ATP1A2 and familial hemiplegic migraine: A few of the mutations in ATP1A2 and ATP1A3 target the same positions (Figure 4), but it is clear from the structural mapping that the ATP1A3 mutations often target the ion binding sites, while that is not the case for ATP1A2, possibly suggesting that impaired ion binding in alpha2 would be incompatible with life or that they cause other symptoms than FHM.