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Autosomal dominant in cis D4Z4 repeat array duplication alleles in facioscapulohumeral dystrophy

Lemmers, Richard JLF; Butterfield, Russell; van der Vliet, Patrick J; de Bleecker, Jan L; van der Pol, Ludo; Dunn, Diane M; Erasmus, Corrie E; ... van der Maarel, Silvère M; + view all (2023) Autosomal dominant in cis D4Z4 repeat array duplication alleles in facioscapulohumeral dystrophy. Brain awad312. 10.1093/brain/awad312. Green open access

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Abstract

Facioscapulohumeral dystrophy (FSHD) has a unique genetic etiology resulting in partial chromatin relaxation of the D4Z4 macrosatellite repeat array on 4qter. This D4Z4 chromatin relaxation facilitates inappropriate expression of the transcription factor DUX4 in skeletal muscle. DUX4 is encoded by a retrogene which is embedded within the distal region of the D4Z4 repeat array. In the European population, the D4Z4 repeat array is usually organized in a single array that ranges between 8-100 units. D4Z4 chromatin relaxation and DUX4 derepression in FSHD is most often caused by repeat array contraction to 1-10 units (FSHD1) or by a digenic mechanism requiring pathogenic variants in a D4Z4 chromatin repressor like SMCHD1, combined with a repeat array between 8-20 units (FSHD2). With a prevalence of 1.5% in the European population, in cis duplications of the D4Z4 repeat array, where two adjacent D4Z4 arrays are interrupted by a spacer sequence, are relatively common but their relationship to FSHD is not well understood. In cis duplication alleles were shown to be pathogenic in FSHD2 patients, however, there is inconsistent evidence for the necessity of an SMCHD1 mutation for disease development. To explore the pathogenic nature of these alleles we compared in cis duplication alleles in FSHD patients with or without pathogenic SMCHD1 variant. For both groups we showed duplication-allele-specific DUX4 expression. We studied these alleles in detail using pulsed-field gel electrophoresis-based Southern blotting and molecular combing, emphasizing the challenges in the characterization of these rearrangements. Nanopore sequencing was instrumental to study the composition and methylation of the duplicated D4Z4 repeat arrays and to identify the breakpoints and the spacer sequence between the arrays. By comparing the composition of the D4Z4 repeat array of in cis duplication alleles in both groups, we found that specific combinations of proximal and distal repeat array sizes determine their pathogenicity. Supported by our algorithm to predict pathogenicity, diagnostic laboratories should now be furnished to accurately interpret these in cis D4Z4 repeat array duplications, alleles which can easily be missed in routine settings.

Type: Article
Title: Autosomal dominant in cis D4Z4 repeat array duplication alleles in facioscapulohumeral dystrophy
Location: England
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/brain/awad312
Publisher version: http://dx.doi.org/10.1093/brain/awad312
Language: English
Additional information: © The Author(s) 2023. Published by Oxford University Press on behalf of the Guarantors of Brain. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (https://creativecommons.org/licenses/bync/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com
Keywords: D4Z4, DUX4, FSHD, duplications, facioscapulohumeral muscular dystrophy
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology > Department of Neuromuscular Diseases
URI: https://discovery.ucl.ac.uk/id/eprint/10185895
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