The molecular mechanisms of c-MYC and REX1 for proliferation and differentiation in adult stem cells

Abstract

c-MYC and REX1, the transcription factors, are considered as pluripotent markers genes in embryonic stem cells. They have multiple functions in cell proliferation, differentiation and cellular transformations in stem cells including mesenchymal stem cells (MSCs). Molecular mechanistic studies through histone modification for c-MYC and p38 MAPK signal pathways for REX1 are performed in MSCs. Lentiviral vector based gene knock-down studies were performed for c-MYC and REX1 as well as lenti-viral vector system based c-MYC over expression also done. Cell proliferation and differentiation status was dramatically decreased in c-MYC knocked-down cells; however it was improved in c-MYC over-expression cells. Cell proliferation status in REX1 inhibited cells was found to be similar as of c- MYC, but more adipogenic positive cells were found in REX1 inhibited cells. On the other hand, osteogenic differentiation was dramatically decreased in REX1 inhibited cells. The results of RT-PCR and Western blot showed the regulatory role of c-MYC over HDAC2 and polycomb group (PcG) genes. Similar studies of REX1 showed the inverse relation between the expressions of REX1 and MKK3, upstream activator of p38 MAPK. Finally, they were confirmed as cell fate determinants for proliferation and differentiation in human MSCs. Chromatin immuno-precipitation assay confirmed that c-MYC bound in HDAC2 and REX1 bound in MKK3 directly. From this study, it is concluded that c-MYC has influential role for cell proliferation and differentiation via chromosomal modification, and REX1 plays similar role through p38 MAPK signal pathways in human adult stem cells.