Publications by authors named "Myriam Rai"

24 Publications

  • Page 1 of 1

Cerebellar cognitive disorder parallels cerebellar motor symptoms in Friedreich ataxia.

Ann Clin Transl Neurol 2020 06 8;7(6):1050-1054. Epub 2020 Jun 8.

Department of Neurology, CUB Hôpital Erasme, Université libre de Bruxelles (ULB), Brussels, Belgium.

Dentate nuclei (DN) are involved in cerebellar modulation of motor and cognitive functions, whose impairment causes ataxia and cerebellar cognitive affective syndrome (CCAS). Friedreich ataxia (FRDA) disease progression relates to degeneration of the dentate nucleus and dentato-thalamic pathways, causing cerebellar ataxia. Volumetric MRI also shows mild loss in the cerebellar cortex, brainstem, and motor cortex. Cognitive deficits occur in FRDA, but their relationship with ataxia progression is not fully characterized. We found a significant positive correlation between severity of patients' ataxia and more marked CCAS as assessed with the CCAS-Scale. This relation could be related to progressive DN impairment.
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http://dx.doi.org/10.1002/acn3.51079DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7317641PMC
June 2020

Primary proprioceptive neurons from human induced pluripotent stem cells: a cell model for afferent ataxias.

Sci Rep 2020 05 8;10(1):7752. Epub 2020 May 8.

Laboratory of Experimental Neurology, Université Libre de Bruxelles (ULB), 1070, Brussels, Belgium.

Human induced pluripotent stem cells (iPSCs) are used to generate models of human diseases that recapitulate the pathogenic process as it occurs in affected cells. Many differentiated cell types can currently be obtained from iPSCs, but no validated protocol is yet available to specifically generate primary proprioceptive neurons. Proprioceptors are affected in a number of genetic and acquired diseases, including Friedreich ataxia (FRDA). To develop a cell model that can be applied to conditions primarily affecting proprioceptors, we set up a protocol to differentiate iPSCs into primary proprioceptive neurons. We modified the dual-SMAD inhibition/WNT activation protocol, previously used to generate nociceptor-enriched cultures of primary sensory neurons from iPSCs, to favor instead the generation of proprioceptors. We succeeded in substantially enriching iPSC-derived primary sensory neuron cultures for proprioceptors, up to 50% of finally differentiated neurons, largely exceeding the proportion of 7.5% normally represented by these cells in dorsal root ganglia. We also showed that almost pure populations of proprioceptors can be purified from these cultures by fluorescence-activated cell sorting. Finally, we demonstrated that the protocol can be used to generate proprioceptors from iPSCs from FRDA patients, providing a cell model for this genetic sensory neuronopathy.
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http://dx.doi.org/10.1038/s41598-020-64831-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7210273PMC
May 2020

Cerebellar ataxia, neuropathy, hearing loss, and intellectual disability due to AIFM1 mutation.

Neurol Genet 2020 Jun 9;6(3):e420. Epub 2020 Apr 9.

Neurology Service (M.P., G.R.), Hôpital Erasme; Laboratory of Experimental Neurology (M.P., M.R.); and Medical Genetics Service (L.D., I.V.), Hôpital Erasme, Université Libre de Bruxelles, Belgium.

Objective: To describe the clinical and molecular genetic findings in a family segregating a novel mutation in the gene on the X chromosome.

Methods: We studied the clinical features and performed brain MRI scans, nerve conduction studies, audiometry, cognitive testing, and clinical exome sequencing (CES) in the proband, his mother, and maternal uncle. We used in silico tools, X chromosome inactivation assessment, and Western blot analysis to predict the consequences of an variant identified by CES and demonstrate its pathogenicity.

Results: The proband and his maternal uncle presented with childhood-onset nonprogressive cerebellar ataxia, hearing loss, intellectual disability (ID), peripheral neuropathy, and mood and behavioral disorder. The proband's mother had mild cerebellar ataxia, ID, and mood and behavior disorder, but no neuropathy or hearing loss. The 3 subjects shared a variant (c.1195G>A; p.Gly399Ser) in exon 12 of the gene, which is not reported in the exome/genome sequence databases, affecting a critical amino acid for protein function involved in NAD(H) binding and predicted to be pathogenic with very high probability by variant analysis programs. X chromosome inactivation was highly skewed in the proband's mother. The mutation did not cause quantitative changes in protein abundance.

Conclusions: Our report extends the molecular and phenotypic spectrum of mutations. Specific findings include limited progression of neurologic abnormalities after the first decade and the coexistence of mood and behavior disorder. This family also shows the confounding effect on the phenotype of nongenetic factors, such as alcohol and drug use and side effects of medication.
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http://dx.doi.org/10.1212/NXG.0000000000000420DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7164969PMC
June 2020

Exenatide induces frataxin expression and improves mitochondrial function in Friedreich ataxia.

JCI Insight 2020 01 30;5(2). Epub 2020 Jan 30.

ULB Center for Diabetes Research and.

