Fig 1. Illustration of an intronic splicing unit.

An intronic splicing unit is defined as a set of splicing events that share a common splicing site (i.e., donor or receiver) in the intronic domain. Each intronic splicing unit consists of an isoform usage distribution of each sample in each locus. Here, the splice-site usage distribution is calculated by the number of RNA-seq reads that support each alternative splice-site (shown in red, purple, and green in the figure).