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FARAFARA Cure FA

 

Scientific News

FARA funds research progress

In this section, you will find the most recent FA research publications, many of which are funded by FARA, as well as information on upcoming conferences and symposiums. You can search for articles by date using the archive box in the right hand column. To locate FARA Funded or Supported Research, click the hyperlink in the right hand column. You may also search for specific content using key words or phrases in the search button at the top right of your screen. Please be sure to visit other key research sections of our website for information on FARA’s Grant Program and the Treatment Pipeline.

 


 

Nonataxia symptoms in Friedreich Ataxia: Report from the Registry of the European Friedreich's Ataxia Consortium for Translational Studies (EFACTS)

This paper describes a systematic evaluation of the broad clinical variability in Friedreich ataxia (FRDA), a multisystem disorder presenting mainly with afferent ataxia but also a complex phenotype of nonataxia symptoms. The authors studied 650 patients with genetically confirmed FRDA from the large database of the European Friedreich's Ataxia Consortium for Translational Studies. Detailed data of medical history documentation, questionnaires, and reports on clinical features were analyzed to provide in-depth description of the clinical profile and frequency rates of phenotypical features with a focus on differences between typical-onset and late-onset FRDA. Logistic regression modeling was used to identify predictors for the presence of the most common clinical features. The most frequent clinical features beyond afferent ataxia were abnormal eye movements (90.5%), scoliosis (73.5%), deformities of the feet (58.8%), urinary dysfunction (42.8%), cardiomyopathy and cardiac hypertrophy (40.3%), followed by decreased visual acuity (36.8%); less frequent features were, among others, depression (14.1%) and diabetes (7.1%). Most of these features were more common in the typical-onset group compared to the late-onset group. Logistic regression models for the presence of these symptoms demonstrated the predictive value of GAA repeat length on the shorter allele and age at onset, but also severity of ataxia signs, sex, and presence of neonatal problems. This joint European effort demonstrates the multisystem nature of this neurodegenerative disease encompassing most the central nervous, neuromuscular, cardiologic, and sensory systems. A distinct and deeper knowledge of this rare and chronic disease is highly relevant for clinical practice and designs of clinical trials.

Read the entire article HERE

Activating frataxin expression by single-stranded siRNAs targeting the GAA repeat expansion

Friedreich's ataxia (FRDA) is an incurable neurodegenerative disorder caused by reduced expression of the mitochondrial protein frataxin (FXN). The genetic cause of the disease is an expanded GAA repeat within the FXN gene. Agents that increase expression of FXN protein are a potential approach to therapy. This group has previously described anti-trinucleotide GAA duplex RNAs (dsRNAs) and antisense oligonucleotides (ASOs) that activate FXN protein expression in multiple patient derived cell lines. Here they test two distinct series of compounds for their ability to increase FXN expression. ASOs with butane linkers showed low potency, which is consistent with the low Tm values and suggesting that flexible conformation impairs activity. By contrast, single-stranded siRNAs (ss-siRNAs) that combine the strengths of dsRNA and ASO approaches had nanomolar potencies. ss-siRNAs provide an additional option for developing nucleic acid therapeutics to treat FRDA.

Read the entire article HERE

Novel Nrf2-Inducer Prevents Mitochondrial Defects and Oxidative Stress in Friedreich's Ataxia Models

