Fig. 4: MPS IIIA iPSC-derived neurons develop neurotypical action potential firing and kinetics over long-term maturation.

A Representative traces of action potential firing from MPS IIIA (red) and neurotypical (black) neurons, indicating similar firing and kinetics properties. B Proportion of action potential types in MPS IIIA and neurotypical neurons are similar over neurodevelopment. The data represents the proportion of each action potential type in each individual neurotypical donor, MPS IIIA patient or the playground model (Neurotypical n = 6 donors in both time points, MPS IIIA n = 7 patients in both time points). C MPS IIIA and neurotypical neurons require similar amounts of injected current to elicit the same action potential firing response (30–60 days: Neurotypical n = 185 neurons, MPS IIIA n = 179 neurons; 90–120 days: Neurotypical n = 253 neurons, MPS IIIA n = 266 neurons). D Phase plots of MPS IIIA and neurotypical action potential kinetics were calculated on the first action potential in the maximal firing sweep (30–60 days: Neurotypical n = 185 neurons, MPS IIIA n = 179 neurons; 90–120 days: Neurotypical n = 253 neurons, MPS IIIA n = 266 neurons). E The kinetics of action potentials evoked from MPS IIIA and neurotypical neurons are similar over neurodevelopment (30–60 days: Neurotypical n = 172–185 neurons, MPS IIIA n = 164–179 neurons; 90–120 days: Neurotypical n = 246–253 neurons, MPS IIIA n = 256–266 neurons). F Representative traces of voltage-gated sodium currents and voltage-gated fast-inactivating potassium currents evoked by neurotypical and MPS IIIA neurons. G Activation curves of voltage-gated sodium channels across membrane depolarisation potentials in MPS IIIA and neurotypical neurons over neurodevelopment (30–60 days: Neurotypical n = 188 neurons, MPS IIIA n = 183 neurons; 90–120 days: Neurotypical n = 258 neurons, MPS IIIA n = 265 neurons). H Maximum voltage-gated sodium channel peak and its corresponding membrane depolarisation voltage are similar between neurotypical and MPS IIIA neurons over neurodevelopment (30–60 days: Neurotypical n = 188 neurons, MPS IIIA n = 183 neurons; 90–120 days: Neurotypical n = 258 neurons, MPS IIIA n = 265 neurons). I Activation curves of the voltage-gated potassium channel peak across membrane hyperpolarisation potentials, which is calculated by subtracting the slow-inactivating potassium currents from the fast-inactivating potassium currents (30–60 days: Neurotypical n = 188 neurons, MPS IIIA n = 183 neurons; 90–120 days: Neurotypical n = 258 neurons, MPS IIIA n = 265 neurons). J Maximum voltage-gated potassium channel peak is larger in MPS IIIA at 90–120 days, but the membrane hyperpolarisation voltages that these are evoked at are similar between neurotypical and MPS IIIA neurons (30–60 days: Neurotypical n = 188 neurons, MPS IIIA n = 183 neurons; 90–120 days: Neurotypical n = 258 neurons, MPS IIIA n = 265 neurons). For box and whisker plots, the box represents the median and 25th to 75th percentiles, with the whiskers representing the 10th to 90th percentile. The blue plus sign represents the mean of the data. Data points in the graphs are neurons that fall outside of the box and whisker ranges. B and all box and whisker plots were analysed using a Kruskal–Wallis test with Dunn’s correction. In (C, D, and G), the bold red and black lines represent the mean for all individual neurons patched, with the error bars indicating ± SEM. The dashed lines represent the mean of each individual neurotypical donor, MPS IIIA patient or the playground model. These were analysed using a two-tailed non-parametric Mann–Whitney U test for area under the curve. See also Supplementary Figs. 14 and 15. ns not significant is defined as P > 0.05. Black/Grey indicates neurotypical donors; Red/Peach indicates MPSIIIA patient-derived lines. Source data are provided as a Source Data file. AP action potential, Hz hertz, ms millisecond, mV millivolt, MPS IIIA mucopolysaccharidosis type IIIA, pA picoampere, Nav voltage-gated sodium channel, Kv voltage-gated potassium channel.