rs3889728 — AGT AGT Intronic Variant

AGT rs3889728 — A Blood-Pressure Gene Variant with Pregnancy Implications

The angiotensinogen gene (AGT) sits at the top of the renin-angiotensin-aldosterone system (RAAS), the body's primary hormonal axis for controlling blood pressure and fluid balance. Angiotensinogen is the sole precursor substrate for all angiotensin peptides¹¹ Angiotensinogen is the sole precursor substrate for all angiotensin peptides
renin cleaves AGT to produce angiotensin I, which ACE converts to the vasoconstrictor angiotensin II. During pregnancy, RAAS activity is tightly regulated: the system must expand blood volume to support the growing fetus while preventing excessive vasoconstriction that can compromise placental perfusion. When this balance fails, the result is gestational hypertension or preeclampsia — a condition affecting 3–5% of pregnancies and responsible for roughly 14% of maternal deaths worldwide.

The rs3889728 variant lies within an intron of AGT on chromosome 1 (GRCh38 position 230,713,085). The AGT gene runs on the minus strand, so the T allele in genome files corresponds to an A on the coding strand — the allele designation sometimes used in older papers. This variant has been incorporated into a diastolic blood pressure prediction model alongside two other SNPs (rs5193 and rs7305099) in a Han Chinese cohort study, suggesting it tags a regulatory region that modulates AGT expression or splicing in contexts relevant to blood pressure control.

The Mechanism

As an intron variant, rs3889728 does not alter the AGT protein directly. Its effect is likely mediated through a regulatory element²² regulatory element
intronic enhancers, silencers, or splice-branch-point sequences that influence how much mRNA is produced and how efficiently it is processed embedded within the intron. Elevated AGT levels (whether from coding variants or regulatory changes) increase angiotensin II production, raising vascular tone and sodium retention. In pregnancy, this has particular consequences: the maternal vascular system must dilate substantially to accommodate increased cardiac output, and any genetic factor that tips RAAS toward excess activation can impair the spiral artery remodeling that supplies the placenta.

The preeclampsia connection to AGT is well-established at the gene level. The most-studied AGT variant, M235T (rs699), encodes a threonine at position 235 that increases AGT plasma concentrations by approximately 20% in TT homozygotes compared to MM individuals. A large meta-analysis found TT homozygotes have approximately 61% higher odds of preeclampsia Lin et al. 2012, 31 studies, 2,555 cases³³ Lin et al. 2012, 31 studies, 2,555 cases
Angiotensinogen gene M235T and T174M polymorphisms and susceptibility of pre-eclampsia: a meta-analysis. Ann Hum Genet. The rs3889728 variant may influence AGT expression through a parallel intronic regulatory mechanism, making it a biologically plausible though less-studied contributor to this same pathway.

The Evidence

Direct evidence for rs3889728 specifically comes from a cross-sectional study of 965 Northern Han Chinese adults by Li et al. 2019⁴⁴ Li et al. 2019
A Prediction Model of Essential Hypertension Based on Genetic and Environmental Risk Factors in Northern Han Chinese. Int J Med Sci. The authors genotyped multiple candidate SNPs in RAAS genes and found that rs3889728, together with rs5193 and rs7305099, formed the genetic component of their best-performing diastolic blood pressure prediction model (AUC 0.817). The study does not report allele-specific odds ratios for rs3889728 in isolation, limiting the precision of individual-level risk estimates.

Broader evidence for RAAS gene variants in preeclampsia is substantial. A review of RAAS polymorphisms by Wang et al. 2023⁵⁵ Wang et al. 2023
Pertinence between risk of preeclampsia and RAAS gene polymorphisms. Pregnancy Hypertens found that AGT variants (particularly the 235T allele) and AT1R 1166C are among the most replicated genetic contributors to preeclampsia risk across diverse populations. A separate meta-analysis of 40 studies by Wang et al. 2020⁶⁶ Wang et al. 2020
Three polymorphisms of renin-angiotensin system and preeclampsia risk found AGT T704C (another intronic-region AGT variant) associated with preeclampsia in the dominant model (OR 1.33, 95% CI 1.12–1.59). The fact that multiple intronic and regulatory AGT variants show association with blood pressure outcomes makes it plausible that rs3889728 participates in the same regulatory landscape.

The T allele of rs3889728 is common globally (~25% in Europeans, ~55% in East Asians), making it a variant that tags a common haplotype rather than a rare pathogenic mutation. The evidence level is emerging: the variant is incorporated in one hypertension prediction model, sits in a gene with strong preeclampsia biology, but lacks its own dedicated preeclampsia association study or ClinVar entry.

Practical Actions

For women carrying one or two T alleles, the primary implications are during pregnancy. The RAAS context means that blood pressure monitoring during pregnancy is particularly important — early detection of gestational hypertension allows timely intervention before preeclampsia develops. Low-dose aspirin (81 mg/day from 12–16 weeks) is guideline-recommended for moderate-to-high-risk pregnancies and acts partly by improving placental perfusion and modulating RAAS-mediated vasoconstriction.

Outside pregnancy, the blood pressure relevance of rs3889728 may be modest but meaningful in the context of a RAAS genetic profile. Salt sensitivity and fluid balance are domains where RAAS gene variants cluster — higher sodium intake is associated with greater AGT pathway activation in genetically susceptible individuals.

Interactions

The most relevant interaction is with AT1R rs5186 (A1166C), the angiotensin II type 1 receptor gene variant. AGT produces angiotensin II; AT1R is where angiotensin II acts. Carrying risk alleles in both genes (elevated angiotensin II production from AGT variants and increased receptor sensitivity from AT1R 1166C) compounds the blood pressure effect and has been proposed as a particularly high-risk combination for preeclampsia in several case-control studies. See rs5186 for the AT1R profile. The NPR3 variant rs13154066 affects a complementary vasodilatory pathway (natriuretic peptide clearance); women carrying hypertension-risk alleles in both the RAAS (AGT, AT1R) and natriuretic peptide (NPR3) pathways face convergent pressure toward gestational blood pressure elevation.