Modeling Amyotrophic Lateral Sclerosis (ALS) with human induced pluripotent stem cells (iPSCs) aims to reenact embryogenesis, maturation, and aging of spinal motor neurons (spMNs) in vitro. As the maturity of spMNs grown in vitro compared to spMNs in vivo remains largely unaddressed, it is unclear to what extent this in vitro system captures critical aspects of spMN development and molecular signatures associated with ALS. Here, the Inventors compared transcriptomes among iPSC-derived spMNs, fetal, and adult spinal tissues. The Inventors resolved gene networks and pathways associated with spMN maturation and aging. These networks enriched for familial ALS genetic variants and were affected in sporadic ALS. Altogether, the Inventors' findings suggest that developing strategies to further mature and age iPSC-derived spMNs will provide more effective iPSC models of ALS.