Variability in genome organization drives differential gene expression and shapes cellular diversity, yet whether transcription actively instructs genome structure and how this relationship is exploited in disease remains unclear. We show that transcription and cohesin direct the spatial positioning of lamina-associated domain (LAD) boundary genes. Transcriptional repression repositions LAD boundary genes to the nuclear lamina in a cohesin loop extrusion-dependent manner. Conversely, overactive cohesin is sufficient to reposition and silence LAD boundary genes, an effect counteracted by maintaining transcription. In Friedreich’s ataxia, we demonstrate improper positioning of the pathogenically repressed LAD boundary gene FRATAXIN (FXN) at the nuclear periphery reflects an imbalance between transcription and cohesin dynamics. Importantly, modulating either transcription or cohesin activity restores FXN positioning and reactivates expression. Our findings establish transcription and cohesin as tunable molecular rheostats orchestrating LAD boundary spatial positioning and reveal how the flexible and dynamic nature of genome architecture is hijacked in disease.

We explored the ability of the low molecular weight, polyphenol-rich fractions obtained from chestnut shells to inhibit ferroptosis in Friedreich Ataxia (FRDA), an inherited neuro- and cardio-degenerative disease. We prepared an aqueous extract by an eco-sustainable method and obtained a polyphenol-rich fraction (fraction D) of molecular weight less than 1.0 kDa after molecular size fractionation. The total phenols were 173.28 ± 4.97 μg gallic acid equivalents/mg fraction, and analysis by UHPLC-ITMSn and RP-HPLC-UV revealed thirteen phenolic compounds with gallic acid and protocatechuic acid (PCA) as the most abundant (26.29 ± 2.19 and 4.93 ± 0.19 μg/mg fraction, respectively). Using a cellular assay based on patient-derived FRDA fibroblasts, we observed that chestnut shell dry extract at 20 µg/mL increased the survival of cells stressed with the ferroptosis inducer erastin from 8% to 45% and that this activity was dose-dependent. Fraction D at 20 µg/mL showed similar strong activity, increasing cell survival from 0.5% to 14% and decreasing lipid peroxidation by 42%. PCA, the most efficacious compound, doubled cell survival and decreased lipid peroxidation by 20%. Moreover, PCA increased the survival of cells in which frataxin was knocked down 1.5-fold and decreased ALOX12 expression. Our data suggest that PCA could be a promising molecule to explore FRDA pathophysiology.

Friedreich ataxia (FRDA) is a slowly progressive neurological disease resulting from decreased levels of the protein frataxin, a small mitochondrial protein that facilitates the synthesis of iron-sulfur clusters in the mitochondrion. It is caused by GAA (guanine-adenine-adenine) repeat expansions in the FXN gene in 96% of patients, with 4% of patients carrying other mutations (missense, nonsense, deletion) in the FXN gene. Compound heterozygote patients with one expanded GAA allele and a non-GAA repeat mutation can have subtle differences in phenotype from typical FRDA, including, in patients with selected missense mutations, both more severe features and less severe features in the same patient. In this review, we propose explanations for such phenotypes based on the potential for activities of frataxin other than enhancement of iron-sulfur cluster synthesis, as well as crucial future experiments for fully understanding the role of frataxin in cells.

Friedreich’s ataxia (FRDA) is a multisystem, autosomal recessive disorder caused by mutations in the frataxin (FXN) gene. As FRDA is considered an FXN deficiency disorder, numerous therapeutic approaches in development or clinical trials aim to supplement FXN or restore endogenous FXN expression. These include gene therapy, protein supplementation, genome editing or upregulation of FXN transcription. To evaluate efficacy of these therapies, potency assays capable of quantitative determination of FXN biological activity are needed. Herein, we evaluate the suitability of mouse embryonic fibroblasts derived from Fxn G127V knockin mice (MUT MEFs) as a candidate for cell-based potency assays. We demonstrate that these cells, when immortalized, continue to express minute amounts of Fxn and exhibit a broad range of phenotypes that result from severe Fxn deficiency. Exogenous FXN supplementation reverses these phenotypes. Thus, immortalized MUT MEFs are an excellent tool for developing potency assays to validate novel FRDA therapies. Care needs to be exercised while utilizing these cell lines, as extended passaging results in molecular changes that spontaneously reverse FRDA-like phenotypes without increasing Fxn expression. Based on transcriptome analyses, we identified the Warburg effect as the mechanism allowing cells expressing a minimal level of Fxn to thrive under standard cell culture conditions.

