Publications by authors named "Christine Ioos"

15 Publications

  • Page 1 of 1

Clinical phenotype and loss of the slow skeletal muscle troponin T in three new patients with recessive TNNT1 nemaline myopathy.

J Med Genet 2020 Sep 29. Epub 2020 Sep 29.

Neuropediatric Department, University Hospital Centre Toulouse, Toulouse, France

Background: Congenital nemaline myopathies are rare pathologies characterised by muscle weakness and rod-shaped inclusions in the muscle fibres.

Methods: Using next-generation sequencing, we identified three patients with pathogenic variants in the () gene, coding for the troponin T (TNT) skeletal muscle isoform.

Results: The clinical phenotype was similar in all patients, associating hypotonia, orthopaedic deformities and progressive chronic respiratory failure, leading to early death. The anatomopathological phenotype was characterised by a disproportion in the muscle fibre size, endomysial fibrosis and nemaline rods. Molecular analyses of revealed a homozygous deletion of exons 8 and 9 in patient 1; a heterozygous nonsense mutation in exon 9 and retention of part of intron 4 in muscle transcripts in patient 2; and a homozygous, very early nonsense mutation in patient 3.Western blot analyses confirmed the absence of the TNT protein resulting from these mutations.

Discussion: The clinical and anatomopathological presentations of our patients reinforce the homogeneous character of the phenotype associated with recessive mutations. Previous studies revealed an impact of recessive variants on the tropomyosin-binding affinity of TNT. We report in our patients a complete loss of TNT protein due to open reading frame disruption or to post-translational degradation of TNT.
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http://dx.doi.org/10.1136/jmedgenet-2019-106714DOI Listing
September 2020

Movement disorders in patients with alternating hemiplegia: "Soft" and "stiff" at the same time.

Neurology 2020 03 2;94(13):e1378-e1385. Epub 2020 Mar 2.

From Sleep Disorders and Functional Neurology (E.P., A.A.), Department of Paediatric Clinical Epileptology, University Hospitals of Lyon, member of the ERN EpiCARE; Service de Neurologie Pédiatrique (D.D., T.B.), Hôpital Trousseau, APHP, Paris; Centre d'Investigation Clinique (E.N., N.N.), CHU Montpellier; Department of Medical Genetics (G.L.), Centre de Biologie Est, Lyon University Hospital, Hospices Civils de Lyon, member of the ERN EpiCARE; Laboratoire de Génétique (F.R.), Groupe Hospitalier Lariboisière-Fernand Widal AP-HP, Paris; IGF (S.N.), Univ Montpellier, CNRS, INSERM; Département de Neuropédiatrie (C.D., A.R.), CHU Gui de Chauliac, Montpellier; Service de Neuropédiatrie et Handicaps (M.A.B.), Hôpital Gatien de Clocheville, CHU Tours, France; Pediatric Neurology Unit (M.C.N.), Cliniques Universitaires Saint-Luc, UCLouvain, Brussels, Belgium; Service de Neuropédiatrie (A.D.), CHU de Bicêtre, Kremlin-Bicêtre; Service de Neuropédiatrie (L.V.), CHU Lille; Service de Neurochirurgie Pédiatrique (M.B.), Hôpital Necker-Enfants Malades, APHP, Paris; Service de Neurologie Pédiatrique (C.I.), Hôpital Raymond Poincarré, AP-HP, Garches; Service de Neurophysiologie (C.G.), Hôpital Necker, AP-HP, Paris; Département de Pédiatrie (C.L.), CHU Limoges; Service de Neurologie Pédiatrique (M.M.), CHU Timone Enfants, Marseille; Centre de Référence "Déficiences Intellectuelles de Causes Rares" (V.D.P.), Hôpital Femme Mère Enfant, Hospices Civils de Lyon, Bron, Université de Lyon; and INSERM U 1051 (A.R.), Institut des Neurosciences de Montpellier, France.

Objective: To assess nonparoxysmal movement disorders in mutation-positive patients with alternating hemiplegia of childhood (AHC).

