As MSNs undergo preferential degeneration in HD, the majority of HD iPSC studies used striatal differentiation protocols, albeit with varying success of DARPP32+ neuron generation (0–80% of neurons DARPP32+ [22,24,25,30,32,33,35,36,40,41,42,43,45,47,62,64,65,68]). This evidence concerns the gene PPP1R1B and Huntington disease.