rs6795209 — HTR1F

HTR1F and Migraine Risk — A Drug Target Written in Your DNA

The serotonin system runs through almost every aspect of headache biology. One of its receptors, the 5-HT1F receptor¹¹ 5-HT1F receptor
encoded by the HTR1F gene on chromosome 3, expressed in trigeminal neurons and brainstem pain-modulation nuclei, sits at the exact intersection of genetic migraine susceptibility and modern pharmacology. HTR1F is the direct molecular target of lasmiditan (Reyvow), the first FDA-approved ditan-class²² ditan-class
a new category of migraine drug distinct from triptans — same serotonin pathway, different receptor subtype, no vasoconstriction migraine medication. The variant rs6795209, located in the HTR1F genomic region, links your migraine susceptibility directly to this pharmacological target.

The Mechanism

HTR1F encodes a G protein-coupled receptor that, when activated by serotonin or by synthetic agonists like lasmiditan, inhibits adenylate cyclase and reduces neuronal firing. In the context of migraine, 5-HT1F receptor activation in trigeminal ganglia³³ trigeminal ganglia
clusters of pain-sensing neurons that innervate the head, meninges, and blood vessels; their aberrant activation is the proximate cause of migraine pain and brainstem nuclei suppresses the trigeminovascular cascade — the chain of events that generates the throbbing head pain, nausea, and light sensitivity of a migraine attack. Unlike triptans (which act on 5-HT1B and 5-HT1D receptors and cause vasoconstriction), 5-HT1F has no expression in vascular smooth muscle, making lasmiditan effective without cardiovascular risk — a critical distinction for the millions of migraineurs who also have hypertension, coronary artery disease, or prior stroke.

rs6795209 is an intergenic variant 3.3 kb downstream of C3orf38 and approximately 167 kb downstream of the HTR1F coding sequence. Like most GWAS tag SNPs, it likely acts as a regulatory marker — in linkage disequilibrium with functional variants that alter HTR1F expression levels in trigeminal or brainstem tissue rather than changing the protein sequence. The A allele (GRCh38 reference, population minor) is the risk allele: carrying one or two copies increases migraine susceptibility by tagging a haplotype associated with subtly altered HTR1F expression.

The Evidence

The primary evidence comes 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 to date. The study analysed 102,084 migraine cases and 771,257 controls, identifying 123 risk loci. The rs6795209 A allele reached genome-wide significance at the HTR1F locus with OR = 1.042 (95% CI 1.03–1.06, p = 1×10⁻⁸) — a modest but well-powered effect consistent with the polygenic architecture of migraine. HTR1F was explicitly highlighted in the paper as a pharmacologically important locus because it is the target of lasmiditan, establishing a direct line from genetic epidemiology to clinical pharmacology.

The pharmacological case for HTR1F rests on large Phase 3 trials. Goadsby et al. 2019⁵⁵ Goadsby et al. 2019
Phase 3 randomized, placebo-controlled, double-blind study of lasmiditan for acute treatment of migraine. Brain demonstrated pain freedom at 2 hours in 31.4% (100 mg) and 38.8% (200 mg) of lasmiditan-treated patients versus 21.3% on placebo (p<0.001 for both doses, n=2,583 safety population). This confirmed that selective 5-HT1F agonism is an effective, vasoconstriction-free mechanism for acute migraine — validating HTR1F as a true therapeutic target and making GWAS hits at this locus clinically meaningful.

The effect size at rs6795209 (OR 1.042) is typical of common GWAS variants — this is one of many loci collectively contributing to migraine heritability, not a single deterministic mutation. Population frequency of the risk A allele is approximately 19% globally, somewhat lower in European populations (~15%) and higher in African populations (~36%).

Practical Actions

For A allele carriers: migraine is substantially polygenic, and a single variant with OR 1.042 explains only a fraction of individual risk. The clinical relevance of rs6795209 is primarily pharmacological — it flags that the HTR1F pathway is genetically implicated in your migraine biology, which has direct implications if you suffer from migraines and are choosing acute treatments, particularly if triptans are contraindicated due to cardiovascular risk.

For all migraine sufferers regardless of genotype: lasmiditan's mechanism (selective 5-HT1F agonism) means it works through the exact pathway this locus tags. The drug does not require any specific genotype at rs6795209 to be effective — clinical trials enrolled unselected migraine patients — but the presence of this GWAS signal adds biological context for treatment choice discussions.

Interactions

Migraine is highly polygenic. rs6795209 at HTR1F represents one node in a network of 123+ risk loci identified by Hautakangas 2022. Other serotonin-system and trigeminovascular loci include rs10166942 (TRPM8, cold-pain sensitivity and migraine), rs1835740 (near MTDH/SLC2A9, migraine with aura), and rs2651899 (PRDM16, migraine and cardiovascular pleiotropy). Each adds an independent fractional contribution to migraine liability. Polygenic risk scoring across all migraine loci will ultimately be more clinically useful than individual locus interpretation, but HTR1F is notable because the gene is a validated pharmacological target.