Development of Human IPS-Derived Upper Motor Neurons to Model ALS
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that results in the progressive loss of both upper motor neurons (UMNs) and lower motor neurons (LMNs). Due to the complex etiology and epiphenomena observed in ALS, the mechanisms that generate neuronal dysfunction and death are not completely understood. Stem cell differentiation protocols have been used to generate sufficient human LMNs for in vitro disease modeling studies to reveal pathophysiological phenotypes associated with ALS including prostaglandin signaling, cell stress from reactive oxygen species, and functional hyperexcitability which decrease LMN survival. However, current differentiation methods generate too few UMNs with too much heterogeneity to use for similar disease modelling experiments. Herein we validate a reporter for the gene FEZ Family Zinc Finger 2 (FEZF2) and demonstrate the usefulness of this reporter for enriching and characterizing identity and function of sub cerebral projection neurons (SCPNs) derived from induced pluripotent stem (iPS) cells patterned through an accelerated 2D forebrain differentiation protocol. We then utilize these SCPNs in an in vitro disease model of ALS where UMNs within the SCPN population demonstrate pathophysiological phenotypes when co-cultured with mouse glia expressing a mutant human SOD1G93A transgene to show that prostaglandin signaling confers toxicity onto UMNs to a significant extent, yet alone appears to be insufficient to account for the survival deficit observed from UMNs. Generating a substantial an enriched population of SCPNs from human stem cells opens avenues for rebuilding cortical-motor neuron circuitry, provides new tools for modeling disease phenotypes, and enables high-throughput drug screens for motor neuron diseases.