Dominant-negative mutations in the genes that encode the three major α chains of
collagen type VI, COL6A1, COL6A2, and COL6A3, account for more than 50% of
Ullrich congenital muscular dystrophy patients and nearly all Bethlem myopathy patients. Gapmer
antisense oligonucleotides (AONs) are usually used for gene silencing by stimulating RNA cleavage through the recruitment of an endogenous
endonuclease known as
RNase H to cleave the
RNA strand of
a DNA-
RNA duplex. In this study, we exploited the application of the allele-specific silencing approach by gapmer AON as a potential therapy for
Collagen-VI-related congenital
muscular dystrophy (COL6-CMD). A series of AONs were designed to selectively target an 18-nt heterozygous genomic deletion in exon 15 of COL6A3 at the
mRNA and
pre-mRNA level. We showed that gapmer AONs can selectively suppress the expression of mutant transcripts at both
pre-mRNA and
mRNA levels, and that the latter strategy had a far stronger efficiency than the former. More importantly, we found that silencing of the mutant transcripts by gapmer AONs increased the deposition of
collagen VI
protein into the extracellular matrix, thus restoring functional
protein production. Our findings provide a clear proof of concept for AON allele-specific silencing as a therapeutic approach for COL6-CMD.