The characteristics of global gene expression patterns during umbilical cord blood (UCB)-CD34+ stem cell-derived erythropoiesis are not clearly elucidated. In this study, UCB-stem cells were grown in liquid culture as a model for this process. We observed a high proliferative capacity of UCB-stem cells producing over 10 billion viable cells in culture. Normal erythroid maturation was confirmed by increased expression of CD71 and CD235a biomarkers. Furthermore, the gamma- to beta-globin gene switch was observed around day 45 indicating extended gamma-globin gene expression in fetal erythroid cells. To study global gene expression patterns, microarray analysis was performed on days 21, 42, 49 and 56. Forty-five transcription factors were silenced during the culture period (Profile-1) including CUX1 and HES5 among others. Conversely, 30 transcription factors were activated by day 56 (Profile-2) such as KLF1, GATA1, and MAFB. Both datasets were analyzed further using the MIMI Cytoscape platform which defined transcription factor networks around KLF4 and GATA2 from Profile-1 genes and KLF1 and GATA1 for Profile-2 genes. The characteristics of UCB-CD34+ stem cells including high proliferative capacity and prolonged gamma-globin expression combined with novel transcription factor networks suggest novel mechanisms of fetal UCB-stem cell-derived erythropoiesis.

Cd34 cell from umbilical cord blood were grown in three independent cultures using the one-phase protocol. Cells were cultured in aMEM containing 30% fetal bovine serum, 1% deionized BSA with penicillin (100 U/mL) and streptomycin (0.1 mg/mL) at 37°C and 5% CO2. The following growth factors were added on day 0: stem cell factor (50 ng/mL), interleukin-3 (10 ng/mL) and erythropoietin (4 U/mL). Approximately 1.5 million cells were harvested from each culture (triplicate samples) on day 21, 42, 49 and 56 for microarray analysis on the whole-genome Illumina HumanWG-12 V4 Expression BeadChip.