rs10405121 — CACNA1A

CACNA1A — The Hemiplegic Migraine Gene and the First Common Risk Variant for Migraine with Aura

CACNA1A¹¹ CACNA1A
calcium voltage-gated channel subunit alpha1-A; encodes the pore-forming subunit of P/Q-type voltage-gated calcium channels expressed predominantly in cerebellar Purkinje cells and cortical and brainstem neurons is one of the best-characterised neurological genes in genetics. Rare, highly penetrant mutations in this gene cause three distinct Mendelian disorders: familial hemiplegic migraine type 1 (FHM1), episodic ataxia type 2 (EA2), and spinocerebellar ataxia type 6 (SCA6). The same gene now yields a common population-level risk variant for ordinary migraine with aura — rs10405121 — making it the bridge between rare channelopathies and the genetic architecture of one of the world's most prevalent neurological conditions.

rs10405121 sits in an intron of CACNA1A on chromosome 19 (GRCh38 position 13,228,314). It does not change the protein sequence. Its biological effect is presumed to operate through altered splicing efficiency or regulatory element function within the intronic sequence, modulating CACNA1A expression levels in neurons. The G allele — the population-common reference allele present in about 55–66% of chromosomes across populations — is the allele associated with slightly higher migraine susceptibility, while the A allele confers modest protection.

The Mechanism

P/Q-type calcium channels encoded by CACNA1A²² encoded by CACNA1A
the alpha-1A subunit forms the ion-conducting pore; the channel is the primary route for calcium entry at presynaptic terminals in neurons of the cerebellum, cortex, and trigeminovascular system control neurotransmitter release at excitatory synapses throughout the brain. In the trigeminovascular system — the nerve network that carries pain signals from meningeal vessels to the trigeminal nucleus — P/Q-type channels regulate the threshold for cortical spreading depression³³ cortical spreading depression
CSD; a slow wave of neuronal and glial depolarization that propagates across the cortex at 3-5 mm/min and is believed to be the electrophysiological correlate of the migraine aura. Rare FHM1 mutations in CACNA1A increase channel gain-of-function, lowering the CSD threshold and accounting for the aura phenotype that characterises FHM1. The common rs10405121 variant likely exerts an analogous but quantitatively far smaller effect — enough to shift the population distribution of CSD threshold rather than to cause hemiplegic episodes.

The Evidence

The primary evidence is from Hautakangas et al. 2022⁴⁴ Hautakangas et al. 2022
Genome-wide analysis of 102,084 migraine cases identifies 123 risk loci and subtype-specific risk alleles. Nature Genetics, the largest migraine GWAS published to date. In this meta-analysis of 102,084 cases and 771,257 controls, rs10405121 reached genome-wide significance for migraine overall (G allele: OR 1.034, 95% CI 1.02–1.04, p = 5×10⁻¹⁰). Crucially, stratification using 29,679 cases with subtype information identified the CACNA1A locus — along with HMOX2 and MPPED2 — as appearing specific for migraine with aura rather than migraine without aura. This is the first common variant in CACNA1A to reach genome-wide significance for migraine and places rs10405121 in a biologically coherent position: a regulatory intronic variant in the gene whose rare mutations define FHM1, an aura-prominent condition.

A smaller case-control study (Szymanowicz et al. 2025⁵⁵ Szymanowicz et al. 2025
CACNA1A Genetic Variants and Their Potential Involvement in Migraine Pathogenesis. Int J Mol Sci, n = 150) found that the rs10405121 AA genotype occurred exclusively in familial migraine cases, suggesting that the protective A allele homozygote is enriched in individuals without strong family history. However, this study's small sample size means it should be interpreted cautiously alongside the large GWAS data.

Practical Actions

The effect size for rs10405121 is modest (OR 1.034 per G allele), meaning that genotype alone is a minor contributor to individual migraine risk. The clinical value lies in understanding which calcium channel pathway underlies aura susceptibility — relevant when choosing preventive medications. Calcium channel blockers, particularly flunarizine⁶⁶ flunarizine
a selective calcium channel antagonist approved for migraine prevention in Europe and many other countries; inhibits L-type and T-type channels and has indirect modulation of P/Q-type channel activity, target the same calcium channel biology and represent a pharmacologically rational preventive option for GG or AG individuals who experience frequent migraine with aura.

For those carrying two G alleles who experience migraine with aura: calcium channel-modulating preventives may be worth discussing with a neurologist, as the CACNA1A biological pathway is directly implicated.

Interactions

CACNA1A is one of several ion channel genes in the GeneOps neurology-cognition database with migraine relevance. rs10166942 in TRPM8 (a cold-sensing channel upregulated in trigeminal neurons) is independently associated with migraine susceptibility and operates through a distinct receptor pathway. rs8065080 (SCN1A, a sodium channel gene) is also in the migraine genetic architecture. Individuals carrying risk variants at multiple ion channel loci may have an additive susceptibility load, though no published compound interaction data exist specifically for rs10405121 with these variants.

The rare FHM1-causing CACNA1A mutations (e.g., R192Q, T666M) are not captured by rs10405121 — they are rare pathogenic coding variants typically identified by clinical sequencing, not population genotyping.