Methods: Twenty-eight patients underwent neurologic examination with particular focus on movement phenomenology by a specialist in movement disorders. Video recordings were reviewed by another movement disorders specialist and data were correlated with patients' characteristics.

Results: Ten patients were diagnosed with chorea, 16 with dystonia (nonparoxysmal), 4 with myoclonus, and 2 with ataxia. Nine patients had more than one movement disorder and 8 patients had none. The degree of movement disorder was moderate to severe in 12/28 patients. At inclusion, dystonic patients (n = 16) were older ( = 0.007) than nondystonic patients. Moreover, patients (n = 18) with dystonia or chorea, or both, had earlier disease onset ( = 0.042) and more severe neurologic impairment ( = 0.012), but this did not correlate with genotype. All patients presented with hypotonia, which was characterized as moderate or severe in 16/28. Patients with dystonia or chorea (n = 18) had more pronounced hypotonia ( = 0.011). Bradykinesia (n = 16) was associated with an early age at assessment ( < 0.01). Significant dysarthria was diagnosed in 11/25 cases. A history of acute neurologic deterioration and further regression of motor function, typically after a stressful event, was reported in 7 patients.

Conclusions: Despite the relatively limited number of patients and the cross-sectional nature of the study, this detailed categorization of movement disorders in patients with AHC offers valuable insight into their precise characterization. Further longitudinal studies on this topic are needed.
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http://dx.doi.org/10.1212/WNL.0000000000009175DOI Listing
March 2020

Functional classification of ATM variants in ataxia-telangiectasia patients.

Hum Mutat 2019 10 17;40(10):1713-1730. Epub 2019 May 17.

CHU de Nancy, Service de Neurologie, Nancy, France.

Ataxia-telangiectasia (A-T) is a recessive disorder caused by biallelic pathogenic variants of ataxia-telangiectasia mutated (ATM). This disease is characterized by progressive ataxia, telangiectasia, immune deficiency, predisposition to malignancies, and radiosensitivity. However, hypomorphic variants may be discovered associated with very atypical phenotypes, raising the importance of evaluating their pathogenic effects. In this study, multiple functional analyses were performed on lymphoblastoid cell lines from 36 patients, comprising 49 ATM variants, 24 being of uncertain significance. Thirteen patients with atypical phenotype and presumably hypomorphic variants were of particular interest to test strength of functional analyses and to highlight discrepancies with typical patients. Western-blot combined with transcript analyses allowed the identification of one missing variant, confirmed suspected splice defects and revealed unsuspected minor transcripts. Subcellular localization analyses confirmed the low level and abnormal cytoplasmic localization of ATM for most A-T cell lines. Interestingly, atypical patients had lower kinase defect and less altered cell-cycle distribution after genotoxic stress than typical patients. In conclusion, this study demonstrated the pathogenic effects of the 49 variants, highlighted the strength of KAP1 phosphorylation test for pathogenicity assessment and allowed the establishment of the Ataxia-TeLangiectasia Atypical Score to predict atypical phenotype. Altogether, we propose strategies for ATM variant detection and classification.
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http://dx.doi.org/10.1002/humu.23778DOI Listing
October 2019

16p13.11 microduplication in 45 new patients: refined clinical significance and genotype-phenotype correlations.

J Med Genet 2020 05 4;57(5):301-307. Epub 2018 Oct 4.

Neuropediatrics department, Hôpital Raymond Poincaré, Assistance Publique des Hôpitaux de Paris, Garches, France.

Background: The clinical significance of 16p13.11 duplications remains controversial while frequently detected in patients with developmental delay (DD), intellectual deficiency (ID) or autism spectrum disorder (ASD). Previously reported patients were not or poorly characterised. The absence of consensual recommendations leads to interpretation discrepancy and makes genetic counselling challenging. This study aims to decipher the genotype-phenotype correlations to improve genetic counselling and patients' medical care.

