Publications by authors named "Genevieve Bernard"

107 Publications

Adult Hereditary White Matter Diseases With Psychiatric Presentation: Clinical Pointers and MRI Algorithm to Guide the Diagnostic Process.

J Neuropsychiatry Clin Neurosci 2021 May 6:appineuropsych20110294. Epub 2021 May 6.

Department of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montreal (Costei, Brais, La Piana); Department of Psychiatry, McGill University (Barbarosie); Departments of Neurology and Neurosurgery, Pediatrics and Human Genetics, McGill University (Bernard); Department of Specialized Medicine, Division of Medical Genetics, McGill University Health Center, Montreal (Bernard); Child Health and Human Development Program, Research Institute of the McGill University Health Center (Bernard); and Department of Diagnostic Radiology, McGill University (La Piana).

Objective: The investigators aimed to provide clinical and MRI guidelines for determining when genetic workup should be considered in order to exclude hereditary leukoencephalopathies in affected patients with a psychiatric presentation.

Methods: A systematic literature review was conducted, and clinical cases are provided. Given the central role of MRI pattern recognition in the diagnosis of white matter disorders, the investigators adapted an MRI algorithm that guides the interpretation of MRI findings and thus directs further investigations, such as genetic testing.

Results: Twelve genetic leukoencephalopathies that can present with psychiatric symptoms were identified. As examples of presentations that can occur in clinical practice, five clinical vignettes from patients assessed at a referral center for adult genetic leukoencephalopathies are provided.

Conclusions: Features such as drug-resistant symptoms, presence of long-standing somatic features, trigger events, consanguinity, and positive family history should orient the clinician toward diagnostic workup to exclude the presence of a genetic white matter disorder. The identification of MRI white matter abnormalities, especially when presenting a specific pattern of involvement, should prompt genetic testing for known forms of genetic leukoencephalopathies.
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http://dx.doi.org/10.1176/appi.neuropsych.20110294DOI Listing
May 2021

POLR3-related leukodystrophy: How do mutations affecting RNA polymerase III subunits cause hypomyelination?

Fac Rev 2021 5;10:12. Epub 2021 Feb 5.

Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montréal, QC, Canada.

Hypomyelinating leukodystrophies are a group of genetic disorders characterized by insufficient myelin deposition during development. A subset of hypomyelinating leukodystrophies, named RNA polymerase III (Pol III or POLR3)-related leukodystrophy or 4H (Hypomyelination, Hypodontia and Hypogonadotropic Hypogonadism) leukodystrophy, was found to be caused by biallelic variants in genes encoding subunits of the enzyme Pol III, including POLR3A, POLR3B, POLR3K, and POLR1C. Pol III is one of the three nuclear RNA polymerases that synthesizes small non-coding RNAs, such as tRNAs, 5S RNA, and others, that are involved in the regulation of essential cellular processes, including transcription, translation and RNA maturation. Affinity purification coupled with mass spectrometry (AP-MS) revealed that a number of mutations causing POLR3-related leukodystrophy impair normal assembly or biogenesis of Pol III, often causing a retention of the unassembled subunits in the cytoplasm. Even though these proteomic studies have helped to understand the molecular defects associated with leukodystrophy, how these mutations cause hypomyelination has yet to be defined. In this review we propose two main hypotheses to explain how mutations affecting Pol III subunits can cause hypomyelination.
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http://dx.doi.org/10.12703/r/10-12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7894263PMC
February 2021

POLR3-Related Leukodystrophy: Exploring Potential Therapeutic Approaches.

Front Cell Neurosci 2020 28;14:631802. Epub 2021 Jan 28.

Department of Neurology and Neurosurgery, McGill University, Montréal, QC, Canada.

Leukodystrophies are a class of rare inherited central nervous system (CNS) disorders that affect the white matter of the brain, typically leading to progressive neurodegeneration and early death. Hypomyelinating leukodystrophies are characterized by the abnormal formation of the myelin sheath during development. POLR3-related or 4H (hypomyelination, hypodontia, and hypogonadotropic hypogonadism) leukodystrophy is one of the most common types of hypomyelinating leukodystrophy for which no curative treatment or disease-modifying therapy is available. This review aims to describe potential therapies that could be further studied for effectiveness in pre-clinical studies, for an eventual translation to the clinic to treat the neurological manifestations associated with POLR3-related leukodystrophy. Here, we discuss the therapeutic approaches that have shown promise in other leukodystrophies, as well as other genetic diseases, and consider their use in treating POLR3-related leukodystrophy. More specifically, we explore the approaches of using stem cell transplantation, gene replacement therapy, and gene editing as potential treatment options, and discuss their possible benefits and limitations as future therapeutic directions.
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http://dx.doi.org/10.3389/fncel.2020.631802DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7902007PMC
January 2021

Classifying Hypomyelination: A Critical (White) Matter.

Child Neurol Open 2020 Jan-Dec;7:2329048X20983761. Epub 2020 Dec 24.

Department of Neurology and Neurosurgery, McGill University, Montréal, Québec, Canada.

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http://dx.doi.org/10.1177/2329048X20983761DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7768829PMC
December 2020

De novo variants in POLR3B cause ataxia, spasticity, and demyelinating neuropathy.

Am J Hum Genet 2021 01;108(1):186-193

Division of Neurology, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, ON M5G 1X8, Canada; Division of Clinical and Metabolic Genetics, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, ON, M5G 1X8, Canada. Electronic address:

POLR3B encodes the second-largest catalytic subunit of RNA polymerase III, an enzyme involved in transcription. Bi-allelic pathogenic variants in POLR3B are a well-established cause of hypomyelinating leukodystrophy. We describe six unrelated individuals with de novo missense variants in POLR3B and a clinical presentation substantially different from POLR3-related leukodystrophy. These individuals had afferent ataxia, spasticity, variable intellectual disability and epilepsy, and predominantly demyelinating sensory motor peripheral neuropathy. Protein modeling and proteomic analysis revealed a distinct mechanism of pathogenicity; the de novo POLR3B variants caused aberrant association of individual enzyme subunits rather than affecting overall enzyme assembly or stability. We expand the spectrum of disorders associated with pathogenic variants in POLR3B to include a de novo heterozygous POLR3B-related disorder.
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http://dx.doi.org/10.1016/j.ajhg.2020.12.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7820722PMC
January 2021

Endocrine and Growth Abnormalities in 4H Leukodystrophy Caused by Variants in POLR3A, POLR3B, and POLR1C.

