Analysis of the IVS3+1_+4delGTAA mutation in transfected COS-7 cells.

(A) Electrophoresis profile of the uncloned RT-PCR product. M denotes the 1-kb ladder DNA size marker. (B) Sequence of the uncloned RT-PCR product. The IVS3+1_+4delGTAA mutation leads to exon 3 skipping. (C) Cloning of the RT-PCR reaction shows that this product accounts for more than 99% of the aberrant transcripts (148 of 149 clones); fewer than 1% of clones (1 of 149) showed exon 2 and exon 3 skipping.