Biology subjects

Giunti, P.

Publications and source records attributed to Giunti, P..

5 recordsLinked to original sources

bioRxiv2025

Transcriptomic analysis of repeat expansion-ataxias uncovers distinct non-neuronal cell type-specific signatures of disease across the human brain

Hereditary ataxias are a heterogeneous group of neurogenetic conditions characterised by the clinical syndrome of progressive loss of coordination from neurodegeneration of the cerebellum. A commonality across the most prevalent ataxias is the underlying disease mechanism secondary to expansions of short tandem DNA repeats. There is currently an incomplete understanding of the pathogenic mechanisms of these repeat expansion disorders, a core feature of which revolves around RNA-dysregulation. In this study, we used both bulk and single nuclear RNA-sequencing to study post-mortem brain tissue of human donors with a range of repeat-expansion ataxias to reveal further mechanistic insights. We compared post-mortem paired cerebellar and frontal cortex tissue bulk RNA-sequencing data from 23 ataxia patients and 22 sex-, age-matched controls from two brain banks (spinocerebellar ataxia (SCA)1, SCA2, SCA6, SCA7, SCA17, Friedreichs ataxia (FRDA), and 7 cases with unknown molecular diagnoses). We analysed bulk RNA-sequencing data for transcript usage, differential and cell-type-specific expression to transcriptomically profile these diseases. We also generated single nuclear RNA-sequencing data of the cerebellum from donors with SCA1, SCA2, SCA6 and FRDA to decipher changes in cell type proportions in the disease state. Using this approach, we found that: (i) despite the commonalities in the genetics of ataxia, there were components of their transcriptional signatures which were distinct; (ii) there were extensive transcriptional changes evident not only in the cerebellum but also the frontal cortex in ataxia cases; (iii) activation of immune and inflammatory pathways, as well as involvement of non-neuronal cell types was a feature of all ataxias to a lesser or greater extent. This study provides a novel resource to understand the mechanisms of disease in ataxia. Furthermore, taken together, these results highlight immune pathways and the role of non-neuronal cell types as early and potentially important therapeutic targets. These findings provide a map of transcriptomic changes in ataxia to further understanding of the underlying pathogenesis.

neuroscience↗

bioRxiv2024

Mitochondria drive microglial NRLP3 inflammasome activation via TSPO

Uncontrolled microglial response is core to neuroinflammatory brain diseases. The correlation between the mitochondrial protein TSPO and inflammation has so far failed to explain whether TSPO positively or negatively regulates microglial function. The recent evidence on the species specificity of TSPO in microglia demands a deeper understanding of the protein biology in these brain-resident macrophages. To this end, we have here enrolled a murine model of microglial cells showing that TSPO is required for the priming of mitochondria to inflammation and a conduit for its escalation. Namely, in response to inflammatory cues TSPO is stabilised on the mitochondria where it binds and sequesters NOD-like receptor (NLR) protein (i), represses the PARK2-mediated mitophagy (ii) and engages the retrograde communication with the nucleus via the accumulation of the Nf-kB to promote the expression of pro-inflammatory genes (iii). Notably, the TSPO sustained inflammatory response drives cellular demise and ultimately leads to excitotoxicity (iv). Our findings advance the current knowledge of TSPO widening the understanding of mitochondria in inflammation and indicating a target for their regulation.

cell biology↗

bioRxiv2024

Small non-coding RNA content in plasma-derived extracellular vesicles distinguish ataxic SCA3 mutation carriers from pre-ataxic and control subjects

Spinocerebellar ataxia type 3 (SCA3), a neurodegenerative disorder caused by a CAG expansion in the ATXN3 gene, is the most common spinocerebellar ataxia subtype worldwide. Currently, there is no therapy to stop or prevent disease progression. Promising therapeutic strategies are emerging, but their translation into clinical practice requires sensitive and reliable biomarkers. Blood circulating extracellular vesicles constitute a promising source of biomarkers with potential to track alterations of the central nervous system due to their ability to cross the blood brain barrier. Here, we perform sequencing analysis of small RNAs from plasma-derived extracellular vesicles from SCA3 mutation carriers (10 pre-ataxic and 10 ataxic) and 12 control subjects to identify potential RNA biomarker candidates for this disease. Data showed that plasma-derived extracellular vesicles from ataxic SCA3 mutation carriers are enriched in mitochondrial, nuclear, and nucleolar RNA biotypes compared to pre-ataxic and control subjects. Moreover, ataxic mutation carriers could be discriminated from control and pre-ataxic subjects based on the miRNAs or piRNAs content, but not tRNA. Furthermore, we identified a subset of differentially expressed miRNAs and piRNAs that clearly differentiate ataxic mutation carriers from pre-ataxic and control subjects. These findings open new avenues for further investigation on the role of these RNAs in the pathogenesis of SCA3 and their potential as biomarkers for this disease.

