Regulation of lineage choices during granulopoiesis

Abstract

Aberrant regulation of hematopoiesis can lead to severe clinical conditions ranging from myeloproliferative disorder to severe immune deficiencies. It is therefore important to understand the molecular mechanisms underlying these processes. Regulation of maturation during granulopoiesis in vivo is mediated by secretion of specific cytokines and adhesion to stromal cells. The studies described in this thesis have investigated the roles of several transcription factors and intracellular signalling molecules in regulation of eosinophil and neutrophil development. To accomplish this, an ex-vivo differentiation system was utilized, which allowed us to investigate the mechanisms underlying granulocyte differentiation in human cord blood derived CD34+ cells. Retroviral transduction experiments enabled us to ectopically express genes of interest and to determine their role in regulating granulopoiesis. We demonstrate that several transcription factors play a critical role in regulating granulopoiesis in general, including STAT5 and Id2, whereas other transcription factors, such as Id1, appear to play a role in determining specific lineage choices. In addition, we presented evidence that PKB plays a critical role in regulation of cell fate determination. Although these results enhance our knowledge regarding the mechanisms regulating granulopoiesis, further research is critical to understand the precise role of stromal cells in cell fate choices and to understand exactly how PKB activity is regulated and what the specific downstream targets of this kinase are that can regulate cell fate.