CACNA1B and proximal spinal muscular atrophy: Similar symptoms regarding Cav2.2 clustering, growth cone formation and defects in neurotransmission at neuromuscular synapses were observed in mouse models for spinal muscular atrophy (Kong et al., 2009; Park et al., 2010; Ruiz et al., 2010; Tejero et al., 2016; Jablonka and Sendtner, 2017).