J Clin Endocrinol Metab 2021 Jan;106(2):e660-e674

Department of Child Neurology, University Children's Hospital Tübingen, Tübingen, Germany.

Context: 4H or POLR3-related leukodystrophy is an autosomal recessive disorder typically characterized by hypomyelination, hypodontia, and hypogonadotropic hypogonadism, caused by biallelic pathogenic variants in POLR3A, POLR3B, POLR1C, and POLR3K. The endocrine and growth abnormalities associated with this disorder have not been thoroughly investigated to date.

Objective: To systematically characterize endocrine abnormalities of patients with 4H leukodystrophy.

Design: An international cross-sectional study was performed on 150 patients with genetically confirmed 4H leukodystrophy between 2015 and 2016. Endocrine and growth abnormalities were evaluated, and neurological and other non-neurological features were reviewed. Potential genotype/phenotype associations were also investigated.

Setting: This was a multicenter retrospective study using information collected from 3 predominant centers.

Patients: A total of 150 patients with 4H leukodystrophy and pathogenic variants in POLR3A, POLR3B, or POLR1C were included.

Main Outcome Measures: Variables used to evaluate endocrine and growth abnormalities included pubertal history, hormone levels (estradiol, testosterone, stimulated LH and FSH, stimulated GH, IGF-I, prolactin, ACTH, cortisol, TSH, and T4), and height and head circumference charts.

Results: The most common endocrine abnormalities were delayed puberty (57/74; 77% overall, 64% in males, 89% in females) and short stature (57/93; 61%), when evaluated according to physician assessment. Abnormal thyroid function was reported in 22% (13/59) of patients.

Conclusions: Our results confirm pubertal abnormalities and short stature are the most common endocrine features seen in 4H leukodystrophy. However, we noted that endocrine abnormalities are typically underinvestigated in this patient population. A prospective study is required to formulate evidence-based recommendations for management of the endocrine manifestations of this disorder.
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http://dx.doi.org/10.1210/clinem/dgaa700DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7823228PMC
January 2021

Response to Correspondence on "Stress in Parents of Children With Genetically Determined Leukoencephalopathies: A Pilot Study".

J Child Neurol 2021 Mar 27;36(3):245-246. Epub 2020 Sep 27.

Department of Neurology and Neurosurgery, McGill University, Montréal, Québec, Canada.

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http://dx.doi.org/10.1177/0883073820960984DOI Listing
March 2021

Expanding the phenotypic and molecular spectrum of RNA polymerase III-related leukodystrophy.

Neurol Genet 2020 Jun 11;6(3):e425. Epub 2020 May 11.

Department of Neurology and Neurosurgery (S.P., L.G., M.A.M.-R., L.T.T., K.G., L.D., M. Srour, K.P., G.B.), McGill University; Child Health and Human Development Program (S.P., M.A.M.-R., L.T.T., K.G., L.D., M. Srour, G.B.), Research Institute of the McGill University Health Centre; Department of Pediatrics (L.G., L.T.T., K.G., L.D., M. Srour, G.B.), McGill University, Montreal, Quebec, Canada; Division of Clinical and Metabolic Genetics (L.G.), Division of Neurology, the Hospital for Sick Children, University of Toronto, Ontario, Canada; Department of Pathology (C.F.-B.), CHU Sainte-Justine, Université de Montreal, Quebec, Canada; Division of Pathology and Laboratory Medicine (M.K.D.), Phoenix Children's Hospital, AZ; Department of Human Genetics (L.T.T., K.G., L.D., G.B.), McGill University, Montreal, Quebec, Canada; McGill University (K.P.), Brain Tumour Research Center Montreal Neurological Institute and Hospital, Quebec, Canada; Department of Neurology (D.L.R.), Department of Clinical Genomics, Department of Pediatrics, Mayo Clinic, Rochester, MN; Department of Pediatrics (M. Saito), University of California Riverside School of Medicine, Riverside Medical Clinic, CA; Department of Pediatrics (S.C.), Beaver Medical Group, Redlands, CA; Division of Pediatric Neurology (S.L.), Department of Pediatrics, Klinikum Dritter Orden, Munich, Germany; Institute of Human Genetics (B.A., T.B.H.), Technische Universität München, Munich, Germany; Institute of Medical Genetics and Applied Genomics (T.B.H.), University of Tübingen, Germany; Department of Neurology (I.T.-M., F.I.M., N.R.-E.), Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Canary Islands, Spain; Department of Neurology (D.P.), Children's Hospital of Eastern Ontario, University of Ottawa, Ontario, Canada; Department of Pediatrics (S.N.) and Department of Neurology (A.G.), Wake Forest School of Medicine, Winston-Salem, NC; Adult and Paediatric National Metabolic Service (E.G.), Starship Children's Hospital, Auckland, New Zealand; and Division of Medical Genetics (G.B.), Department of Specialized Medicine, Montreal Children's Hospital and McGill University Health Centre, Quebec, Canada.

Objective: To expand the phenotypic spectrum of severity of POLR3-related leukodystrophy and identify genotype-phenotype correlations through study of patients with extremely severe phenotypes.

Methods: We performed an international cross-sectional study on patients with genetically proven POLR3-related leukodystrophy and atypical phenotypes to identify 6 children, 3 males and 3 females, with an extremely severe phenotype compared with that typically reported. Clinical, radiologic, and molecular features were evaluated for all patients, and functional and neuropathologic studies were performed on 1 patient.

Results: Each patient presented between 1 and 3 months of age with failure to thrive, severe dysphagia, and developmental delay. Four of the 6 children died before age 3 years. MRI of all patients revealed a novel pattern with atypical characteristics, including progressive basal ganglia and thalami abnormalities. Neuropathologic studies revealed patchy areas of decreased myelin in the cerebral hemispheres, cerebellum, brainstem, and spinal cord, with astrocytic gliosis in the white matter and microglial activation. Cellular vacuolization was observed in the thalamus and basal ganglia, and neuronal loss was evident in the putamen and caudate. Genotypic similarities were also present between all 6 patients, with one allele containing a variant causing a premature stop codon and the other containing a specific intronic splicing variant (c.1771-7C>G), which produces 2 aberrant transcripts along with some wild-type transcript.

