Deregulated splicing induces DNA damage and interferes with DNA repair in the hematopoietic system

Abstract

Leukemia is the most prevalent form of pediatric cancer, among which acute myeloid leukemia (AML) is the second most common form of pediatric leukemia. Even though the overall survival rate increased over the past decades, still 1 out of 4 children with AML does not reach the 5-year survival after diagnosis. Even if the children survive, they often encounter severe therapy-related side effects. Recently, it was found that splicing is often disturbed in pediatric AML (pAML). This finding led to the question whether splicing deregulation is involved in the development of pAML, since splicing factor hotspot mutations are also frequently found in adult AML. In this study, we mimicked splicing deregulation by treating human hematopoietic stem- and progenitor cells (HSPCs) with the splicing inhibitor pladienolide B. In addition, we generated a DNA methyltransferase 3A (DNMT3A) knock-out, since DNMT3A is one of the most prevalent mutated genes in adult AML and recently it was found that DNMT3A is also involved in splicing regulation. We observed an increase in double-stranded breaks and a major decrease in R-loops in splicing deregulated HSPCs. Interestingly, this decrease in R-loops is contradictory to the increase that was often observed in comparable studies with different cell lines. Future studies about splicing deregulation in the hematopoietic system can eventually contribute to prevent the development of pAML and stimulate the development of new targeted therapies.