggregates of a protein called “tau” are one of the factors involved in causing Alzheimer’s disease and other dementias. In this manuscript, Dr. Miller and colleagues show that lowering levels of tau protein prevented loss of neurons and reversed previous build up of tau protein in mouse models of Alzheimer’s disease. Additionally, using the same tau lowering strategy, researchers saw similar results when the drug was given to non-human primates. This study was the first to show that markers of neurodegeneration that accumulate in Alzheimer’s disease may ractually be reversed by treatment with antisense oligonucleotides.
Tau protein has been implicated in many neurodegenerative disorders, such as Alzheimer’s disease. These disorders all have different brain regions, progression rates, and protein aggregation patterns that are affected by differences in tau protein. This article aimed to expand upon previous work and determine the relationship between tau protein strains and the characteristics of various neurodegenerative disorders. The authors found that different strains of tau protein were sufficient to account for the different neuropathological presentations of disease in mouse models. The authors conclude that further study of the strains and their effects could establish an increased understanding of human tauopathies.
Natural history data is often used to help researchers understand disease characteristics and can be especially beneficial when considering how to design therapeutic clinical trials for a disease. In this manuscript, Dr. Miller’s group examined the natural history of ALS patients with mutations in the SOD1 gene in an attempt to provide updated information from a previous study that dated back to 1997. 15 medical centers contributed data from more than 175 ALS-SOD1 patients, and various disease measures such as age of onset were examined. The researchers concluded that the updated data was primarily unchanged from the previous study, showing support for the use of ALS natural history data in the design and implementation of clinical trials in the ALS-SOD1 patient population.
Aggregates of a protein called “tau” are one of the factors involved in causing Alzheimer’s disease and other dementias. However, the tau protein has several different forms and it was not known which form of the protein was more detrimental and thus which form could be targeted for therapy in Alzheimer’s disease. In this manuscript, Dr. Kathleen Schoch of Dr. Miller’s group demonstrated, for the first time, that the “4R” form of tau was more toxic in mouse models of Alzheimer’s disease. Additionally, she showed that 4R tau could be effectively reduced in mice, indicating that a similar approach to lowering toxic 4R tau could be used to treat Alzheimer’s disease and other tauopathies in future studies
Changes in the C9orf72 gene account for about 30% of familial ALS and 5-10% of sporadic ALS. The “orf” part of the gene name stands for “open reading frame,” which in genetic terms means we know that this is an important part of the genome, but the function of the gene is unclear. One way to determine the importance of an unknown gene region is to delete that region in mice and determine how this affects the mouse model. Dr. Miller’s collaborators at Cedars Sinai Medical Center in Los Angeles, led by Dr. Robert Baloh, took this approach. Somewhat surprisingly, they found that loss of this gene region led to changes in cells of the immune system, thus refocusing ALS researchers on what these immune system related cells might be doing in ALS. Dr. Baloh and colleagues recognized the importance of linking these new findings to humans with the disease and subsequently used spinal cord samples donated from ALS patients at Washington University in St. Louis. Strikingly, these human samples showed some changes similar to the mouse models and thus helped demonstrate the relevance of the mouse studies to humans.
Understanding risk and prognostic factors for diseases can help researchers understand the disease better and develop therapeutics more effectively. This study attempted to determine whether a history of pre-morbid type 2 diabetes mellitus (DM2) is a prognostic factor in ALS. Dr. Miller and colleagues examined the relationship between DM2 and survival in a population of 1,322 participants from 6 clinical trials and found that survival did not differ depending on whether or not the patients had DM2. However, it was discovered that survival did differ depending on the patient’s BMI. The researchers concluded that a history of pre-morbid DM2 is not an independent prognostic factor in ALS.
Mutations in the SOD1 gene are known to cause some forms of familial ALS. Researchers are developing a treatment to reduce the level of SOD1 in familial ALS, but it is essential to understand how long SOD1 stays in the body to determine if the new treatment is effective in reducing SOD1. This manuscript aimed to determine the half-life of the protein in the cerebral spinal fluid using a new mass spectrometry technique called silk-isotope labeling kinetics (SILK). Researchers found that in rat models of ALS, SOD1 is a long-lived protein with a similar half-life in the cerebral spinal fluid and in the central nervous system. When applied to human participants, the SILK method worked successfully and confirmed the long half-life of SOD1. This study provided important insights into the kinetics of SOD1 and will help to develop future interventions for ALS.
