In 1995 (five years after the SMA locus was mapped to chromosome 5q13), two candidate genes responsible for SMA were cloned from the same region: the Survival of Motor Neuron 1 gene (SMN1 or TBCD541) and the telomeric Neuronal Apoptosis Inhibitory Protein (telomeric NAIP) gene [12,35]. Here, SMN1 is linked to proximal spinal muscular atrophy.