Unknown,Transcriptomics,Genomics,Proteomics

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HMGB1 contributes to mitochondrial DNA damage repair and extends lifespan in mutant ataxin-1 knock-in mice

ABSTRACT: Mutant ataxin-1 (Atxn1), which causes spinocerebellar ataxia type 1 (SCA1), binds to and impairs the function of high mobility group box 1 (HMGB1), a critical nuclear protein that regulates DNA architectural changes essential for DNA damage repair and transcription. In this study, we established that transgenic or virus vector-mediated supplementation of HMGB1 ameliorates motor dysfunction and elongates lifespan in mutant Atxn1 knock-in (Atxn1-KI) mice. We identified mitochondrial DNA damage repair by HMGB1 as a novel molecular basis for this effect, in addition to the mechanisms already associated with HMGB1 function, such as nuclear DNA damage repair and nuclear transcription. The dysfunction and the improvement of mitochondrial DNA damage repair functions are tightly associated with the exacerbation and rescue, respectively, of symptoms, supporting the involvement of mitochondrial DNA quality control by HMGB1 in SCA1 pathology. Moreover, we show that the rescue of Purkinje cell dendrites and dendritic spines by HMGB1 could be downstream effects. Although extracellular HMGB1 triggers inflammation mediated by toll-like receptor and receptor for advanced glycation end products, upregulation of intracellular HMGB1 does not induce such side effects. Thus, viral delivery of HMGB1 is a candidate approach by which to modify the disease progression of SCA1 even after its onset.

ORGANISM(S): Mus musculus

SUBMITTER: Hidenori Homma

PROVIDER: E-MTAB-2987 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Mitochondrial dysfunction is a common feature in neurodegeneration and aging. We identify mitochondrial dysfunction in xeroderma pigmentosum group A (XPA), a nucleotide excision DNA repair disorder with severe neurodegeneration, in silico and in vivo. XPA deficient cells show defective mitophagy with excessive cleavage of PINK1 and increased mitochondrial membrane potential. The mitochondrial abnormalities appear to be caused by decreased activation of the NAD+-SIRT1-PGC-1? axis triggered by hyperactivation of the DNA damage sensor PARP1. This phenotype is rescued by PARP1 inhibition or by supplementation with NAD+ precursors that also rescue the lifespan defect in xpa-1 nematodes. Importantly, this pathogenesis appears common to ataxia-telangiectasia and Cockayne syndrome, two other DNA repair disorders with neurodegeneration, but absent in XPC, a DNA repair disorder without neurodegeneration. Our findings reveal a novel nuclear-mitochondrial cross-talk that is critical for the maintenance of mitochondrial health. Mice carrying WT, or CX (Csa-/-/Xpa-/-) alleles in a C57BL/6 background were maintained under standard laboratory conditions and allowed free access to water and control casein pelleted diet (Research Diets D12450B). At 3 months of age, 3 replicates of each of the CX and WT mice were given subcutaneous interscapular injections of 500 mg of Nicotinamide riboside/kg body weight/day or the equivalent volume of saline for 14 consecutive days at 4:00 pm. On day 15, the mice were sacrificed and half of the cerebellum was harvested for purification of mitochondria, with the left half snap-frozen, homogenized, and aliquoted for RNA isolation. Total RNA extraction was done using a TRIzol Plus RNA purification kit as per manufacturer’s protocol. Quality and quantity of the total RNA was tested using the Agilent 2100 Bio-Analyzer and RNA 6000 nano kits. The RNA was labeled using the standard Illumina protocol and hybed overnight to Mouse Ref-8 Illumina arrays. The arrays were scanned using the Beadstation 500 X from Illumina.

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HMGB1 contributes to mitochondrial DNA damage repair and extends lifespan in mutant ataxin-1 knock-in mice

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