Of particular interest in the context of SMA pathology is SNRPN (this protein is also known as SmN, denoted with a lowercase ‘m’), which is expressed in neural tissues (Schmauss et al., 1992) and can replace SNRPB in the heptameric Sm protein ring (Huntriss et al., 1993). Here, SNRPN is linked to proximal spinal muscular atrophy.