Identification of exitrons (EIs) and consequences of their splicing. Splice junction and exonic reads aligning to a single annotated protein-coding exon were used to identify EIs. As an EI (dark blue) is an internal part of a protein-coding exon, a full-length protein is produced when the EI is not spliced out (shown by a thicker green arrow, as EI-containing transcripts are the major isoforms). Splicing of an EI with a length of a multiple of three results in an internally deleted protein isoform. Splicing of other EIs leads to a frame-shift downstream from the splice junction and results in changed protein C-termini (orange) or can produce NMD-sensitive transcripts (red No sign indicates premature termination codon [PTC]).