Background: Friedreich's ataxia (FRDA), most commonly caused by a GAA triplet repeat (GAA-TR) expansion in intron 1 of the FXN gene, is characterized by deficiency of frataxin protein and clinical features such as progressive ataxia, dysarthria, impaired proprioception and vibration, abolished deep tendon reflexes, Babinski sign, and vision loss in association with non-neurological features such as skeletal anomalies, hearing loss, cardiomyopathy, and diabetes. Pathogenic GAA-TRs range in size from 60 to 1500 triplets and negatively correlate with age of onset. Clinical severity is predicted by a combination of GAA-TR length and disease duration (DD) via multivariable regressions, which cannot typically be used for the small sample sizes in most studies on this rare disease. Objective: We aimed to develop a single metric, which we call "disease burden" (DB), that encompasses both GAA-TR length and DD for predicting disease features of FRDA in small sample sizes. Methods: Linear regression and multivariable regression analysis was used to determine correlation coefficients between different disease features of FRDA. Results: Using large datasets for validation, we found that DB predicts measures of neurological dysfunction in FRDA better than GAA-TR length or DD. Analogous results were found using small datasets. Conclusions: FRDA DB is a novel metric of disease severity that has utility in small datasets to demonstrate correlations that would not otherwise be evident with either GAA-TR or DD alone. This is important for discovering new biomarkers, as well as improving the prediction of severity of disease features in FRDA. (c) 2023 International Parkinson and Movement Disorder Society.

Friedreich’s ataxia (FRDA) is an autosomal recessive neurodegenerative disorder caused by a triplet guanine-adenine-adenine (GAA) repeat expansion in intron 1 of the FXN gene, which leads to decreased levels of the frataxin protein. Frataxin is involved in the formation of iron-sulfur (Fe-S) cluster prosthetic groups for various metabolic enzymes. To provide a better understanding of the metabolic status of patients with FRDA, here we used patient-derived fibroblast cells as a surrogate tissue for metabolic and lipidomic profiling by liquid chromatography-high resolution mass spectrometry. We found elevated HMG-CoA and β-hydroxybutyrate-CoA levels, implying dysregulated fatty acid oxidation, which was further demonstrated by elevated acyl-carnitine levels. Lipidomic profiling identified dysregulated levels of several lipid classes in FRDA fibroblast cells when compared with non-FRDA fibroblast cells. For example, levels of several ceramides were significantly increased in FRDA fibroblast cells; these results positively correlated with the GAA repeat length and negatively correlated with the frataxin protein levels. Furthermore, stable isotope tracing experiments indicated increased ceramide synthesis, especially for long-chain fatty acid-ceramides, in FRDA fibroblast cells compared with ceramide synthesis in healthy control fibroblast cells. In addition, PUFA-containing triglycerides and phosphatidylglycerols were enriched in FRDA fibroblast cells and negatively correlated with frataxin levels, suggesting lipid remodeling as a result of FXN deficiency. Altogether, we demonstrate patient-derived fibroblast cells exhibited dysregulated metabolic capabilities, and their lipid dysfunction predicted the severity of FRDA, making them a useful surrogate to study the metabolic status in FRDA.

