Activation of cryptic splice sites is a frequent splicing defect mechanism caused by mutations in exon and intron sequences of the OPA1 gene.

Mutations in OPA1 are the most frequent cause underlying autosomal dominant optic atrophy (adOA). Until now only few putative splicing mutations in the OPA1 gene have been investigated at the mRNA level and all these result in exon skipping. Here, we report the identification and cDNA analysis of four intronic and three exonic OPA1 gene mutations that cause a variety of splicing defects including activation of cryptic splice sites in either flanking exon or intron sequences, and a leaky splicing mutation. Our results show that cDNA analysis is of prime importance for the full evaluation of the effect of putative splicing mutations in the OPA1 gene.