Figure 5

Functional assessment of HGprt deficiency. All control iPSC lines (red, n = 6) demonstrated readily detectable activity in the HGprt enzyme assay, while all LND iPSC lines (blue, n = 6) had no detectable activity (A). Results are shown as box plots with results for each line shown separately. There was no obvious difference in the growth of the control and LND lines in the absence of 6TG (blue lines, B). However, the control lines showed a clear toxic effect of 6TG, while the LND lines appeared to be resistant to it (red lines, B). In these growth curves, the error bars show the standard deviation. HGprt plays an important role in the metabolism of hypoxanthine (C), leading to marked hypoxanthine accumulation that is released into the tissue culture medium; with no apparent impact on intracellular purines (D). In this panel, controls are shown in red and LND in blue, with error bars reflecting standard deviations. Among 109 genes in the KEGG pathway for purine metabolism, only 6 were significantly different between control (red) and LND (blue) iPSC lines at FDR < 0.05 (E).