COL6A3 and Ullrich congenital muscular dystrophy: Allele-specific knockdown using siRNA has been reported to efficiently and selectively silence the mutant mRNA transcripts in UCMD with dominant mutations in COL6 genes, such as the heterozygous exon 16 deletion in the COL6A3 gene,15 and the missense c.850G > A (p.G284R) mutation in the COL6A1 gene.16