KIF5A and amyotrophic lateral sclerosis: Together, these results suggest that most biochemical features characterising the ALS-linked N999Vfs*40 KIF5A mutant appear exacerbated for the NEIMY-related C975Vfs*73 KIF5A, providing a possible explanation for the higher severity of its associated neurodevelopmental phenotype compared to KIF5A-linked neurodegeneration.