Conclusions: We describe genotype-phenotype correlations at the extreme end of severity of the POLR3-related leukodystrophy spectrum and shed light on the complex disease pathophysiology.
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http://dx.doi.org/10.1212/NXG.0000000000000425DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7238899PMC
June 2020

Randomized Clinical Trial of First-Line Genome Sequencing in Pediatric White Matter Disorders.

Ann Neurol 2020 08 9;88(2):264-273. Epub 2020 Jun 9.

Illumina, San Diego, California, USA.

Objective: Genome sequencing (GS) is promising for unsolved leukodystrophies, but its efficacy has not been prospectively studied.

Methods: A prospective time-delayed crossover design trial of GS to assess the efficacy of GS as a first-line diagnostic tool for genetic white matter disorders took place between December 1, 2015 and September 27, 2017. Patients were randomized to receive GS immediately with concurrent standard of care (SoC) testing, or to receive SoC testing for 4 months followed by GS.

Results: Thirty-four individuals were assessed at interim review. The genetic origin of 2 patient's leukoencephalopathy was resolved before randomization. Nine patients were stratified to the immediate intervention group and 23 patients to the delayed-GS arm. The efficacy of GS was significant relative to SoC in the immediate (5/9 [56%] vs 0/9 [0%]; Wild-Seber, p < 0.005) and delayed (control) arms (14/23 [61%] vs 5/23 [22%]; Wild-Seber, p < 0.005). The time to diagnosis was significantly shorter in the immediate-GS group (log-rank test, p = 0.04). The overall diagnostic efficacy of combined GS and SoC approaches was 26 of 34 (76.5%, 95% confidence interval = 58.8-89.3%) in <4 months, greater than historical norms of <50% over 5 years. Owing to loss of clinical equipoise, the trial design was altered to a single-arm observational study.

Interpretation: In this study, first-line GS provided earlier and greater diagnostic efficacy in white matter disorders. We provide an evidence-based diagnostic testing algorithm to enable appropriate clinical GS utilization in this population. ANN NEUROL 2020;88:264-273.
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http://dx.doi.org/10.1002/ana.25757DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8061316PMC
August 2020

4H leukodystrophy: Mild clinical phenotype and comorbidity with multiple sclerosis.

Neurol Genet 2020 Apr 11;6(2):e409. Epub 2020 Mar 11.

Faculty of Medicine (S.M.D., D.P.), University of Ottawa, ON, Canada; Departments of Neurology and Neurosurgery, Pediatrics and Human Genetics (G.B.), McGill University; Department Specialized Medicine (G.B.), Division of Medical Genetics, McGill University Health Center; Child Health and Human Development Program (G.B.), Research Institute of the McGill University Health Center; MyeliNeuroGene Laboratory (G.B.), Research Institute of the McGill University Health Center, Montreal, Quebec, Canada; Department of Pediatric Neurology (N.I.W.), Emma Children's Hospital, Amsterdam, Netherlands; Amsterdam Neuroscience (N.I.W.), Vrije Universiteit, Netherlands; and Department of Medical Imaging (E.M.) and Division of Neurology (D.P.), CHEO, University of Ottawa, ON, Canada.

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http://dx.doi.org/10.1212/NXG.0000000000000409DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7164972PMC
April 2020

Clinical spectrum of POLR3-related leukodystrophy caused by biallelic pathogenic variants.

Neurol Genet 2019 Dec 30;5(6):e369. Epub 2019 Oct 30.

Department of Neurology and Neurosurgery (L.G., L.T.T., K.G., G.B.), McGill University, Montreal, Canada; Department of Pediatrics (L.G., L.T.T., K.G., G.B.), McGill University, Montreal, Canada; Division of Clinical and Metabolic Genetics and Division of Neurology (L.G., G.Y.), The Hospital for Sick Children, University of Toronto, Toronto, Canada; Department of Child Neurology (F.K.C., M.S.V.D.K., N.I.W.), Emma Children's Hospital, Amsterdam University Medical Centers, Vrije Universiteit Amsterdam, and Amsterdam Neuroscience, Amsterdam, The Netherlands; Department of Clinical Genetics (F.K.C., R.M.V.S.), VU University Medical Center, Amsterdam, The Netherlands; Department of Human Genetics (F.K.C.), Center for Biomedical Research, Diponegoro University, Semarang, Indonesia; Department of Pediatrics (L.S.), Faculty of Medicine, University of Szeged, Szeged, Hungary; Child Health and Human Development Program (L.T.T., K.G., G.B.), Research Institute of the McGill University Health Center, Montreal, Canada; Division of Medical Genetics, Department of Specialized Medicine (L.T.T., K.G., G.B.), McGill University Health Center, Montreal, Canada; Centre de Référence Neurogénétique (F.H., C.G.), Service de Génétique, CHU Bordeaux, Bordeaux, France; Department of Pediatrics (E.L.F.), Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China; Developmental Neurology Department (S.D.A.), Fondazione IRCCS Istituto Neurologico C. Besta, Milan, Italy; Neuroscience and Neurorehabilitation Department (G.V.), Bambino Gesu Children's Hospital, Rome, Italy; Center for Pediatric Genomic Medicine (I.T.), Children's Mercy Hospitals and Clinics, Kansas City, MO; University of Missouri-Kansas City School of Medicine (I.T.), Kansas City, MO; Department of Pathology and Laboratory Medicine (I.T.), Children's Mercy Hospitals, Kansas City, MO; Department of Pediatrics (D.M.N.), Section of Medical Genetics, Ochsner for Children, New Orleans, LA; GeneDx (R.P.), Gaithersburg, MD; Division of Neurology (K.S.L.), Barrow Neurological Institute, Phoenix Children's Hospital, Phoenix, AZ; Department of Pediatric Neurology (E.W.), Birmingham Children's Hospital, Birmingham, United Kingdom; Department of Medical Genetics (T.P.), Telemark Hospital, Skien, Norway; Department of Paediatric Neurology (P.F.), St Georges University Hospital NHS Foundation Trust, London, United Kingdom; Clinical Genetics Service (M.M.), St George's University Hospitals NHS Foundation Trust, London, United Kingdom; Clinical Genetics Department (J.R.), Royal Devon and Exeter Hospital NHS Trust, Exeter, United Kingdom; Department of Neurology and Neurosurgery (R.W.), The Children's Hospital at Westmead, Westmead, New South Wales, Australia; Center of Developmental Neurology (H.P.), Frankfurt, Germany; Department of Neurology (B.V.D.W.), Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands; Department of Neurology (D.T.), Essen University Hospital, University of Duisburg-Essen, Essen, Germany; Department of Clinical Genetics (A.D., C.S.), Nottingham University Hospitals NHS Trust, Nottingham, United Kingdom; Wellcome Sanger Institute (DDD Study), Wellcome Genome Campus, Cambridge, United Kingdom; Department of Pediatrics (N.T.), Division of Child Neurology, University of Texas Health Science Center, Houston, TX, United States of America; Movement Disorders Center and Neurogenetics Research Program (M.C.K.), Barrow Neurological Institute, Phoenix Children's Hospital, Phoenix, AZ; Program in Neuroscience (M.C.K.), Arizona State University, Tempe, AZ, United States of America; Division of Neurology (S.S.), Department of Pediatrics, Lady Hardinge Medical College and Associated Kalawati Saran Children's Hospital, New Delhi, India; Division of Neurology (A.V.), Children's Hospital of Philadelphia, Philadelphia, PA; Department of Neurology (A.V.), Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States of America; Department of Child Neurology (D.T.), Neurological Institute C. Besta Foundation IRCCS, Milan, Italy; Department of Functional Genomics (M.S.V.D.K.), VU University, Amsterdam, The Netherlands; Unit of Neuromuscular and Neurodegenerative Disorders (E.B.), Laboratory of Molecular Medicine, Bambino Gesu Children's Hospital, Rome, Italy; Laboratoire MRGM, INSERM U1211, University Bordeaux, Bordeaux, France; Université de Bordeaux (S.F.), INSERM U1212, CNRS 5320, Bordeaux, France; and Department of Human Genetics (G.B.), McGill University, Montreal, Canada.

