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.


METHODS
We applied molecular combing (MC) to directly visualize allelic combinations associated with FSHD.


RESULTS
MC enabled the accurate diagnosis of 32 FSHD patients. Unreported haplotypes and rearrangements, as well as somatic mosaicism, which is common in the 10 to 30% of cases that are sporadic, were detectable by MC.


CONCLUSIONS
MC enables the detailed exploration of the FSHD locus and accurate diagnosis of FSHD, the first Mendelian disease to benefit from this technique. MC is also likely to be applicable to other copy number-variant or repeat expansion-associated human diseases.
Assistance Publique-Hôpitaux de Marseille, Department of Medical Genetics, Timone Children's Hospital, Marseille, France.
Karine
K
Nguyen
Pierre
P
Walrafen
Rafaëlle
R
Bernard
Shahram
S
Attarian
Charlène
C
Chaix
Catherine
C
Vovan
Emilie
E
Renard
Nathalie
N
Dufrane
Jean
J
Pouget
Anne
A
Vannier
Aaron
A
Bensimon
Nicolas
N
Lévy
D000293:Adolescent; D000328:Adult; D000483:Alleles; D002894:Chromosomes, Human, Pair 4 / Q000235:genetics*; D005260:Female; D006239:Haplotypes; D006801:Humans; D008297:Male; D057054:Molecular Imaging / Q000379:methods*; D009030:Mosaicism; D020391:Muscular Dystrophy, Facioscapulohumeral / Q000235:genetics*; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA / Q000379:methods*