Identification and characterization of novel collagen VI non-canonical splicing mutations causing Ullrich congenital muscular dystrophy.
Splicing mutations occurring outside the invariant GT and AG dinucleotides are frequent in disease genes and the definition of their pathogenic potential is often challenging. We have identified four patients affected by Ullrich congenital muscular dystrophy and carrying unusual mutations of COL6 genes affecting RNA splicing. In three cases the mutations occurred in the COL6A2 gene and consisted of nucleotide substitutions within the degenerated sequences flanking the canonical dinucleotides. In the fourth case, a genomic deletion occurred which removed the exon8-intron8 junction of the COL6A1 gene. These mutations induced variable splicing phenotypes, consisting of exon skipping, intron retention and cryptic splice site activation/usage. A quantitative RNA assay revealed a reduced level of transcription of the mutated in-frame mRNA originating from a COL6A2 point mutation at intronic position +3. At variance, the transcription level of the mutated in-frame mRNA originating from a genomic deletion which removed the splicing sequences of COL6A1 exon 8 was normal. These findings suggest a different transcriptional efficiency of a regulatory splicing mutation compared to a genomic deletion causing a splicing defect.
Martoni
Elena
E
Department of Experimental and Diagnostic Medicine, Section of Medical Genetics, University of Ferrara, Italy.
Urciuolo
Anna
A
Sabatelli
Patrizia
P
Fabris
Marina
M
Bovolenta
Matteo
M
Neri
Marcella
M
Grumati
Paolo
P
D'Amico
Adele
A
Pane
Marika
M
Mercuri
Eugenio
E
Bertini
Enrico
E
Merlini
Luciano
L
Bonaldo
Paolo
P
Ferlini
Alessandra
A
Gualandi
Francesca
F
D000293:Adolescent; D015153:Blotting, Western; D016022:Case-Control Studies; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D018389:Codon, Nonsense / Q000235:genetics; D024142:Collagen Type VI / Q000235:genetics* / Q000378:metabolism; D005091:Exons / Q000235:genetics; D005260:Female; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology; D005455:Fluorescent Antibody Technique; D006579:Heterozygote; D006801:Humans; D040582:Inheritance Patterns / Q000235:genetics; D007438:Introns / Q000235:genetics; D008297:Male; D009136:Muscular Dystrophies / Q000151:congenital* / Q000235:genetics* / Q000473:pathology; D009154:Mutation / Q000235:genetics*; D012326:RNA Splicing / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion
C504344:COL6A2 protein, human; D018389:Codon, Nonsense; D024142:Collagen Type VI; D012333:RNA, Messenger