Publications by authors named "Nadège Calmels"

17 Publications

  • Page 1 of 1

Expanding the clinical spectrum of STIP1 homology and U-box containing protein 1-associated ataxia.

J Neurol 2021 Jan 8. Epub 2021 Jan 8.

Service de Génétique Médicale, Hôpitaux de Brabois, CHRU de Nancy, Rue du Morvan, 54500, Vandoeuvre-lès-Nancy, France.

Background: STUB1 has been first associated with autosomal recessive (SCAR16, MIM# 615768) and later with dominant forms of ataxia (SCA48, MIM# 618093). Pathogenic variations in STUB1 are now considered a frequent cause of cerebellar ataxia.

Objective: We aimed to improve the clinical, radiological, and molecular delineation of SCAR16 and SCA48.

Methods: Retrospective collection of patients with SCAR16 or SCA48 diagnosed in three French genetic centers (Montpellier, Strasbourg and Nancy).

Results: Here, we report four SCAR16 and nine SCA48 patients from two SCAR16 and five SCA48 unrelated French families. All presented with slowly progressive cerebellar ataxia. Additional findings included cognitive decline, dystonia, parkinsonism and swallowing difficulties. The age at onset was highly variable, ranging from 14 to 76 years. Brain MRI showed marked cerebellar atrophy in all patients. Phenotypic findings associated with STUB1 pathogenic variations cover a broad spectrum, ranging from isolated slowly progressive ataxia to severe encephalopathy, and include extrapyramidal features. We described five new pathogenic variations, two previously reported pathogenic variations, and two rare variants of unknown significance in association with STUB1-related disorders. We also report the first pathogenic variation associated with both dominant and recessive forms of inheritance (SCAR16 and SCA48).

Conclusion: Even though differences are observed between the recessive and dominant forms, it appears that a continuum exists between these two entities. While adding new symptoms associated with STUB1 pathogenic variations, we insist on the difficulty of genetic counselling in STUB1-related pathologies. Finally, we underscore the usefulness of DAT-scan as an additional clue for diagnosis.
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http://dx.doi.org/10.1007/s00415-020-10348-xDOI Listing
January 2021

Growth charts in Cockayne syndrome type 1 and type 2.

Eur J Med Genet 2021 Jan 20;64(1):104105. Epub 2020 Nov 20.

Service de Pédiatrie 1, Hôpital de Hautepierre, Hôpitaux Universitaires de Strasbourg, Strasbourg, France; Laboratoire de Génétique médicale, INSERM U1112, Institut de génétique médicale d'Alsace, Faculté de Médecine de Strasbourg, Hôpitaux Universitaires de Strasbourg, France.

Cockayne syndrome (CS) is a multisystem degenerative disorder divided in 3 overlapping subtypes, with a continuous phenotypic spectrum: CS2 being the most severe form, CS1 the classical form and CS3 the late-onset form. Failure to thrive and growth difficulties are among the most consistent features of CS, leaving affected individuals vulnerable to numerous medical complications, including adverse effects of undernutrition, abrupt overhydration and overfeeding. There is thus a significant need for specific growth charts. We retrospectively collected growth parameters from genetically-confirmed CS1 and CS2 patients, used the GAMLSS package to construct specific CS growth charts compared to healthy children from WHO and CDC databases. Growth data were obtained from 88 CS patients with a total of 1626 individual growth data points. 49 patients were classified as CS1 and 39 as CS2 with confirmed mutations in CSB/ERCC6, CSA/ERCC8 or ERCC1 genes. Individuals with CS1 initially have normal growth parameters; microcephaly occurs from 2 months whereas onset of weight and height restrictions appear later, between 5 and 22 months. In CS2, growth parameters are already below standard references at birth or drop below the 5th percentile before 3 months. Microcephaly is the first parameter to show a delay, appearing around 2 months in CS1 and at birth in CS2. Height and head circumference are more severely affected in CS2 compared to CS1 whereas weight curves are similar in CS1 and CS2 patients. These new growth charts will serve as a practical tool to improve the nutritional management of children with CS.
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http://dx.doi.org/10.1016/j.ejmg.2020.104105DOI Listing
January 2021

X-linked muscular dystrophy in a Labrador Retriever strain: phenotypic and molecular characterisation.

