Analysis of sorted, transduced Gaucher fibroblasts by flow cytometry and by the MUGlu lysate assay. (A) After loading in the presence of 1 mmol/L CMFDGlu, 30,000 cells were sorted on the basis of fluorescein fluorescence and cultured for further analysis. The threshold chosen for sorting excluded all transduced cells with fluorescence values overlapping those of the nontransduced population. The sorted population was reanalyzed by FACS 34 days later. Relative fluorescence levels are given for each sample and were calculated by setting the median fluorescence value of the nontransduced population in each experiment to 1.0. (B) Forty days postsorting, 30,000 cells were harvested, lysed, and the relative GC activity was measured using the MUGlu assay. Mean Methylumbelliferone fluorescence levels are shown for the nontransduced, transduced, and sorted populations. Lysate analysis was conducted in triplicate.