Objective: To determine the clinical, radiologic, and molecular characteristics of RNA polymerase III-related leukodystrophy (POLR3-HLD) caused by biallelic pathogenic variants.

Methods: A cross-sectional observational study involving 25 centers worldwide was conducted. Clinical and molecular information was collected on 23 unreported and previously reported patients with POLR3-HLD and biallelic pathogenic variants in . Brain MRI studies were reviewed.

Results: Fourteen female and 9 male patients aged 7 days to 23 years were included in the study. Most participants presented early in life (birth to 6 years), and motor deterioration was seen during childhood. A notable proportion of patients required a wheelchair before adolescence, suggesting a more severe phenotype than previously described in POLR3-HLD. Dental, ocular, and endocrine features were not invariably present (70%, 50%, and 50%, respectively). Five patients (22%) had a combination of hypomyelinating leukodystrophy and abnormal craniofacial development, including 1 individual with clear Treacher Collins syndrome (TCS) features. Brain MRI revealed hypomyelination in all cases, often with areas of pronounced T2 hyperintensity corresponding to T1 hypointensity of the white matter. Twenty-nine different pathogenic variants (including 12 new disease-causing variants) in were identified.

Conclusions: This study provides a comprehensive description of POLR3-HLD caused by biallelic pathogenic variants based on the largest cohort of patients to date. These results suggest distinct characteristics of POLR1C-related disorder, with a spectrum of clinical involvement characterized by hypomyelinating leukodystrophy with or without abnormal craniofacial development reminiscent of TCS.
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http://dx.doi.org/10.1212/NXG.0000000000000369DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6927361PMC
December 2019

POLR3A variants with striatal involvement and extrapyramidal movement disorder.

Neurogenetics 2020 04 15;21(2):121-133. Epub 2020 Jan 15.

Department of Child Neurology, Center for Childhood White Matter Diseases, Emma Children's Hospital, Vrije Universiteit, and Amsterdam Neuroscience, Amsterdam University Medical Centers, Amsterdam, The Netherlands.

Biallelic variants in POLR3A cause 4H leukodystrophy, characterized by hypomyelination in combination with cerebellar and pyramidal signs and variable non-neurological manifestations. Basal ganglia are spared in 4H leukodystrophy, and dystonia is not prominent. Three patients with variants in POLR3A, an atypical presentation with dystonia, and MR involvement of putamen and caudate nucleus (striatum) and red nucleus have previously been reported. Genetic, clinical findings and 18 MRI scans from nine patients with homozygous or compound heterozygous POLR3A variants and predominant striatal changes were retrospectively reviewed in order to characterize the striatal variant of POLR3A-associated disease. Prominent extrapyramidal involvement was the predominant clinical sign in all patients. The three youngest children were severely affected with muscle hypotonia, impaired head control, and choreic movements. Presentation of the six older patients was milder. Two brothers diagnosed with juvenile parkinsonism were homozygous for the c.1771-6C > G variant in POLR3A; the other seven either carried c.1771-6C > G (n = 1) or c.1771-7C > G (n = 7) together with another variant (missense, synonymous, or intronic). Striatal T2-hyperintensity and atrophy together with involvement of the superior cerebellar peduncles were characteristic. Additional MRI findings were involvement of dentate nuclei, hila, or peridentate white matter (3, 6, and 4/9), inferior cerebellar peduncles (6/9), red nuclei (2/9), and abnormal myelination of pyramidal and visual tracts (6/9) but no frank hypomyelination. Clinical and MRI findings in patients with a striatal variant of POLR3A-related disease are distinct from 4H leukodystrophy and associated with one of two intronic variants, c.1771-6C > G or c.1771-7C > G, in combination with another POLR3A variant.
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http://dx.doi.org/10.1007/s10048-019-00602-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7064625PMC
April 2020

Genome sequencing in persistently unsolved white matter disorders.

Ann Clin Transl Neurol 2020 01 7;7(1):144-152. Epub 2020 Jan 7.

Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.

