Strength of potential splice sites as measured by their CVs. The statistical rules of Shapiro and Senopathy were applied to assign a CV expressed in percentage of homology to the consensus sequence.7 A score of 100 represents the best match; 0, the worst match. The CV of the IVS6 donor site and the authentic and mutated IVS7 donor splice site were rated according to this procedure, and potential cryptic sites along exon 7 and in each 37-bp element of the IVS7 minisatellite were researched alike. Because the CV of the GT-containing sequence in the close vicinity of the mutated splice site ranged from 53.9 to 74.7, we chose the value 53.9 as a threshold to define a potential alternative splice site. On the vertical axis are given the location and the sequence of the potential cryptic sites. Position IVS7+1 corresponds to the first nucleotide of IVS7, and position IVS7-1 to the last nucleotide of exon 7. Capital letters denote exonic sequences and lowercase letters intronic sequences. Underlined boldface letters indicate the position of the splicing site. The horizontal axis shows the CV assigned for each position. The black arrow indicates the activated site. In the insert figure, the CV changes caused by the IVS7+2 T>G mutation (black columns) and the cryptic site subsequently activated (black arrow and asterisk pointing to the mutated nucleotide) are shown.