Background: Long-chain polyunsaturated fatty acids (PUFAs) are important modulators of red blood cell (RBC) rheology. Dietary PUFAs are readily incorporated into the RBC membrane, improving RBC deformability, fluidity, and hydration. However, enriching the lipid membrane with PUFAs increases the potential for peroxidation in oxidative environments (e.g., refrigerated storage), resulting in membrane damage. Substitution of bis-allylic hydrogens with deuterium ions in PUFAs decreases hydrogen abstraction, thereby inhibiting peroxidation. If lipid peroxidation is a causal factor in the RBC storage lesion, incorporation of deuterated linoleic acid (DLA) into the RBC membrane should decrease lipid peroxidation, thereby improving RBC lifespan, deformability, filterability, and post-transfusion recovery (PTR) after cold storage. Study Design and Methods: Mice associated with good (C57BL/6J) and poor (FVB) RBC storage quality received diets containing 11,11-D2-LA Ethyl Ester (1.0 g/100 g diet; deuterated linoleic acid) or non-deuterated LA Ethyl Ester (control) for 8 weeks. Deformability, filterability, lipidomics, and lipid peroxidation markers were evaluated in fresh and stored RBCs. Results: DLA was incorporated into RBC membranes in both mouse strains. DLA diet decreased lipid peroxidation (malondialdehyde) by 25.4 and 31% percent in C57 mice and 12.9 and 79.9% in FVB mice before and after cold storage, respectively. In FVB, but not C57 mice, deformability filterability, and post-transfusion recovery were significantly improved. Discussion: In a mouse model of poor RBC storage, with elevated reactive oxygen species production, DLA attenuated lipid peroxidation and significantly improved RBC storage quality.

Friedreich ataxia, the most common hereditary ataxia, is a neuro- and cardio-degenerative disorder caused, in most cases, by decreased expression of the mitochondrial protein frataxin. Cardiomyopathy is the leading cause of premature death. Frataxin functions in the biogenesis of iron-sulfur clusters, which are prosthetic groups that are found in proteins involved in many biological processes. To study the changes associated with decreased frataxin in human cardiomyocytes, we developed a novel isogenic model by acutely knocking down frataxin, post-differentiation, in cardiomyocytes derived from induced pluripotent stem cells (iPSCs). Transcriptome analysis of four biological replicates identified severe mitochondrial dysfunction and a type I interferon response as the pathways most affected by frataxin knockdown. We confirmed that, in iPSC-derived cardiomyocytes, loss of frataxin leads to mitochondrial dysfunction. The type I interferon response was activated in multiple cell types following acute frataxin knockdown and was caused, at least in part, by release of mitochondrial DNA into the cytosol, activating the cGAS-STING sensor pathway.

OPINION article Front. Neurosci., 02 March 2021Sec. Neurodegeneration Volume 15 - 2021 | https://doi.org/10.3389/fnins.2021.653241

Cancer lineage/tissue-of-origin assignment in cancers of unknown primary remains a challenge even when aided by massively parallel sequencing. The stakes are high for patients as many contemporary therapeutic strategies are disease-specific, and the biological differences can influence the patients’ responses. Herein, we provide an example of how Bayesian analysis can be used to merge data from clinical history, histology, immunohistochemistry (IHC) and cancer DNA sequencing to assist in tissue-of-origin assignment. Iterative Bayesian analysis is performed through a set of simple calculations to calculate the OR between the differential diagnoses. We illustrate a clinical case, where the distinction between a primary lung versus metastatic bladder cancer was aided meaningfully by iterative Bayesian analyses, incorporating IHC and sequencing data.

Friedreich ataxia (FRDA) is an inherited neurodegenerative disorder for which there is no cure or approved treatment. It is characterized by the loss or impaired activity of frataxin protein, which is involved in the biogenesis of iron-sulfur clusters. Our previous studies suggested that cell death in FRDA may involve ferroptosis, an iron-dependent form of cell death requiring lipid peroxidation. Based on reports that oleic acid acts as a ferroptosis inhibitor, we evaluated whether it, other fatty acids, and fatty acid derivatives could rescue viability in cellular models of FRDA. We identified a trifluoromethyl alcohol analog of oleic acid that was significantly more potent than oleic acid itself. Further evaluation indicated that the effects were stereoselective, although a specific molecular target has not yet been identified. This work provides a potential starting point for therapeutics to treat FRDA, as well as a valuable probe molecule to interrogate FRDA pathophysiology.

