SPI1 and Huntington disease: This suggests that if the expression and activity of myeloid lineage-determining factors such as PU.1, C/EBPα and C/EBPβ are altered in differentiating human HD PSC-derived cells, as they are in mutant HTT fragment-expressing mouse microglial-like cells [26], the effects are not sufficient to overtly affect the overall maturity of the cells generated, at least in this PSC context.