a, Sanger sequencing of pgFARM-edited CPSF4 poison exon in HeLa/iCas9 cells. Annotations of eliminated (X) or disrupted (↓) sequence elements are indicated. b, RNA-seq read coverage across the entire CPSF4 locus in HeLa/iCas9 cells expressing a CPSF4 poison exon-targeting pgRNA (pgCPSF4; n = 1). We observed no read coverage indicative of cryptic splicing in pgCPSF4-treated cells. The two sets of splice junction reads downstream of the CPSF4 poison exon correspond to usage of endogenous (naturally occurring in unedited cells) competing 3′ splice sites. c, As (b), but for an SMG1 poison exon-targeting pgRNA (pgSMG1; n = 1). d, Scatter plot comparing normalized fold-changes for pgRNAs targeting a poison exon compared to matched upstream coding exon within the same gene.