Dengue virus-induced thrombocytopenia is mediated by dysregulation of the RUNX1–MYH9 axis

Dengue virus (DENV) infection causes an acute febrile illness that is usually self-limiting but can become fatal. Thrombocytopenia, or a decrease in circulating platelets, is a major clinical feature of dengue and is strongly associated with the progression to dengue hemorrhagic fever and dengue shock syndrome. In this report, MYH9, a cytoskeletal protein involved in platelet maturation and release, was found to be down-regulated in DENV-infected Huh7 cell lines. The expression of RUNX1, an important transcription factor involved in megakaryopoiesis, was also decreased following DENV-infection. In-silico analysis identified three potential RUNX1 transcription-factor binding sites in the promoter region of the MYH9 gene. We therefore investigated whether RUNX1 regulates MYH9 expression during DENV-infection. Luciferase and ChIP assays showed that DENV infection affects RUNX1 binding to the MYH9 promoter, providing insight into the molecular basis of reduced MYH9 expression. Furthermore, the megakaryocyte differentiation markers GATA1, ITGB3, and MYH9 were upregulated in PMA-induced K562-cells. However, DENV infection downregulated these genes and increased the expression of the apoptosis marker gene CYCS. These findings suggest that dengue affects megakaryopoiesis through multiple mechanisms, potentially reducing platelet production while also promoting platelet destruction. Additionally, Fluorescence and electron microscopy revealed that functional defects of MYH9 may affect megakaryopoiesis biogenesis. Overall, this study provides insights into the molecular mechanisms contributing to thrombocytopenia during DENV infection.