Quantitative RT-PCR expression analysis of miR-17 in human CD34+ thymocyte progenitors after 5 and 2 days, respectively, of coculture on OP9-DLL1 stromal cells in the presence of 5 µM DAPT (GSI). Graphs show mean expression, relative to the sample cultured in the presence of control DMSO (F) (n=2 independent experiments with different donors; error bars indicate SEM - the two data points are shown). 