rs10947690 — MDGA1 Leu61Pro

Missense variant in the inhibitory synapse regulator MDGA1 that impairs neuroligin-2/neurexin interaction, reducing GABAergic tone and increasing insomnia risk

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MDGA1 Leu61Pro — The Inhibitory Synapse Gate and Sleep

Deep sleep depends on the brain's ability to quiet itself. That quieting is controlled by GABAergic neurons11 GABAergic neurons
Inhibitory neurons that release gamma-aminobutyric acid (GABA), the brain's primary inhibitory neurotransmitter, to reduce neural excitability — and the precise assembly of their synapses is governed by a molecular handshake between two proteins: neuroligin-2 (NL2) and neurexin. MDGA1 (MAM Domain Containing Glycosylphosphatidylinositol Anchor 1) acts as a gatekeeper that regulates this handshake, and the rs10947690 Leu61Pro variant shifts the balance in a direction that weakens GABAergic signaling and, in large-scale human genetics studies, reliably increases the risk of chronic insomnia.

The Mechanism

Inhibitory synapses form when neuroligin-2 (on the postsynaptic membrane) binds to neurexin22 neurexin
A presynaptic adhesion protein that anchors the synapse and recruits the GABA release machinery on the sending neuron on the presynaptic side. MDGA1 binds NL2 through three contact interfaces and physically blocks the neurexin-binding site, preventing the trans-synaptic adhesion required for inhibitory synapse formation.

The 2017 crystal structure study33 2017 crystal structure study
Kim JA et al. Structural Insights into Modulation of Neurexin-Neuroligin Trans-synaptic Adhesion by MDGA1/Neuroligin-2 Complex. Neuron, 2017 showed that all three MDGA1-NL2 contact points are required for full suppression of synaptogenic activity, and that MDGA1 selectively targets NL2 (the inhibitory-synapse neuroligin) rather than NL1 (the excitatory-synapse neuroligin). This selectivity means MDGA1 is a dedicated brake on inhibitory circuit assembly.

The Leu61Pro substitution falls in the immunoglobulin domain 1 (Ig1) of MDGA1, one of the three contact interfaces. Proline introduces a rigid kink in the protein backbone that destabilizes the Ig1 fold. A structurally perturbed Ig1 domain has reduced affinity for NL2 — meaning the MDGA1 brake becomes hyperactive, or alternatively, the protein adopts an aberrant conformation that interferes with normal NL2 trafficking. Either outcome reduces functional inhibitory synapse density.

A 2025 study in the lateral habenula44 2025 study in the lateral habenula
Wang et al. Chronic stress induces depression through MDGA1-Neuroligin2 mediated suppression of inhibitory synapses in the lateral habenula. Theranostics, 2025 showed that elevated MDGA1-Nlgn2 interaction suppresses GABAergic synapse density; blocking this interaction increased inhibitory transmission and conferred resistance to stress-induced depressive behavior. This convergent evidence supports the model that rs10947690-G, by disrupting normal MDGA1 structure, perturbs the inhibitory synapse set-point in brain circuits regulating sleep and arousal.

The Evidence

The strongest evidence comes from two landmark 2019 GWAS studies published simultaneously in Nature Genetics.

Jansen et al. (2019)55 Jansen et al. (2019)
Jansen PR et al. Genome-wide analysis of insomnia in 1,331,010 individuals identifies new risk loci and functional pathways. Nature Genetics, 2019 — the largest insomnia GWAS to date — identified rs10947690-G as a genome-wide significant insomnia locus (OR 1.048, p = 4×10⁻¹²), with a sex-stratified female analysis also reaching significance (OR 1.049, p = 2×10⁻⁸). The 202 loci identified explained 2.6% of the variance in insomnia, with enrichment in striatal, hypothalamic, and claustrum neurons — all regions involved in sleep-wake regulation.

Lane et al. (2019)66 Lane et al. (2019)
Lane JM et al. Biological and clinical insights from genetics of insomnia symptoms. Nature Genetics, 2019 independently identified 57 insomnia loci across 453,379 UK Biobank participants and validation cohorts totaling over 160,000 additional individuals. Both studies found enrichment in ubiquitin-mediated proteolysis pathways and multiple brain region expression signatures consistent with the synaptic regulation hypothesis.

Watanabe et al. (2022)77 Watanabe et al. (2022)
Watanabe K et al. Genome-wide meta-analysis of insomnia prioritizes genes associated with metabolic and psychiatric pathways. Nature Genetics, 2022 extended the analysis to 2.4 million individuals, identifying 554 risk loci. Gene prioritization among 3,898 candidates highlighted synaptic signaling and neuronal differentiation as the primary functional pathways — consistent with MDGA1's role.