Skelet Muscle 2020 08 7;10(1):23. Epub 2020 Aug 7.

U955 - IMRB, Team 10 - Biology of the neuromuscular system, Inserm, UPEC, EFS, Ecole nationale vétérinaire d'Alfort, 94700, Maisons-Alfort, France.

Background: Canine models of Duchenne muscular dystrophy (DMD) are a valuable tool to evaluate potential therapies because they faithfully reproduce the human disease. Several cases of dystrophinopathies have been described in canines, but the Golden Retriever muscular dystrophy (GRMD) model remains the most used in preclinical studies. Here, we report a new spontaneous dystrophinopathy in a Labrador Retriever strain, named Labrador Retriever muscular dystrophy (LRMD).

Methods: A colony of LRMD dogs was established from spontaneous cases. Fourteen LRMD dogs were followed-up and compared to the GRMD standard using several functional tests. The disease causing mutation was studied by several molecular techniques and identified using RNA-sequencing.

Results: The main clinical features of the GRMD disease were found in LRMD dogs; the functional tests provided data roughly overlapping with those measured in GRMD dogs, with similar inter-individual heterogeneity. The LRMD causal mutation was shown to be a 2.2-Mb inversion disrupting the DMD gene within intron 20 and involving the TMEM47 gene. In skeletal muscle, the Dp71 isoform was ectopically expressed, probably as a consequence of the mutation. We found no evidence of polymorphism in either of the two described modifier genes LTBP4 and Jagged1. No differences were found in Pitpna mRNA expression levels that would explain the inter-individual variability.

Conclusions: This study provides a full comparative description of a new spontaneous canine model of dystrophinopathy, found to be phenotypically equivalent to the GRMD model. We report a novel large DNA mutation within the DMD gene and provide evidence that LRMD is a relevant model to pinpoint additional DMD modifier genes.
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http://dx.doi.org/10.1186/s13395-020-00239-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7412789PMC
August 2020

Early-onset nucleotide excision repair disorders with neurological impairment: Clues for early diagnosis and prognostic counseling.

Clin Genet 2020 09 28;98(3):251-260. Epub 2020 Jul 28.

Laboratoires de Diagnostic Génétique, Institut de génétique médicale d'Alsace, Nouvel Hôpital Civil, Hôpitaux Universitaires de Strasbourg, Strasbourg, France.

Nucleotide excision repair associated diseases comprise overlapping phenotypes and a wide range of outcomes. The early stages still remain under-investigated and underdiagnosed, even although an early recognition of the first symptoms is of utmost importance for appropriate care and genetic counseling. We systematically collected clinical and molecular data from the literature and from newly diagnosed NER patients with neurological impairment, presenting clinical symptoms before the age of 12 months, including foetal cases. One hundred and eighty-five patients were included, 13 with specific symptoms during foetal life. Arthrogryposis, microcephaly, cataracts, and skin anomalies are the most frequently reported signs in early subtypes. Non ERCC6/CSB or ERCC8/CSA genes are overrepresented compared to later onset cohorts: 19% patients of this cohort presented variants in ERCC1, ERCC2/XPD, ERCC3/XPB or ERCC5/XPG. ERCC5/XPG is even the most frequently involved gene in foetal cases (10/13 cases, [4/7 families]). In this cohort, the mutated gene, the age of onset, the type of disease, severe global developmental delay, IUGR and skin anomalies were associated with earlier death. This large survey focuses on specific symptoms that should attract the attention of clinicians towards early-onset NER diagnosis in foetal and neonatal period, without waiting for the completeness of classical criteria.
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http://dx.doi.org/10.1111/cge.13798DOI Listing
September 2020

Prenatal diagnosis of cerebro-oculo-facio-skeletal syndrome: Report of three fetuses and review of the literature.

Am J Med Genet A 2020 05 13;182(5):1236-1242. Epub 2020 Feb 13.

Unité de Fœtopathologie, Service de Pathologie, Hôpitaux Universitaires de Strasbourg, Strasbourg, France.