Friedreich ataxia is an autosomal recessive neurodegenerative disease associated with a high diabetes prevalence. No treatment is available to prevent or delay disease progression. Friedreich ataxia is caused by intronic GAA trinucleotide repeat expansions in the frataxin-encoding FXN gene that reduce frataxin expression, impair iron-sulfur cluster biogenesis, cause oxidative stress, and result in mitochondrial dysfunction and apoptosis. Here we examined the metabolic, neuroprotective, and frataxin-inducing effects of glucagon-like peptide-1 (GLP-1) analogs in in vivo and in vitro models and in patients with Friedreich ataxia. The GLP-1 analog exenatide improved glucose homeostasis of frataxin-deficient mice through enhanced insulin content and secretion in pancreatic β cells. Exenatide induced frataxin and iron-sulfur cluster-containing proteins in β cells and brain and was protective to sensory neurons in dorsal root ganglia. GLP-1 analogs also induced frataxin expression, reduced oxidative stress, and improved mitochondrial function in Friedreich ataxia patients' induced pluripotent stem cell-derived β cells and sensory neurons. The frataxin-inducing effect of exenatide was confirmed in a pilot trial in Friedreich ataxia patients, showing modest frataxin induction in platelets over a 5-week treatment course. Taken together, GLP-1 analogs improve mitochondrial function in frataxin-deficient cells and induce frataxin expression. Our findings identify incretin receptors as a therapeutic target in Friedreich ataxia.
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http://dx.doi.org/10.1172/jci.insight.134221DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7098728PMC
January 2020

Urinary, bowel and sexual symptoms in a cohort of patients with Friedreich's ataxia.

Orphanet J Rare Dis 2017 09 26;12(1):158. Epub 2017 Sep 26.

Department of Molecular Neuroscience, Ataxia Centre, UCL Institute of Neurology and National Hospital for Neurology & Neurosurgery, Queen Square, London, WC1N 3BG, UK.

Background: Pelvic symptoms are distressing symptoms experienced by patients with Friedreich's Ataxia (FRDA). The aim of this study was to describe the prevalence of lower urinary tract symptoms (LUTS), bowel and sexual symptoms in FRDA.

Methods: Questionnaire scores measuring LUTS, bowel and sexual symptoms were analysed with descriptive statistics as a cohort and as subgroups (Early/Late-onset and Early/Late-stage FRDA) They were also correlated with validated measures of disease severity including those of ataxia severity, non-ataxic symptoms and activities of daily living.

Results: 80% (n = 46/56) of patients reported LUTS, 64% (n = 38/59) reported bowel symptoms and 83% (n = 30/36) reported sexual symptoms. Urinary and bowel or sexual symptoms were significantly likely to co-exist among patients. Late-onset FRDA patients were also more likely to report LUTS than early-onset ones. Patients with a longer disease duration reported higher LUTS scores and poorer quality of life scores related to urinary symptoms.

Conclusions: A high proportion of FRDA have symptoms suggestive of LUTS, bowel and sexual dysfunction. This is more marked with greater disease duration and later disease onset. These symptoms need to be addressed by clinicians as they can have a detrimental effect on patients.
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http://dx.doi.org/10.1186/s13023-017-0709-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5615455PMC
September 2017

Erythropoietin and small molecule agonists of the tissue-protective erythropoietin receptor increase FXN expression in neuronal cells in vitro and in Fxn-deficient KIKO mice in vivo.

Neuropharmacology 2017 Sep 11;123:34-45. Epub 2017 May 11.

STATegics, Inc., 428 Oakmead Pkwy, Sunnyvale, CA 94085, USA. Electronic address:

Friedreich's ataxia (FA) is a progressive neurodegenerative disease caused by reduced levels of the mitochondrial protein frataxin (FXN). Recombinant human erythropoietin (rhEPO) increased FXN protein in vitro and in early clinical studies, while no published reports evaluate rhEPO in animal models of FA. STS-E412 and STS-E424 are novel small molecule agonists of the tissue-protective, but not the erythropoietic EPO receptor. We find that rhEPO, STS-E412 and STS-E424 increase FXN expression in vitro and in vivo. RhEPO, STS-E412 and STS-E424 increase FXN by up to 2-fold in primary human cortical cells and in retinoic-acid differentiated murine P19 cells. In primary human cortical cells, the increase in FXN protein was accompanied by an increase in FXN mRNA, detectable within 4 h. RhEPO and low nanomolar concentrations of STS-E412 and STS-E424 also increase FXN in normal and FA patient-derived PBMC by 20%-40% within 24 h, an effect that was comparable to that by HDAC inhibitor 4b. In vivo, STS-E412 increased Fxn mRNA and protein in wild-type C57BL6/j mice. RhEPO, STS-E412, and STS-E424 increase FXN expression in the heart of FXN-deficient KIKO mice. In contrast, FXN expression in the brains of KIKO mice increased following treatment with STS-E412 and STS-E424, but not following treatment with rhEPO. Unexpectedly, rhEPO-treated KIKO mice developed severe splenomegaly, while no splenomegaly was observed in STS-E412- or STS-E424-treated mice. RhEPO, STS-E412 and STS-E424 upregulate FXN expression in vitro at equal efficacy, however, the effects of the small molecules on FXN expression in the CNS are superior to rhEPO in vivo.
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http://dx.doi.org/10.1016/j.neuropharm.2017.05.011DOI Listing
September 2017

Friedreich ataxia-induced pluripotent stem cell-derived neurons show a cellular phenotype that is corrected by a benzamide HDAC inhibitor.

Hum Mol Genet 2016 11;25(22):4847-4855

Laboratoire de Neurologie Expérimentale, Université Libre de Bruxelles (ULB), 1070 Brussels, Belgium.

