Data from Mis-splicing of Mitotic Regulators Sensitizes SF3B1-Mutated Human HSCs to CHK1 Inhibition

<div>Abstract<p>Splicing factor <i>SF3B1</i> mutations are frequent somatic lesions in myeloid neoplasms that transform hematopoietic stem cells (HSCs) by inducing mis-splicing of target genes. However, the molecular and functional consequences of <i>SF3B1</i> mutations in human HSCs and progenitors (HSPCs) remain unclear. Here, we identify the mis-splicing program in human HSPCs as a targetable vulnerability by precise gene editing of <i>SF3B1</i> K700E mutations in primary CD34⁺ cells. Mutant SF3B1 induced pervasive mis-splicing and reduced expression of genes regulating mitosis and genome maintenance leading to altered differentiation, delayed G2/M progression, and profound sensitivity to CHK1 inhibition (CHK1i). Mis-splicing or reduced expression of mitotic regulators <i>BUBR1</i> and <i>CDC27</i> delayed G2/M transit and promoted CHK1i sensitivity. Clinical CHK1i prexasertib selectively targeted <i>SF3B1</i>-mutant immunophenotypic HSCs and abrogated engraftment <i>in vivo</i>. These findings identify mis-splicing of mitotic regulators in <i>SF3B1</i>-mutant HSPCs as a targetable vulnerability engaged by pharmacological CHK1 inhibition.</p><p><b>Significance:</b> In this study, we engineer precise <i>SF3B1</i> mutations in human HSPCs and identify CHK1 inhibition as a selective vulnerability promoted by mis-splicing of mitotic regulators. These findings uncover the mis-splicing program induced by mutant SF3B1 in human HSPCs and show that it can be therapeutically targeted by clinical CHK1 inhibitors.</p></div>