Features of retained introns. (A) Size distribution of different intron classes. [I(All)] All introns in our sample, (IC) the constitutive introns, (IC+IA−IR) and (IA−IR) the categories without retained introns either including or excluding constitutive introns, respectively, (IR+IA) retained introns that are also involved in other AS events, (IR) introns that are only retained. (B) GC content distribution of constitutive introns (IC) and retained introns (IR). (C) Splice site score distribution of constitutive introns (IC) and retained introns (IR). (D) Histogram of number of introns in each intron retention ratio (IRR) category. (E) Boxplots of splice site score distribution by IRR category. (F) Boxplots of GC content distribution by IRR category. (G) Boxplots of stop codons distribution by IRR category. For the splice site score distributions in C and E, the means of 5′ and 3′ splice sites scores (calculated according to Sheth et al. 2006) were used.