We employed induced pluripotent stem cell (iPSC)-derived neurons obtained from Friedreich ataxia (FRDA) patients and healthy subjects, FRDA neurons and CT neurons, respectively, to unveil phenotypic alterations related to frataxin (FXN) deficiency and investigate if they can be reversed by treatments that upregulate FXN. FRDA and control iPSCs were equally capable of differentiating into a neuronal or astrocytic phenotype. FRDA neurons showed lower levels of iron–sulfur (Fe–S) and lipoic acid-containing proteins, higher labile iron pool (LIP), higher expression of mitochondrial superoxide dismutase (SOD2), increased reactive oxygen species (ROS) and lower reduced glutathione (GSH) levels, and enhanced sensitivity to oxidants compared with CT neurons, indicating deficient Fe–S cluster biogenesis, altered iron metabolism, and oxidative stress. Treatment with the benzamide HDAC inhibitor 109 significantly upregulated FXN expression and increased Fe–S and lipoic acid-containing protein levels, downregulated SOD2 levels, normalized LIP and ROS levels, and almost fully protected FRDA neurons from oxidative stress-mediated cell death. Our findings suggest that correction of FXN deficiency may not only stop disease progression, but also lead to clinical improvement by rescuing still surviving, but dysfunctional neurons.
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http://dx.doi.org/10.1093/hmg/ddw308DOI Listing
November 2016

Progression characteristics of the European Friedreich's Ataxia Consortium for Translational Studies (EFACTS): a 2 year cohort study.

Lancet Neurol 2016 Dec;15(13):1346-1354

Department of Neurology, RWTH Aachen University, Aachen, Germany; JARA-BRAIN Institute of Molecular Neuroscience and Neuroimaging, Forschungszentrum Jülich GmbH and RWTH Aachen University, Aachen, Germany. Electronic address:

Background: The European Friedreich's Ataxia Consortium for Translational Studies (EFACTS) is a prospective international registry investigating the natural history of Friedreich's ataxia. We used data from EFACTS to assess disease progression and the predictive value of disease-related factors on progression, and estimated sample sizes for interventional randomised clinical trials.

Methods: We enrolled patients with genetically confirmed Friedreich's ataxia from 11 European study sites in Austria, Belgium, France, Germany, Italy, Spain, and the UK. Patients were seen at three visits-baseline, 1 year, and 2 years. Our primary endpoint was the Scale for the Assessment and Rating of Ataxia (SARA). Secondary outcomes were the Inventory of Non-Ataxia Signs (INAS), the Spinocerebellar Ataxia Functional Index (SCAFI), phonemic verbal fluency (PVF), and the quality of life measures activities of daily living (ADL) and EQ-5D-3L index. We estimated the yearly progression for each outcome with linear mixed-effect modelling. This study is registered with ClinicalTrials.gov, number NCT02069509, and follow-up assessments and recruitment of new patients are ongoing.

Findings: Between Sept 15, 2010, and Nov 21, 2013, we enrolled 605 patients with Friedreich's ataxia. 546 patients (90%) contributed data with at least one follow-up visit. The progression rate on SARA was 0·77 points per year (SE 0·06) in the overall cohort. Deterioration in SARA was associated with younger age of onset (-0·02 points per year [0·01] per year of age) and lower SARA baseline scores (-0·07 points per year [0·01] per baseline point). Patients with more than 353 GAA repeats on the shorter allele of the FXN locus had a higher SARA progression rate (0·09 points per year [0·02] per additional 100 repeats) than did patients with fewer than 353 repeats. Annual worsening was 0·10 points per year (0·03) for INAS, -0·04 points per year (0·01) for SCAFI, 0·93 points per year (0·06) for ADL, and -0·02 points per year (0·004) for EQ-5D-3L. PVF performance improved by 0·99 words per year (0·14). To detect a 50% reduction in SARA progression at 80% power, 548 patients would be needed in a 1 year clinical trial and 184 would be needed for a 2 year trial.

Interpretation: Our results show that SARA is a suitable clinical rating scale to detect deterioration of ataxia symptoms over time; ADL is an appropriate measure to monitor changes in daily self-care activities; and younger age at disease onset is a major predictor for faster disease progression. The results of the EFACTS longitudinal analysis provide suitable outcome measures and sample size calculations for the design of upcoming clinical trials of Friedreich's ataxia.

Funding: European Commission.
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http://dx.doi.org/10.1016/S1474-4422(16)30287-3DOI Listing
December 2016

MME mutation in dominant spinocerebellar ataxia with neuropathy (SCA43).

Neurol Genet 2016 Oct 18;2(5):e94. Epub 2016 Aug 18.

Department of Neurology (C.D., M.M., M.P.), Department of Medical Genetics (N.S.), Hôpital Erasme, Laboratory of Experimental Neurology (C.D., S.D., M.R., M.M.), Université Libre de Bruxelles; Department of Physical Medicine and Rehabilitation (F.C.W.), University of Liège, University Hospital; and Fonds National de la Recherche Scientifique (M.M.), Brussels, Belgium.

Objective: To identify the causative gene mutation in a 5-generation Belgian family with dominantly inherited spinocerebellar ataxia and polyneuropathy, in which known genetic etiologies had been excluded.

Methods: We collected DNA samples of 28 family members, including 7 living affected individuals, whose clinical records were reviewed by a neurologist experienced in ataxia. We combined linkage data of 21 family members with whole exome sequencing in 2 affected individuals to identify shared heterozygous variants mapping to potentially linked regions. Variants were screened for rarity and for predicted damaging effect. A candidate mutation was confirmed by Sanger sequencing and tested for cosegregation with the disease.

