Predifferentiation Neurotoxicity of GenX Exposure on hiPSC-Derived Cortical Neurons.

Hexafluoropropylene oxide dimer acid (HFPO-DA), commercially known as GenX, was introduced as a potentially safer substitute for an older type of per- and polyfluorinated substance (PFAS) named perfluorooctanoic acid (PFOA). Emerging evidence suggests that GenX may possess neurotoxicity comparable to or greater than that of PFOA, underscoring the need for evaluating its potential to induce adverse health effects on the central nervous system. Here, we performed a systematic evaluation of predifferentiation GenX exposure and its neurotoxic effects utilizing human induced pluripotent stem cell (hiPSC)-derived cortical neurons. Neurons exposed to 0.4 and 4 ppb GenX prior to differentiation possess altered neuronal characteristics including synaptic density and neural activity, accompanied by transcriptomic changes associated with neurodegeneration, including enriched differentially expressed genes (DEGs) in the Alzheimer's disease (AD) pathway and predicted dysregulation of amyloid processing. Consistent with the transcriptomic alterations, GenX exposure altered multiple APP processing readouts, including increased sAPPβ/sAPPα ratios and intracellular C99 accumulation, accompanied by reduced extracellular Aβ40 and Aβ42 levels. Hyperphosphorylation of tau was also observed along with lipid droplet accumulation and reduced global translational activity, indicating broader disruptions. Collectively, our findings suggest that GenX exposure prior to differentiation, mimicking developmental exposure, can lead to persistent molecular and functional alterations in human cortical neurons that resemble key features observed in neurodegenerative diseases.