Genetic white matter disorders have heterogeneous etiologies and overlapping clinical presentations. We performed a study of the diagnostic efficacy of genome sequencing in 41 unsolved cases with prior exome sequencing, resolving an additional 14 from an historical cohort (n = 191). Reanalysis in the context of novel disease-associated genes and improved variant curation and annotation resolved 64% of cases. The remaining diagnoses were directly attributable to genome sequencing, including cases with small and large copy number variants (CNVs) and variants in deep intronic and technically difficult regions. Genome sequencing, in combination with other methodologies, achieved a diagnostic yield of 85% in this retrospective cohort.
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http://dx.doi.org/10.1002/acn3.50957DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6952322PMC
January 2020

RARS1-related hypomyelinating leukodystrophy: Expanding the spectrum.

Ann Clin Transl Neurol 2020 01 8;7(1):83-93. Epub 2019 Dec 8.

Metabolic Unit, Department of Clinical Chemistry, Amsterdam Neuroscience, Amsterdam Gastroenterology & Metabolism, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands.

Objective: Biallelic variants in RARS1, encoding the cytoplasmic tRNA synthetase for arginine (ArgRS), cause a hypomyelinating leukodystrophy. This study aimed to investigate clinical, neuroradiological and genetic features of patients with RARS1-related disease, and to identify possible genotype-phenotype relationships.

Methods: We performed a multinational cross-sectional survey among 20 patients with biallelic RARS1 variants identified by next-generation sequencing techniques. Clinical data, brain MRI findings and genetic results were analyzed. Additionally, ArgRS activity was measured in fibroblasts of four patients, and translation of long and short ArgRS isoforms was quantified by western blot.

Results: Clinical presentation ranged from severe (onset in the first 3 months, usually with refractory epilepsy and early brain atrophy), to intermediate (onset in the first year with nystagmus and spasticity), and mild (onset around or after 12 months with minimal cognitive impairment and preserved independent walking). The most frequent RARS1 variant, c.5A>G, led to mild or intermediate phenotypes, whereas truncating variants and variants affecting amino acids close to the ArgRS active centre led to severe phenotypes. ArgRS activity was significantly reduced in three patients with intermediate and severe phenotypes; in a fourth patient with intermediate to severe presentation, we measured normal ArgRS activity, but found translation mainly of the short instead of the long ArgRS isoform.

Interpretation: Variants in RARS1 impair ArgRS activity and do not only lead to a classic hypomyelination presentation with nystagmus and spasticity, but to a wide spectrum, ranging from severe, early-onset epileptic encephalopathy with brain atrophy to mild disease with relatively preserved myelination.
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http://dx.doi.org/10.1002/acn3.50960DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6952319PMC
January 2020

A variant of neonatal progeroid syndrome, or Wiedemann-Rautenstrauch syndrome, is associated with a nonsense variant in POLR3GL.

Eur J Hum Genet 2020 04 6;28(4):461-468. Epub 2019 Nov 6.

Medical Genetics Division, Department of Pediatrics, Sainte-Justine University Hospital Center, Montreal, QC, Canada.

Neonatal progeroid syndrome, also known as Wiedemann-Rautenstrauch syndrome, is a rare condition characterized by severe growth retardation, apparent macrocephaly with prominent scalp veins, and lipodystrophy. It is caused by biallelic variants in POLR3A, a gene encoding for a subunit of RNA polymerase III. All variants reported in the literature lead to at least a partial loss-of-function (when considering both alleles together). Here, we describe an individual with several clinical features of neonatal progeroid syndrome in whom exome sequencing revealed a homozygous nonsense variant in POLR3GL (NM_032305.2:c.358C>T; p.(Arg120Ter)). POLR3GL also encodes a subunit of RNA polymerase III and has recently been associated with endosteal hyperostosis and oligodontia in three patients with a phenotype distinct from the patient described here. Given the important role of POLR3GL in the same complex as the protein implicated in neonatal progeroid syndrome, the nature of the variant identified, our RNA studies suggesting nonsense-mediated decay, and the clinical overlap, we propose POLR3GL as a gene causing a variant of neonatal progeroid syndrome and therefore expand the phenotype associated with POLR3GL variants.
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http://dx.doi.org/10.1038/s41431-019-0539-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7080780PMC
April 2020

HSD10 mitochondrial disease: p.Leu122Val variant, mild clinical phenotype, and founder effect in French-Canadian patients from Quebec.

Mol Genet Genomic Med 2019 12 26;7(12):e1000. Epub 2019 Oct 26.

Medical Genetics, Department of Pediatrics, Université de Sherbrooke-CHUS, Sherbrooke, QC, Canada.

Background: HSD10 mitochondrial disease (HSD10MD), originally described as a deficiency of 2-methyl-3-hydroxybutyryl-CoA dehydrogenase (MHBD), is a rare X-linked disorder of a moonlighting protein encoded by the HSD17B10. The diagnosis is usually first suspected on finding elevated isoleucine degradation metabolites in urine, reflecting decreased MHBD activity. However, it is now known that clinical disease pathogenesis reflects other independent functions of the HSD10 protein; particularly its essential role in mitochondrial transcript processing and tRNA maturation. The classical phenotype of HSD10MD in affected males is an infantile-onset progressive neurodegenerative disorder associated with severe mitochondrial dysfunction.

Patients, Methods, And Results: In four unrelated families, we identified index patients with MHBD deficiency, which implied a diagnosis of HSD10MD. Each index patient was independently investigated because of neurological or developmental concerns. All had persistent elevations of urinary 2-methyl-3-hydroxybutyric acid and tiglylglycine. Analysis of HSD17B10 identified a single missense variant, c.364C>G, p.Leu122Val, in each case. This rare variant (1/183336 alleles in gnomAD) was previously reported in one Dutch patient and was described as pathogenic. The geographic origins of our families and results of haplotype analysis together provide evidence of a founder effect for this variant in Quebec. Notably, we identified an asymptomatic hemizygous adult male in one family, while a second independent genetic disorder contributed substantially to the clinical phenotypes observed in probands from two other families.

Conclusion: The phenotype associated with p.Leu122Val in HSD17B10 currently appears to be attenuated and nonprogressive. This report widens the spectrum of phenotypic severity of HSD10MD and contributes to genotype-phenotype correlation. At present, we consider p.Leu122Val a "variant of uncertain significance." Nonetheless, careful follow-up of our patients remains advisable, to assess long-term clinical course and ensure appropriate management. It will also be important to identify other potential patients in our population and to characterize their phenotype.
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http://dx.doi.org/10.1002/mgg3.1000DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6900358PMC
December 2019

Postzygotic inactivating mutations of RHOA cause a mosaic neuroectodermal syndrome.