Results: Affected individuals presented with late-onset sensorimotor axonal polyneuropathy; all but one also had cerebellar ataxia. We identified a variant in the MME gene, p.C143Y, that was absent from control databases, cosegregated with the phenotype, and was predicted to have a strong damaging effect on the encoded protein by all algorithms we used.

Conclusions: MME encodes neprilysin (NEP), a zinc-dependent metalloprotease expressed in most tissues, including the central and peripheral nervous systems. The mutated cysteine 143 forms a disulfide bridge, which is 100% conserved in NEP and in similar enzymes. The recent identification of recessive MME mutations in 10 unrelated individuals from Japan with axonal polyneuropathy further supports the causality of the mutation, despite the dominant mode of inheritance and the presence of cerebellar involvement in our study family. Functional studies are needed to identify the mechanisms underlying these differences.
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http://dx.doi.org/10.1212/NXG.0000000000000094DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4991603PMC
October 2016

Delayed-onset Friedreich's ataxia revisited.

Mov Disord 2016 Jan 21;31(1):62-9. Epub 2015 Sep 21.

Département de Neurologie, Hôpital de Hautepierre, CHU de Strasbourg, France Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM-U964/CNRS-UMR7104/Université de Strasbourg, Illkirch, France; and Fédération de Médecine Translationnelle de Strasbourg (FMTS), Université de Strasbourg, Strasbourg, France.

Background: Friedreich's ataxia usually occurs before the age of 25. Rare variants have been described, such as late-onset Friedreich's ataxia and very-late-onset Friedreich's ataxia, occurring after 25 and 40 years, respectively. We describe the clinical, functional, and molecular findings from a large series of late-onset Friedreich's ataxia and very-late-onset Friedreich's ataxia and compare them with typical-onset Friedreich's ataxia.

Methods: Phenotypic and genotypic comparison of 44 late-onset Friedreich's ataxia, 30 very late-onset Friedreich's ataxia, and 180 typical Friedreich's ataxia was undertaken.

Results: Delayed-onset Friedreich's ataxia (late-onset Friedreich's ataxia and very-late-onset Friedreich's ataxia) had less frequently dysarthria, abolished tendon reflexes, extensor plantar reflexes, weakness, amyotrophy, ganglionopathy, cerebellar atrophy, scoliosis, and cardiomyopathy than typical-onset Friedreich's ataxia, along with less severe functional disability and shorter GAA expansion on the smaller allele (P < 0.001). Delayed-onset Friedreich's ataxia had lower scale for the assessment and rating of ataxia and spinocerebellar degeneration functional scores and longer disease duration before wheelchair confinement (P < 0.001). Both GAA expansions were negatively correlated to age at disease onset (P < 0.001), but the smaller GAA expansion accounted for 62.9% of age at onset variation and the larger GAA expansion for 15.6%. In this comparative study of late-onset Friedreich's ataxia and very-late-onset Friedreich's ataxia, no differences between these phenotypes were demonstrated.

Conclusion: Typical- and delayed-onset Friedreich's ataxia are different and Friedreich's ataxia is heterogeneous. Late-onset Friedreich's ataxia and very-late-onset Friedreich's ataxia appear to belong to the same clinical and molecular continuum and should be considered together as "delayed-onset Friedreich's ataxia." As the most frequently inherited ataxia, Friedreich's ataxia should be considered facing compatible pictures, including atypical phenotypes (spastic ataxia, retained reflexes, lack of dysarthria, and lack of extraneurological signs), delayed disease onset (even after 60 years of age), and/or slow disease progression.
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http://dx.doi.org/10.1002/mds.26382DOI Listing
January 2016

Epigenetic therapy for Friedreich ataxia.

Ann Neurol 2014 Oct 16;76(4):489-508. Epub 2014 Sep 16.

Departments of Cell and Molecular Biology, Scripps Research Institute, La Jolla, CA.

Objective: To investigate whether a histone deacetylase inhibitor (HDACi) would be effective in an in vitro model for the neurodegenerative disease Friedreich ataxia (FRDA) and to evaluate safety and surrogate markers of efficacy in a phase I clinical trial in patients.

Methods: We used a human FRDA neuronal cell model, derived from patient induced pluripotent stem cells, to determine the efficacy of a 2-aminobenzamide HDACi (109) as a modulator of FXN gene expression and chromatin histone modifications. FRDA patients were dosed in 4 cohorts, ranging from 30mg/day to 240mg/day of the formulated drug product of HDACi 109, RG2833. Patients were monitored for adverse effects as well as for increases in FXN mRNA, frataxin protein, and chromatin modification in blood cells.

Results: In the neuronal cell model, HDACi 109/RG2833 increases FXN mRNA levels and frataxin protein, with concomitant changes in the epigenetic state of the gene. Chromatin signatures indicate that histone H3 lysine 9 is a key residue for gene silencing through methylation and reactivation through acetylation, mediated by the HDACi. Drug treatment in FRDA patients demonstrated increased FXN mRNA and H3 lysine 9 acetylation in peripheral blood mononuclear cells. No safety issues were encountered.

