The expression of kainate receptors and voltage-gated Ca2+ channels in iPSC-derived motor neurons, cell surface levels of the NMDA receptor GluN1 and the AMPA receptor GluR1 on neurites, and dendritic spines of iMNs from C9orf72 ALS/FTD patients are found to be markedly elevated compared to controls [34,52,53]. Here, GRIA1 is linked to amyotrophic lateral sclerosis.