Methods: We retrospectively analysed data from 16 013 patients referred to 12 genetic centers for DD, ID or ASD, and who had a chromosomal microarray analysis. The referring geneticists of patients for whom a 16p13.11 duplication was detected were asked to complete a questionnaire for detailed clinical and genetic data for the patients and their parents.

Results: Clinical features are mainly speech delay and learning disabilities followed by ASD. A significant risk of cardiovascular disease was noted. About 90% of the patients inherited the duplication from a parent. At least one out of four parents carrying the duplication displayed a similar phenotype to the propositus. Genotype-phenotype correlations show no impact of the size of the duplicated segment on the severity of the phenotype. However, and miR-484 seem to have an essential role in the neurocognitive phenotype.

Conclusion: Our study shows that 16p13.11 microduplications are likely pathogenic when detected in the context of DD/ID/ASD and supports an essential role of and miR-484 in the neurocognitive phenotype. Moreover, it suggests the need for cardiac evaluation and follow-up and a large study to evaluate the aortic disease risk.
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http://dx.doi.org/10.1136/jmedgenet-2018-105389DOI Listing
May 2020

Correction: IQSEC2-related encephalopathy in males and females: a comparative study including 37 novel patients.

Genet Med 2019 Aug;21(8):1897-1898

APHP, Service de genetique medicale, Necker- Enfants Malades Hospital, Imagine Institute, Paris Descartes University, Paris, France.

This Article was originally published under Nature Research's License to Publish, but has now been made available under a CC BY 4.0 license. The PDF and HTML versions of the Article have been modified accordingly.
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http://dx.doi.org/10.1038/s41436-018-0327-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7608434PMC
August 2019

IQSEC2-related encephalopathy in males and females: a comparative study including 37 novel patients.

Genet Med 2019 04 12;21(4):837-849. Epub 2018 Sep 12.

APHP, Service de genetique medicale, Necker-Enfants Malades Hospital, Imagine Institute, Paris Descartes University, Paris, France.

Purpose: Variants in IQSEC2, escaping X inactivation, cause X-linked intellectual disability with frequent epilepsy in males and females. We aimed to investigate sex-specific differences.

Methods: We collected the data of 37 unpublished patients (18 males and 19 females) with IQSEC2 pathogenic variants and 5 individuals with variants of unknown significance and reviewed published variants. We compared variant types and phenotypes in males and females and performed an analysis of IQSEC2 isoforms.

Results: IQSEC2 pathogenic variants mainly led to premature truncation and were scattered throughout the longest brain-specific isoform, encoding the synaptic IQSEC2/BRAG1 protein. Variants occurred de novo in females but were either de novo (2/3) or inherited (1/3) in males, with missense variants being predominantly inherited. Developmental delay and intellectual disability were overall more severe in males than in females. Likewise, seizures were more frequently observed and intractable, and started earlier in males than in females. No correlation was observed between the age at seizure onset and severity of intellectual disability or resistance to antiepileptic treatments.

Conclusion: This study provides a comprehensive overview of IQSEC2-related encephalopathy in males and females, and suggests that an accurate dosage of IQSEC2 at the synapse is crucial during normal brain development.
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http://dx.doi.org/10.1038/s41436-018-0268-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6752297PMC
April 2019

Diagnostic approach to neurotransmitter monoamine disorders: experience from clinical, biochemical, and genetic profiles.

J Inherit Metab Dis 2018 01 18;41(1):129-139. Epub 2017 Sep 18.

Metabolomic and proteomic Biochemical department, Necker Enfants-Malades Hospital, Paris Descartes University, Paris, France.

Background And Aim: To improve the diagnostic work-up of patients with diverse neurological diseases, we have elaborated specific clinical and CSF neurotransmitter patterns.

Methods: Neurotransmitter determinations in CSF from 1200 patients revealed abnormal values in 228 (19%) cases. In 54/228 (24%) patients, a final diagnosis was identified.

