Amyotrophic lateral sclerosis (ALS) is a rapidly fatal disease for which there is currently no effective therapy. The present review describes the current progress of existing molecular therapies in ...the clinical trial pipeline and highlights promising future antisense oligonucleotide (ASO) and viral therapeutic strategies for treating ALS.
The immense progress in the design of clinical trials and generation of ASO therapies directed towards superoxide dismutase-1 (SOD1) and chromosome 9 open reading frame 72 (C9orf72) repeat expansion related disease have been propelled by fundamental work to identify the genetic underpinnings of familial ALS and develop relevant disease models. Preclinical studies have also identified promising targets for sporadic ALS (sALS). Moreover, encouraging results in adeno-associated virus (AAV)-based therapies for spinal muscular atrophy (SMA) provide a roadmap for continued improvement in delivery and design of molecular therapies for ALS.
Advances in preclinical and clinical studies of ASO and viral directed approaches to neuromuscular disease, particularly ALS, indicate that these approaches have high specificity and are relatively well tolerated.
In a forward screen for genes affecting neurotransmission in
Drosophila, we identified mutations in
dynamin-related protein (
drp1). DRP1 is required for proper cellular distribution of mitochondria, ...and in mutant neurons, mitochondria are largely absent from synapses, thus providing a genetic tool to assess the role of mitochondria at synapses. Although resting Ca
2+ is elevated at
drp1 NMJs, basal synaptic properties are barely affected. However, during intense stimulation, mutants fail to maintain normal neurotransmission. Surprisingly, FM1-43 labeling indicates normal exo- and endocytosis, but a specific inability to mobilize reserve pool vesicles, which is partially rescued by exogenous ATP. Using a variety of drugs, we provide evidence that reserve pool recruitment depends on mitochondrial ATP production downstream of PKA signaling and that mitochondrial ATP limits myosin-propelled mobilization of reserve pool vesicles. Our data suggest a specific role for mitochondria in regulating synaptic strength.
Mitochondria at the Synapse Ly, Cindy V.; Verstreken, Patrik
The Neuroscientist (Baltimore, Md.),
08/2006, Letnik:
12, Številka:
4
Journal Article
Recenzirano
Synapses are packed with mitochondria, complex organelles with roles in energy metabolism, cell signaling, and calcium homeostasis. However, the precise mechanisms by which mitochondria influence ...neurotrans mission remain undefined. In this review, the authors discuss pharmacological and genetic analyses of synaptic mitochondrial function, focusing on their role in Ca2+ buffering and ATP production. Additionally, they will summarize recent data that implicate synaptic mitochondria in the regulation of neurotransmitter release during intense neuronal activity and link these findings to the pathogenesis of neurodegenerative diseases that feature disrupted synaptic mitochondria, including amyotrophic lateral sclerosis and hereditary spastic paraplegia.
Amyotrophic lateral sclerosis (ALS) is a progressive, neurodegenerative disease of the lower and upper motor neurons with sporadic or hereditary occurrence. Age of onset, pattern of motor neuron ...degeneration and disease progression vary widely among individuals with ALS. Various cellular processes may drive ALS pathomechanisms, but a monogenic direct metabolic disturbance has not been causally linked to ALS. Here we show SPTLC1 variants that result in unrestrained sphingoid base synthesis cause a monogenic form of ALS. We identified four specific, dominantly acting SPTLC1 variants in seven families manifesting as childhood-onset ALS. These variants disrupt the normal homeostatic regulation of serine palmitoyltransferase (SPT) by ORMDL proteins, resulting in unregulated SPT activity and elevated levels of canonical SPT products. Notably, this is in contrast with SPTLC1 variants that shift SPT amino acid usage from serine to alanine, result in elevated levels of deoxysphingolipids and manifest with the alternate phenotype of hereditary sensory and autonomic neuropathy. We custom designed small interfering RNAs that selectively target the SPTLC1 ALS allele for degradation, leave the normal allele intact and normalize sphingolipid levels in vitro. The role of primary metabolic disturbances in ALS has been elusive; this study defines excess sphingolipid biosynthesis as a fundamental metabolic mechanism for motor neuron disease.
Synaptic vesicle (SV) exo- and endocytosis are tightly coupled to sustain neurotransmission in presynaptic terminals, and both are regulated by Ca(2+). Ca(2+) influx triggered by voltage-gated Ca(2+) ...channels is necessary for SV fusion. However, extracellular Ca(2+) has also been shown to be required for endocytosis. The intracellular Ca(2+) levels (<1 microM) that trigger endocytosis are typically much lower than those (>10 microM) needed to induce exocytosis, and endocytosis is inhibited when the Ca(2+) level exceeds 1 microM. Here, we identify and characterize a transmembrane protein associated with SVs that, upon SV fusion, localizes at periactive zones. Loss of Flower results in impaired intracellular resting Ca(2+) levels and impaired endocytosis. Flower multimerizes and is able to form a channel to control Ca(2+) influx. We propose that Flower functions as a Ca(2+) channel to regulate synaptic endocytosis and hence couples exo- with endocytosis.
