Studies on the Role of Polycomb Group Proteins in Stem Cell Self Renewal and Differentiation

Abstract

Understanding the mechanism of stem cell self-renewal is critical because the number of freshly isolated stem cells from various sources is extremely low and prolonged maintenance of stem cells in culture results in loss of stem cell properties. On the other hand, exquisite control of differentiation is essential for clinical application of stem cell therapy. Recent studies with polycomb group (PcG) proteins suggest their role in stem cell self-renewal and/or differentiation. Expression of various PcG genes were tested in the mesenchymal stem cells isolated from human cord blood at various passage numbers which were examined as a self-renewal model system. As for differentiation, HL-60 leukemia cell line treated with all-trans retinoic acid was tested. Various PcG gene expression was tested at both mRNA and proteins levels by semi-quantitative RT-PCR and immunoblotting, respectively. The examined PcG genes include Mel-18, Bmi-1, Ezh2, Suz12, YY1, Cbx7 and EED.