In this review, Dr. Miller and his colleague, Dr. Linga Reddy, examined new RNA-targeted therapeutic approaches for the treatment of ALS. Several of these RNA-targeted approaches include small-interfering RNA (siRNA) and antisense oligonucleotide (ASO) strategies that work by inhibiting levels of toxic proteins in ALS. They concluded that ALS provides a unique opportunity for the use of these RNA inhibition strategies because animal models of ALS are well-defined, extensive information is available regarding the genetics of ALS, and recent clinical trials for ALS employed ASO therapeutics with success.
Aggregates of a protein called “tau” cause disease in tauopathies such as Alzheimer’s disease. In this manuscript, Dr. Miller and colleagues aimed to characterize the properties of tau, such as the protein’s structure, and determine whether different strains of tau might correspond to different tauopathies in humans. The researchers used a cell system to isolate tau strains from 29 patients with 5 different tauopathies and found that different diseases are associated with different sets of strains. This information will help investigators understand the properties of the tau strains in order to make more accurate diagnoses in the clinic and ultimately therapies for the treatment of these diseases.
In Alzheimer’s disease and other neurodegenerative diseases, it was recently discovered that a variant (p.R47H) in the TREM2 gene increases the risk of contracting these diseases. However, it was not known whether the TREM2 variant also increases the risk of developing ALS. Dr. Miller and colleagues examined DNA from 923 individuals with singleton ALS and 1854 healthy control individuals from ALS clinics in the United States and tested the DNA for the p.R47H TREM2 variant. They found that the TREM2 variant is indeed a risk factor for ALS, thus identifying the TREM2 signaling pathway as a therapeutic target for ALS.
MicroRNAs are small molecules located throughout the body that can regulate various processes inside cells. For this reason, they are being investigated as potential therapeutic targets in a variety of diseases. In this manuscript, Dr. Miller’s group identified microRNAs that were changed in a rat model of ALS compared to normal rats. Six of these microRNAs were also found to be changed in human ALS tissues. The researchers then developed antisense oligonucleotide (ASO) inhibitors of the microRNA in order to test whether decreasing levels of one of the microRNAs, miR-155, would be beneficial in the ALS model. It was discovered that the ASO drug inhibited miR-155 across the brain and caused an increase in survival by 10 days and disease duration by 15 days (38%) versus control animals. This study provided support for the use of ASOs to successfully inhibit microRNAs throughout the brain and spinal cord as a way to treat ALS.
Canine degenerative myelopathy is a disabling neurodegenerative disorder affecting specific breeds of dogs characterized by progressive loss of motor neurons and paralysis until death. This disease is the first and only naturally occurring non-human model of ALS. Researchers wanted to understand the role of canine SOD1 protein in this disease and compare it to the toxic role of human SOD1 protein in ALS in order to understand the parallels between both disorders. The investigators were able to establish close parallels for the role the SOD1 mutant protein plays in both canine and human disorders.
The progression of many neurodegenerative diseases is often driven by aggregated proteins that form clumps and then interact with other proteins, which causes them to become aggregated as well in a feed-forward cycle. However, the actual mechanism by which aggregated proteins, such as tau and alpha-synuclein, interact with and trigger other proteins is unknown. In this manuscript, researchers investigated a cell surface molecule called heparan sulface proteoglycans (HSPGs) and found that HSPGs facilitate the spreading of tau aggregates as well as alpha-synuclein proteins. This work demonstrated a common mechanism of propagation for tauopathy and synucleinopathy, which could then potentially be targeted as a therapeutic strategy in future studies of these neurodegenerative diseases.
Tau is a protein that forms aggregates in Alzheimer’s disease and causes hyperexcitability in neurons, which contributes to disease progression. Previous studies have shown that genetic deletion of tau substantially reduces hyperexicitability in various mouse models of Alzheimer’s disease, induced seizure models, and genetic models of epilepsy. However, researchers in Dr. Miller’s lab wanted to test a more translatable method of tau reduction in adult animals in order to determine whether this strategy could be applied to human patients. They found that antisense oligonucleotide (ASO)-mediated tau reduction decreased tau expression throughout the mouse central nervous system and caused less severe seizures compared to control mice. These results demonstrate that tau reducing ASOs could benefit those with epilepsy and potentially other disorders associated with tau-mediated neuronal hyperexcitability.
