2026-08-10 | Impaired Glur2 palmitoylation in cerebellar Purkinje cells of a Friedreich ataxia mouse model.

Friedreich's ataxia (FRDA) is a neurodegenerative disorder caused by frataxin deficiency, characterized by progressive cerebellar dysfunction and neuronal loss. Although synaptic abnormalities are an early feature of FRDA, the molecular mechanisms linking frataxin deficiency to synaptic dysfunction remain incompletely defined. In this study, we investigated post-translational regulation of the AMPA receptor subunit GluR2 in the cerebellum of the frataxin knockdown (FRDAkd) mouse model. GluR2 protein levels are reduced early following frataxin knockdown, despite unchanged mRNA expression and preserved Purkinje cell number. Phosphorylation of GluR2 at regulatory sites (Ser880 and Tyr876) is unchanged relative to total protein, indicating that altered phosphorylation does not account for reduced GluR2 levels. In contrast, acyl-biotin exchange assays and proximity ligation analysis reveal a significant reduction in GluR2 palmitoylation, localized primarily to Purkinje cell somata. This deficit is selective, as palmitoylation of other synaptic proteins is variably affected. Mechanistically, reduced GluR2 palmitoylation associates with decreased expression and palmitoylation of the palmitoyl acyltransferase DHHC3, while levels of depalmitoylating enzymes remain unchanged. In vitro, DHHC3 enhances GluR2 palmitoylation, supporting a direct enzymatic relationship. Partial restoration of frataxin expression rescues GluR2 and DHHC3 protein levels and partially restores GluR2 palmitoylation. These findings identify impaired GluR2 palmitoylation as an early, selective synaptic alteration in FRDA and implicate dysregulated lipid-dependent post-translational modification as a mechanism linking frataxin deficiency to cerebellar synaptic vulnerability.

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2026-08-06 | BRD4 recruitment into HP1 condensates desilences transcription without erasure of repressive chromatin.

How genes are desilenced without erasure of repressive chromatin is a poorly understood phenomenon. A dominant mode of repression occurs through methylation of lysine 9 of histone H3 (H3K9me3), a mark that engages heterochromatin protein 1 (HP1) to drive chromatin compaction and transcriptional silencing. The erasure and replacement of this repressive mark with acetyl/acyl groups recruits positive factors such as BRD4/BET to elicit gene transcription. Here we report that, in Friedreich's ataxia, a synthetic gene regulator (SynGR1/SynTEF1) licenses transcription across repressive chromatin without removal or replacement of H3K9me3 or HP1. By recruiting BRD4/BET into repressive GAA repeats in frataxin (FXN), SynGR1 creates a paradoxical state wherein gene transcription and repressive chromatin coexist. Contrary to convention, we find that BRD4 partitions into phase separated HP1 condensates in vitro and into HP1 puncta in patient-derived cells, thus offering a mechanistic explanation for desilencing transcription without the dispersal of mesoscale repressive chromatin. More broadly, our study highlights the dynamic nature of repressive chromatin and the context dependence of epigenetic marks in regulating gene expression.

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2026-07-30 | Limiting intestinal iron absorption rescues glial defects and extends lifespan in a Drosophila model of Friedreich's ataxia.

Friedreich ataxia (FRDA) is a neurodegenerative and cardiac disease caused by GAA repeat expansions within the first intron of the FXN gene, leading to reduced frataxin expression. Frataxin is involved in iron sulfur cluster (ISC) biosynthesis, and its deficiency results in multiple cellular dysfunctions, including mitochondrial iron overload. Although altered iron homeostasis has been reported in several frataxin-deficient models and in FRDA patients, its contribution to disease progression remains debated. Here, we used a GAA expansion-based Drosophila model of FRDA, termed fh-GAAs, to investigate the impact of reducing intestinal iron absorption on disease progression. We first found that iron accumulation was tissue-specific and predominantly affected the central nervous system. Furthermore, glial cells were affected more severely than neurons, suggesting an increased vulnerability of glia to frataxin deficiency. Reducing intestinal iron uptake, either through treatment with bathophenanthroline disulfonic acid (BPS), an extracellular iron chelator, or by gut-specific silencing of the gene encoding the iron transporter Malvolio, nearly doubled fly survival. BPS treatment also improved sensitivity to dietary iron, enhanced locomotor performance, fully restored normal brain size, and prevented glial alterations. Altogether, our findings identify glial cells as early and preferential targets of frataxin deficiency in an iron-dependent manner and support the in vivo relevance of intestinal iron uptake as a potential modulator of disease severity in FRDA.

