II. To test the impact of RING ubiquitin ligases on differentiation of human mesenchymal precursor cells: to test the impact of RING ubiquitin ligases on the differentiation of mesenchymal precursor cell from the collected tissue by testing the expression of classical differentiational bone markers by flow cytometry (fibronectin, CD105) and by Alkaline phosphatase (ALP) activity assay. For this aim we developed both a constitutive and Dox-regulated conditional RING ubiquitin ligases overexpression and shRNA lenti-viral systems that enables efficient modulation of RING ubiquitin ligases level.