Complex 4q35 and 10q26 Rearrangements: A Challenge for Molecular Diagnosis of Patients With Facioscapulohumeral Dystrophy.

Background And Objectives: After clinical evaluation, the molecular diagnosis of type 1 facioscapulohumeral dystrophy (FSHD1) relies in most laboratories on the detection of a shortened D4Z4 array at the 4q35 locus by Southern blotting. In many instances, this molecular diagnosis remains inconclusive and requires additional experiments to determine the number of D4Z4 units or identify somatic mosaicism, 4q-10q translocations, and proximal p13E-11 deletions. These limitations highlight the need for alternative methodologies, illustrated by the recent emergence of novel technologies such as molecular combing (MC), single molecule optical mapping (SMOM), or Oxford Nanopore-based long-read sequencing providing a more comprehensive analysis of 4q and 10q loci.

Methylation hotspots evidenced by deep sequencing in patients with facioscapulohumeral dystrophy and mosaicism.

Objective: To investigate the distribution of cytosine-guanine dinucleotide (CpG) sites with a variable level of DNA methylation of the D4Z4 macrosatellite element in patients with facioscapulohumeral dystrophy (FSHD).

Methods: By adapting bisulfite modification to deep sequencing, we performed a comprehensive analysis of D4Z4 methylation across D4Z4 repeats and adjacent 4qA sequence in DNA from patients with FSHD1, FSHD2, or mosaicism and controls.

Results: Using hierarchical clustering, we identified clusters with different levels of methylation and separated, thereby the different groups of samples (controls, FSHD1, and FSHD2) based on their respective level of methylation.

Deciphering the complexity of the 4q and 10q subtelomeres by molecular combing in healthy individuals and patients with facioscapulohumeral dystrophy.

Background: Subtelomeres are variable regions between telomeres and chromosomal-specific regions. One of the most studied pathologies linked to subtelomeric imbalance is facioscapulohumeral dystrophy (FSHD). In most cases, this disease involves shortening of an array of D4Z4 macrosatellite elements at the 4q35 locus.

Inflammatory facioscapulohumeral muscular dystrophy type 2 in 18p deletion syndrome.

Facioscapulohumeral muscular dystrophy (FSHD) has been shown to be related to genetic and epigenetic derepression of DUX4 (mapping to chromosome 4), a gene located within a repeat array of D4Z4 sequences of polymorphic length. FSHD type 1 (FSHD1) is associated with pathogenic D4Z4 repeat array contraction, while FSHD type 2 (FSHD2) is associated with SMCHD1 variants (a chromatin modifier gene that maps to the short arm of chromosome 18). Both FSHD types require permissive polyadenylation signal (4qA) downstream of the D4Z4 array.

Molecular combing reveals complex 4q35 rearrangements in Facioscapulohumeral dystrophy.

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.

Segregation between SMCHD1 mutation, D4Z4 hypomethylation and Facio-Scapulo-Humeral Dystrophy: a case report.

Background: The main form of Facio-Scapulo-Humeral muscular Dystrophy is linked to copy number reduction of the 4q D4Z4 macrosatellite (FSHD1). In 5 % of cases, FSHD phenotype appears in the absence of D4Z4 reduction (FSHD2). In 70-80 % of these patients, variants of the SMCHD1 gene segregate with 4qA haplotypes and D4Z4 hypomethylation.

Differential DNA methylation of the D4Z4 repeat in patients with FSHD and asymptomatic carriers.

Objective: We investigated the link between DNA hypomethylation and clinical penetrance in facioscapulohumeral dystrophy (FSHD) because hypomethylation is moderate and heterogeneous in patients and could not thus far be correlated with disease presence or severity.

Methods: To investigate the link between clinical signs of FSHD and DNA methylation, we explored 95 cases (37 FSHD1, 29 asymptomatic individuals carrying a shortened D4Z4 array, 9 patients with FSHD2, and 20 controls) by implementing 2 approaches: methylated DNA immunoprecipitation and sodium bisulfite sequencing.

Results: Both methods revealed statistically significant differences between asymptomatic carriers or controls and individuals with clinical FSHD, especially in the proximal region of the repeat.

Molecular combing reveals allelic combinations in facioscapulohumeral dystrophy.

Objective: The genetic variation underlying facioscapulohumeral muscular dystrophy (FSHD), 1 of the most common hereditary neuromuscular disorders, is complex, and associated with the contraction of a repeat array (D4Z4) at the subtelomeric end of chromosome 4q. Nonpathogenic variants of 4q and the presence of a homologous array on chromosome 10q make FSHD diagnosis extremely challenging, at least in individuals with nonstandard D4Z4 arrays. We aimed to improve FSHD molecular analysis by proposing an alternative technique to the Southern blot.

New multiplex PCR-based protocol allowing indirect diagnosis of FSHD on single cells: can PGD be offered despite high risk of recombination?

Molecular pathophysiology of facioscapulohumeral muscular dystrophy (FSHD) involves the heterozygous contraction of the number of tandemly repeated D4Z4 units at chromosome 4q35.2. FSHD is associated with a range of 1-10 D4Z4 units instead of 11-150 in normal controls.