In our analysis, genes with at least two fold change and pvalue, 0.01 were considered differentially expressed. Only 159 differentially expressed genes were common to all three tissues. Regardless of engraftment potential, several genes undergo differential LDN-193189 expression when cells migrate from mitotic quiescence to active phases of cell cycle. Since we used CD34 + cells from 3 different tissues with distinct engraftment potential, we were able to subtract genes that were differentially expressedmerely due to cell cycle progression and focus on engraftment related genes only. Nine genes, ADAMTS1, THBS1, TIMP3, PTGS1, NCKAP1, EVI1, MFGE8, ITGA2, ENST00000353442, with embryonic development function were upregulated in engrafted cells. A number of these genes have an already identified role in maintaining hematopoietic stem cells directly or indirectly by altering the expression of genes implicated in the maintenance of stem cell function such as sonic hedgehog. Many of these genes play critical roles in embryonic differentiation, implantation, and tissue homeostasis, in embryonic body morphogenesis and gastrulation, and in organ morphogenesis and limb patterning. How these genes collectively participate in controlling hematopoietic stem cell engraftment remains to be fully elucidated. Interestingly, we found that the expression of several target genes upregulated in engrafted cells can be inversely affected by the expression of genes that were upregulated in non-engrafted cells. For instance, growth arrest and DNA-damageinducible, alpha, an essential component of many metabolic pathways that control proliferating cancer cells had relatively high expression levels in engrafted cells. B-cell CLL/ lymphoma 2 protein which was highly expressed in nonengrafted cells has been previously shown to suppress the expression of human GADD45A protein. Whether over expression of BCL2 in non-engrafted cells negatively regulates the expression of GADD45A thereby promoting a loss of engraftment potential requires closer examination. Similarly, expression of thrombospondin1 which has a role in the activation of MAPK, anti-apoptosis, and cell cycle arrest was upregulated in engrafted cells. THBS1 protein decreases the secretion of IL2, which, as noted above and in Figure 3, is associated with Torin 1 non-engrafting cells. Integrin, alpha 2 which is involved in cell adhesion and cell-surface mediated signaling was upregulated in engrafted cells while the androgen receptor was overexpressed in non-engrafting cells. Interestingly, 5alphadihydrotestosterone has been previously shown to decrease the expression of ITGA2. It would have been very interesting and informative if we could have extended these analyses to cells in S/ G+M phases of cell cycle. Unfortunately, only a very small percentage of UCB and MPB-derived CD34 + cells are in S/ G2+M, making the isolation of sufficient numbers of these cells extremely difficult.