Our focus in this proposal was to understand the role of miRNAs in the development of hematopoietic stem cells from human embryonic stem cells. Our work, and that of other over the past few years has demonstrated how difficult it is to generate hematopoietic stem cells from human embryonic stem cells. In fact, to date, nobody in the world has achieved that goal. However, along the way, we have come to realize that our system can help us identify and understand miRNAs involved in the critical developmental ‘fork in the road’ that leads to hematopoietic vs. cells that line blood vessels (endothelial cells). We worked in 2010-2011 to identify those miRNAs.
Because of the difficulty in generating hematopoietic stem cells from human embryonic stem cells, we stepped back and worked to established better reagents for understanding hematopoietic stem cell development from human embryonic stem cells. To that end, we have used homologous recombination to directly insert a reporter gene into the genome of a human embryonic stem cell. We have been characterizing this cell line, and we hope that it will help advance the field of hematopoietic stem cell development from human embryonic stem cells, both to serve our needs and those of other embryonic stem cell researchers. Using similar sophisticated techniques, we have removed (targeted) from human embryonic stem cells a critical gene required for blood development to provide yet another tool to help us understand this process. We hope that these new reagents will further our understanding of hematopoietic development.