Molecular combing reveals complex 4q35 rearrangements in Facioscapulohumeral dystrophy |
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Authors: | Karine Nguyen Francesca Puppo Stéphane Roche Marie‐Cécile Gaillard Charlène Chaix Arnaud Lagarde Marjorie Pierret Catherine Vovan Sylviane Olschwang Emmanuelle Salort‐Campana Shahram Attarian Marc Bartoli Rafaëlle Bernard Nicolas Levy |
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Affiliation: | 1. Aix Marseille Université, INSERM GMGF UMR S_910, Marseille, France;2. APHM, Département de Génétique Médicale, H?pital d'enfants de la Timone, Marseille, FranceFrédérique Magdinier and Nicolas Levy are the co‐last authors.;3. APHM, Département de Génétique Médicale, H?pital d'enfants de la Timone, Marseille, France;4. Genomic Vision, Bagneux, France;5. Groupe Ramsay Générale de Santé, H?pital Clairval, Marseille, France;6. APHM, Centre de Référence des Maladies Neuromusculaires et de la SLA, H?pital de la Timone, Marseille, France |
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Abstract: | Facioscapulohumeral dystrophy (FSHD), one of the most common hereditary neuromuscular disorders, is associated with a complex combination of genetic variations at the subtelomeric 4q35 locus. As molecular diagnosis relying on Southern blot (SB) might be challenging in some cases, molecular combing (MC) was recently developed as an additional technique for FSHD diagnosis and exploration of the genomic organization of the 4q35 and 10q26 regions. In complement to the usual SB, we applied MC in a large cohort of 586 individuals with clinical FSHD. In 332 subjects, the two 4q alleles were normal in size, allowing exclusion of FSHD1 while we confirmed FSHD1 in 230 patients. In 14 patients from 10 families, we identified a recurrent complex heterozygous rearrangement at 4q35 consisting of a duplication of the D4Z4 array and a 4qA haplotype, irresolvable by the SB technique. In five families, we further identified variations in the SMCHD1 gene. Impact of the different mutations was tested using a minigene assay and we analyzed DNA methylation after sodium bisulfite modification and NGS sequencing. We discuss the involvement of this rearrangement in FSHD since all mutations in SMCHD1 are not associated with D4Z4 hypomethylation and do not always segregate with the disease. |
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Keywords: | D4Z4 FSHD methylation minigene complementation assay (pCAS) Molecular Combing SMCHD1 |
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