III. Determine the role of RING ubiquitin ligases in proliferation and survival of human mesenchymal precursor cells: Via inhibition or overexpression of ligases in mesenchymal progenitor cells we will test the role of these ligases in proliferation and survival of mesenchymal precursors by using MTT assay, Propidion-Iodid (PI) and tunnel assays in flow cytometry analysis.