Results: We have reported primary (30/54, 56%) and secondary (24/54, 44%) monoamine neurotransmitter disorders. For primary deficiencies, the most frequently mutated gene was DDC (n = 9), and the others included PAH with neuropsychiatric features (n = 4), PTS (n = 5), QDPR (n = 3), SR (n = 1), and TH (n = 1). We have also identified mutations in SLC6A3, FOXG1 (n = 1 of each), MTHFR (n = 3), FOLR1, and MTHFD (n = 1 of each), for dopamine transporter, neuronal development, and folate metabolism disorders, respectively. For secondary deficiencies, we have identified POLG (n = 3), ACSF3 (n = 1), NFU1, and SDHD (n = 1 of each), playing a role in mitochondrial function. Other mutated genes included: ADAR, RNASEH2B, RNASET2, SLC7A2-IT1 A/B lncRNA, and EXOSC3 involved in nuclear and cytoplasmic metabolism; RanBP2 and CASK implicated in post-traductional and scaffolding modifications; SLC6A19 regulating amino acid transport; MTM1, KCNQ2 (n = 2), and ATP1A3 playing a role in nerve cell electrophysiological state. Chromosome abnormalities, del(8)(p23)/dup(12) (p23) (n = 1), del(6)(q21) (n = 1), dup(17)(p13.3) (n = 1), and non-genetic etiologies (n = 3) were also identified.

Conclusion: We have classified the final 54 diagnoses in 11 distinctive biochemical profiles and described them through 20 clinical features. To identify the specific molecular cause of abnormal NT profiles, (targeted) genomics might be used, to improve diagnosis and allow early treatment of complex and rare neurological genetic diseases.
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http://dx.doi.org/10.1007/s10545-017-0079-6DOI Listing
January 2018

Pediatric laminopathies: Whole-body magnetic resonance imaging fingerprint and comparison with Sepn1 myopathy.

Muscle Nerve 2016 08 22;54(2):192-202. Epub 2016 Feb 22.

Assistance Publique des Hôpitaux de Paris, Service de Pédiatrie, Hôpital Raymond Poincaré, Garches, Hôpitaux Universitaires Paris-Ile-de-France Ouest, Université de Versailles-St Quentin, U1179 UVSQ-INSERM, France.

Introduction: We sought to define the whole-body MRI (WB-MRI) fingerprint of muscle involvement in pediatric LMNA-related dystrophy (LMNA-RD) and to compare it with SEPN1-related myopathy (SEPN1-RM).

Methods: Signal abnormality and atrophy in 109 muscles were scored by semiquantitative scales in 8 children with LMNA-RD and represented by heatmaps. These features were compared with those from 9 SEPN1-RM patients by random forests.

Results: LMNA-RD showed predominant signal abnormalities in erector spinae, serratus anterior, subscapularis, gluteus medius and minimus, vastii, adductor magnus and longus, semimembranosus, medial gastrocnemius, and soleus muscles. Psoas, sternocleidomastoid, gracilis, and sartorius muscles often had normal signal but showed atrophy. Cranial, flexor digitorum longus, and tibialis posterior muscles were spared. According to random forests, atrophied semimembranosus in SEPN1-RM was the most relevant feature to distinguish these patients from LMNA-RD.

Conclusions: A selective pattern in WB-MRI for pediatric LMNA-RD exists and can be differentiated from SEPN1-RM by machine learning. Muscle Nerve 54: 192-202, 2016.
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http://dx.doi.org/10.1002/mus.25018DOI Listing
August 2016

Agrin mutations lead to a congenital myasthenic syndrome with distal muscle weakness and atrophy.

Brain 2014 Sep 20;137(Pt 9):2429-43. Epub 2014 Jun 20.