neuroscience↗

bioRxiv2023

Blood and cerebellar abundance of ATXN3 splice variants in spinocerebellar ataxia type 3/Machado-Joseph disease

BackgroundSpinocerebellar ataxia type 3 (SCA3)/Machado-Joseph disease (MJD) is an autosomal dominant polyglutamine disease. SCA3/MJD causative gene, ATXN3, is known to undergo alternative splicing (AS) and 54 transcripts are currently annotated. Differences in the toxicity of ataxin-3 protein isoforms, harbouring on its C-terminus two or three ubiquitin interacting motifs (UIMs), were previously uncovered, raising the hypothesis that specific ATXN3 splice variants play key roles in promoting the selective toxicity displayed in SCA3/MJD. MethodsUsing RNA-seq datasets we identified and determined the abundance of annotated ATXN3 transcripts in blood (n=60) and cerebellum (n=12) of SCA3/MJD subjects and controls. ResultsGlobally, the number and the abundance of individual ATXN3 transcripts were higher in the cerebellum than in the blood. While the most abundant transcript in the cerebellum was a protein with a coding sequence not defined of unknown function (ATXN3-208), the transcript with the highest abundance in blood was the reference transcript (ATXN3-251) which translates into an ataxin-3 isoform harboring three UIMs. Noteworthy, the abundance of ATXN3-251 and ATXN3-214, two out of the four transcripts that encode full-length ataxin-3 protein isoforms but differ in the C-terminus were strongly related with tissue expression specificity: ATXN3-251 (3UIM) was expressed in blood 50-fold more than in cerebellum, whereas ATXN3-214 (2UIM) was expressed in the cerebellum 20-fold more than in blood. ConclusionsThese findings provide new insights into the elucidation of ATXN3 AS in different tissues, contributing for a better understanding of SCA3/MJD pathogenesis and providing information for the development of future effective ATXN3 mRNA-lowering therapies.

genetics↗

bioRxiv2020

Whole genome sequencing for diagnosis of neurological repeat expansion disorders

BackgroundRepeat expansion (RE) disorders affect ~1 in 3000 individuals and are clinically heterogeneous diseases caused by expansions of short tandem DNA repeats. Genetic testing is often locus-specific, resulting in under diagnosis of atypical clinical presentations, especially in paediatric patients without a prior positive family history. Whole genome sequencing (WGS) is emerging as a first-line test for rare genetic disorders, but until recently REs were thought to be undetectable by this approach. MethodsWGS pipelines for RE disorder detection were deployed by the 100,000 Genomes Project and Illumina Clinical Services Laboratory. Performance was retrospectively assessed across the 13 most common neurological RE loci using 793 samples with prior orthogonal testing (182 with expanded alleles and 611 with alleles within normal size) and prospectively interrogated in 13,331 patients with suspected genetic neurological disorders. FindingsWGS RE detection showed minimum 97{middle dot}3% sensitivity and 99{middle dot}6% specificity across all 13 disease-associated loci. Applying the pipeline to patients from the 100,000 Genomes Project identified pathogenic repeat expansions which were confirmed in 69 patients, including seven paediatric patients with no reported family history of RE disorders, with a 0.09% false positive rate. InterpretationWe show here for the first time that WGS enables the detection of causative repeat expansions with high sensitivity and specificity, and that it can be used to resolve previously undiagnosed neurological disorders. This includes children with no prior suspicion of a RE disorder. These findings are leading to diagnostic implementation of this analytical pipeline in the NHS Genomic Medicine Centres in England. FundingMedical Research Council, Department of Health and Social Care, National Health Service England, National Institute for Health Research, Illumina Inc

genomics↗