In this review, Dr. Sarah DeVos and Dr. Miller examine new antisense oligonucleotide therapeutic strategies to treat various neurodegenerative diseases. Antisense oligonucleotides are molecules that can be relatively easily modified to target the RNA of a disease-associated gene and consequently reduce or increase levels of the disease-associated protein. Application to mouse models of neurodegenerative diseases has shown the ability of ASOs to rescue disease-associated phenotypes in vivo. These preclinical animal data have prompted the translation of ASOs from bench to clinic, and multiple human clinical trials of ASOs are now underway. The researchers conclude that although ASO technology is still somewhat early in development, translating ASOs into human patients for neurodegeneration appears promising.
Dr. Sarah DeVos and Dr. Timothy Miller demonstrate two methods that are commonly used to deliver antisense oligonucleotide drugs to the central nervous system of mouse models.
Dr. Miller and colleagues present the results of the first-in-man Phase I clinical trial of antisense oligonucleotides (ASOs) targeted to SOD1 in familial ALS patients in this publication. Mutations in the gene SOD1 cause approximately 13% of genetically inherited ALS. ASOs targeting SOD1 prolonged survival in preclinical animal studies. The goal of this clinical trial was to assess the safety, tolerability, and pharmacokinetics of an SOD1 ASO (ISIS 333611) after intrathecal administration in patients with SOD1 related ALS. No dose-limiting toxic effects or any safety or tolerability concerns related to ISIS 333611 were noted and no serious adverse events occurred in patients given the drug. This was the first clinical study of intrathecal delivery of an ASO, and the researchers concluded that ISIS 333611 was well-tolerated when administered as an intrathecal infusion. Additional clinical trials are now underway.
Therapies designed to lower levels of the toxic SOD1 protein in ALS patients are currently in clinical trials. However, there must be a method in place to assess the effectiveness of these therapies; thus, researchers must establish a way to make sure SOD1 protein levels are decreasing in the central nervous system. In this manuscript, investigators attempted to understand whether SOD1 protein levels in the cerebral spinal fluid (CSF), which bathes the brain and spinal cord, may be a good proxy for levels of SOD1 in the CNS. They found that CSF levels of SOD1 were very similar to CNS SOD1 levels and concluded that SOD1 protein in the CSF will be an excellent pharmacodynamics marker for future SOD1-lowering therapies such as antisense oligonucleotides.
Mutations in the SOD1 gene cause about one-fifth of familial ALS. There are many proposed mechanisms for how the mutant protein becomes toxic to neurons, and mitochondrial dysfunction is one of these potential mechanisms since mutant SOD1 has been found to associate with mitochondria in rodent models of SOD1 mutant-mediated disease. In this manuscript, researchers investigated how mutant SOD1 affects the protein content of spinal cord mitochondrial before disease initiation in rodent models that develop ALS-like disease. They determine that altered mitochondiral protein content accompanied by selective decreases in protein import into spinal cord mitochondria comprises part of the mitochondrial damage arising from mutant SOD1. These data are important for understanding ALS disease mechanisms and whether the disease-causing pathways can be targeted for therapies.
In this manuscript, a large family with ALS caused by a I113T mutation in the SOD1 gene is examined. Although this one mutation is passed down through many family members, the age of onset, clinical characteristics, disease progression, and penetrance of the mutation was extremely variable. For instance, some family members developed ALS at age 39, while others were asymptomatic at age 86 and showed no signs of disease. These types of studies are important for understanding how specific genetic mutations can affect families, especially when existing literature about a particular mutation is not detailed and comprehensive enough.
Wegorzewska I, Bell S, Cairns NJ, Miller TM, Baloh RH. TDP-43 mutant transgenic mice develop features of ALS and frontotemporal lobar degeneration. Proc Natl Acad Sci U S A 2009;106(44):18809-18814. PMID: 19833869.
Miller TM, Smith RA, Kordasiewicz H, Kaspar BK. Gene-targeted therapies for the central nervous system. Arch Neurol 2008;65(4):447-451. PMID: 18268183.
Vande Velde C, Miller TM, Cashman NR, Cleveland DW. Selective association of misfolded ALS-linked mutant SOD1 with the cytoplasmic face of mitochondria. Proc Natl Acad Sci U S A 2008;105(10):4022-4027. PMID: 18296640.
Bailey AO, Miller TM, Dong MQ, Vande Velde C, Cleveland DW, Yates JR. RCADiA: simple automation platform for comparative multidimensional protein identification technology. Anal Chem 2007;79(16):6410-6418. PMID: 17616168.