Amyotrophic lateral sclerosis (ALS) is a rapidly progressive neurodegenerative disease with average lifespan of 2–5 years after diagnosis. The identification of novel prognostic and pharmacodynamic ...biomarkers are needed to facilitate therapeutic development. Metalloprotein human superoxide dismutase 1 (SOD1) is known to accumulate and form aggregates in patient neural tissue with familial ALS linked to mutations in their
SOD1
gene. Aggregates of SOD1 have also been detected in other forms of ALS, including the sporadic form and the most common familial form linked to abnormal hexanucleotide repeat expansions in the Chromosome 9 open reading frame 72 (
C9ORF72
) gene. Here, we report the development of a real-time quaking-induced conversion (RT-QuIC) seed amplification assay using a recombinant human SOD1 substrate to measure SOD1 seeding activity in postmortem spinal cord and motor cortex tissue from persons with different ALS etiologies. Our SOD1 RT-QuIC assay detected SOD1 seeds in motor cortex and spinal cord dilutions down to 10
–5
. Importantly, we detected SOD1 seeding activity in specimens from both sporadic and familial ALS cases, with the latter having mutations in either their
SOD1
or
C9ORF72
genes. Analyses of RT-QuIC parameters indicated similar lag phases in spinal cords of sporadic and familial ALS patients, but higher ThT fluorescence maxima by
SOD1
familial ALS specimens and sporadic ALS thoracic cord specimens. For a subset of sporadic ALS patients, motor cortex and spinal cords were examined, with seeding activity in both anatomical regions. Our results suggest SOD1 seeds are in ALS patient neural tissues not linked to
SOD1
mutation, suggesting that SOD1 seeding activity may be a promising biomarker, particularly in sporadic ALS cases for whom genetic testing is uninformative.
Huntington's disease (HD) is a dominantly inherited neurodegenerative disorder caused by expansion of a translated CAG repeat in the N terminus of the huntingtin (htt) protein. Here we describe the ...generation and characterization of a full-length HD Drosophila model to reveal a previously unknown disease mechanism that occurs early in the course of pathogenesis, before expanded htt is imported into the nucleus in detectable amounts. We find that expanded full-length htt (128QhttFL) leads to behavioral, neurodegenerative, and electrophysiological phenotypes. These phenotypes are caused by a Ca2+-dependent increase in neurotransmitter release efficiency in 128QhttFL animals. Partial loss of function in synaptic transmission (syntaxin, Snap, Rop) and voltage-gated Ca2+ channel genes suppresses both the electrophysiological and the neurodegenerative phenotypes. Thus, our data indicate that increased neurotransmission is at the root of neuronal degeneration caused by expanded full-length htt during early stages of pathogenesis.
Worldwide, acute, and chronic pain affects 20% of the adult population and represents an enormous financial and emotional burden. Using genome-wide neuronal-specific RNAi knockdown in
Drosophila, we ...report a global screen for an innate behavior and identify hundreds of genes implicated in heat nociception, including the α2δ family calcium channel subunit
straightjacket (
stj). Mice mutant for the
stj ortholog
CACNA2D3 (
α2δ3) also exhibit impaired behavioral heat pain sensitivity. In addition, in humans,
α2δ3 SNP variants associate with reduced sensitivity to acute noxious heat and chronic back pain. Functional imaging in
α2δ3 mutant mice revealed impaired transmission of thermal pain-evoked signals from the thalamus to higher-order pain centers. Intriguingly, in
α2δ3 mutant mice, thermal pain and tactile stimulation triggered strong cross-activation, or synesthesia, of brain regions involved in vision, olfaction, and hearing.
Display omitted
► Whole-genome in vivo RNAi screen for noxious heat avoidance in
Drosophila ► Identification of
α2-δ as a “pain” gene in fly ► Mouse and human homologs of
α2-δ (
α2δ3) are also pain genes ► Loss of
α2δ3 in mice results in sensory cross-activation, or synesthesia
Worldwide, acute, and chronic pain affects 20% of the adult population and represents an enormous financial and emotional burden. Using genome-wide neuronal-specific RNAi knockdown in Drosophila, we ...report a global screen for an innate behavior and identify hundreds of genes implicated in heat nociception, including the alpha 2 delta family calcium channel subunit straightjacket (stj). Mice mutant for the stj ortholog CACNA2D3 ( alpha 2 delta 3) also exhibit impaired behavioral heat pain sensitivity. In addition, in humans, alpha 2 delta 3 SNP variants associate with reduced sensitivity to acute noxious heat and chronic back pain. Functional imaging in alpha 2 delta 3 mutant mice revealed impaired transmission of thermal pain-evoked signals from the thalamus to higher-order pain centers. Intriguingly, in alpha 2 delta 3 mutant mice, thermal pain and tactile stimulation triggered strong cross-activation, or synesthesia, of brain regions involved in vision, olfaction, and hearing.
Synaptic vesicle endocytosis is critical for maintaining synaptic communication during intense stimulation. Here we describe Tweek, a conserved protein that is required for synaptic vesicle ...recycling.
tweek mutants show reduced FM1-43 uptake, cannot maintain release during intense stimulation, and harbor larger than normal synaptic vesicles, implicating it in vesicle recycling at the synapse. Interestingly, the levels of a fluorescent PI(4,5)P
2 reporter are reduced at
tweek mutant synapses, and the probe is aberrantly localized during stimulation. In addition, various endocytic adaptors known to bind PI(4,5)P
2 are mislocalized and the defects in FM1-43 dye uptake and adaptor localization are partially suppressed by removing one copy of the phosphoinositide phosphatase
synaptojanin, suggesting a role for Tweek in maintaining proper phosphoinositide levels at synapses. Our data implicate Tweek in regulating synaptic vesicle recycling via an action mediated at least in part by the regulation of PI(4,5)P
2 levels or availability at the synapse.
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