Friedreich ataxia (FRDA) is a progressive neuro- and cardio-degenerative disorder characterized by ataxia, sensory loss, and hypertrophic cardiomyopathy. In most cases, the disorder is caused by GAA repeat expansions in the first introns of both alleles of the FXN gene, resulting in decreased expression of the encoded protein, frataxin. Frataxin localizes to the mitochondrial matrix and is required for iron-sulfur-cluster biosynthesis. Decreased expression of frataxin is associated with mitochondrial dysfunction, mitochondrial iron accumulation, and increased oxidative stress. Ferropotosis is a recently identified pathway of regulated, iron-dependent cell death, which is biochemically distinct from apoptosis. We evaluated whether there is evidence for ferroptotic pathway activation in cellular models of FRDA. We found that primary patient-derived fibroblasts, murine fibroblasts with FRDA-associated mutations, and murine fibroblasts in which a repeat expansion had been introduced (knockin/knockout) were more sensitive than normal control cells to erastin, a known ferroptosis inducer. We also found that the ferroptosis inhibitors ethyl 3-(benzylamino)-4-(cyclohexylamino)benzoate (SRS11-92) and ethyl 3-amino-4-(cyclohexylamino)benzoate, used at 500 nM, were efficacious in protecting human and mouse cellular models of FRDA treated with ferric ammonium citrate (FAC) and an inhibitor of glutathione synthesis [L-buthionine (S,R)-sulfoximine (BSO)], whereas caspase-3 inhibitors failed to show significant biologic activity. Cells treated with FAC and BSO consistently showed decreased glutathione-dependent peroxidase activity and increased lipid peroxidation, both hallmarks of ferroptosis. Finally, the ferroptosis inhibitor SRS11-92 decreased the cell death associated with frataxin knockdown in healthy human fibroblasts. Taken together, these data suggest that ferroptosis inhibitors may have therapeutic potential in FRDA.

Friedreich ataxia (FRDA) is an autosomal recessive neuro- and cardio-degenerative disorder caused by decreased expression of frataxin, a protein that localizes to mitochondria and is critical for iron-sulfur-cluster (ISC) assembly. There are no proven effective treatments for FRDA. We previously screened a random shRNA library and identified a synthetic shRNA (gFA11) that reverses the growth defect of FRDA cells in culture. We now report that gFA11 decreases cytokine secretion in primary FRDA fibroblasts and reverts other changes associated with cell senescence. The gene-expression profile induced by gFA11 is remarkably similar to the gene-expression profile induced by the p38 MAPK inhibitor SB203580. We found that p38 phosphorylation, indicating activation of the p38 pathway, is higher in FRDA cells than in normal control cells, and that siRNA knockdown of frataxin in normal fibroblasts also increases p38 phosphorylation. Treatment of FRDA cells with p38 inhibitors recapitulates the reversal of the slow-growth phenotype induced by clone gFA11. These data highlight the involvement of the p38 MAPK pathway in the pathogenesis of FRDA and the potential use of p38 inhibitors as a treatment for FRDA.

Friedreich Ataxia (FA) is a hereditary ataxia disorder with an associated hypertrophic cardiomyopathy, caused by a deficiency in the mitochondrial protein frataxin. Heart disease is the most common cause of premature death in FA, but little is known about the utility of various biomarkers in FA-related cardiomyopathy. We hypothesized that serum markers of cardiac injury, stress, fibrosis, and inflammation are higher in FA subjects than non-FA controls, and these markers correlate with echocardiographic markers of cardiomyopathy. A cross-sectional analysis of nine biomarkers from stored samples of asymptomatic FA subjects and non-FA controls was performed: highly-sensitive troponin T (TnT), galectin-3 (gal-3), highly sensitive C-reactive protein (hsCRP), N-terminal pro-brain natriuretic peptide (NT-proBNP), ferritin, soluble ST2 (sST2), soluble Fms-like tyrosine kinase receptor 1 (sFlt-1), tissue inhibitor of matrix metalloproteinase type 1 (TIMP-1), and N-terminal propeptide of type III procollagen (PIIINP). In a cohort of 86 FA subjects (50% male, mean age 29.1 yrs) and 20 non-FA controls (50% male, mean age 36.7 yrs), TnT was detectable in 20% of FA (range <0.006 - 0.109 pg/mL) and 0 controls. Gal-3 was higher in FA vs non-FA subjects (14.2 ± 6.0 vs 9.6 ± 3.3 ng/mL, p=0.006); there were no other biomarker differences between cases and controls. In a subset of 32 FA subjects in whom single reader echo data was available, ferritin and ST2 showed moderate correlation with measures of left ventricular thickness (Table 1); for ferritin, this association persisted on regression analysis when adjusted for covariates of age of onset and GAA triplet repeat length. TnT, gal-3, ST2, and ferritin show promise as markers of cardiac disease in FA. Longitudinal and prospective studies are needed to validate these biomarkers as possible aids in diagnosis, prognosis, and identification of targets for therapeutic intervention.

