Differentiation of D-HD-iPSCs into neural progenitors, immature and mature functional neurons. A: A sample image of a neurosphere generated from the D-HD-iPSC line using the feeder-free differentiation protocol. B: Nestin-positive neural progenitors displaying rosette formation and immature (TUJ1+) neurons. C: Phase contrast image of neurons derived from D-HD-iPSCs. D: Mature (MAP2ab+) and doublecortin (DCX+) expressing neurons. E: Neural progenitor derived from D-HD-iPSCs using the PA6 cell line. Stromal cell monolayer observed in the background. F: Large networks of TUJ1+ neurons emanating from neural progenitors using the PA6 stromal cell line for induction. Scale bars: 100 μm. G: D-HD-iPSC derived neurons express both mutant and wild type HTT proteins by Western blot analysis. H: Action potentials recorded from neurons derived from D-HD-iPSCs and from C1-iPSCs. I: Miniature excitatory post-synaptic currents (mEPSCs) recorded from iPSC-derived neurons.