Cerebro-oculo-facio-skeletal syndrome (COFS) is a rare autosomal recessive neurodegenerative disease belonging to the family of DNA repair disorders, characterized by microcephaly, congenital cataracts, facial dysmorphism and arthrogryposis. Here, we describe the detailed morphological and microscopic phenotype of three fetuses from two families harboring ERCC5/XPG likely pathogenic variants, and review the five previously reported fetal cases. In addition to the classical features of COFS, the fetuses display thymus hyperplasia, splenomegaly and increased hematopoiesis. Microencephaly is present in the three fetuses with delayed development of the gyri, but normal microscopic anatomy at the supratentorial level. Microscopic anomalies reminiscent of pontocerebellar hypoplasia are present at the infratentorial level. In conclusion, COFS syndrome should be considered in fetuses when intrauterine growth retardation is associated with microcephaly, arthrogryposis and ocular anomalies. Further studies are needed to better understand XPG functions during human development.
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http://dx.doi.org/10.1002/ajmg.a.61520DOI Listing
May 2020

Defective transcription of ATF3 responsive genes, a marker for Cockayne Syndrome.

Sci Rep 2020 01 24;10(1):1105. Epub 2020 Jan 24.

IGBMC, Department of Functional Genomics and Cancer, Equipe Labellisée Ligue 2014, CNRS/INSERM/University of Strasbourg, BP 163, 67404 Illkirch Cedex, C.U., Strasbourg, France.

Cockayne syndrome (CS) is a rare genetic disorder caused by mutations (dysfunction) in CSA and CSB. CS patients exhibit mild photosensitivity and severe neurological problems. Currently, CS diagnosis is based on the inefficiency of CS cells to recover RNA synthesis upon genotoxic (UV) stress. Indeed, upon genotoxic stress, ATF3, an immediate early gene is activated to repress up to 5000 genes encompassing its responsive element for a short period of time. On the contrary in CS cells, CSA and CSB dysfunction impairs the degradation of the chromatin-bound ATF3, leading to a permanent transcriptional arrest as observed by immunofluorescence and ChIP followed by RT-PCR. We analysed ChIP-seq of Pol II and ATF3 promoter occupation analysis and RNA sequencing-based gene expression profiling in CS cells, as well as performed immunofluorescence study of ATF3 protein stability and quantitative RT-PCR screening in 64 patient cell lines. We show that the analysis of few amount (as for example CDK5RAP2, NIPBL and NRG1) of ATF3 dependent genes, could serve as prominent molecular markers to discriminate between CS and non-CS patient's cells. Such assay can significantly simplify the timing and the complexity of the CS diagnostic procedure in comparison to the currently available methods.
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http://dx.doi.org/10.1038/s41598-020-57999-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6981198PMC
January 2020

A severe case of Frank-ter Haar syndrome and literature review: Further delineation of the phenotypical spectrum.

Eur J Med Genet 2020 Apr 21;63(4):103857. Epub 2020 Jan 21.

Service de génétique médicale, Institut de Génétique Médicale d'Alsace (IGMA), Hôpitaux Universitaires de Strasbourg, Hôpital de Hautepierre, Strasbourg, France. Electronic address:

Frank-ter Haar syndrome (FTHS) is a rare autosomal recessive syndrome resulting from mutations in the SH3PXD2B gene involved in the formation of podosomes and invadopodia which have a role in extracellular matrix remodelling and cell migration. FTHS is characterized by facial dysmorphism, megalocornea, inconstant glaucoma, variable developmental delay, skeletal and cardiac anomalies. To date, 40 patients have been reported in the literature with a clinical diagnosis of FTHS, only 20 patients having identified mutations. We present a review of these 20 reported patients and describe a patient born to non-consanguineous parents, with intrauterine growth retardation, hypotonia, congenital glaucoma, caudal appendix, scoliosis, camptodactyly, ventricular septal defect, thin corpus callosum and craniofacial features suggestive of FTHS. Clinical evolution resulted in buphthalmos worsening, coarsening of the facial features and respiratory failure leading to death at 4,5 months. Diagnosis was confirmed by the identification of a previously known homozygous mutation c.969delG, p.(Arg324Glyfs*19) in SH3PXD2B. This is the first description of very severe phenotype with lethal respiratory impairment in FTHS. Since very few patients are described in the literature, and 2 out of the 3 patients carrying the c.969delG mutation had a favourable clinical course, more cases are needed to better characterize the phenotype and understand the natural history of this syndrome. Furthermore, we hypothesize that the alteration of podosomes function could lead to a reduction of the extracellular matrix degradation and accumulation of the latter in the extracellular space, which might explain the coarsening of the facial features and the severe refractory glaucoma.
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http://dx.doi.org/10.1016/j.ejmg.2020.103857DOI Listing
April 2020

Renal disease in Cockayne syndrome.

