Transcription factor cassette exon analysis. This figure illustrates the distribution of 324 cassette exons within variant TF transcripts. These 324 exons are from 287 different variant MouSDB3 clusters. When 76 of the 324 cassette exons are skipped, the altered transcripts are in-frame; exclusion of remaining exons either introduces an amino-acid substitution or causes frameshifting. Of the in-frame exons, 53 alter domain architecture and 13 do not. Of the exons that cause domain alteration, 36 are in coding regions for domains and 17 are proximal to these coding regions. In-frame cassette exon sequences, sequences of their transcripts and annotations of the domains they alter are provided on our web page .