In Friedreich's Ataxia, increased oxidative stress leads to a chronic depletion of endogenous antioxidants, which affects the survival of the cells and causes neurodegeneration. In particular, cerebellar granule neurons (CGNs) show a significant increase of reactive oxygen species (ROS), lipid peroxidation and lower level of reduced glutathione (GSH). In FRDA, one of the major pathways of oxidant scavengers, the Nrf2 antioxidant pathway, is defective. Previous studies on FRDA-like CGNs showed that the reduced level of frataxin and the oxidative stress induce mitochondrial impairments. By triggering the Nrf2 pathway pharmacologically we determined whether this could promote mitochondrial fitness and counteract oxidative stress. In this work, we sought to investigate the beneficial effect of a promising Nrf2-inducer, omaveloxolone (omav), in CGNs from two FRDA mouse models, KIKO and YG8R, and human fibroblasts from patients. We found that CGNs from both KIKO and YG8R presented Complex I deficiency and that omav was able to restore substrate availability and Complex I activity. This was also confirmed in human primary fibroblasts from FRDA patients. Although fibroblasts are not the major tissue affected, we found that they show significant differences recapitulating the disease; this is therefore an important tool to investigate patients' pathophysiology. Interestingly, we found that patient fibroblasts had an increased level of endogenous lipid peroxidation and mitochondrial ROS (mROS), and lower GSH at rest. Omav was able to reverse this phenotype, protecting the cells against oxidative stress. By stimulating the cells with hydrogen peroxide (H2O2) and looking for potential mitochondrial pathophysiology, we found that fibroblasts could not maintain their mitochondrial membrane potential (ΔΨm). Remarkably, omav was protective to mitochondrial depolarization, promoting mitochondrial respiration and preventing cell death. Our results show that omav promotes Complex I activity and protect cells from oxidative stress. Omav could, therefore, be used as a novel therapeutic drug to ameliorate the pathophysiology of FRDA.

Read the entire article HERE

Longitudinal analysis of contrast acuity in Friedreich ataxia

In the Friedreich Ataxia-Clinical Outcome Measures Study, participants (n = 764) underwent binocular high- and low-contrast visual acuity testing at annual study visits. Mixed-effects linear regression was used to model visual acuity as a function of time, with random intercepts and slopes to account for intraindividual correlation of repeated measurements. A time-varying covariate was used to adjust for diabetes, and interaction terms were used to assess for effect modification by GAA repeat length, disease duration, and other variables.

Across a median of 4.4 years of follow-up, visual acuity decreased significantly at 100% contrast (-0.37 letters/y, 95% confidence interval [CI]: -0.52 to -0.21), 2.5% contrast (-0.81 letters/year, 95% CI: -0.99 to -0.65), and 1.25% contrast (-1.12 letters/y, 95% CI: -1.29 to -0.96 letters/year). There was a significant interaction between time and GAA repeat length such that the rate of decrease in visual acuity was greater for patients with higher GAA repeat lengths at 2.5% contrast (p = 0.018) and 1.25% contrast (p = 0.043) but not 100% contrast. There was no effect modification by age at onset after adjusting for GAA repeat length.

Low-contrast visual acuity decreases linearly over time in Friedreich ataxia, and the rate of decrease is greater at higher GAA repeat lengths. Contrast sensitivity has the potential to serve as a biomarker and surrogate outcome in future studies of Friedreich ataxia.

Read the entire article HERE

RNA-Dependent Epigenetic Silencing Directs Transcriptional Downregulation Caused by Intronic Repeat Expansions

Transcriptional downregulation caused by intronic triplet repeat expansions underlies diseases such as Friedreich's ataxia. This downregulation of gene expression is coupled with epigenetic changes, but the underlying mechanisms are unknown. Here, we show that an intronic GAA/TTC triplet expansion within the IIL1 gene of Arabidopsis thaliana results in accumulation of 24-nucleotide short interfering RNAs (siRNAs) and repressive histone marks at the IIL1 locus, which in turn causes its transcriptional downregulation and an associated phenotype. Knocking down DICER LIKE-3 (DCL3), which produces 24-nucleotide siRNAs, suppressed transcriptional downregulation of IIL1 and the triplet expansion-associated phenotype. Furthermore, knocking down additional components of the RNA-dependent DNA methylation (RdDM) pathway also suppressed both transcriptional downregulation of IIL1 and the repeat expansion-associated phenotype. Thus, our results show that triplet repeat expansions can lead to local siRNA biogenesis, which in turn downregulates transcription through an RdDM-dependent epigenetic modification.

Read the entire article HERE

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