The role of p202 in regulating hematopoietic cell proliferation and differentiation.

HIN-200 proteins are interferon (IFN)-inducible proteins that can regulate cell proliferation and differentiation in vitro. Characterization of the lineage and cell type-dependent expression of Ifi202 revealed little or no expression of Ifi202 in the Lin(-)/c-Kit+ fraction enriched for immature hematopoietic progenitor cells (HPCs) but higher levels in more differentiated Lin(-)/c-Kit(-) and Lin+ populations. The highest levels of Ifi202 expression were observed in CD11b+/Gr-1dim immature granulocytes in the bone marrow.

Identification of in vitro growth conditions for c-Kit-negative hematopoietic stem cells.

Our laboratory recently identified a quiescent class of pluripotent hematopoietic stem cells (PHSCs) that are lineage negative (Linneg), lack c-Kit, and are able to give rise to c-Kit-positive (c-Kitpos) PHSCs in vivo. This population fails to proliferate in vitro but has delayed reconstituting activity in vivo. In this study, we purified these cells to enrich for the PHSCs and we identified in vitro conditions capable of supporting their maturation.

In vivo retroviral gene transfer by direct intrafemoral injection results in correction of the SCID phenotype in Jak3 knock-out animals.

Efficient retroviral gene transfer to pluripotential hematopoietic stem cells (PHSCs) requires ex vivo culture in multiple hematopoietic growth factors (HGFs) to promote cell division. While treatment of PHSCs with HGF can render stem cells viable targets for retroviral infection, HGFs can promote differentiation, loss of self-renewal potential, and affect the homing/engraftment capacity of PHSCs. To avoid the negative impacts observed with ex vivo transduction protocols, we developed a murine model for in vivo retroviral infection by direct intrafemoral injection (DII), thus abolishing the need for removal of cells from their native microenvironment and the signals necessary to maintain their unique physiology.