Neural differentiation of HPRT1 knock-out cell lines. A: Neuronal phenotypes in isogenic HPRT1 mutant hESC lines. Beta-III-tubulin-stained CNS neurons derived from 5 independent HPRT1 mutant lines and isogenic wild-type control. Note the higher numbers with more pronounced neurites in wild-type compared to mutant cells. B: High-content imaging-based quantification of neuron formation frequencies and neurite lengths of cultures shown in A. P-values are based on unpaired t-tests between individual clones and wild-type control samples. *: p ≤ 0.05; **: p ≤ 0.01; ***p ≤ 0.001. C: Neurons growing out in a radial manner from plated embryoid bodies induced to differentiate into BRN3A-positive PNS neurons. Images show representative outgrowths stained for beta-III-tubulin under 50x magnification. Sphere radius values served as an approximation for quantifying relative neurite lengths. D: Quantification of sizes of replicate plated spheres shown in C (n ≥ 7). E: Quantification of sizes of replicate plated spheres from HPRT1 knock-out hiPSCs differentiated into sensory-like neurons as in C (n ≥ 8). P-values are based on unpaired t-tests between individual clones and wild-type controls. **: p ≤ 0.01; ***p ≤ 0.001.