Introduction

FHM is a form of migraine with aura characterized by the presence of motor weakness [1], associated with at least one other aura symptom and, in 55–69% of the patients, by basilar-type symptoms. At least three different genes are involved: CACNA1A [2], mapped on chromosome 19p13 [3]; ATP1A2 [4], mapped on chromosome 1q21–q23 [5], and SCN1A, mapped on chromosome 2 and mutated in a few familial percentage. CACNA1A encodes the pore-forming alfa1A subunit of P/Q-type voltage-dependent neuronal calcium channels, expressed exclusively in neurons, and which plays a major role in the control of neurotransmitter release, postsynaptic calcium fluxes, and neuronal excitability. The missense CACNA1A mutations are identified in familial and sporadic cases, and studied by electrophysiology and in mutant mice, demonstrate a “gain of function” responsible for an enhanced calcium influx through single P/Q channels. ATP1A2 encodes the catalytic subunit of Na+/K+ ATPase pumps, expressed mainly in neurones and in astrocytes and which utilize ATP hydrolysis to actively maintain the sodium gradient across the cell membrane. All the ATP1A2 mutations described in familial and sporadic cases induce a “loss of function” which inhibits the pumping activity [5]. SCN1A (chromosome 2q24) encodes the alpha1 subunit of Nav1.1-type voltage-dependent neuronal sodium channels which are expressed in the nervous system. In SHM, the great majority of the patients may have the same pathophysiologic background of typical migraine with aura, but the few performed genetic studies demonstrate the involvement of FHM genes, particularly of ATP1A2 [6].

Materials and methods

Since 2007, 24 patients, 18 females and 6 males, came to our attention due to migraine attacks, without cerebellar signs and/or epileptic seizures, fulfilling the HIS revised criteria for familial (n = 13) and sporadic (n = 11) hemiplegic migraine. All the 24 patients underwent a genetic screening together with another healthy family member and, in the familial cases, also together with at least another affected family member. For this reason, we finally screened 61 patients. After obtaining written informed consent, we purified DNA from blood of all individuals using the IsoQuick Nucleic Acid Extraction kit (ORCA Research, Bothell, WA, USA). Sequences were prepared with a Big Dye Terminator sequencing Kit (version 3.1 Applied Biosystem), run on Applied Biosystems ABI 3130XL Genetic Analyzer and analyzed with Sequencing Analysis Software version 3.7 NT. Two hundred healthy subjects were available as controls. Mutation nomenclature follows the rules indicated in http://www.hgvs.org/mutnomen and genotyping of the families was carried out with polymorphic markers available at the ATP1A2 locus. We have initially screened the CACNA1A gene in the familial cases and the ATP1A2 gene in the sporadic patients.

Results and conclusion

In 21 patients (12 FHM and 9 SHM), we have not found genetic mutations. Only in three cases, 1 FHM and 2 SHM patients, we have described three new mutations in the ATP1A2 gene. The first mutation (Tyr9Asn), in a sporadic case (Table 1), is a novel missense mutation changing a codon for tyrosine in exon 2 [7]. The second mutation (Arg65Trp), in a FHM case (Table 1), is a novel missense mutation in the exon 4, described in the proband and in other two affected relatives [7]. The third mutation (Tyr1009), in a young sporadic patient, is a novel heterozygous nonsense mutation in exon 22 which probably leads to an early truncation of the protein [8]. The presence of the mutations only in the screened affected individuals and their absence in the 200 control individuals confirm their pathogenetic roles and exclude the possibility of phenotypic variants. Moreover, the presence of the nonsense mutation in the patient with the most severe phenotype (Table 1) and with epileptic seizures underlines the pathogenetic involvement of the Na+/K+ ATPase pump in the hemiplegic migraine. In our opinion, our results confirm the more frequent involvement of the ATP1A2 gene in SHM, as described by Vries in 2007, and demonstrate its involvement in Italian FHM patients, at least in FHM patients without cerebellar signs during the attacks. On the other hand, the presence of genetic mutations only in 1 FHM patient suggests the involvement of other unknown genes which we could analyze in the future thanks to the creation of this biobank. In conclusion, the identification of many causative mutations should point out if hemiplegic migraine is a particular form of migraine with aura or a distinct genetic disease, with a distinct underlying pathogenesis.

Table 1 clinical features of the three patients with genetic mutations
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