Interpretation: Drug exposure inducing epigenetic changes in neurons in vitro is comparable to the exposure required in patients to see epigenetic changes in circulating lymphoid cells and increases in gene expression. These findings provide a proof of concept for the development of an epigenetic therapy for this fatal neurological disease.
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http://dx.doi.org/10.1002/ana.24260DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4361037PMC
October 2014

Autosomal recessive cerebellar ataxia of adult onset due to STUB1 mutations.

Neurology 2014 May 9;82(19):1749-50. Epub 2014 Apr 9.

From Hôpital Erasme (C.D., N.S., R.v.H., M.A., M.P.), Université Libre de Bruxelles (C.D., S.D., M.R., M.P.); and Algemeen Ziekenhuis Sint-Jan (M.D.), Brugge, Belgium.

Autosomal recessive ataxias affect about 1 person in 20,000. Friedreich ataxia accounts for one-third of the cases in Caucasians; the others are due to a growing list of very rare molecular defects, including mild forms of metabolic diseases. In nearly 50%, the genetic cause remains undetermined.
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http://dx.doi.org/10.1212/WNL.0000000000000416DOI Listing
May 2014

Mutations in TNK2 in severe autosomal recessive infantile onset epilepsy.

Ann Neurol 2013 Sep 4;74(3):496-501. Epub 2013 Sep 4.

Duke Center for Human Genome Variation, Duke University School of Medicine, Durham, NC.

We identified a small family with autosomal recessive, infantile onset epilepsy and intellectual disability. Exome sequencing identified a homozygous missense variant in the gene TNK2, encoding a brain-expressed tyrosine kinase. Sequencing of the coding region of TNK2 in 110 patients with a similar phenotype failed to detect further homozygote or compound heterozygote mutations. Pathogenicity of the variant is supported by the results of our functional studies, which demonstrated that the variant abolishes NEDD4 binding to TNK2, preventing its degradation after epidermal growth factor stimulation. Definitive proof of pathogenicity will require confirmation in unrelated patients.
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http://dx.doi.org/10.1002/ana.23934DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4527160PMC
September 2013

Central role and mechanisms of β-cell dysfunction and death in friedreich ataxia-associated diabetes.

Ann Neurol 2012 Dec;72(6):971-82

Laboratory of Experimental Medicine, Universite Libre de Bruxelles, Brussels, Belgium.

Objective: Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative disease caused in almost all cases by homozygosity for a GAA trinucleotide repeat expansion in the frataxin gene. Frataxin is a mitochondrial protein involved in iron homeostasis. FRDA patients have a high prevalence of diabetes, the pathogenesis of which is not known. We aimed to evaluate the relative contribution of insulin resistance and β-cell failure and the pathogenic mechanisms involved in FRDA diabetes.

Methods: Forty-one FRDA patients, 26 heterozygous carriers of a GAA expansion, and 53 controls underwent oral and intravenous glucose tolerance tests. β-Cell proportion was quantified in postmortem pancreas sections from 9 unrelated FRDA patients. Using an in vitro disease model, we studied how frataxin deficiency affects β-cell function and survival.

Results: FRDA patients had increased abdominal fat and were insulin resistant. This was not compensated for by increased insulin secretion, resulting in a markedly reduced disposition index, indicative of pancreatic β-cell failure. Loss of glucose tolerance was driven by β-cell dysfunction, which correlated with abdominal fatness. In postmortem pancreas sections, pancreatic islets of FRDA patients had a lower β-cell content. RNA interference-mediated frataxin knockdown impaired glucose-stimulated insulin secretion and induced apoptosis in rat β cells and human islets. Frataxin deficiency sensitized β cells to oleate-induced and endoplasmic reticulum stress-induced apoptosis, which could be prevented by the incretins glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide.

Interpretation: Pancreatic β-cell dysfunction is central to diabetes development in FRDA as a result of mitochondrial dysfunction and higher sensitivity to metabolic and endoplasmic reticulum stress-induced β-cell death.
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http://dx.doi.org/10.1002/ana.23698DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4900175PMC
December 2012

Neurons and cardiomyocytes derived from induced pluripotent stem cells as a model for mitochondrial defects in Friedreich's ataxia.

Dis Model Mech 2013 May 7;6(3):608-21. Epub 2012 Nov 7.

Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), 67404 Illkirch, France.

Friedreich's ataxia (FRDA) is a recessive neurodegenerative disorder commonly associated with hypertrophic cardiomyopathy. FRDA is due to expanded GAA repeats within the first intron of the gene encoding frataxin, a conserved mitochondrial protein involved in iron-sulphur cluster biosynthesis. This mutation leads to partial gene silencing and substantial reduction of the frataxin level. To overcome limitations of current cellular models of FRDA, we derived induced pluripotent stem cells (iPSCs) from two FRDA patients and successfully differentiated them into neurons and cardiomyocytes, two affected cell types in FRDA. All FRDA iPSC lines displayed expanded GAA alleles prone to high instability and decreased levels of frataxin, but no biochemical phenotype was observed. Interestingly, both FRDA iPSC-derived neurons and cardiomyocytes exhibited signs of impaired mitochondrial function, with decreased mitochondrial membrane potential and progressive mitochondrial degeneration, respectively. Our data show for the first time that FRDA iPSCs and their neuronal and cardiac derivatives represent promising models for the study of mitochondrial damage and GAA expansion instability in FRDA.
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http://dx.doi.org/10.1242/dmm.010900DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3634645PMC
May 2013

A gene expression phenotype in lymphocytes from Friedreich ataxia patients.

