Huntington's disease associated resistance to Mn neurotoxicity is neurodevelopmental stage and neuronal lineage dependent

Manganese (Mn) is essential for neuronal health but neurotoxic in excess. Mn levels vary across brain regions and neurodevelopment. While Mn requirements during infanthood and childhood are significantly higher than in adulthood, the relative vulnerability to excess extracellular Mn across human neuronal developmental time and between distinct neural lineages is unknown. Neurological disease is associated with changes in brain Mn homeostasis and pathology associated with Mn neurotoxicity is not uniform across brain regions. For example, mutations associated with Huntington's disease (HD) decrease Mn bioavailability and increase resistance to Mn cytotoxicity in human and mouse striatal neuronal progenitors. Here, we sought to compare the differences in Mn cytotoxicity between control and HD human-induced pluripotent stem cells (hiPSCs)-derived neuroprogenitor cells (NPCs) and maturing neurons. We hypothesized that there would be differences in Mn sensitivity between lineages and developmental stages. However, we found that the different NPC lineage specific media substantially influenced Mn cytotoxicity in the hiPSC derived human NPCs and did so consistently even in a non-human cell line. This limited the ability to determine which human neuronal sub-types were more sensitive to Mn. Nonetheless, we compared within neuronal subtypes and developmental stage the sensitivity to Mn cytotoxicity between control and HD patient derived neuronal lineages. Consistent with studies in other striatal model systems the HD genotype was associated with resistance to Mn cytotoxicity in human striatal NPCs. In addition, we report an HD genotype-dependent resistance to Mn cytotoxicity in cortical NPCs and hiPSCs. Unexpectedly, the HD genotype conferred increased sensitivity to Mn in early post-mitotic midbrain neurons but had no effect on Mn sensitivity in midbrain NPCs or post-mitotic cortical neurons. Overall, our data suggest that sensitivity to Mn cytotoxicity is influenced by HD genotype in a human neuronal lineage type and stage of development dependent manner.