YAP1 regulates thrombopoiesis by binding to MYH9 in immune thrombocytopenia

Immune thrombocytopenia (ITP) is a complicated bleeding disease characterized by sharp platelet reduction. As a dominating element involved in ITP, megakaryocytes (MKs) are responsible for thrombopoiesis. However, the mechanism behind the dysregulation of thrombopoiesis in ITP remains undetermined. In this study, we examined the role of YAP1, Yes-associated protein 1, in thrombopoiesis during ITP. We observed a reduced YAP1 expression with cytoskeletal actin misalignment in MKs of ITP patients. Using experimental ITP mice, we showed that YAP1 reduction induced aberrant MK distribution, reduced the percentage of late MKs in total MKs, and caused submaximal platelet recovery. Mechanistically, YAP1 upregulation by GATA1 binding to its promoter promoted MK maturation. Phosphorylated YAP1 facilitated cytoskeletal activation by binding of its WW2 domain to MYH9, facilitating thrombopoiesis. Targeting YAP1 by its activator XMU-MP-1 was sufficient to rescue cytoskeleton defects and thrombopoiesis in YAP1+/- ITP mice and ITP patients. Taken together, these results demonstrate a crucial role for YAP1 in thrombopoiesis, providing a potential for the development of diagnostic markers and therapeutic options for ITP.