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Mutations of POLR3A encoding a catalytic subunit of RNA polymerase Pol III cause a recessive hypomyelinating leukodystrophy.
Geneviève Bernard, Eliane Chouery, Maria Lisa Putorti, Martine Tétreault, Asako Takanohashi, Giovanni Carosso, Isabelle Clément, Odile Boespflug-Tanguy, Diana Rodriguez, Valérie Delague, Joelle Abou Ghoch, Nadine Jalkh, Imen Dorboz, Sebastien Fribourg, Martin Teichmann, André Megarbane, Raphael Schiffmann, Adeline Vanderver, Bernard Brais,
Leukodystrophies are a heterogeneous group of inherited neurodegenerative disorders characterized by abnormal white matter visible by brain imaging. It is estimated that at least 30% to 40% of individuals remain without a precise diagnosis despite extensive investigations. We mapped tremor-ataxia with central hypomyelination (TACH) to 10q22.3-23.1 in French-Canadian families and sequenced candidate genes within this interval. Two missense and one insertion mutations in five individuals with TACH were uncovered in POLR3A, which codes for the largest subunit of RNA polymerase III (Pol III). Because these families were mapped to the same locus as leukodystrophy with oligodontia (LO) and presented clinical and radiological overlap with individuals with hypomyelination, hypodontia and hypogonadotropic hypogonadism (4H) syndrome, we sequenced this gene in nine individuals with 4H and eight with LO. In total, 14 recessive mutations were found in 19 individuals with TACH, 4H, or LO, establishing that these leukodystrophies are allelic. No individual was found to carry two nonsense mutations. Immunoblots on 4H fibroblasts and on the autopsied brain of an individual diagnosed with 4H documented a significant decrease in POLR3A levels, and there was a more significant decrease in the cerebral white matter compared to that in the cortex. Pol III has a wide set of target RNA transcripts, including all nuclear-coded tRNA. We hypothesize that the decrease in POLR3A leads to dysregulation of the expression of certain Pol III targets and thereby perturbs cytoplasmic protein synthesis. This type of broad alteration in protein synthesis is predicted to occur in other leukoencephalopathies such as hypomyelinating leukodystrophy-3, caused by mutations in aminoacyl-tRNA synthetase complex-interacting multifunctional protein 1 (AIMP1).
American journal of human genetics - Sep 2011
Brain magnetic resonance imaging (MRI) pattern recognition in Pol III-related leukodystrophies.
Roberta La Piana, Davide Tonduti, Heather Gordish Dressman, Johanna L Schmidt, Jonathan Murnick, Bernard Brais, Genevieve Bernard, Adeline Vanderver,
Pol III-related leukodystrophies are caused by mutations in POLR3A and POLR3B genes and all share peculiar imaging and clinical features. The objectives of this study are (1) to define the neuroradiologic pattern in a cohort of POLR3A and POLR3B subjects and (2) to compare the neuroradiologic pattern of Pol III-related leukodystrophies with other hypomyelinating disorders. The magnetic resonance imaging (MRI) examinations of 13 patients with POLR3A and POLR3B mutations and of 14 patients with other hypomyelinating disorders were analyzed. All the subjects with Pol III-related leukodystrophies presented hypomyelination associated with T2 hypointensity of the thalami and/or the pallida. Twelve subjects (92%) presented T2 hypointensity of the optic radiations. Cerebellar atrophy was observed in most patients (92%). The combination of the analyzed criteria identified patients with Pol III-related leukodystrophies with a sensitivity of 84.6% and a specificity of 92.9%.
Journal of child neurology - Feb 2014
Clinical spectrum of 4H leukodystrophy caused by POLR3A and POLR3B mutations.
Nicole I Wolf, Adeline Vanderver, Rosalina M L van Spaendonk, Raphael Schiffmann, Bernard Brais, Marianna Bugiani, Erik Sistermans, Coriene Catsman-Berrevoets, Johan M Kros, Pedro Soares Pinto, Daniela Pohl, Sandya Tirupathi, Petter Strømme, Ton de Grauw, Sébastien Fribourg, Michelle Demos, Amy Pizzino, Sakkubai Naidu, Kether Guerrero, Marjo S van der Knaap, Geneviève Bernard, ,
To study the clinical and radiologic spectrum and genotype-phenotype correlation of 4H (hypomyelination, hypodontia, hypogonadotropic hypogonadism) leukodystrophy caused by mutations in POLR3A or POLR3B.
Neurology - Nov 2014