BICD2 and proximal spinal muscular atrophy: The importance of these BicD2-dependent pathways in brain and muscle development is demonstrated by the fact that BICD2 mutations cause devastating brain and muscle development diseases, including a subset of cases of spinal muscular atrophy, which is in combination the most common genetic cause of death in infants (Neveling et al, 2013; Oates et al, 2013; Rossor et al, 2020; Yi et al, 2023).