Nat Genet 2019 10 30;51(10):1438-1441. Epub 2019 Sep 30.

Center for Neurogenetics, Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA.

Hypopigmentation along Blaschko's lines is a hallmark of a poorly defined group of mosaic syndromes whose genetic causes are unknown. Here we show that postzygotic inactivating mutations of RHOA cause a neuroectodermal syndrome combining linear hypopigmentation, alopecia, apparently asymptomatic leukoencephalopathy, and facial, ocular, dental and acral anomalies. Our findings pave the way toward elucidating the etiology of pigmentary mosaicism and highlight the role of RHOA in human development and disease.
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http://dx.doi.org/10.1038/s41588-019-0498-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6858542PMC
October 2019

Patient-Derived Stem Cells, Another Model, or the Missing Link Toward Novel Therapies for Autism Spectrum Disorders?

Front Pediatr 2019 6;7:225. Epub 2019 Jun 6.

Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, McGill University, Montreal, QC, Canada.

Autism Spectrum Disorders (ASDs) is a multigenic and multifactorial neurodevelopmental group of disorders diagnosed in early childhood, leading to deficits in social interaction, verbal and non-verbal communication and characterized by restricted and repetitive behaviors and interests. To date, genetic, descriptive and mechanistic aspects of the ASDs have been investigated using mouse models and post-mortem brain tissue. More recently, the technology to generate stem cells from patients' samples has brought a new avenue for modeling ASD through 2D and 3D neuronal models that are derived from a patient's own cells, with the goal of building new therapeutic strategies for treating ASDs. This review analyses how studies performed on mouse models and human samples can complement each other, advancing our current knowledge into the pathophysiology of the ASDs. Regardless of the genetic and phenotypic heterogeneities of ASDs, convergent information regarding the molecular and cellular mechanisms involved in these disorders can be extracted from these models. Thus, considering the complexities of these disorders, patient-derived models have immense potential to elucidate molecular deregulations that contributed to the different autistic phenotypes. Through these direct investigations with the human models, they offer the potential for opening new therapeutic avenues that can be translated into the clinic.
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http://dx.doi.org/10.3389/fped.2019.00225DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6562499PMC
June 2019

Leukodystrophy-associated mutations down-regulate the RNA polymerase III transcript and important regulatory RNA .

J Biol Chem 2019 05 21;294(18):7445-7459. Epub 2019 Mar 21.

From the Department of Human Genetics, McGill University, Montréal, Québec H3A 0C7, Canada,

RNA polymerase III (Pol III) is an essential enzyme responsible for the synthesis of several small noncoding RNAs, a number of which are involved in mRNA translation. Recessive mutations in , encoding the largest subunit of Pol III, cause POLR3-related hypomyelinating leukodystrophy (POLR3-HLD), characterized by deficient central nervous system myelination. Identification of the downstream effectors of pathogenic POLR3A mutations has so far been elusive. Here, we used CRISPR-Cas9 to introduce the mutation c.2554A→G (p.M852V) into human cell lines and assessed its impact on Pol III biogenesis, nuclear import, DNA occupancy, transcription, and protein levels. Transcriptomic profiling uncovered a subset of transcripts vulnerable to Pol III hypofunction, including a global reduction in tRNA levels. The brain cytoplasmic BC200 RNA (), involved in translation regulation, was consistently affected in all our cellular models, including patient-derived fibroblasts. Genomic deletion in an oligodendroglial cell line led to major transcriptomic and proteomic changes, having a larger impact than those of mutations. Upon differentiation, mRNA levels of the gene, encoding myelin basic protein, were significantly decreased in -mutant cells. Our findings provide the first evidence for impaired Pol III transcription in cellular models of POLR3-HLD and identify several candidate effectors, including BC200 RNA, having a potential role in oligodendrocyte biology and involvement in the disease.
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http://dx.doi.org/10.1074/jbc.RA118.006271DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6509492PMC
May 2019

Dystonia in RNA Polymerase III-Related Leukodystrophy.

Mov Disord Clin Pract 2019 Feb 9;6(2):155-159. Epub 2019 Jan 9.

Department of Neurology and Neurosurgery McGill University Montreal Canada.

Objectives: To identify the prevalence of dystonia in a RNA Polymerase III (POLR3)-related leukodystrophy patient cohort and to further characterize their dystonic features.

Background: POLR3-related leukodystrophy is a hypomyelinating leukodystrophy characterized by neurological and non-neurological features. Dystonia remains a challenging and under-recognized feature.

Methods: A retrospective chart review was performed in a cohort of 20 patients for whom videos of a standardized neurological examination were available. Patients were recruited at the Montreal Children's Hospital of the McGill University Health Center and the Myelin Disorders Bioregistry Project. Families were consented at the initial assessment and the following data was recorded: age and symptoms at clinical presentation, investigations, causal gene and mutation(s), type and severity of dystonia, and treatment response when needed. Standardized examination videos were reviewed by three independent reviewers and scored using the Global Dystonia Scale.

Results: 10 males and 10 females were included in this study; 12/20 had mutations, while 8/20 had mutations; 19/20 patients had documented dystonia, with 3/19 requiring therapy. There was a good response in two patients to a single agent, and a poor response in one patient to three agents; the majority had mild-to-moderate multifocal dystonia without a functional impact.

Conclusions: Dystonia is a common, yet underdiagnosed, slowly progressive manifestation of POLR3-related leukodystrophy, and in most cases has limited-to-no functional impact. When treatment is needed, good response to typically used medication may occur. Further studies are needed to assess evolution of dystonia over time, patients' functional outcome, and response to therapy (when needed).
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http://dx.doi.org/10.1002/mdc3.12715DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6384176PMC
February 2019

Biallelic mutations in valyl-tRNA synthetase gene VARS are associated with a progressive neurodevelopmental epileptic encephalopathy.

Nat Commun 2019 02 12;10(1):707. Epub 2019 Feb 12.

Department of Neurosciences, University of California San Diego, La Jolla, CA, 92093, USA.

