Dystrophinopathy caused by mid-intronic substitutions activating cryptic exons in the DMD gene.
In the course of a mutation search performed by muscle dystrophin transcript analysis in 72 Duchenne and Becker Muscular Dystrophies (DMD/BMD) patients without gross gene defect, we encountered four unrelated cases with additional out-of-frame sequences precisely intercalated between two intact exons of the mature muscle dystrophin mRNA. An in silico search of the whole dystrophin genomic sequence revealed that these inserts correspond to cryptic exons flanked by one strong and one weak consensus splice site and located in the mid-part of large introns (introns 60, 9, 1M, and 62, respectively). In each case we identified an intronic point mutation activating the cryptic donor or acceptor splice site. The patients exhibited a BMD/intermediate phenotype consistent with the presence of reduced amounts of normally spliced transcript and normal dystrophin. The frequency of this new type of mutation is not negligible (6% of our series of 65 patients with 'small' mutations). It would be missed if the exploration of the DMD gene is exclusively performed on exons and flanking sequences of genomic DNA.
Béroud
Christophe
C
Institut Cochin and Laboratory of Molecular Genetics, Cochin Hospital, Paris, France.
Carrié
Alain
A
Beldjord
Chérif
C
Deburgrave
Nathalie
N
Llense
Stéphane
S
Carelle
Nadège
N
Peccate
Cécile
C
Cuisset
Jean Marie
JM
Pandit
Florence
F
Carré-Pigeon
Frédérique
F
Mayer
Michèle
M
Bellance
Rémi
R
Récan
Dominique
D
Chelly
Jamel
J
Kaplan
Jean Claude
JC
Leturcq
France
F
D000293:Adolescent; D000328:Adult; D001483:Base Sequence / Q000235:genetics; D004252:DNA Mutational Analysis; D016189:Dystrophin / Q000172:deficiency* / Q000235:genetics; D005091:Exons / Q000235:genetics*; D005260:Female; D005820:Genetic Testing; D006801:Humans; D007438:Introns / Q000235:genetics*; D008297:Male; D008969:Molecular Sequence Data; D020388:Muscular Dystrophy, Duchenne / Q000235:genetics* / Q000503:physiopathology; D016366:Open Reading Frames / Q000235:genetics; D010375:Pedigree; D017354:Point Mutation / Q000235:genetics*; D022821:RNA Splice Sites / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics
D016189:Dystrophin; D022821:RNA Splice Sites; D012333:RNA, Messenger