Fig. 2. Target sites of the dfna5 morpholinos and aberrant splicing of dfna5 transcript. (A) Genomic organization of human DFNA5 and zebrafish Dfna5. The exon/intron boundaries of DFNA5 are entirely conserved between human and zebrafish. (a) Individuals with DFNA5 mutations carry an insertion/deletion mutation in intron 7, which leads to skipping of exon 8 (indicated in red). Absence of exon 8 causes a frameshift after amino acid 330, resulting in an aberrant stretch of 41 amino acids followed by a premature stop. (b) The two morpholino antisense oligos designed against Dfna5 mRNA are indicated in red. The splice site antisense oligo ('GT-MO') directed against the donor site of exon 8 leads to skipping of the targeted exon (indicated in red), resembling the human mutation. (B) RT-PCR time course of aberrant splicing of dfna5 mRNA caused by the dfna5 GT-MO. At 28 hpf, wild-type dfna5 transcript is not detectable by RT-PCR, only PCR products lacking exon 8 (indicated with exon 8) or with partial retention of the following intron (arrowhead) are present. Wild-type transcript recovers starting at day 2, but the morpholino-modulated transcripts are still present at day 7.