Identification and Functional Characterization of Genes Expressed Preferentially in Human Embryonic, Hematopoietic, and/or Mesenchymal Stem Cells

Abstract

Stem cells are unique cell populations with the ability to undergo both self-renewal and differentiation into specific cell types simultaneously. Although a wide variety of stem cells including human embryonic stem cells (ESC) is identified and stem cell plasticity is recently reported, neither detailed molecular mechanisms underlying nor fate signaling genes involved in stemness and plasticity are known. To identify genes involved in the control of stemness as well as to characterize each stem cells, we carried out gene expression profiling of three types of human stem or immature progenitor cells: Embryonic (ESC), hematopoietic (CD34+ and CD133+), and mesenchymal stem cells (MSC). The universal human reference RNA (Clontech) was employed as a reference for microarray gene profiling experiments. Comparative analyses of their expression to the reference RNA identified putative candidate clones that highly expressed or not expressed in specific stem cells. Specifically, eight and fifteen genes are identified to be highly expressed and not expressed, respectively, by all three stem cells. The expression pattern of several candidate clones was further characterized in several cell lines as well as in differentiating stem cells by RT-PCR. Furthermore, to systematically characterize the functional role of each candidate gene for the maintenance of stemness or differentiation, we employed a tetracycline-inducible lentiviral knock down strategy. Knockdown effects of several candidate genes, including WDHD1, GDF3, Stellar, and ZNF217, have been demonstrated in both undifferentiated and differentiating ESCs in vitro. In this presentation, we will also discuss putative functional roles of candidate genes in ESC, MSC, and/or CD133+ HSC. Our results may open the door to fully understand the nature of the stem cells and molecular mechanisms of mammalian development and differentiation.