Aminoacyl-tRNA synthetases (ARSs) function to transfer amino acids to cognate tRNA molecules, which are required for protein translation. To date, biallelic mutations in 31 ARS genes are known to cause recessive, early-onset severe multi-organ diseases. VARS encodes the only known valine cytoplasmic-localized aminoacyl-tRNA synthetase. Here, we report seven patients from five unrelated families with five different biallelic missense variants in VARS. Subjects present with a range of global developmental delay, epileptic encephalopathy and primary or progressive microcephaly. Longitudinal assessment demonstrates progressive cortical atrophy and white matter volume loss. Variants map to the VARS tRNA binding domain and adjacent to the anticodon domain, and disrupt highly conserved residues. Patient primary cells show intact VARS protein but reduced enzymatic activity, suggesting partial loss of function. The implication of VARS in pediatric neurodegeneration broadens the spectrum of human diseases due to mutations in tRNA synthetase genes.
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http://dx.doi.org/10.1038/s41467-018-07067-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6372641PMC
February 2019

Cancer-associated fibroblasts induce epithelial-mesenchymal transition of bladder cancer cells through paracrine IL-6 signalling.

BMC Cancer 2019 Feb 11;19(1):137. Epub 2019 Feb 11.

Centre de recherche en organogénèse expérimentale/LOEX, Regenerative Medicine Division, CHU de Québec-Université Laval Research Center, QC, Québec, Canada.

Background: Cancer-associated fibroblasts (CAFs), activated by tumour cells, are the predominant type of stromal cells in cancer tissue and play an important role in interacting with neoplastic cells to promote cancer progression. Epithelial-mesenchymal transition (EMT) is a key feature of metastatic cells. However, the mechanism by which CAFs induce EMT program in bladder cancer cells remains unclear.

Methods: To investigate the role of CAFs in bladder cancer progression, healthy primary bladder fibroblasts (HFs) were induced into CAFs (iCAFs) by bladder cancer-derived exosomes. Effect of conditioned medium from iCAFs (CM ) on EMT markers expression of non-invasive RT4 bladder cancer cell line was determined by qPCR and Western blot. IL6 expression in iCAFs was evaluated by ELISA and Western blot. RT4 cell proliferation, migration and invasion were assessed in CM +/- anti-IL6 neutralizing antibody using cyQUANT assay, scratch test and transwell chamber respectively. We investigated IL6 expression relevance for bladder cancer progression by querying gene expression datasets of human bladder cancer specimens from TCGA and GEO genomic data platforms.

Results: Cancer exosome-treated HFs showed CAFs characteristics with high expression levels of αSMA and FAP. We showed that the CM induces the upregulation of mesenchymal markers, such as N-cadherin and vimentin, while repressing epithelial markers E-cadherin and p-ß-catenin expression in non-invasive RT4 cells. Moreover, EMT transcription factors SNAIL1, TWIST1 and ZEB1 were upregulated in CM -cultured RT4 cells compared to control. We also showed that the IL-6 cytokine was highly expressed by CAFs, and its receptor IL-6R was found on RT4 bladder cancer cells. The culture of RT4 bladder cancer cells with CM resulted in markedly promoted cell growth, migration and invasion. Importantly, inhibition of CAFs-secreted IL-6 by neutralizing antibody significantly reversed the IL-6-induced EMT phenotype, suggesting that this cytokine is necessary for CAF-induced EMT in the progression of human bladder cancer. Finally, we observed that IL6 expression is up-regulated in aggressive bladder cancer and correlate with CAF marker ACTA2.

Conclusions: We conclude that CAFs promote aggressive phenotypes of non-invasive bladder cancer cells through an EMT induced by the secretion of IL-6.
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http://dx.doi.org/10.1186/s12885-019-5353-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6371428PMC
February 2019

Biallelic Loss-of-Function Variants in AIMP1 Cause a Rare Neurodegenerative Disease.

J Child Neurol 2019 02 28;34(2):74-80. Epub 2018 Nov 28.

1 Departments of Neurology and Neurosurgery, Pediatrics and Human Genetics, McGill University, Montreal, Canada.

AIMP1/p43, is a noncatalytic component of the mammalian multi-tRNA synthetase complex that catalyzes the ligation of amino acids to their cognate tRNAs. AIMP1 is largely expressed in the central nervous system, where it is part of the regulatory machine of the neurofilament assembly, playing a crucial role in neuronal development and function. To date, nonsense mutations in AIMP1 have been associated with a primary neurodegenerative disorder consisting of cerebral atrophy, hypomyelination, microcephaly and epilepsy, whereas missense mutations have recently been linked to intellectual disability without neurodegeneration. Here, we report the first French-Canadian patient with a novel frameshift AIMP1 homozygous mutation (c.191_192delAA, p.Gln64Argfs*25), resulting in a severe neurodegenerative phenotype. We review and discuss the phenotypic spectrum associated with AIMP1 pathogenic variants.
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http://dx.doi.org/10.1177/0883073818811223DOI Listing
February 2019

Health-Related Quality of Life for Patients With Genetically Determined Leukoencephalopathy.

Pediatr Neurol 2018 07 9;84:21-26. Epub 2018 Apr 9.

Department of Medical Genetics, Montreal Children's Hospital, McGill University Health Centre, Montreal, Quebec, Canada; Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada; Department of Pediatrics, McGill University, Montreal, Quebec, Canada; Child Health and Human Development Program, Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada. Electronic address:

Background: We attempted to characterize the health-related quality of life in patients with genetically determined leukoencephalopathies as it relates to the severity of clinical features and the presence or absence of a precise molecular diagnosis.

Methods: Health-related quality of life was assessed using the Pediatric Quality of Life Inventory model (Pediatric Quality of Life Inventory 4.0 Self- and Proxy-reports) on 59 patients diagnosed with genetically determined leukoencephalopathies. In total, 38 male and 21 female patients ranging from one to 32 years of age (mean nine years), as well as their parents, completed the Pediatric Quality of Life Inventory health-related quality of life measures. In addition, participants completed detailed standardized clinical assessments or questionnaires. The correlation between health-related quality of life results and the severity of the clinical features, as well as the presence or absence of a molecular diagnosis, were analyzed.