Eur J Med Genet 2020 Jan 7;63(1):103612. Epub 2019 Jan 7.

Service de Pédiatrie 1, Hôpital de Hautepierre, Hôpitaux Universitaires de Strasbourg, Strasbourg, France. Electronic address:

Background: Cockayne Syndrome (CS) is a rare autosomal recessive multi-systemic disorder, characterized; by developmental delay, microcephaly, severe growth failure and sensorial impairment. Renal complications have been reported but remain underinvestigated. The objective of this study was to perform a review of renal disease in a cohort of CS patients.

Methods: We retrospectively collected relevant clinical, biochemical and genetic data from a cohort of 136 genetically confirmed CS patients. Blood pressure (BP), proteinuria, albuminemia, uric acid, creatinine clearance, renal ultrasounds and renal biopsy result were analysed.

Results: Thirty-two patients had a renal investigation. We found that 69% of investigated patients had a renal disorder and/or an elevated BP. Fifteen out of 21 patients (71% of investigated patients) had an increased BP, 10 out of 16 patients (62% of investigated patients) presented with proteinuria and 4 of them had a nephrotic syndrome. Thirteen patients out of 29 (45%) had a decreased Glomerular Filtration Rate (GFR), 18 out of 25 patients (72%) had a hyperuricemia. No correlation with the genetic background or clinical types of CS was found, except for the renal clearance.

Conclusions: Renal disease, increased blood pressure and hyperuricemia were highly prevalent in our study. We believe that CS patients should benefit from a nephrological follow-up and that anti-uric acid drug and Angiotensin-converting enzyme (ACE) inhibitor should be discussed in these patients.
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http://dx.doi.org/10.1016/j.ejmg.2019.01.002DOI Listing
January 2020

Functional and clinical relevance of novel mutations in a large cohort of patients with Cockayne syndrome.

J Med Genet 2018 05 23;55(5):329-343. Epub 2018 Mar 23.

Genome Damage and Stability Centre, University of Sussex, Brighton, UK.

Background: Cockayne syndrome (CS) is a rare, autosomal recessive multisystem disorder characterised by prenatal or postnatal growth failure, progressive neurological dysfunction, ocular and skeletal abnormalities and premature ageing. About half of the patients with symptoms diagnostic for CS show cutaneous photosensitivity and an abnormal cellular response to UV light due to mutations in either the / or / gene. Studies performed thus far have failed to delineate clear genotype-phenotype relationships. We have carried out a four-centre clinical, molecular and cellular analysis of 124 patients with CS.

Methods And Results: We assigned 39 patients to the and 85 to the genes. Most of the genetic variants were truncations. The missense variants were distributed non-randomly with concentrations in relatively short regions of the respective proteins. Our analyses revealed several hotspots and founder mutations in Although no unequivocal genotype-phenotype relationships could be made, patients were more likely to have severe clinical features if the mutation was downstream of the PiggyBac insertion in intron 5 of than if it was upstream. Also a higher proportion of severely affected patients was found with mutations in than in .

Conclusion: By identifying >70 novel homozygous or compound heterozygous genetic variants in 124 patients with CS with different disease severity and ethnic backgrounds, we considerably broaden the and mutation spectrum responsible for CS. Besides providing information relevant for diagnosis of and genetic counselling for this devastating disorder, this study improves the definition of the puzzling genotype-phenotype relationships in patients with CS.
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http://dx.doi.org/10.1136/jmedgenet-2017-104877DOI Listing
May 2018

Deep intronic variation in splicing regulatory element of the ERCC8 gene associated with severe but long-term survival Cockayne syndrome.

Eur J Hum Genet 2018 04 8;26(4):527-536. Epub 2018 Feb 8.

