RUNX1-deficient human megakaryocytes demonstrate thrombopoietic and platelet half-life and functional defects

Area of Science:

• Hematology
• Molecular Biology
• Genetics

Background:

• Heterozygous RUNX1 defects cause familial platelet disorder with myeloid malignancy (FPDMM).
• Existing RUNX1-deficient animal models do not fully replicate FPDMM phenotypes, necessitating better models.
• Previous work established an in vitro megakaryopoiesis system using human CD34+ cells to model FPDMM.

Purpose of the Study:

• To develop and validate an in vivo model for FPDMM.
• To investigate the hemostatic defects associated with RUNX1 deficiency.
• To identify potential therapeutic interventions for FPDMM.

Main Methods:

• Reduced RUNX1 expression in human CD34+ cells using lentiviral shRNA (shRX-megakaryocytes).
• Infusion of shRX-megakaryocytes into immunocompromised NSG mice, including those with a specific von Willebrand Factor mutation (VWFR1326H).
• Assessment of platelet production, lifespan, agonist responsiveness, and thrombus formation; treatment with RepSox.

Main Results:

• shRX-megakaryocytes exhibited reduced agonist responsiveness in vitro.
• Infused shRX-megakaryocytes produced fewer platelets with diminished half-life and impaired agonist response in vivo.
• Platelets were unable to correct thrombus formation in VWFR1326H mice.
• RepSox treatment corrected thrombopoietic defects, thrombus formation, platelet half-life, and agonist response.

Conclusions:

• The developed model accurately recapitulates FPDMM megakaryocyte and platelet defects.
• New insights into thrombopoiesis and platelet half-life defects in RUNX1 deficiency were identified.
• RepSox demonstrated efficacy in reversing RUNX1 deficiency-induced hemostatic defects, offering a potential therapeutic strategy.