5 Institute of Genetic Medicine, MRC Centre for Neuromuscular Diseases, Newcastle University, NE1 3BZ, Newcastle upon Tyne, UK

Congenital myasthenic syndromes are a clinically and genetically heterogeneous group of rare diseases resulting from impaired neuromuscular transmission. Their clinical hallmark is fatigable muscle weakness associated with a decremental muscle response to repetitive nerve stimulation and frequently related to postsynaptic defects. Distal myopathies form another clinically and genetically heterogeneous group of primary muscle disorders where weakness and atrophy are restricted to distal muscles, at least initially. In both congenital myasthenic syndromes and distal myopathies, a significant number of patients remain genetically undiagnosed. Here, we report five patients from three unrelated families with a strikingly homogenous clinical entity combining congenital myasthenia with distal muscle weakness and atrophy reminiscent of a distal myopathy. MRI and neurophysiological studies were compatible with mild myopathy restricted to distal limb muscles, but decrement (up to 72%) in response to 3 Hz repetitive nerve stimulation pointed towards a neuromuscular transmission defect. Post-exercise increment (up to 285%) was observed in the distal limb muscles in all cases suggesting presynaptic congenital myasthenic syndrome. Immunofluorescence and ultrastructural analyses of muscle end-plate regions showed synaptic remodelling with denervation-reinnervation events. We performed whole-exome sequencing in two kinships and Sanger sequencing in one isolated case and identified five new recessive mutations in the gene encoding agrin. This synaptic proteoglycan with critical function at the neuromuscular junction was previously found mutated in more typical forms of congenital myasthenic syndrome. In our patients, we found two missense mutations residing in the N-terminal agrin domain, which reduced acetylcholine receptors clustering activity of agrin in vitro. Our findings expand the spectrum of congenital myasthenic syndromes due to agrin mutations and show an unexpected correlation between the mutated gene and the associated phenotype. This provides a good rationale for examining patients with apparent distal myopathy for a neuromuscular transmission disorder and agrin mutations.
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http://dx.doi.org/10.1093/brain/awu160DOI Listing
September 2014

Spectrum of pontocerebellar hypoplasia in 13 girls and boys with CASK mutations: confirmation of a recognizable phenotype and first description of a male mosaic patient.

Orphanet J Rare Dis 2012 Mar 27;7:18. Epub 2012 Mar 27.

Centre de Référence Maladies Rares « malformations et maladies congénitales du cervelet », Hôpital Trousseau-Paris, CHU de Lyon, CHU de Lille, Paris, France.

Background: Pontocerebellar hypoplasia (PCH) is a heterogeneous group of diseases characterized by lack of development and/or early neurodegeneration of cerebellum and brainstem. According to clinical features, seven subtypes of PCH have been described, PCH type 2 related to TSEN54 mutations being the most frequent. PCH is most often autosomal recessive though de novo anomalies in the X-linked gene CASK have recently been identified in patients, mostly females, presenting with intellectual disability, microcephaly and PCH (MICPCH).

Methods: Fourteen patients (12 females and two males; aged 16 months-14 years) presenting with PCH at neuroimaging and with clinical characteristics unsuggestive of PCH1 or PCH2 were included. The CASK gene screening was performed using Array-CGH and sequencing. Clinical and neuroradiological features were collected.

Results: We observed a high frequency of patients with a CASK mutation (13/14). Ten patients (8 girls and 2 boys) had intragenic mutations and three female patients had a Xp11.4 submicroscopic deletion including the CASK gene. All were de novo mutations. Phenotype was variable in severity but highly similar among the 11 girls and was characterized by psychomotor retardation, severe intellectual disability, progressive microcephaly, dystonia, mild dysmorphism, and scoliosis. Other signs were frequently associated, such as growth retardation, ophthalmologic anomalies (glaucoma, megalocornea and optic atrophy), deafness and epilepsy. As expected in an X-linked disease manifesting mainly in females, the boy hemizygous for a splice mutation had a very severe phenotype with nearly no development and refractory epilepsy. We described a mild phenotype in a boy with a mosaic truncating mutation. We found some degree of correlation between severity of the vermis hypoplasia and clinical phenotype.

Conclusion: This study describes a new series of PCH female patients with CASK inactivating mutations and confirms that these patients have a recognizable although variable phenotype consisting of a specific form of pontocerebellar hypoplasia. In addition, we report the second male patient to present with a severe MICPCH phenotype and a de novo CASK mutation and describe for the first time a mildly affected male patient harboring a mosaic mutation. In our reference centre, CASK related PCH is the second most frequent cause of PCH. The identification of a de novo mutation in these patients enables accurate and reassuring genetic counselling.
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http://dx.doi.org/10.1186/1750-1172-7-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3351739PMC
March 2012

Type I hyperprolinemia: genotype/phenotype correlations.

