DNA Damage Response and DNA Repair in Skeletal Myocytes From a Mouse Model of Spinal Muscular Atrophy

Fayzullina, Saniya; Martin, Lee J.

doi:10.1093/jnen/nlw064

Cited by 9 publications

(10 citation statements)

References 85 publications

(113 reference statements)

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“…However, DNA repair by HR may be sufficient to support the proliferation and growth of dividing SMA patient primary fibroblast cells. The potential for DNA repair in dividing SMA cells is supported by previous finding that showed cultured SMA mouse primary skeletal myocytes were competent of repairing DNA damage induced by γ-radiation and etoposide treatment ( 37 ).…”

Section: Resultsmentioning

confidence: 65%

Combined deficiency of Senataxin and DNA-PKcs causes DNA damage accumulation and neurodegeneration in spinal muscular atrophy

Kannan

Bhatia

Branzei

et al. 2018

Nucleic Acids Research

108

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Chronic low levels of survival motor neuron (SMN) protein cause spinal muscular atrophy (SMA). SMN is ubiquitously expressed, but the mechanisms underlying predominant neuron degeneration in SMA are poorly understood. We report that chronic low levels of SMN cause Senataxin (SETX)-deficiency, which results in increased RNA–DNA hybrids (R-loops) and DNA double-strand breaks (DSBs), and deficiency of DNA-activated protein kinase-catalytic subunit (DNA-PKcs), which impairs DSB repair. Consequently, DNA damage accumulates in patient cells, SMA mice neurons and patient spinal cord tissues. In dividing cells, DSBs are repaired by homologous recombination (HR) and non-homologous end joining (NHEJ) pathways, but neurons predominantly use NHEJ, which relies on DNA-PKcs activity. In SMA dividing cells, HR repairs DSBs and supports cellular proliferation. In SMA neurons, DNA-PKcs-deficiency causes defects in NHEJ-mediated repair leading to DNA damage accumulation and neurodegeneration. Restoration of SMN levels rescues SETX and DNA-PKcs deficiencies and DSB accumulation in SMA neurons and patient cells. Moreover, SETX overexpression in SMA neurons reduces R-loops and DNA damage, and rescues neurodegeneration. Our findings identify combined deficiency of SETX and DNA-PKcs stemming downstream of SMN as an underlying cause of DSBs accumulation, genomic instability and neurodegeneration in SMA and suggest SETX as a potential therapeutic target for SMA.

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Section: Resultsmentioning

confidence: 65%

Combined deficiency of Senataxin and DNA-PKcs causes DNA damage accumulation and neurodegeneration in spinal muscular atrophy

Kannan

Bhatia

Branzei

et al. 2018

Nucleic Acids Research

108

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“…Diaphragms were evaluated as whole mounts. NO histochemical preparations were analyzed for fluorescence intensity quantitatively using methods described ( 59 , 60 ).…”

Section: Methodsmentioning

confidence: 99%

“…The diaphragm was removed intact for studying as a whole mount. Skeletal muscle sections were used for terminal deoxynucleotidyl nick-end labeling (TUNEL) to visualize DNA damage (DNA double-strand breaks)-cell death as described ( 59 , 64 ) and immunofluorescence to study the localizations of hSOD1 and satellite cell markers ( 65 ) as described ( 60 , 66 ). Spinal cord sections were used for Nissl (cresyl violet, CV) and silver staining, TUNEL, and immunohistochemistry (IHC).…”

Section: Methodsmentioning

confidence: 99%

Skeletal Muscle-Restricted Expression of Human SOD1 in Transgenic Mice Causes a Fatal ALS-Like Syndrome

Martin

Wong

2020

Front. Neurol.

