Intrinsic and extrinsic effects of mafG deficiency on hematopoietic recovery following bone marrow transplant

Objective: MafG is the small subunit of the transcription factor NF-E2 that controls terminal megakaryocyte maturation and platelet release. Studies were conducted to evaluate the intrinsic and extrinsic effects of mafG deficiency on bone marrow engraftment kinetics.

Materials and methods: We used mafG knockout mice either as donors or recipients in bone marrow transplantations with wild-type mice and compared the engraftment kinetics to transplantations using wild-type donors and recipients. We measured peripheral cell counts, the presence of circulating donor-derived cells by flow cytometry, changes in the cellularity of the bone marrow and splenic weight on day 5, 7, 14, and 1 month post-transplantation.

Results: Compared to wild-type recipients, mafG recipients had delayed platelet and leukocyte recovery and lower spleen weight at early time points after transplantation. Intrinsic effects: When mafG-deficient bone marrow served as donor source, we observed more rapid recovery of bone marrow cellularity and increased splenic hematopoiesis. The finding of increased short-term hematopoietic stem cells and progenitors in the mafG-deficient bone marrow could explain the accelerated hematopoietic recovery after transplantation. Furthermore, the expression of Bach 2, which can form a heterodimer with mafG protein, was found to be greatly reduced, while Notch 1 expression was increased in mafG-deficient mice. Extrinsic effects: When mafG-deficient mice were transplant recipients, there were delays in recovery of normal levels of marrow and splenic hematopoiesis as well as circulating leukocytes and platelets.

Conclusions: Our study demonstrates that mafG expression has intrinsic and extrinsic effects on hematopoietic engraftment following bone marrow transplantation.