Laboratoire de Diagnostic Génétique, Institut de Génétique Médicale d'Alsace (IGMA), Hôpitaux Universitaires de Strasbourg, 1 place de l'hôpital, Strasbourg, 67091, France.

Cockayne syndrome is an autosomal recessive multisystem disorder characterized by intellectual disability, microcephaly, severe growth failure, sensory impairment, peripheral neuropathy, and cutaneous sensitivity. This rare disease is linked to disease-causing variations in the ERCC6 (CSB) and ERCC8 (CSA) genes. Various degrees of severity have been described according to age at onset and survival, without any clear genotype-phenotype correlation. All types of nucleotide changes have been observed in CS genes, including splice variations mainly affecting the splice site consensus sequences. We report here the case of two brothers from a consanguineous family presenting a severe but long-term survival phenotype of Cockayne syndrome. We identified in the patients a homozygous deep intronic nucleotide variation causing the insertion of a cryptic exon in the ERCC8 (CSA) transcript, by modifying intronic regulatory elements important for exon definition. The pathogenesis of the nucleotide variant NG_009289.1(NM_000082.3):c.173+1119G>C was validated in vitro with a reporter minigene system. To our knowledge, these are the first Cockayne patients described with this kind of disease-causing variation, though molecular mechanism underlying early onset symptoms and unexpected slow raise of progression of the disease remain to be elucidated.
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http://dx.doi.org/10.1038/s41431-017-0009-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5891492PMC
April 2018

Affected female carriers of MTM1 mutations display a wide spectrum of clinical and pathological involvement: delineating diagnostic clues.

Acta Neuropathol 2017 Dec 6;134(6):889-904. Epub 2017 Jul 6.

Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.

X-linked myotubular myopathy (XLMTM), a severe congenital myopathy, is caused by mutations in the MTM1 gene located on the X chromosome. A majority of affected males die in the early postnatal period, whereas female carriers are believed to be usually asymptomatic. Nevertheless, several affected females have been reported. To assess the phenotypic and pathological spectra of carrier females and to delineate diagnostic clues, we characterized 17 new unrelated affected females and performed a detailed comparison with previously reported cases at the clinical, muscle imaging, histological, ultrastructural and molecular levels. Taken together, the analysis of this large cohort of 43 cases highlights a wide spectrum of clinical severity ranging from severe neonatal and generalized weakness, similar to XLMTM male, to milder adult forms. Several females show a decline in respiratory function. Asymmetric weakness is a noteworthy frequent specific feature potentially correlated to an increased prevalence of highly skewed X inactivation. Asymmetry of growth was also noted. Other diagnostic clues include facial weakness, ptosis and ophthalmoplegia, skeletal and joint abnormalities, and histopathological signs that are hallmarks of centronuclear myopathy such as centralized nuclei and necklace fibers. The histopathological findings also demonstrate a general disorganization of muscle structure in addition to these specific hallmarks. Thus, MTM1 mutations in carrier females define a specific myopathy, which may be independent of the presence of an XLMTM male in the family. As several of the reported affected females carry large heterozygous MTM1 deletions not detectable by Sanger sequencing, and as milder phenotypes present as adult-onset limb-girdle myopathy, the prevalence of this myopathy is likely to be greatly underestimated. This report should aid diagnosis and thus the clinical management and genetic counseling of MTM1 carrier females. Furthermore, the clinical and pathological history of this cohort may be useful for therapeutic projects in males with XLMTM, as it illustrates the spectrum of possible evolution of the disease in patients surviving long term.
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http://dx.doi.org/10.1007/s00401-017-1748-0DOI Listing
December 2017

Mutations in the ERCC2 (XPD) gene associated with severe fetal ichthyosis and dysmorphic features.

Prenat Diagn 2016 Dec 2;36(13):1276-1279. Epub 2016 Dec 2.

Service de Génétique Médicale, Institut de Génétique Médicale d'Alsace (IGMA), Centre de Référence Maladies Rares Anomalies du Développement et Syndromes Malformatifs de l'Est, Hôpitaux Universitaires de Strasbourg, Hôpital de Hautepierre, Strasbourg, France.

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http://dx.doi.org/10.1002/pd.4965DOI Listing
December 2016

Teaching NeuroImages: The syndrome of cutaneous photosensitivity, growth failure, and basal ganglia calcification.

