In 2003, I joined the Daley lab to study a cell population functionally reminiscent of hematopoietic stem cells (HSC) that the group had recently engineered from murine embryonic stem cells (ESC) and to develop novel methods for the derivation of HSC from ESC.  Despite the group’s success in generating ESC-derived HSC, there was as yet no knowledge of how these cells compared phenotypically and functionally to bona fide bone marrow HSC.  For ESC-derived HSC to achieve clinical utility, we must have a good understanding of their biology.  The main object of my research has been the characterization of the phenotype, function, and in vivo HSC equivalent of the ESC-derived HSC.  As they originate from a developmentally primitive stem cell, I hypothesized that these cells would represent a developmental intermediate in the hierarchy of HSC maturation.  Indeed, I have since demonstrated that ESC-derived HSC present a cell surface phenotype akin to embryonic, rather than bone marrow, HSC.  To glean a better understanding of why ESC-derived HSC are developmentally immature, I am currently comparing the global gene expression profiles of HSC purified from multiple stages of embryonic development to that of ESC-derived HSC and bone marrow HSC.  I have also contributed significant effort to other projects focused on the identification of novel determinants of HSC development both in vivo and from differentiating ESC.