Miller TM, Kim SH, Yamanaka K, Hester M, Umapathi P, Arnson H, Rizo L, Mendell JR, Gage FH, Cleveland DW, Kaspar BK. Gene transfer demonstrates that muscle is not a primary target for non-cell-autonomous toxicity in familial amyotrophic lateral sclerosis. Proc Natl Acad Sci U S A 2006;103(51):19546-19551. PMID: 17164329.
Miller TM, Smith RA, Cleveland DW. Amyotrophic lateral sclerosis and gene therapy. Nat Clin Pract Neurol 2006;2(9):462-463. PMID: 16932606.
Smith RA, Miller TM, Yamanaka K, Monia BP, Condon TP, Hung G, Lobsiger CS, Ward CM, McAlonis-Downes M, Wei H, Wancewicz EV, Bennett CF, Cleveland DW. Antisense oligonucleotide therapy for neurodegenerative disease. J Clin Invest 2006;116(8):2290-2296. PMID: 16878173.
Yamanaka K, Miller TM, McAlonis-Downes M, Chun SJ, Cleveland DW. Progressive spinal axonal degeneration and slowness in ALS2-deficient mice. Ann Neurol 2006;60(1):95-104. PMID: 16802286.
Miller TM, Johnston SC. Should the Babinski sign be part of the routine neurologic examination? Neurology 2005;65(8):1165-1168. PMID: 16247040.
Miller TM, Layzer Rb. Muscle Cramps. Muscle Nerve 2005;32:431-442. PMID: 15902691.
Miller TM, Kaspar BK, Kops GJ, Yamanaka K, Christian LJ, Gage FH, Cleveland DW. Virus-delivered small RNA silencing sustains strength in amyotrophic lateral sclerosis. Ann Neurol 2005;57(5):773-776. PMID: 15852369.
Miller TM, Cleveland DW. Medicine. Treating neurodegenerative diseases with antibiotics. Science 2005;307(5708):361-362. PMID: 15661995.
Miller TM, Dias da Silva MR, Miller HA, Kwiecinski H, Mendell JR, Tawil R, McManis P, Griggs RC, Angelini C, Servidei S, Petajan J, Dalakas MC, Ranum LP, Fu YH, Ptacek LJ. Correlating phenotype and genotype in the periodic paralyses. Neurology 2004;63(9):1647-1655. PMID: 15534250.
Liu J, Lillo C, Jonsson PA, Vande Velde C, Ward CM, Miller TM, Subramaniam JR, Rothstein JD, Marklund S, Andersen PM, Brannstrom T, Gredal O, Wong PC, Williams DS, Cleveland DW. Toxicity of familial ALS-linked SOD1 mutants from selective recruitment to spinal mitochondria. Neuron 2004;43(1):5-17. PMID: 15233913.
Miller TM, Kogelnik AM, Olney RK. Proposed modification to data analysis for statistical motor unit number estimate. Muscle Nerve 2004;29(5):700-706. PMID: 15116374.
Bruijn LI, Miller TM, Cleveland DW. Unraveling the Mechanisms Involved in Motor Neuron Degeneration in ALS. Annu Rev Neurosci 2004;27:723-749. PMID: 15217349.
Miller TM, Cleveland DW. Has gene therapy for ALS arrived? Nat Med 2003;9(10):1256-1257. PMID: 14520369.
2002 and previous years
Miller TM, Moulder KL, Knudson CM, Creedon DJ, Deshmukh M, Korsmeyer SJ, Johnson EM, Jr. Bax deletion further orders the cell death pathway in cerebellar granule cells and suggests a caspase-independent pathway to cell death. J Cell Biol 1997;139(1):205-217. PMID: 9314540.
Miller TM, Tansey MG, Johnson EM, Jr., Creedon DJ. Inhibition of phosphatidylinositol 3-kinase activity blocks depolarization- and insulin-like growth factor I-mediated survival of cerebellar granule cells. J Biol Chem 1997;272(15):9847-9853. PMID: 9092520.
Miller TM, Johnson EM, Jr. Metabolic and genetic analyses of apoptosis in potassium/serum-deprived rat cerebellar granule cells. J Neurosci 1996;16(23):7487-7495. PMID: 8922404.
Hug C, Miller TM, Torres MA, Casella JF, Cooper JA. Identification and characterization of an actin-binding site of CapZ. J Cell Biol 1992;116(4):923-931. PMID: 1370838.