Intragenic Epigenetic Deregulation by IDH2 Mutations Synergizes with SRSF2 Mutations Causing Mis-splicing of Key Transcriptional Regulators [RNA-seq]

Genes impacting DNA methylation (DNAme), like IDH2, are frequently co-mutated with splicing factors, like SRSF2, in acute myeloid leukemia (AML). These co-occurring mutations are associated with more aggressive phenotypes but the underlying molecular mechanisms remain elusive. To address this gap, we profiled wild-type, IDH2R140Q or SRSF2P95 single-mutants and IDH2R140Q/SRSF2P95 double-mutant AMLs at a deep resolution level. We find a unique set of mis-spliced genes and differentially methylated CpGs in double-mutants. Mis-spliced exons are enriched in CCNG splicing enhancers and in the corresponding DNAme changes. Using a machine-learning model, we can accurately predict exon inclusion levels from proximal CpGs. These CpGs are more likely to overlap with footprints of RNA-binding and chromatin-modifying complexes but not transcription factors. We also report unique gene expression profiles associated with each genotype; however, the differentially expressed genes do not overlap with mis-spliced transcripts. Instead, the mis-spliced genes encode for proteins that interact with the gene regulatory complexes that control the expression of these differentially expressed genes. Thus, we propose a mechanism where synergism between aberrant DNAme and splicing leads to the mis-splicing of key components in gene regulatory complexes, thus resulting in the aberrant gene expression profiles characteristic of these AMLs. Overall design: Clinical bone marrow or peripheral blood specimens were collected from 25 de-identified AML specimens. Mononuclear cells (MNC) were isolated through Ficoll density centrifugation at diagnosis. RNA and DNA were extracted for RNA sequencing and Whole Genome Bisulfite Sequencing, respectively.