Hum Mutat 2010 Aug;31(8):961-5

Inserm U614, IHU, 76000 Rouen, France.

Type I hyperprolinemia (HPI) is an autosomal recessive disorder associated with cognitive and psychiatric troubles, caused by alterations of the Proline Dehydrogenase gene (PRODH) at 22q11. HPI results from PRODH deletion and/or missense mutations reducing proline oxidase (POX) activity. The goals of this study were first to measure in controls the frequency of PRODH variations described in HPI patients, second to assess the functional effect of PRODH mutations on POX activity, and finally to establish genotype/enzymatic activity correlations in a new series of HPI patients. Eight of 14 variants occurred at polymorphic frequency in 114 controls. POX activity was determined for six novel mutations and two haplotypes. The c.1331G>A, p.G444D allele has a drastic effect, whereas the c.23C>T, p.P8L allele and the c.[56C>A; 172G>A], p.[Q19P; A58T] haplotype result in a moderate decrease in activity. Among the 19 HPI patients, 10 had a predicted residual activity <50%. Eight out of nine subjects with a predicted residual activity > or = 50% bore at least one c.824C>A, p.T275N allele, which has no detrimental effect on activity but whose frequency in controls is only 3%. Our results suggest that PRODH mutations lead to a decreased POX activity or affect other biological parameters causing hyperprolinemia.
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http://dx.doi.org/10.1002/humu.21296DOI Listing
August 2010

[Jeune'disease (asphyxiating thoracic dystrophy) and respiratory failure: importance of early respiratory management with periodic hyperinsufflation].

Bull Acad Natl Med 2007 Oct;191(7):1411-29; discussion 1429-32

Service de Neuro-Pédiatrie, Hôpital Raymond Poincaré, 92380 Garches.

Asphyxiating thoracic dystrophy (ATD) is a rare autosomal recessive form of chondrodysplasia characterized by short ribs. Respiratory failure is due to the reduced volume and complete immobility of the thoracic cage. There is no consensus on the treatment of this restrictive pulmonary disease. Surgical attempts to enlarge the thoracic cage are disappointing. We report the cases of nine children with ATD treated by periodic respiratory hyperinsufflation. Their clinical outcome was related to the severity of their respiratory distress and their age at the beginning of this treatment. It is possible to use periodic hyperinsufflation very early after birth to prevent secondary respiratory failure. Periodic insufflation can also be used to treat older children with severe restrictive respiratory insufficiency requiring tracheostomy and endotracheal management. This treatment promotes alveolar multiplication and thoracic growth. Four children had laboratory and/or clinical evidence of hepatic dysfunction that improved on ursodeoxycholic acid therapy. Three children who had muscle weakness at birth improved during childhood.
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October 2007

[Pathophysiological characterization of congenital myasthenic syndromes: the example of mutations in the MUSK gene].

J Soc Biol 2005 ;199(1):61-77

INSERM U582 & IFR 14, Institut de Myologie, Hôpital de la Salpêtrière et Université Pierre et Marie Curie, Paris, France.

