Transcription Factor RUNX1 Regulates Coagulation Factor XIII-A ( F13A1 ): Decreased Platelet-Megakaryocyte F13A1...

Area of Science:

• Hematology
• Molecular Biology
• Hemostasis and Thrombosis

Background:

• Germline RUNX1 haplodeficiency (RHD) is linked to thrombocytopenia, platelet dysfunction, and myeloid malignancy risk.
• RHD patients exhibit decreased platelet expression of F13A1, which encodes Factor XIII-A, crucial for clot stabilization.
• Factor XIII-A is synthesized in hematopoietic cells, including megakaryocytes and monocytes.

Purpose of the Study:

• To elucidate RUNX1's regulatory role in F13A1 expression within platelets and megakaryocytes.
• To investigate the mechanisms and consequences of diminished F13A1 levels in RHD.

Main Methods:

• Studies were conducted on platelets, HEL cells, and human CD34+ cell-derived megakaryocytes.
• Small interfering RNA (siRNA) knockdown of RUNX1 or F13A1 was employed.
• Clot contraction assays were performed on treated cells.

Main Results:

• Platelet F13A1 mRNA and protein were reduced in RHD patients and siblings.
• RUNX1 directly regulates F13A1 transcription, with overexpression increasing and KD reducing promoter activity.
• Knockdown of RUNX1 or F13A1 impaired clot contraction, FXIII-A surface expression, and activation-dependent signaling.

Conclusions:

• RUNX1 is a key regulator of F13A1 expression in megakaryocytes and platelets.
• Reduced F13A1 expression contributes to impaired clot contraction in RHD.
• Defective clot contraction in RHD involves multiple disrupted platelet-megakaryocyte mechanisms.