Results: Patients with more severe clinical features showed statistically significant lower total Pediatric Quality of Life Inventory scores. More specifically, lower health-related quality of life was noted in children with sialorrhea, gastrostomy, and dystonia and in children who use a wheelchair.

Conclusions: Patients with more severe clinical features experience a lower quality of life. Our study further highlights the importance of addressing both physical and psychosocial issues and discussing perception of quality of life with both parents and children. A larger multicenter prospective study will be needed to further define the burden of these diseases and to identify modifiable factors.
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http://dx.doi.org/10.1016/j.pediatrneurol.2018.03.015DOI Listing
July 2018

Exosomes Induce Fibroblast Differentiation into Cancer-Associated Fibroblasts through TGFβ Signaling.

Mol Cancer Res 2018 07 10;16(7):1196-1204. Epub 2018 Apr 10.

Urology Division, Department of Surgery, Laval University, Quebec, Canada.

A particularly important tumor microenvironment relationship exists between cancer cells and surrounding stromal cells. Fibroblasts, in response to cancer cells, become activated and exhibit myofibroblastic characteristics that favor invasive growth and metastasis. However, the mechanism by which cancer cells promote activation of healthy fibroblasts into cancer-associated fibroblasts (CAF) is still not well understood. Exosomes are nanometer-sized vesicles that shuttle proteins and nucleic acids between cells to establish intercellular communication. Here, bladder cancer-derived exosomes were investigated to determine their role in the activation of healthy primary vesical fibroblasts. Exosomes released by bladder cancer cells are internalized by fibroblasts and promoted the proliferation and expression of CAF markers. In addition, cancer cell-derived exosomes contain TGFβ and in exosome-induced CAFs SMAD-dependent signaling is activated. Furthermore, TGFβ inhibitors attenuated CAF marker expression in healthy fibroblasts. Therefore, these data demonstrate that bladder cancer cells trigger the differentiation of fibroblasts to CAFs by exosomes-mediated TGFβ transfer and SMAD pathway activation. Finally, exosomal TGFβ localized inside the vesicle and contributes 53.4% to 86.3% of the total TGFβ present in the cancer cell supernatant. This study highlights a new function for bladder cancer exosomes as novel modulators of stromal cell differentiation. This study identifies exosomal TGFβ as new molecular mechanism involved in cancer-associated fibroblast activation. .
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http://dx.doi.org/10.1158/1541-7786.MCR-17-0784DOI Listing
July 2018

Bi-allelic Mutations in EPRS, Encoding the Glutamyl-Prolyl-Aminoacyl-tRNA Synthetase, Cause a Hypomyelinating Leukodystrophy.

Am J Hum Genet 2018 04 22;102(4):676-684. Epub 2018 Mar 22.

Child Health and Human Development Program, Research Institute of the McGill University Health Center, Montreal, QC H4A 3J1, Canada; Department of Neurology and Neurosurgery, McGill University, Montreal, QC H4A 3J1, Canada; Department of Pediatrics, McGill University, Montreal, QC H4A 3J1, Canada; Department of Medical Genetics, Montreal Children's Hospital, McGill University Health Center, Montreal, QC H4A 3J1, Canada. Electronic address:

Hypomyelinating leukodystrophies are genetic disorders characterized by insufficient myelin deposition during development. They are diagnosed on the basis of both clinical and MRI features followed by genetic confirmation. Here, we report on four unrelated affected individuals with hypomyelination and bi-allelic pathogenic variants in EPRS, the gene encoding cytoplasmic glutamyl-prolyl-aminoacyl-tRNA synthetase. EPRS is a bifunctional aminoacyl-tRNA synthetase that catalyzes the aminoacylation of glutamic acid and proline tRNA species. It is a subunit of a large multisynthetase complex composed of eight aminoacyl-tRNA synthetases and its three interacting proteins. In total, five different EPRS mutations were identified. The p.Pro1115Arg variation did not affect the assembly of the multisynthetase complex (MSC) as monitored by affinity purification-mass spectrometry. However, immunoblot analyses on protein extracts from fibroblasts of the two affected individuals sharing the p.Pro1115Arg variant showed reduced EPRS amounts. EPRS activity was reduced in one affected individual's lymphoblasts and in a purified recombinant protein model. Interestingly, two other cytoplasmic aminoacyl-tRNA synthetases have previously been implicated in hypomyelinating leukodystrophies bearing clinical and radiological similarities to those in the individuals we studied. We therefore hypothesized that leukodystrophies caused by mutations in genes encoding cytoplasmic aminoacyl-tRNA synthetases share a common underlying mechanism, such as reduced protein availability, abnormal assembly of the multisynthetase complex, and/or abnormal aminoacylation, all resulting in reduced translation capacity and insufficient myelin deposition in the developing brain.
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http://dx.doi.org/10.1016/j.ajhg.2018.02.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5985283PMC
April 2018

4H Leukodystrophy: Lessons from 3T Imaging.

Neuropediatrics 2018 04 27;49(2):112-117. Epub 2017 Nov 27.

Department of Child Neurology, VU University Medical Center, Amsterdam, The Netherlands.

4H leukodystrophy is characterized by hypomyelination, hypodontia, and hypogonadotropic hypogonadism. With its variability in clinical symptoms, application of pattern recognition to identify specific magnetic resonance imaging (MRI) features proved useful for the diagnosis. We collected 3T MR imaging data of 12 patients with mutations in ( = 8), ( = 3), and ( = 1), all obtained at the same scanner. We assessed these images and compared them with previously obtained 1.5T images in 8 patients. Novel MRI findings were myelin islets, closed eye sign, and a cyst-like lesion in the splenium. Myelin islets were variable numbers of small T1 hyperintense and T2 hypointense dots, mostly in the frontal and parietal white matter, and present in all patients. This interpretation was supported with perivascular staining of myelin protein in the hypomyelinated white matter of a deceased 4H patient. All patients had better myelination of the medial lemniscus with a relatively hypointense signal of this structure on axial T2-weighted (T2W) images ("closed eye sign"). Five patients had a small cyst-like lesion in the splenium. In 10 patients with sagittal T2W images, we also found spinal cord hypomyelination. In conclusion, imaging at 3T identified additional features in 4H leukodystrophy, aiding the MRI diagnosis of this entity.
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http://dx.doi.org/10.1055/s-0037-1608780DOI Listing
April 2018