Intron retention patterns in prenatal and adult human cortex associate with RNA distribution. (A) Proportion of junction reads per sample by group. Prenatal cortex had a higher proportion of splice junctions than adult, and although Ribo-Zero samples had significantly lower junction proportion in nuclear samples (FDR ≤ 0.05), poly(A)+ samples showed nonsignificantly different proportions between fractions. (B) Percentage of introns passing QC in all groups with an IR percentage above each threshold in at least one sample of each group. (C) The IR ratio of introns differentially retained by fraction when measured in adult and prenatal samples, plotted by gene expression measured as log(reads per kilobase per million mapped [RPKM] + 1). Samples are colored by their age:fraction group. (D) Overlap of genes containing introns that were differentially retained by fraction or age (FDR ≤ 0.05).