ATP1A2 and migraine, familial hemiplegic, 2: The gene responsible for the familial hemiplegic migraine type 2 (FHM2) was first identified in 2003 when the gene encoding the α2 subunit, the Na+/K+ ATPase, in neurons and astrocytes—ATP1A2 gene of chromosome 1q23—was discovered in two Italian families [201].