title: Dystrophinopathy caused by mid-intronic substitutions activating cryptic exons in the DMD gene.
abstract: 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.
authors.affiliation: Institut Cochin and Laboratory of Molecular Genetics, Cochin Hospital, Paris, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Béroud
authors.forename: Alain
authors.initials: A
authors.lastname: Carrié
authors.forename: Chérif
authors.initials: C
authors.lastname: Beldjord
authors.forename: Nathalie
authors.initials: N
authors.lastname: Deburgrave
authors.forename: Stéphane
authors.initials: S
authors.lastname: Llense
authors.forename: Nadège
authors.initials: N
authors.lastname: Carelle
authors.forename: Cécile
authors.initials: C
authors.lastname: Peccate
authors.forename: Jean Marie
authors.initials: JM
authors.lastname: Cuisset
authors.forename: Florence
authors.initials: F
authors.lastname: Pandit
authors.forename: Frédérique
authors.initials: F
authors.lastname: Carré-Pigeon
authors.forename: Michèle
authors.initials: M
authors.lastname: Mayer
authors.forename: Rémi
authors.initials: R
authors.lastname: Bellance
authors.forename: Dominique
authors.initials: D
authors.lastname: Récan
authors.forename: Jamel
authors.initials: J
authors.lastname: Chelly
authors.forename: Jean Claude
authors.initials: JC
authors.lastname: Kaplan
authors.forename: France
authors.initials: F
authors.lastname: Leturcq
mesh_terms: 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
chemical_list: D016189:Dystrophin; D022821:RNA Splice Sites; D012333:RNA, Messenger