rs306960 — PTK2

PTK2 — Focal Adhesion Kinase and the Neural Wiring of Restless Legs

The urge to move that defines restless legs syndrome (RLS) — the uncomfortable crawling, pulling, or aching sensations that compel constant leg movement, particularly at rest and in the evening — affects up to 10% of adults and is one of the most heritable common neurological conditions known. rs306960, an intronic variant in PTK2¹¹ PTK2
Protein tyrosine kinase 2, also called focal adhesion kinase (FAK). Encoded on the minus strand of chromosome 8 at position 140,995,145 (GRCh38). PTK2 is a non-receptor tyrosine kinase that transduces signals from integrin receptors and growth factors into cytoskeletal reorganization, controlling how cells move and form connections, reached genome-wide significance in the largest RLS genetic study ever conducted. The connection between a kinase best known for cell motility and a sensory-motor disorder points to how the spinal circuits that process touch and proprioception are assembled during development.

The Mechanism

PTK2 encodes focal adhesion kinase (FAK)²² focal adhesion kinase (FAK)
FAK is a 125-kDa non-receptor protein tyrosine kinase. Its primary substrates include paxillin, talin, and p130Cas at focal adhesions — protein complexes anchoring the cytoskeleton to the extracellular matrix. In neurons, FAK transduces guidance cue signals (netrin, semaphorin, ephrin) into actin and microtubule rearrangements that steer axons and position cell bodies, a hub kinase in neuronal development. FAK is highly expressed in the developing brain and spinal cord, where it controls several processes critical to sensory-motor circuit formation:

• Neuronal migration: FAK phosphorylated by Cdk5 at Ser732 is required for nuclear translocation during radial migration of cortical neurons. Neurons lacking this phosphorylation fail to position correctly in the developing cortex.
• Axon guidance: FAK functions downstream of semaphorin-3A signaling to drive axonal remodeling in hippocampal neurons. It also associates with netrin receptor DCC, linking extracellular guidance cues to cytoskeletal response in pioneer axons.
• Synapse formation: Conditional ablation of FAK from Purkinje cell neurons increases axonal terminal and synapse number, establishing FAK as a negative regulator of synaptogenesis. This regulation operates via FAK–p190RhoGEF interactions that modulate RhoA activity at developing synapses.

rs306960 is intronic and does not change PTK2's protein sequence. The most likely mechanism is a cis-regulatory effect — altered splicing, changed transcription factor binding within the intron, or modified enhancer activity — that subtly shifts PTK2 expression levels or isoform ratios during the developmental window when spinal sensory circuits are being established. The T allele is associated with increased RLS risk, consistent with either reduced FAK activity (insufficient restraint of aberrant synaptogenesis) or altered FAK expression in spinal interneurons processing somatosensory input.

RLS is understood as a disorder of spinal sensorimotor integration³³ spinal sensorimotor integration
The spinal cord continuously integrates sensory signals from the legs with motor commands. In RLS, this integration is disrupted, with abnormal excitability of spinal circuits at rest — particularly in the evening when descending dopaminergic inhibition from the A11 diencephalospinal tract is lowest. The uncomfortable sensations that characterize RLS emerge at rest and resolve with movement, a pattern consistent with hyperexcitability of sensory circuits that normally require active motor engagement to re-calibrate. FAK's role in determining how tightly spinal interneurons connect to each other during development makes PTK2 a plausible contributor to the baseline excitability of these circuits across a lifetime.

The Evidence

The rs306960-T association was established in the 2024 RLS GWAS meta-analysis⁴⁴ 2024 RLS GWAS meta-analysis
Schormair B et al. Genome-wide meta-analyses of restless legs syndrome yield insights into genetic architecture, disease biology and risk prediction. Nat Genet, 2024, the largest genetic study of RLS to date: 116,647 cases and 1,546,466 controls of European ancestry. The study identified 164 risk loci — an eightfold increase from prior work — with rs306960-T achieving a p-value of approximately 1.18 × 10⁻¹³ and a beta of ~0.036 log-OR units per T allele. At a risk allele frequency of 41%, rs306960 is a common variant with a modest per-allele effect, typical of the polygenic architecture of RLS. The study also found that machine learning models integrating all RLS loci achieved AUC = 0.82–0.91 for disease prediction — underscoring the value of profiling all contributing variants.

The biological plausibility rests on extensive neurodevelopmental evidence⁵⁵ extensive neurodevelopmental evidence
Rico B et al. Control of axonal branching and synapse formation by focal adhesion kinase. Nat Neurosci, 2004 for FAK's role in circuit assembly. A comprehensive review of FAK in neuronal development⁶⁶ review of FAK in neuronal development
Navarro AI, Rico B. Focal adhesion kinase function in neuronal development. Curr Opin Neurobiol, 2014 characterizes it as the "orchestra conductor" of neuronal motility, integrating extracellular cues into the cytoskeletal decisions that determine where axons go and which synapses persist. RLS pathophysiology⁷⁷ RLS pathophysiology
Trenkwalder C, Paulus W. Restless legs syndrome: pathophysiology, clinical presentation and management. Nat Rev Neurol, 2010 is attributed to abnormal spinal somatosensory processing — a downstream consequence of the neural wiring decisions that FAK helps make during embryonic and early postnatal development.

Practical Actions

rs306960-T is a risk variant with a modest per-allele effect size. It does not predict that any individual will develop RLS, but it meaningfully shifts population-level probability and makes monitoring and early intervention worthwhile. RLS is highly treatable, and the sooner the diagnosis is recognized the better the outcome.

First-line treatment approaches address the two main modifiable pathophysiological factors⁸⁸ address the two main modifiable pathophysiological factors
Manconi M et al. Restless legs syndrome. Nat Rev Dis Primers, 2021: brain iron deficiency and dopaminergic dysfunction. Serum ferritin below 75 µg/L is a strong secondary driver of RLS symptoms, and intravenous iron infusion can produce dramatic, sustained symptom relief. When dopaminergic function is the primary driver, low-dose dopamine agonists or α2δ ligands are first-line pharmacotherapy.

The genetic variant itself (rs306960-T) reflects developmental wiring that cannot be reversed. However, understanding that your spinal sensorimotor circuits may have subtle developmental differences informs both monitoring strategy and the framing of risk: lifestyle factors that aggravate RLS (iron depletion, certain medications, late-evening heavy exercise) should be managed proactively in T allele carriers with any leg discomfort symptoms.

Interactions

PTK2 is not the only RLS-associated gene. The 2024 meta-analysis confirmed previously established loci at MEIS1, BTBD9, MAP2K5/SKOR1, and PTPRD, as well as novel loci including LMX1B (a transcription factor critical for spinal interneuron identity). These genes converge on spinal circuit development from different angles — MEIS1 through homeobox transcription, BTBD9 through iron homeostasis and synaptic vesicle recycling, PTPRD through axon guidance, and PTK2/FAK through cytoskeletal signaling. Individuals carrying multiple RLS risk alleles across these loci carry substantially higher cumulative risk than any single variant suggests.