Additionally, specific key genes involved in muscle function and calcium-ion handling (1.8-fold enrichment, p value 1.6E−04) are lower (Atp2a2, Casq1, CaBP1, S100a10, Rcan1, and Hrc) and higher in transcript level (Scin, Efhd2, and Myom2) in heart tissue of SMA mice as compared to unaffected mice (Fig. 3b). This evidence concerns the gene ATP2A2 and proximal spinal muscular atrophy.