BCOR and neoplasm: RSEM (RNA-Seq by Expectation-Maximization)17 was used to estimate the relative fractions of mutant and wild-type BCOR transcripts in ITD-positive tumours by remapping unaligned RNA-seq reads to individual tumour-specific synthetic reference transcriptomes, revealing that 96–100% of BCOR expression was contributed by mutant transcripts (data not shown).