rs12752133 — GBA

Intronic GBA variant associated with REM sleep behavior disorder via lysosomal autophagy impairment; the T allele confers OR=2.09 for RBD in the largest GWAS of this condition to date

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GBA rs12752133 — The Intronic Lysosomal Signal for REM Sleep Behavior Disorder

Deep inside your cells, lysosomes serve as the recycling centres responsible for breaking down worn-out proteins, lipids, and cellular debris. One enzyme is central to this process in neurons: glucocerebrosidase (GCase)11 glucocerebrosidase (GCase)
encoded by the GBA1 gene, GCase converts glucosylceramide into glucose and ceramide — a routine lysosomal step whose impairment has outsized consequences for brain health. GBA variants are already established as the strongest known genetic risk factor for Parkinson's disease, and rs12752133 represents an independent intronic signal at the same locus with a large, replicated effect on the earliest detectable stage of this disease spectrum: REM sleep behavior disorder (RBD).

RBD — in which people physically act out vivid dreams during REM sleep — is not merely a sleep disorder. It is now recognised as a prodromal synucleinopathy marker, typically preceding Parkinson's disease diagnosis by a decade or more. Identifying your genetic risk profile at the GBA locus while still in this pre-motor window is the most actionable time to intervene.

The Mechanism

rs12752133 is an intronic variant located 94 nucleotides downstream of exon 11 in GBA1, at chromosomal position chr1:155,235,587 (GRCh38). The GBA gene is transcribed from the minus strand, so the plus-strand C→T change corresponds to a G→A transition on the coding strand within intron 11.

Importantly, rs12752133 and the N409S coding variant (rs76763715) are independent signals at the GBA locus — they sit 256 bp apart and their risk contributions are statistically separable in GWAS analysis.

The Evidence

The clearest evidence for rs12752133 comes from the largest genome-wide association study of REM sleep behavior disorder conducted to date22 the largest genome-wide association study of REM sleep behavior disorder conducted to date
Krohn et al. Genome-wide association study of REM sleep behavior disorder identifies polygenic risk and brain expression effects. Nature Communications, 2022. This meta-analysis enrolled 2,843 RBD cases and 139,636 controls, identifying five genome-wide significant loci: SNCA, GBA, TMEM175, INPP5F, and SCARB2. At the GBA locus, rs12752133-T reached p=5×10⁻¹⁴ with an odds ratio of 2.09 (95% CI 1.73–2.54) — a very large effect size for a GWAS finding. The GBA and TMEM175 loci were notable for being shared across all three main synucleinopathies studied: isolated RBD, Parkinson's disease with probable RBD, and Parkinson's disease without RBD, suggesting a fundamental biological role in the synucleinopathy continuum.

The broader case for GBA as the most consequential Parkinson's disease risk gene was established by the landmark multicenter NEJM study33 the landmark multicenter NEJM study
Sidransky et al. Multicenter analysis of glucocerebrosidase mutations in Parkinson's disease. NEJM, 2009, which analyzed 5,691 PD patients and 4,898 controls across 16 international centers and found an overall OR of 5.43 for any GBA mutation. The Nalls et al. 2019 meta-analysis44 The Nalls et al. 2019 meta-analysis
Nalls et al. Identification of novel risk loci, causal insights, and heritable risk for Parkinson's disease. Lancet Neurology, 2019 — spanning 37,688 cases and 1.4 million controls — confirmed GBA as one of 78 replicated genomic regions, underscoring the locus's biological centrality to PD pathogenesis.

Practical Actions

For T-allele carriers, the GBA mechanism suggests three actionable priorities: supporting lysosomal function and GCase activity, monitoring for prodromal RBD before motor symptoms appear, and avoiding environmental neurotoxins that compound dopaminergic vulnerability. The ambroxol pharmacological chaperone approach — currently in Phase 2 clinical trials targeting GBA-related neurodegeneration — represents the most mechanistically direct intervention available. Ambroxol binds misfolded GCase in the endoplasmic reticulum, stabilising its conformation to increase lysosomal delivery and enzyme activity; preclinical and open-label human data confirm it increases GCase activity in GBA variant carriers.

Interactions

rs12752133 and the coding N409S variant (rs76763715) are independent signals at the GBA locus.

Within the broader synucleinopathy picture, GBA risk alleles interact with SNCA variants (rs356219, rs356182, rs2736990) — elevated alpha-synuclein from SNCA and impaired lysosomal clearance from GBA represent two independent drivers of Lewy body pathology converging on the same dopaminergic neuron population. The TMEM175 lysosomal potassium channel variant (rs76904798) is another locus identified in the same RBD GWAS that impairs lysosomal acidification — a second lysosomal mechanism compound action candidate alongside GBA.

Genotype Interpretations

What each possible genotype means for this variant.

CC No GBA Risk Allele Normal

Reference genotype at this GBA intronic variant — no elevated RBD or Parkinson's risk from this locus

You carry two copies of the C reference allele at rs12752133. This is the common genotype, present in approximately 96.6% of the general European population. You do not carry the T risk allele at this intronic GBA position, meaning this particular variant does not contribute to elevated risk for REM sleep behavior disorder or Parkinson's disease through this locus. Your lysosomal GCase regulation from this intronic position is expected to be typical.

TT Homozygous Risk High Risk

Two T risk alleles at this intronic GBA variant — substantially elevated risk for REM sleep behavior disorder and Parkinson's disease

With two T alleles at this intronic GBA locus, both copies of GBA1 carry the risk-associated variant.

The extremely low population frequency of TT (q²≈0.0003 in Europeans) means formal TT-specific odds ratios are not reliably estimable from existing GWAS data. For reference, CT carriers face OR=2.09 for RBD per allele; TT homozygotes likely face substantially higher risk, though confidence intervals would be very wide.

Given the rarity of TT, a high priority is verifying the genotype call quality in the raw sequencing data, and discussing with a clinical geneticist or movement disorders specialist whether further GBA gene sequencing (including coding variants) is warranted.

CT GBA Intronic Risk Carrier Carrier

One T risk allele at this intronic GBA variant — moderately elevated risk for REM sleep behavior disorder and Parkinson's disease

The T allele at rs12752133 lies 94 nucleotides into intron 11 of GBA1.

The OR of 2.09 from Krohn et al. 2022 is a large effect size for a common intronic GWAS variant. Because RBD is the earliest detectable clinical sign of the synucleinopathy continuum, identifying this risk while you are premotor allows the most impactful interventions: polysomnography to detect subclinical RBD, olfactory testing as a parallel prodromal marker, and strategies to support lysosomal GCase function.

If you also carry the GBA N409S coding variant (rs76763715-C), your combined GBA risk may be further elevated — see that variant's profile for details.