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2026-07-28 | Evolution of Friedreich's Ataxia Management Across Established and Emerging Therapies-Systematic Review and Meta-Analysis.

Background: Friedreich's ataxia (FRDA) is a neurodegenerative disorder driven by frataxin deficiency, resulting in mitochondrial dysfunction and reduced nuclear factor erythroid 2-related factor 2 (Nrf2) signaling. Pharmacologic trials have yielded inconsistent results, prompting an updated synthesis of evidence. Methods: We searched MEDLINE/PubMed, Google Scholar, Cochrane CENTRAL, ClinicalTrials.gov, and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) from database inception to 29 June 2025. Embase, Scopus and Web of Science were not searched due to institutional access limitations. Two reviewers independently screened studies, extracted data, and assessed risk of bias. Random-effects meta-analyses were conducted, and Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) was used. Primary outcomes were modified Friedreich Ataxia Rating Scale (mFARS)/Friedreich Ataxia Rating Scale (FARS); safety outcomes included adverse events (AEs) and serious AEs. Secondary outcomes were Scale for the Assessment and Rating of Ataxia (SARA), International Cooperative Ataxia Rating Scale (ICARS), Nine-Hole Peg Test, and the Timed 25-Foot Walk. Results: Sixteen studies (17 reports, n = 351) met inclusion criteria. Omaveloxolone was the only agent showing a statistically significant improvement in mFARS (mean difference (MD) -2.40; 95% confidence interval (CI) -4.24 to -0.56; p = 0.014), supported by low-certainty evidence. Other therapies showed no consistent benefit. Overall AE risk was comparable to control (risk ratio (RR) 1.00; 95% CI 0.98-1.03). Apparent subgroup differences by therapeutic class or age likely reflected drug-specific effects and small samples. Conclusions: Omaveloxolone was the only agent to reach statistical significance for mFARS and is the most promising and best-supported therapy among those reviewed; however, this rests on low-certainty evidence and needs confirmation in larger trials. No clear difference in overall adverse events was observed between intervention and control groups; however, available safety evidence remains limited by imprecision, small sample sizes, and short follow-up durations. Longer, standardized, and age-stratified randomized controlled trials (RCTs) are needed.

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2026-07-21 | Microglia from Friedreich Ataxia patients are intrinsically primed for neuroinflammation

Abstract Friedreich Ataxia (FRDA) is an autosomal recessive neurodegenerative disorder characterized by progressive loss of cerebellar and proprioceptive neurons that control movement and coordination. In most patients, FRDA is caused by homozygous GAA trinucleotide repeat expansions in the first intron of the frataxin ( FXN ) gene, resulting in reduced expression of frataxin, a mitochondrial protein essential for biogenesis of iron-sulfur clusters and mitochondrial function. Although recent therapeutic advances have provided modest clinical benefit, effective disease-modifying treatments remain lacking. Increasing evidence indicates that microglial cell dysfunction contributes to FRDA pathogenesis, highlighting these cells as potential therapeutic targets. However, the molecular mechanisms underlying FXN-deficient microglial dysfunction remain poorly understood. Here, we show that microglia generated from FRDA patient-derived iPSCs exhibit a cell-autonomous pro-inflammatory phenotype in the absence of exogenous inflammatory stimuli. This phenotype is characterized by coordinated activation of immune transcriptional programs, dysregulated secretion of neuroinflammatory proteins, impaired autophagy-lysosomal function, and activation of inflammasomes pathways involving NLRP2 and NLRP3. These findings demonstrate that FXN deficiency is sufficient to induce intrinsic microglial activation and identify molecular pathways that may represent attractive targets for future FRDA therapies.

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