Hatcher et al. (2019)88 Hatcher et al. (2019)
Hatcher C et al. Leveraging brain cortex-derived molecular data to elucidate epigenetic and transcriptomic drivers of complex traits and disease. Translational Psychiatry, 2019 used Bayesian colocalization of prefrontal cortex gene expression, DNA methylation, and histone acetylation data with GWAS summary statistics, identifying MDGA1 as a novel locus where the same genetic variant influences both brain gene expression and insomnia susceptibility — strengthening the case for a functional, brain-expressed mechanism.

Practical Actions

GABAergic signaling tone can be supported through several nutritional strategies. Magnesium acts as an NMDA receptor antagonist and GABA modulator99 NMDA receptor antagonist and GABA modulator
Magnesium blocks NMDA (excitatory glutamate) receptors and potentiates GABA-A receptor activity, effectively supporting inhibitory tone and has demonstrated sleep improvements in controlled trials — specifically increasing slow-wave sleep and reducing nocturnal cortisol. Glycine, at 3 g before bed, activates NMDA receptors in the suprachiasmatic nucleus to promote sleep onset and has shown reductions in sleep fragmentation in human trials. Taurine potentiates GABA-A and GABA-B receptors and modulates inhibitory tone.

For rs10947690-G carriers, these interventions address the downstream consequence of reduced inhibitory synapse density: insufficient GABAergic tone at the point of sleep onset.

Interactions

MDGA1's role in GABAergic signaling connects it functionally to other sleep-related pathways. GABAergic tone interacts with cortisol rhythms (HPA axis variants like FKBP5, CRHR1) and with circadian regulation (CLOCK, CRY1, PER3 variants). Individuals carrying both MDGA1 Leu61Pro and circadian variants such as rs1801260 (CLOCK) or rs57875989 (CRY1) may experience compounding insomnia susceptibility from two independent pathways — reduced inhibitory synapse density from MDGA1 and disrupted circadian timing from clock gene variants. No published compound genotype data exist, but the pathway logic is robust.

Genotype Interpretations

What each possible genotype means for this variant.

AA Standard Inhibitory Tone Normal

Normal MDGA1 structure — typical GABAergic inhibitory synapse assembly

You carry two copies of the reference A allele, producing MDGA1 protein with an intact leucine-61 residue. Your MDGA1 Ig1 domain engages neuroligin-2 normally, maintaining typical inhibitory synapse formation and GABAergic tone in sleep-regulating brain circuits.

About 62% of people globally share this genotype, making it the most common. In European populations it is similarly predominant, and in East Asian populations it is found in more than 98% of individuals.

AG Reduced Inhibitory Synapse Function Intermediate

One Leu61Pro allele — moderately reduced GABAergic synaptic assembly

With one copy of Leu61Pro, the brain produces a mix of wild-type MDGA1 (from the A allele) and structurally perturbed MDGA1 (from the G allele). The proline substitution introduces a rigid kink in the Ig1 domain, altering the protein conformation at one of three contact interfaces with neuroligin-2.

The 2019 Jansen et al. Nature Genetics GWAS identified this locus at p = 4×10⁻¹² for insomnia, and the sex-stratified female analysis showed OR 1.049 (p = 2×10⁻⁸). The mechanistic basis — reduced inhibitory synapse density in arousal-regulating circuits — is supported by molecular studies showing that MDGA1 perturbation suppresses GABAergic synaptogenesis in lateral habenula and other sleep-relevant brain regions.

GG Low GABAergic Synapse Density High Risk

Two Leu61Pro alleles — substantially reduced inhibitory synapse assembly, elevated insomnia risk

With two copies of Leu61Pro, both MDGA1 proteins carry the proline kink in Ig1, eliminating the protective effect of the wild-type allele. The molecular consequence is a reduction in functional neuroligin-2/neurexin trans-synaptic complexes at GABAergic synapses, leading to sparser inhibitory connectivity in circuits regulating the transition from wakefulness to sleep.

Wang et al. (2025, Theranostics) showed that elevating MDGA1-Nlgn2 interaction suppresses GABAergic synapse density in the lateral habenula, a hub for aversion, arousal, and mood; blocking this interaction protected against stress-induced depression and related sleep disruption. Zeppillo et al. (2024, Communications Biology) showed that loss of MDGA1 ameliorates inhibitory synaptic dysfunction in Nlgn2 knockout models, confirming the tight functional coupling of these proteins.

The GG genotype also falls in the female-enriched insomnia signal (OR 1.049 at p = 2×10⁻⁸ in the sex-stratified GWAS), suggesting a possible interaction with sex hormone modulation of GABAergic systems.

CADD score of 28.8 for this missense variant indicates predicted functional impact well above the genome-wide median, placing it in the top ~1% of deleterious missense substitutions.