Loss-of-function analysis on the role of endogenous TG2 in cartilage formation. Enzymatic activity of TG2 was inhibited with specific compound ERW-1069 (30 μM). A – deposition of the GAG-rich matrix is enhanced by inhibiting endogenous TG2. Alcian blue staining normalized to total cell number detected with Crystal violet vital dye. B – Quantitative RT-PCR analysis of the expression of xylosyltransferase 2, normalized to housekeeping gene Gusb in micromasses cultures grown in the presence of ERW-1069. C – inhibition of endogenous TG2 augments expression of early chondrogenic molecular markers suggesting chondrocyte blocking in early immature stage of differentiation. Real-time PCR analysis, normalization to housekeeping gene Gusb (*, p<0.05, **, p<0.01).