Mutations in SOD1 induce ALS-related phenotypes in 3D iPSC-derived motor neuron (MN) spheroids

A significant challenge in ALS research is the heterogeneity of the disease. Even mutations within the same gene can lead to different disease prognosis. For instance, in silico protein modeling predicts distinct properties for distinct SOD1 mutations. With this in mind, in this study, we generated and characterized 3D iPSC-derived MN spheroids carrying homozygous knock-in SOD1 mutations (D90A and G93A), as well as a double mutation (D90A/G93A), to evaluate potential synergistic effects. An isogenic control line with the same genetic background was used for phenotypic comparisons with the knock-in variants. Mutant SOD1 MN spheroids exhibited multiple ALS-related phenotypes including altered SOD1 expression, reduced cell viability, downregulation of neurofilament (NF) subunit expression, hypoactivity, and altered burst activity. Our results highlight the advantages of using 3D MN spheroids as a disease model and stress the importance of considering phenotype variability at the genetic level in ALS.