Here, we took advantage of iPSC-derived MNs and RNA profiling by digital color-coded molecular barcoding in soma and neurites to gain insight into the molecular mechanisms underlying axonal dysfunctions in ALS, with a specific focus on the interplay between three RBPs: ALS mutant FUS, FMRP and HuD. Here, FMR1 is linked to amyotrophic lateral sclerosis.