Congenital myasthenic syndromes (CMS) are rare genetic diseases affecting the neuromuscular junction (NMJ) and are characterized by a dysfunction of the neurotransmission. They are heterogeneous at their pathophysiological level and can be classified in three categories according to their presynaptic, synaptic and postsynaptic origins. We report here the first case of a human neuromuscular transmission dysfunction due to mutations in the gene encoding a postsynaptic molecule, the muscle-specific receptor tyrosine kinase (MuSK). Gene analysis identified two heteroallelic mutations, a frameshift mutation (c.220insC) and a missense mutation (V790M). The muscle biopsy showed dramatic pre- and postsynaptic structural abnormalities of the neuromuscular junction and severe decrease in acetylcholine receptor (AChR) epsilon-subunit and MuSK expression. In vitro and in vivo expression experiments were performed using mutant MuSK reproducing the human mutations. The frameshift mutation led to the absence of MuSK expression. The missense mutation did not affect MuSK catalytic kinase activity but diminished expression and stability of MuSK leading to decreased agrin-dependent AChR aggregation, a critical step in the formation of the neuromuscular junction. In electroporated mouse muscle, overexpression of the missense mutation induced, within a week, a phenotype similar to the patient muscle biopsy: a severe decrease in synaptic AChR and an aberrant axonal outgrowth. These results strongly suggest that the missense mutation, in the presence of a null mutation on the other allele, is responsible for the dramatic synaptic changes observed in the patient.
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http://dx.doi.org/10.1051/jbio:2005008DOI Listing
October 2005

MUSK, a new target for mutations causing congenital myasthenic syndrome.

Hum Mol Genet 2004 Dec 20;13(24):3229-40. Epub 2004 Oct 20.

INSERM U582 & IFR Cur, Muscle, Vaisseaux, Institut de Myologie, Hôpital de la Salpêtrière and Université Pierre et Marie Curie, Paris, France.

We report the first case of a human neuromuscular transmission dysfunction due to mutations in the gene encoding the muscle-specific receptor tyrosine kinase (MuSK). Gene analysis identified two heteroallelic mutations, a frameshift mutation (c.220insC) and a missense mutation (V790M). The muscle biopsy showed dramatic pre- and postsynaptic structural abnormalities of the neuromuscular junction and severe decrease in acetylcholine receptor (AChR) epsilon-subunit and MuSK expression. In vitro and in vivo expression experiments were performed using mutant MuSK reproducing the human mutations. The frameshift mutation led to the absence of MuSK expression. The missense mutation did not affect MuSK catalytic kinase activity but diminished expression and stability of MuSK leading to decreased agrin-dependent AChR aggregation, a critical step in the formation of the neuromuscular junction. In electroporated mouse muscle, overexpression of the missense mutation induced, within a week, a phenotype similar to the patient muscle biopsy: a severe decrease in synaptic AChR and an aberrant axonal outgrowth. These results strongly suggest that the missense mutation, in the presence of a null mutation on the other allele, is responsible for the dramatic synaptic changes observed in the patient.
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http://dx.doi.org/10.1093/hmg/ddh333DOI Listing
December 2004

Respiratory capacity course in patients with infantile spinal muscular atrophy.

Chest 2004 Sep;126(3):831-7

Department of Pediatric Neurology, Hôpital Raymond Poincaré, 104, Boulevard Raymond Poincaré, 92380 Garches, France.

Study Objectives: To describe the clinical and respiratory course in infantile spinal muscular atrophy (SMA) type I, type II, and type III, and to evaluate the respiratory needs for these patients, using noninvasive or tracheostomy ventilation.

Design: Retrospective cohort study.

Methods: We report 33 patients with SMA true type I (onset before age 3 months), 35 patients with SMA intermediate type I (onset between 3 months and 6 months), 100 patients with SMA type II (onset between 6 months and 18 months), 12 patients with SMA type III (onset after age 18 months). We report the clinical symptoms, respiratory course, and respiratory management: respiratory physiotherapy, periodic hyperinsufflation, nasal nocturnal ventilation (NNV), and tracheostomy. Also, we measured the FVC over several years during childhood and adolescence.

Results: In patients with SMA true type I, 82% of patients died, one third of whom underwent tracheostomy. In patients with SMA intermediate type I, 43% needed NNV, 57% underwent tracheostomy, and 26% died. In patients with SMA type II, 38% needed NNV, 15% underwent tracheostomy, and 4% died. In patients with SMA type III, respiratory impairment was moderate and began during the second decade of life.

Conclusion: This data shows the progressively worsening course of restrictive respiratory insufficiency in patients with SMA, and the importance of early respiratory management to limit pulmonary complications and improve the quality of life for these patients.
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http://dx.doi.org/10.1378/chest.126.3.831DOI Listing
September 2004