Later in 2010, Zhang et al. piloted a study to differentiate and characterize human HD cell model from iPSCs (Zhang et al., 2010). Their iPSC cell model had CAG repeats of the same length as the parental fibroblast cells (72 repeats). Neural induction of these HD-iPSCs was achieved using the previously established EB differentiation method (Park et al., 2008a). Thereafter, further differentiation of the HD-specific NSCs (HD-NSCs) into striatal neurons was carried out by treating them directly with SHH, DKK1, brain-derived neurotrophic factor (BDNF) and ROCK inhibitor Y27632 for 8–10 days as an initial step (stage 1), then with BDNF, cAMP, VPA and Y27632 for an additional 1–3 days (stage 2). At stage 1, cells stained positive for the neuronal markers TUJ1 and GABA, as well as calbindin. Mature striatal neurons at stage 2 expressed, in addition to the aforementioned three markers, an additional medium spiny neuron marker DARPP-32, thus confirming their striatal nature (Zhang et al., 2010).
