Human Embryonic and Mesenchymal Stem Cells Express Different Nuclear Proteomes

Human embryonic stem cells (hESCs) are characterized by their immortality and pluripotency. Human mesenchymal stem cells (hMSC), on the other hand, have limited self-renewal and differentiation capabilities. The underlying molecular differences that account for this characteristic self-renewal and plasticity are, however, poorly understood. This study reports a nuclear proteomic analysis of human embryonic and bone marrow-derived mesenchymal stem cells. Our proteomic screen highlighted a 5-fold difference in the expression of Reptin52. We show, using two-dimensional difference gel electrophoresis (2-DIGE), western analysis, and quantitative reverse transcriptase polymerase chain reaction, that Reptin52 is more abundantly expressed in hESC than hMSC. Moreover, we observed differential expression of Pontin52 and beta-catenin-proteins known to interact with Reptin52. This difference in the expression of Reptin52 and Pontin52 (known regulators of beta-catenin) further supports a role for Wnt signaling in stem cell self-renewal and proliferation.