Related Experiment Video
Updated: Feb 7, 2026

Bone Marrow Transplantation Procedures in Mice to Study Clonal Hematopoiesis
Published on: May 26, 2021
Phosphatidylinositol transfer proteins regulate megakaryocyte TGF-β1 secretion and hematopoiesis in mice
Maegan Capitano1, Liang Zhao2, Scott Cooper1
1Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN.
Abstract:
We hypothesized that megakaryocyte (MK) phosphoinositide signaling mediated by phosphatidylinositol transfer proteins (PITPs) contributes to hematopoietic stem cell (HSC) and hematopoietic progenitor cell (HPC) regulation. Conditional knockout mice lacking PITPs specifically in MKs and platelets (pitpα-/- and pitpα-/-/β-/-) bone marrow (BM) manifested decreased numbers of HSCs, MK-erythrocyte progenitors, and cycling HPCs. Further, pitpα-/-/β-/- BM had significantly reduced engrafting capability in competitive transplantation and limiting dilution analysis. Conditioned media (CM) from cultured pitpα-/- and pitpα-/-/β-/- BM MKs contained higher levels of transforming growth factor β1 (TGF-β1) and interleukin-4 (IL-4), among other myelosuppressive cytokines, than wild-type BM MKs. Correspondingly, BM flush fluid from pitpα-/- and pitpα-/-/β-/- mice had higher concentrations of TGF-β1. CM from pitpα-/- and pitpα-/-/β-/- MKs significantly suppressed HPC colony formation, which was completely extinguished in vitro by neutralizing anti-TGF-β antibody, and treatment of pitpα-/-/β-/- mice in vivo with anti-TGF-β antibodies completely reverted their defects in BM HSC and HPC numbers. TGF-β and IL-4 synergized to inhibit HPC colony formation in vitro. Electron microscopy analysis of pitpα-/-/β-/- MKs revealed ultrastructural defects with depleted α-granules and large, misshaped multivesicular bodies. Von Willebrand factor and thrombospondin-1, like TGF-β, are stored in MK α-granules and were also elevated in CM of cultured pitpα-/-/β-/- MKs. Altogether, these data show that ablating PITPs in MKs indirectly dysregulates hematopoiesis in the BM by disrupting α-granule physiology and secretion of TGF-β1.
Related Concept Videos
Regulation of Hormone Secretion
Humoral...
Regulated Protein Degradation
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
Regulated Protein Degradation
Hematopoiesis
Covalently Linked Protein Regulators
These groups modify specific amino acids in a protein....
Covalently Linked Protein Regulators