From the viewpoint of the clinical laboratory, the consolidation of as many assays and types of assays as possible onto a single and existing automated analyzer (platform) is desirable. Such consolidation, which reduces the complexity and overall cost of a laboratory operation, is exemplified by the implementation of nonseparation (homogeneous) immunoassays such as enzyme multiplied immunoassay technique (EMIT),2 cloned enzyme donor immunoassay (CEDIA), and luminescent oxygen channeling immunoassay (LOCI) onto routine automated clinical chemistry analyzers (1). For relatively complex nucleic acid assays, automation of all or part of the assay has also been accomplished on dedicated analyzers but with relatively limited menus (2). Now there is the prospect of implementing nucleic acid assays on a routine immunoassay analyzer. An article in this issue of Clinical Chemistry addresses the problem of the compatibility of nucleic acid testing with high-throughput clinical laboratory workflows and describes the adaptation of nonamplification microRNA (miRNA) assays to a standard commercial immunoassay analyzer (3). miRNAs are small, noncoding RNAs, 19–25 nucleotides in length, that function as posttranscriptional regulators of up to half of all protein-encoding genes. Their utility as biomarkers derives from their important regulatory roles in most cellular and developmental processes, and from their remarkable stability, even in body fluids such as …

Friedreich ataxia (FRDA) is an autosomal recessive neuro- and cardio-degenerative disorder for which there are no proven effective treatments. FRDA is caused by decreased expression and/or function of the protein frataxin. Frataxin chaperones iron in the mitochondrial matrix and regulates the iron–sulfur cluster (ISC) assembly complex. ISCs are prosthetic groups critical for the function of the Krebs cycle and the mitochondrial electron transport chain. Decreased expression of frataxin is associated with decreased ISC assembly, mitochondrial iron accumulation, and increased oxidative stress, all of which contribute to mitochondrial dysfunction. In media with beta-hydroxybutyrate (BHB) as carbon source, primary FRDA fibroblasts grow poorly and/or lose viability over several days. We screened a random, short-hairpin-RNA (shRNA)-expressing library in primary FRDA fibroblasts and identified two shRNAs that reverse the growth/viability defect in BHB media. One of these two clones increases frataxin expression in primary FRDA fibroblasts, either as a vector-expressed shRNA or as a transfected short-interfering RNA (siRNA).

OBJECTIVE:Friedreich ataxia (FRDA) is an autosomal recessive ataxia resulting from mutations in the frataxin gene (FXN). Such mutations, usually expanded guanine-adenine-adenine (GAA) repeats, give rise to decreased levels of frataxin protein in both affected and unaffected tissues. The goal was to understand the relationship of frataxin levels in peripheral tissues to disease status.METHODS:Frataxin levels were measured in buccal cells and blood, and analyzed in relation to disease features. Site-directed mutant frataxin was also transfected into human embryonic kidney cells to model results from specific point mutations.RESULTS:There was no evidence for change in frataxin levels over time with repeated measures analysis, although linear regression analysis of cross-sectional data predicted a small increase over decades. GAA repeat length predicted frataxin levels in both tissues, and frataxin levels themselves predicted neurological ratings (accounting for age). Compound heterozygous patients for a GAA expansion and a point mutation in FXN generally had lower levels of frataxin than those homozygous for the presence of two GAA repeat expansions, though levels varied dramatically between tissues in some compound heterozygotes for point mutations. The G130V mutation led to decreased levels of frataxin in vitro as well as in vivo, while the R165C mutation produced normal immunoreactive levels of frataxin both in vitro and in vivo. Start codon mutations led to low levels of frataxin in buccal cells but preserved immunoreactive frataxin levels in blood.INTERPRETATION:The present data show that peripheral frataxin levels reflect disease features in FRDA, but emphasize the need for interpretation of such levels in the context of specific mutations.