rs11220465 — ST3GAL4 ST3GAL4 VWF/FVIII Modifier

ST3GAL4 rs11220465 — The Common Sialyltransferase Variant That Nudges Clotting Factor Levels

Every protein in your blood has a molecular expiration date stamped on its surface as a sugar code. Von Willebrand factor (VWF)¹¹ Von Willebrand factor (VWF)
A large multimeric glycoprotein that anchors platelets to damaged vessel walls and carries Factor VIII through the circulation; plasma level is a major determinant of clotting tendency and Factor VIII (FVIII)²² Factor VIII (FVIII)
The cofactor in the intrinsic coagulation pathway; the two molecules circulate as a non-covalent complex and their plasma levels are tightly correlated both carry a coating of sialic acid residues on their glycan chains. When these sialic acids are intact, the proteins circulate freely. When they are absent or reduced, galactose residues on the protein surface become exposed and the liver's asialoglycoprotein receptors (ASGPR) recognize them as disposal targets — pulling them out of circulation. The ST3GAL4 enzyme determines how thoroughly this protective sialic acid coat is applied. Variants in its first intron, including rs11220465, tune this activity up or down in ways that directly shift the steady-state plasma levels of VWF and FVIII.

The Mechanism

ST3GAL4 (ST3 beta-galactoside alpha-2,3-sialyltransferase 4)³³ ST3GAL4 (ST3 beta-galactoside alpha-2,3-sialyltransferase 4)
One of the six ST3GAL family enzymes; acts in the Golgi apparatus to transfer sialic acid onto galactose residues at the termini of N- and O-linked glycan chains is expressed in endothelial cells (where VWF is synthesized and secreted) and hepatocytes. rs11220465 is an intronic variant located in the first intron of the ST3GAL4 gene at chr11:126387884 (GRCh38). It does not alter the enzyme's amino acid sequence. Instead, it sits in a regulatory region that likely contains transcription factor binding sites — bioinformatic analysis of the region identifies multiple regulatory motifs whose affinity changes with the A allele. The downstream consequence is a modest shift in ST3GAL4 activity that alters how completely VWF and FVIII are sialylated before secretion.

The causal mouse model is compelling: Ellies et al. 2002⁴⁴ Ellies et al. 2002
Knockout mice lacking ST3Gal-IV have plasma VWF levels approximately 50% of normal; intravenous asialofetuin (which competes for ASGPR binding sites) restores VWF half-life, directly demonstrating that ASGPR-mediated clearance of under-sialylated VWF is the mechanism. In humans, the A allele at rs11220465 appears to reduce effective sialylation rather than eliminate it, producing a quantitatively milder but directionally consistent shift toward faster VWF/FVIII clearance and lower steady-state levels. This is the opposite direction from the rarer rs35257264 T allele (which increases sialylation and raises VWF/FVIII) — an important contrast since both variants act at the same locus via the same enzyme.

The Evidence

The definitive human genetic study is Song et al. 2016⁵⁵ Song et al. 2016
Analysis of 12,117 participants from the multi-ethnic Atherosclerosis Risk in Communities (ARIC) cohort; associations tested for 14 ST3GAL4 SNPs against VWF antigen and FVIII activity; adjustment for age, sex, BMI, hypertension, diabetes, ever-smoking status, and ABO blood group. Among three ST3GAL4 intronic SNPs associated with both VWF and FVIII, rs11220465 showed a VWF difference of approximately 10% between GG homozygotes (mean ~99% of normal) and AA homozygotes (mean ~109%), and was significantly associated with FVIII activity after full covariate adjustment (p=0.0002).

The VWF and FVIII association with VTE risk is well-documented in epidemiological data. Rietveld et al. 2019⁶⁶ Rietveld et al. 2019
Case-control study; 2,377 venous thrombosis cases and 2,940 controls; tested eight coagulation factors; VWF and FVIII showed by far the strongest associations with VTE among all factors tested found that VWF above the 99th percentile carries an OR of 24.0 (95% CI 15.3–37.3) for VTE, and FVIII an OR of 23.0 — the strongest associations among all coagulation factors studied. Edvardsen et al. 2021⁷⁷ Edvardsen et al. 2021
Prospective cohort with incident VTE events; dose-response analysis across quartiles; strongest association seen for unprovoked VTE and DVT found a dose-dependent VTE risk across VWF quartiles: highest vs. lowest quartile OR 1.45 overall (95% CI 1.03–2.03), rising to OR 2.74 (95% CI 1.66–4.54) for unprovoked VTE.

For rs11220465 specifically, the effect on VWF/FVIII is modest — roughly 5–10% per A allele at the population mean level — placing it solidly in the moderate rather than strong evidence tier for direct thrombosis risk prediction. The variant is nonetheless clinically informative as part of a cumulative VWF/FVIII risk picture, particularly when VWF or FVIII levels are elevated on direct measurement.

Practical Actions

Because the A allele's effect operates through quantitative elevation of VWF and FVIII, the most actionable step is to measure these proteins directly to determine whether your levels fall in a clinically elevated range. The ~10% shift seen between GG and AA homozygotes can combine with other factors — ABO blood type (non-O individuals already have ~25% higher VWF), oral contraceptive use, obesity, and age — to push total VWF into the range where VTE risk becomes clinically significant.

Co-inherited thrombophilic variants (Factor V Leiden rs6025, prothrombin G20210A rs1799963) act through mechanistically independent pathways and their effects are additive with VWF/FVIII elevation. If you also carry rs35257264 T allele (the rarer, sialylation-upregulating ST3GAL4 variant), both operate at the same locus but may show some non-additivity depending on haplotype structure.

Interactions

rs11220465 clusters within ~4 kb of rs2186717 and rs7928391 in the first intron of ST3GAL4 (Song et al. 2016). These three variants were identified as distinct signals — rs11220465 was not in perfect linkage disequilibrium with the other two, suggesting it may tag a partially independent regulatory element. The nearby rs35257264 (chr11:126426921) is a rarer variant (~2% MAF in Europeans) at a different intronic position with stronger per-allele effects and direct replication in VTE GWAS meta-analyses.

ABO blood type is the dominant genetic modifier of VWF levels; non-O blood groups inhibit VWF clearance through a separate mechanism and raise VWF approximately 25% above blood group O levels. The ST3GAL4 rs11220465 effect was confirmed independent of ABO in the Song et al. analysis, meaning both effects contribute additively to total VWF level.