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Amyotrophic lateral sclerosis (ALS) is a fatal heterogeneous neurodegenerative disease that causes motor neuron (MN) loss and skeletal muscle paralysis. It is uncertain whether this degeneration of MNs is triggered intrinsically and is autonomous, or if the disease initiating mechanisms are extrinsic to MNs. We hypothesized that skeletal muscle is a primary site of pathogenesis in ALS that triggers MN degeneration. Some inherited forms of ALS are caused by mutations in the superoxide dismutase-1 (SOD1) gene, that encodes an antioxidant protein, so we created transgenic (tg) mice expressing wild-type-, G37R-, and G93A-human SOD1 gene variants only in skeletal muscle. Presence of human SOD1 (hSOD1) protein in skeletal muscle was verified by western blotting, enzyme activity gels, and immunofluorescence in myofibers and satellite cells. These tg mice developed limb weakness and paresis with motor deficits, limb and chest muscle wasting, diaphragm atrophy, and age-related fatal disease with a lifespan shortening of 10–16%. Brown and white adipose tissue also became wasted. Myofibers of tg mice developed crystalline-like inclusions, individualized sarcomere destruction, mitochondriopathy with vesiculation, DNA damage, and activated p53. Satellite cells became apoptotic. The diaphragm developed severe loss of neuromuscular junction presynaptic and postsynaptic integrity, including decreased innervation, loss of synaptophysin, nitration of synaptophysin, and loss of nicotinic acetylcholine receptor and scaffold protein rapsyn. Co-immunoprecipitation identified hSOD1 interaction with rapsyn. Spinal cords of tg mice developed gross atrophy. Spinal MNs formed cytoplasmic and nuclear inclusions, axonopathy, mitochondriopathy, accumulated DNA damage, activated p53 and cleaved caspase-3, and died. Tg mice had a 40–50% loss of MNs. This work shows that hSOD1 in skeletal muscle is a driver of pathogenesis in ALS, that involves myofiber and satellite cell toxicity, and apparent muscle-adipose tissue disease relationships. It also identifies a non-autonomous mechanism for MN degeneration explaining their selective vulnerability as likely a form of target-deprivation retrograde neurodegeneration.

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“…Images were acquired and analyzed using Slidebook or Spot software. Comets were manually counted and comet moments were calculated as described (45,46).…”

Section: Comet Assay For Dna Damage and Dna Repairmentioning

confidence: 99%

DNA Damage Response and Repair, DNA Methylation, and Cell Death in Human Neurons and Experimental Animal Neurons Are Different

Martin

Chang²

2018

Journal of Neuropathology &Amp; Experimental Neurology

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Neurological disorders affecting individuals in infancy to old age elude interventions for meaningful protection against neurodegeneration, and preclinical work has not translated to humans. We studied human neuron responses to injury and death stimuli compared to those of animal neurons in culture under similar settings of insult (excitotoxicity, oxidative stress, and DNA damage). Human neurons were differentiated from a cortical neuron cell line and the embryonic stem cell-derived H9 line. Mouse neurons were differentiated from forebrain neural stem cells and embryonic cerebral cortex; pig neurons were derived from forebrain neural stem cells. Mitochondrial morphology was different in human and mouse neurons. Human and mouse neurons challenged with DNA-damaging agent camptothecin showed different chromatin condensation, cell death, and DNA damage sensor activation. DNA damage accumulation and repair kinetics differed among human, mouse, and pig neurons. Promoter CpG island methylation microarrays showed significant differential DNA methylation in human and mouse neurons after injury. Therefore, DNA damage response, DNA repair, DNA methylation, and autonomous cell death mechanisms in human neurons and experimental animal neurons are different.

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DNA Damage Response and DNA Repair in Skeletal Myocytes From a Mouse Model of Spinal Muscular Atrophy

Cited by 9 publications

References 85 publications

Combined deficiency of Senataxin and DNA-PKcs causes DNA damage accumulation and neurodegeneration in spinal muscular atrophy

Combined deficiency of Senataxin and DNA-PKcs causes DNA damage accumulation and neurodegeneration in spinal muscular atrophy

Skeletal Muscle-Restricted Expression of Human SOD1 in Transgenic Mice Causes a Fatal ALS-Like Syndrome

DNA Damage Response and Repair, DNA Methylation, and Cell Death in Human Neurons and Experimental Animal Neurons Are Different

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