Ann Neurol 2011 Nov;70(5):790-804

Program in Neurogenetics, Department of Neurology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA.

Objective: Gene expression studies in peripheral tissues from patients with neurodegenerative disorders can provide insights into disease pathogenesis, and identify potential biomarkers, an important goal of translational research in neurodegeneration. Friedreich Ataxia (FRDA) is a chronic neurodegenerative disease caused by reduced transcription of frataxin, a ubiquitously expressed protein. We studied in vitro lymphocytes from FRDA patients and carriers to identify a peripheral gene expression phenotype. Peripheral biomarkers related to disease status would be extremely valuable for assessing drug efficacy and could provide new pathophysiological insights.

Methods: We characterized the gene expression profiles in peripheral blood mononuclear cells (PBMCs) from FRDA patients, compared with controls and related carriers. Cells were studied both before and after in vitro treatment with compounds that increase frataxin levels. Quantitative real-time polymerase chain reaction and additional microarrays were used to confirm a core set of genes in multiple independent series.

Results: We identified a subset of genes changed in cells from patients with pathological frataxin deficiency, and a core set of these genes were confirmed in independent series. Changes in gene expression were related to the mitochondria, lipid metabolism, cell cycle, and DNA repair, consistent with FRDA's known pathophysiology. We evaluated the in vitro effect of multiple compounds (histone deacetylase inhibitors) on this putative biomarker set, and found that this biochemical phenotype was ameliorated in accordance with drug efficacy.

Interpretation: Frataxin downregulation is associated with robust changes in gene expression in PBMCs, providing pathogenetic insights and a core subset of genes that, if verified in vivo, could be used as a peripheral biomarker.
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http://dx.doi.org/10.1002/ana.22526DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3646419PMC
November 2011

Normal left ventricular ejection fraction and mass but subclinical myocardial dysfunction in patients with Friedreich's ataxia.

Eur Heart J Cardiovasc Imaging 2012 Apr 28;13(4):346-52. Epub 2011 Nov 28.

Department of Cardiology, Erasme Hospital, Université Libre de Bruxelles, 808 Route de Lennik, Brussels, Belgium.

Aims: Myocardial involvement in Friedreich's ataxia (FRDA) is characterized by iron deposits, diffuse fibrosis, and focal necrosis. We hypothesized that subclinical left ventricular (LV) dysfunction may occur in 'FRDA patients who have normal LV ejection fraction (LVEF) and mass.

Methods And Results: Twenty patients homozygous for the GAA expansion in the frataxin gene (mean age: 35 ± 16 years) and twenty age- and sex-matched controls (mean age: 34 ± 15 years) were studied using conventional echocardiography and speckle-tracking imaging. The two groups did not differ in terms of the LVEF (68 ± 6 vs. 67 ± 6%, in patients and controls, respectively) or LV mass (91 ± 20 vs. 82 ± 17 g/m(2)). Global systolic longitudinal (-15.3 ± 2.1 vs. -17.5 ± 1.6%, P = 0.001) and circumferential (-19.5 ± 2.9 vs. -21.4 ± 2.6%, P = 0.034) strain, and peak LV twist (9.2 ± 3.3 vs. 11.7 ± 2.3°, P = 0.008) were significantly reduced in patients compared with controls. Indexed stroke volume was also significantly lower in patients (36 ± 5 vs. 43 ± 8 mL/m(2), P = 0.0012) and this decreased LV pump performance was associated with a concentric remodelling pattern (relative wall thickness: 0.47 ± 0.08 vs. 0.35 ± 0.05, P < 0.001).

Conclusion: There is evidence of morphological and functional abnormalities in FRDA patients with normal LVEF and mass.
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http://dx.doi.org/10.1093/ejechocard/jer267DOI Listing
April 2012

Niemann-Pick type C fibroblasts have a distinct microRNA profile related to lipid metabolism and certain cellular components.

Biochem Biophys Res Commun 2010 Dec 12;403(3-4):316-21. Epub 2010 Nov 12.

Department of Clinical Chemistry, Tampere University Hospital and University of Tampere, Finland.

MicroRNAs (miRNAs) are non-coding RNAs that regulate gene expression at post-transcriptional level. Dysregulation of miRNA expression may lead to severe pathophysiologies in human cells. Niemann-Pick type C (NPC) disease is a complex lipid storage disease characterized by late endosomal-lysosomal accumulation of multiple lipid molecules. Our aim was to characterize the miRNA profile in NPC fibroblasts as they may play an active role in the NPC disease associated changes in the cellular physiology. To investigate the miRNA expression, total RNAs were isolated from cultured human NPC fibroblasts and healthy fibroblasts and then, TaqMan Low-Density Array system containing 365 mature human miRNAs was used. Expression differences between the healthy and NPC cells were detected according to the relative quantification values. Target genes were predicted by using three different algorithms and classified regarding NPC related biological processes and cellular components. We found that three miRNAs, miR-196a, miR-196b and miR-296 were up-regulated (>3.5-fold increase, p<0.05) whereas 38 miRNAs were significantly down-regulated in NPC cells (>3.5-fold decrease, p<0.05). Among these non-coding RNAs, miR-98 was the most down-regulated (-33.3-fold) miRNA and miR-143, the lipid biosynthesis associated miRNA, had a 20-fold decreased expression in the NPC cells. Additionally, gene ontology analyses of the target genes suggested a distinct role for each miRNA. Our results show that NPC fibroblasts have an altered miRNA expression profile and certain miRNAs have importance in disease pathogenesis as well as the therapeutic capacity to correct lipid related pathophysiologies in the NPC cells.
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http://dx.doi.org/10.1016/j.bbrc.2010.11.026DOI Listing
December 2010

Two new pimelic diphenylamide HDAC inhibitors induce sustained frataxin upregulation in cells from Friedreich's ataxia patients and in a mouse model.