Neurology 2016 08;87(6):e56-7

From Pediatric Neurology and Neurodevelopment Unit, Department of Pediatrics (A.G.S., N.S., P.S.), and Department of Radiodiagnosis (S.V.), Post Graduate Institute of Medical Education and Research, Chandigarh, India; Laboratory of Medical Genetics (V.L.), Faculte de Medecine; and Laboratoire de Diagnostic Génétique (N.C.), Hôpitaux Universitaires de Strasbourg, France.

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http://dx.doi.org/10.1212/WNL.0000000000002949DOI Listing
August 2016

Uncommon nucleotide excision repair phenotypes revealed by targeted high-throughput sequencing.

Orphanet J Rare Dis 2016 Mar 22;11:26. Epub 2016 Mar 22.

Laboratoire de Génétique Médicale - INSERM U1112, Institut de Génétique Médicale d'Alsace (IGMA), Faculté de médecine de Strasbourg, 11 rue Humann, Strasbourg, France.

Background: Deficient nucleotide excision repair (NER) activity causes a variety of autosomal recessive diseases including xeroderma pigmentosum (XP) a disorder which pre-disposes to skin cancer, and the severe multisystem condition known as Cockayne syndrome (CS). In view of the clinical overlap between NER-related disorders, as well as the existence of multiple phenotypes and the numerous genes involved, we developed a new diagnostic approach based on the enrichment of 16 NER-related genes by multiplex amplification coupled with next-generation sequencing (NGS).

Methods: Our test cohort consisted of 11 DNA samples, all with known mutations and/or non pathogenic SNPs in two of the tested genes. We then used the same technique to analyse samples from a prospective cohort of 40 patients. Multiplex amplification and sequencing were performed using AmpliSeq protocol on the Ion Torrent PGM (Life Technologies).

Results: We identified causative mutations in 17 out of the 40 patients (43%). Four patients showed biallelic mutations in the ERCC6(CSB) gene, five in the ERCC8(CSA) gene: most of them had classical CS features but some had very mild and incomplete phenotypes. A small cohort of 4 unrelated classic XP patients from the Basque country (Northern Spain) revealed a common splicing mutation in POLH (XP-variant), demonstrating a new founder effect in this population. Interestingly, our results also found ERCC2(XPD), ERCC3(XPB) or ERCC5(XPG) mutations in two cases of UV-sensitive syndrome and in two cases with mixed XP/CS phenotypes.

Conclusions: Our study confirms that NGS is an efficient technique for the analysis of NER-related disorders on a molecular level. It is particularly useful for phenotypes with combined features or unusually mild symptoms. Targeted NGS used in conjunction with DNA repair functional tests and precise clinical evaluation permits rapid and cost-effective diagnosis in patients with NER-defects.
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http://dx.doi.org/10.1186/s13023-016-0408-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4804614PMC
March 2016

Progressive demyelinating neuropathy correlates with clinical severity in Cockayne syndrome.

Clin Neurophysiol 2015 Jul 20;126(7):1435-9. Epub 2014 Oct 20.

Laboratoire de Génétique Médicale, INSERM 1112, Faculté de Médecine, F-67085 Strasbourg, France.

Objective: Cockayne syndrome (CS) is characterized by postnatal growth failure and progressive multi-organ dysfunctions. CSA and CSB gene mutations account for the majority of cases and three degrees of severity are delineated. A peripheral neuropathy is known to be associated with CS but the type, severity and correlation of the nerve involvement with CS subtypes remain unknown in genetically identified patients.

Methods: Clinical and nerve conduction studies (NCS) in 25 CS patients with CSA (n=13) CSB (n=12) mutations.

Results: NCS show a widespread decrease in motor and sensory conduction velocities (CV) in all severe and classical form of CS. In one patient, CV were normal at age 8months but severe slowing was detected at 2years. Conduction block and/or temporal dispersion were observed in 68% of patients.

Conclusions: CS is associated with a progressive sensory and motor neuropathy. Signs of segmental demyelination, including conduction blocks, may not be obvious before the age of 2years. CV slowing is correlated with the CS clinical severity.

