Clinical presentation and differential splicing of SRSF2, U2AF1 and SF3B1 mutations in patients with Acute Myeloid Leukaemia

Previous studies demonstrated that splicing factor mutations are recurrent events in hematopoietic malignancies with both clinical and functional implications. However, their aberrant splicing patterns in acute myeloid leukaemia remain largely unexplored. In this study we characterized mutations in SRSF2, U2AF1 and SF3B1, the most commonly mutated splicing factors. In our clinical analysis of 2678 patients, splicing factor mutations showed inferior relapse-free and overall survival, however, these mutations did not represent independent prognostic markers. RNA-sequencing of 246 and independent validation in 177 patients revealed an isoform expression profile highly characteristic for each individual mutation, with several isoforms showing a strong dysregulation. By establishing a custom differential splice junction usage pipeline we accurately detected aberrant splicing in splicing factor mutated samples. Mutated samples were characterized predominantly by decreased junction usage. A large proportion of differentially used junctions were novel. Targets of splicing dysregulation included several genes with a known role in leukaemia. In SRSF2(P95H) mutants we further explored the possibility of a cascading effect through the dysregulation of the splicing pathway. We conclude that splicing factor mutations do not represent independent prognostic markers. However, they do have genome-wide consequences on gene splicing leading to dysregulated isoform expression of several genes.