PLoS One 2010 Jan 21;5(1):e8825. Epub 2010 Jan 21.

Laboratoire de Neurologie Expérimentale, Hôpital Erasme, Brussels, Belgium.

Background: Friedreich's ataxia (FRDA), the most common recessive ataxia in Caucasians, is due to severely reduced levels of frataxin, a highly conserved protein, that result from a large GAA triplet repeat expansion within the first intron of the frataxin gene (FXN). Typical marks of heterochromatin are found near the expanded GAA repeat in FRDA patient cells and mouse models. Histone deacetylase inhibitors (HDACIs) with a pimelic diphenylamide structure and HDAC3 specificity can decondense the chromatin structure at the FXN gene and restore frataxin levels in cells from FRDA patients and in a GAA repeat based FRDA mouse model, KIKI, providing an appealing approach for FRDA therapeutics.

Methodology/principal Findings: In an effort to further improve the pharmacological profile of pimelic diphenylamide HDACIs as potential therapeutics for FRDA, we synthesized additional compounds with this basic structure and screened them for HDAC3 specificity. We characterized two of these compounds, 136 and 109, in FRDA patients' peripheral blood lymphocytes and in the KIKI mouse model. We tested their ability to upregulate frataxin at a range of concentrations in order to determine a minimal effective dose. We then determined in both systems the duration of effect of these drugs on frataxin mRNA and protein, and on total and local histone acetylation. The effects of these compounds exceeded the time of direct exposure in both systems.

Conclusions/significance: Our results support the pre-clinical development of a therapeutic approach based on pimelic diphenylamide HDACIs for FRDA and provide information for the design of future human trials of these drugs, suggesting an intermittent administration of the drug.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0008825PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2809102PMC
January 2010

Grafting neural precursor cells promotes functional recovery in an SCA1 mouse model.

J Neurosci 2009 Oct;29(42):13126-35

Laboratory of Experimental Neurology and 2Laboratory of Neurophysiology, Brussels Free University (ULB), Brussels, Belgium.

The B05 transgenic SCA1 mice, expressing human ataxin-1 with an expanded polyglutamine tract in cerebellar Purkinje cells (PCs), recapitulate many pathological and behavioral characteristics of the neurodegenerative disease spinocerebellar ataxia type 1 (SCA1), including progressive ataxia and PC loss. We transplanted neural precursor cells (NPCs) derived from the subventricular zone of GFP-expressing adult mice into the cerebellar white matter of SCA1 mice when they showed absent (5 weeks), initial (13 weeks), and significant (24 weeks) PC loss. Only in mice with significant cell loss, grafted NPCs migrated into the cerebellar cortex. These animals showed improved motor skills compared with sham-treated controls. No grafted cell adopted the morphological and immunohistochemical characteristics of PCs, but the cerebellar cortex in NPC-grafted SCA1 mice had a significantly thicker molecular layer and more surviving PCs. Perforated patch-clamp recordings revealed a normalization of the PC basal membrane potential, which was abnormally depolarized in sham-treated animals. No significant increase in levels of several neurotrophic factors was observed, suggesting, along with morphological observation, that the neuroprotective effect of grafted NPCs was mediated by direct contact with the host PCs. We postulate that a similar neuroprotective effect of NPCs may be applicable to other cerebellar degenerative diseases.
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http://dx.doi.org/10.1523/JNEUROSCI.0647-09.2009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6665209PMC
October 2009

Functional genomic analysis of frataxin deficiency reveals tissue-specific alterations and identifies the PPARgamma pathway as a therapeutic target in Friedreich's ataxia.

Hum Mol Genet 2009 Jul 17;18(13):2452-61. Epub 2009 Apr 17.

Department of Neurology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA.

Friedreich's ataxia (FRDA), the most common inherited ataxia, is characterized by focal neurodegeneration, diabetes mellitus and life-threatening cardiomyopathy. Frataxin, which is significantly reduced in patients with this recessive disorder, is a mitochondrial iron-binding protein, but how its deficiency leads to neurodegeneration and metabolic derangements is not known. We performed microarray analysis of heart and skeletal muscle in a mouse model of frataxin deficiency, and found molecular evidence of increased lipogenesis in skeletal muscle, and alteration of fiber-type composition in heart, consistent with insulin resistance and cardiomyopathy, respectively. Since the peroxisome proliferator-activated receptor gamma (PPARgamma) pathway is known to regulate both processes, we hypothesized that dysregulation of this pathway could play a key role in frataxin deficiency. We confirmed this by showing a coordinate dysregulation of the PPARgamma coactivator Pgc1a and transcription factor Srebp1 in cellular and animal models of frataxin deficiency, and in cells from FRDA patients, who have marked insulin resistance. Finally, we show that genetic modulation of the PPARgamma pathway affects frataxin levels in vitro, supporting PPARgamma as a novel therapeutic target in FRDA.
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http://dx.doi.org/10.1093/hmg/ddp183DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2694693PMC
July 2009

HDAC inhibitors correct frataxin deficiency in a Friedreich ataxia mouse model.