Significance: NCS should be performed in patients with suspected CS as an additional tool to guide the diagnosis before molecular studies. Further studies focused on NCS course are required in order to assess its relevance as a biomarker in research therapy projects.
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http://dx.doi.org/10.1016/j.clinph.2014.10.014DOI Listing
July 2015

Limitations in a frataxin knockdown cell model for Friedreich ataxia in a high-throughput drug screen.

BMC Neurol 2009 Aug 24;9:46. Epub 2009 Aug 24.

IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), CNRS/INSERM/Université Louis Pasteur, Illkirch cedex, France.

Background: Pharmacological high-throughput screening (HTS) represents a powerful strategy for drug discovery in genetic diseases, particularly when the full spectrum of pathological dysfunctions remains unclear, such as in Friedreich ataxia (FRDA). FRDA, the most common recessive ataxia, results from a generalized deficiency of mitochondrial and cytosolic iron-sulfur cluster (ISC) proteins activity, due to a partial loss of frataxin function, a mitochondrial protein proposed to function as an iron-chaperone for ISC biosynthesis. In the absence of measurable catalytic function for frataxin, a cell-based assay is required for HTS assay.

Methods: Using a targeted ribozyme strategy in murine fibroblasts, we have developed a cellular model with strongly reduced levels of frataxin. We have used this model to screen the Prestwick Chemical Library, a collection of one thousand off-patent drugs, for potential molecules for FRDA.

Results: The frataxin deficient cell lines exhibit a proliferation defect, associated with an ISC enzyme deficit. Using the growth defect as end-point criteria, we screened the Prestwick Chemical Library. However no molecule presented a significant and reproducible effect on the proliferation rate of frataxin deficient cells. Moreover over numerous passages, the antisense ribozyme fibroblast cell lines revealed an increase in frataxin residual level associated with the normalization of ISC enzyme activities. However, the ribozyme cell lines and FRDA patient cells presented an increase in Mthfd2 transcript, a mitochondrial enzyme that was previously shown to be upregulated at very early stages of the pathogenesis in the cardiac mouse model.

Conclusion: Although no active hit has been identified, the present study demonstrates the feasibility of using a cell-based approach to HTS for FRDA. Furthermore, it highlights the difficulty in the development of a stable frataxin-deficient cell model, an essential condition for productive HTS in the future.
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http://dx.doi.org/10.1186/1471-2377-9-46DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2744904PMC
August 2009

The first cellular models based on frataxin missense mutations that reproduce spontaneously the defects associated with Friedreich ataxia.

PLoS One 2009 Jul 24;4(7):e6379. Epub 2009 Jul 24.

Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.

Background: Friedreich ataxia (FRDA), the most common form of recessive ataxia, is due to reduced levels of frataxin, a highly conserved mitochondrial iron-chaperone involved in iron-sulfur cluster (ISC) biogenesis. Most patients are homozygous for a (GAA)(n) expansion within the first intron of the frataxin gene. A few patients, either with typical or atypical clinical presentation, are compound heterozygous for the GAA expansion and a micromutation.

Methodology: We have developed a new strategy to generate murine cellular models for FRDA: cell lines carrying a frataxin conditional allele were used in combination with an EGFP-Cre recombinase to create murine cellular models depleted for endogenous frataxin and expressing missense-mutated human frataxin. We showed that complete absence of murine frataxin in fibroblasts inhibits cell division and leads to cell death. This lethal phenotype was rescued through transgenic expression of human wild type as well as mutant (hFXN(G130V) and hFXN(I154F)) frataxin. Interestingly, cells expressing the mutated frataxin presented a FRDA-like biochemical phenotype. Though both mutations affected mitochondrial ISC enzymes activities and mitochondria ultrastructure, the hFXN(I154F) mutant presented a more severe phenotype with affected cytosolic and nuclear ISC enzyme activities, mitochondrial iron accumulation and an increased sensitivity to oxidative stress. The differential phenotype correlates with disease severity observed in FRDA patients.

Conclusions: These new cellular models, which are the first to spontaneously reproduce all the biochemical phenotypes associated with FRDA, are important tools to gain new insights into the in vivo consequences of pathological missense mutations as well as for large-scale pharmacological screening aimed at compensating frataxin deficiency.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0006379PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2710521PMC
July 2009