PLoS One 2008 Apr 9;3(4):e1958. Epub 2008 Apr 9.

Laboratoire de Neurologie Expérimentale, Hôpital Erasme, Université Libre de Bruxelles (ULB), Brussels, Belgium.

Background: Friedreich ataxia, an autosomal recessive neurodegenerative and cardiac disease, is caused by abnormally low levels of frataxin, an essential mitochondrial protein. All Friedreich ataxia patients carry a GAATTC repeat expansion in the first intron of the frataxin gene, either in the homozygous state or in compound heterozygosity with other loss-of-function mutations. The GAA expansion inhibits frataxin expression through a heterochromatin-mediated repression mechanism. Histone modifications that are characteristic of silenced genes in heterochromatic regions occur at expanded alleles in cells from Friedreich ataxia patients, including increased trimethylation of histone H3 at lysine 9 and hypoacetylation of histones H3 and H4.

Methodology/principal Findings: By chromatin immunoprecipitation, we detected the same heterochromatin marks in homozygous mice carrying a (GAA)(230) repeat in the first intron of the mouse frataxin gene (KIKI mice). These animals have decreased frataxin levels and, by microarray analysis, show significant gene expression changes in several tissues. We treated KIKI mice with a novel histone deacetylase inhibitor, compound 106, which substantially increases frataxin mRNA levels in cells from Friedreich ataxia individuals. Treatment increased histone H3 and H4 acetylation in chromatin near the GAA repeat and restored wild-type frataxin levels in the nervous system and heart, as determined by quantitative RT-PCR and semiquantitative western blot analysis. No toxicity was observed. Furthermore, most of the differentially expressed genes in KIKI mice reverted towards wild-type levels.

Conclusions/significance: Lack of acute toxicity, normalization of frataxin levels and of the transcription profile changes resulting from frataxin deficiency provide strong support to a possible efficacy of this or related compounds in reverting the pathological process in Friedreich ataxia, a so far incurable neurodegenerative disease.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0001958PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2373517PMC
April 2008

Gene set enrichment analysis reveals several globally affected pathways due to SKI-1/S1P inhibition in HepG2 cells.

DNA Cell Biol 2007 Nov;26(11):765-72

Department of Neurology, Free University of Brussels, Brussels, Belgium.

Sterol regulatory element-binding proteins (SREBPs) are transcription factors governing transcription of genes related to cholesterol and fatty acid metabolism. To become active, SREBPs must undergo a proteolytic cleavage to allow an active NH(2)-terminal segment to translocate into the nucleus. SKI-1/S1P is the first protease in the proteolytic activation cascade of SREBPs. SREBP inhibition may be useful, for example, in the treatment of liver steatosis caused by homocysteine-induced lipid synthesis. Accordingly, we overexpressed inhibitory prodomains (proSKI) of SKI-1/S1P in HepG2 cells to block SREBP activation to evaluate the potential of SKI-1/S1P in controlling cellular cholesterol synthesis. SKI-1/S1P inhibition resulted in reduced cholesterol synthesis and mRNA levels of the rate-limiting enzymes, HMG-CoA reductase and squalene epoxidase, in the cholesterol synthetic pathway. The inhibitory effect was maintained in the presence of homocysteine-induced endoplasmic reticulum stress. A gene set enrichment analysis was performed to elucidate other metabolic effects caused by SKI-1/S1P inhibition. SKI-1/S1P inhibition was observed to affect a number of other metabolic pathways, including glycolysis and citric acid cycle. These results demonstrate that inhibition of SREBPs decreases cholesterol synthesis in HepG2 cells both in the absence and presence of homocysteine. SKI-1/S1P inhibition may cause widespread changes in other key metabolic pathways.
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http://dx.doi.org/10.1089/dna.2007.0624DOI Listing
November 2007

Gene set enrichment analyses revealed several affected pathways in Niemann-pick disease type C fibroblasts.

DNA Cell Biol 2007 Sep;26(9):665-71

Department of Neurology and Laboratory of Experimental Neurology, ULB Erasme Hospital, Brussels, Belgium, and Turku Centre for Biotechnology, University of Turku, Finland.

Niemann-pick type C (NPC) disease is characterized by endosomal and lysosomal accumulation of lipids, impaired tubulovesicular trafficking, and neurodegeneration leading to premature death. Current treatment options are limited to mainly symptomatic treatments. Thus, new and efficient drug targets are needed, and therefore we performed a Gene Set Enrichment Analysis (GSEA) on NPC and healthy fibroblasts to identify globally affected pathways in NPC that could serve as targets for later drug discovery programs. Cell lines were characterized by analyzing cellular concentrations of cholesterol, its precursors and metabolites, as well as cellular plant sterol levels. Gene expression analyses were performed with Sentrix Human-8 Expression BeadChips, analyzing 23,000 transcripts. Pathway analysis of the expression data was performed using the GSEA method. Twenty-seven upregulated and 33 downregulated pathways emerged as globally affected in the GSEA analysis. These pathways included, for example, mitochondrial pathway, caspase cascade, as well as prostaglandin and leukotriene metabolism. Based on the present results and earlier published data, anti-inflammatory and antiapoptotic treatment could be beneficial in NPC.
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http://dx.doi.org/10.1089/dna.2006.0570DOI Listing
September 2007