rs1333040 — CDKN2B-AS1

The 9p21 Chromosome Region — Shared Genetic Risk Across Your Arteries

The chromosome 9p21.3 region is one of the most studied genetic risk loci in human disease, harboring the long non-coding RNA gene CDKN2B-AS1¹¹ long non-coding RNA gene CDKN2B-AS1
Also called ANRIL — antisense noncoding RNA in the INK4 locus. rs1333040 is an intronic variant within this gene that has been independently associated with two major forms of arterial disease: coronary artery disease (CAD) and intracranial aneurysm (IA). The fact that a single locus influences vascular disease across different arterial beds — coronary arteries in the heart and cerebral arteries in the brain — suggests a shared biological mechanism affecting arterial wall integrity and cell proliferation throughout the vascular system.

The Mechanism

CDKN2B-AS1 (ANRIL) is a regulatory RNA that controls expression of neighboring genes²² controls expression of neighboring genes
ANRIL recruits polycomb repressive complexes PRC1 and PRC2 to silence CDKN2A and CDKN2B, including the cell cycle inhibitors CDKN2A (p16) and CDKN2B (p15). The rs1333040-T risk allele is associated with altered ANRIL expression — Cunnington et al. found that 9p21 risk SNPs correlate with up to 2-fold changes in ANRIL transcript levels. This disrupts the normal regulation of vascular smooth muscle cell proliferation and arterial wall remodeling. Reduced expression of p16/p15 allows smooth muscle cells to proliferate more freely, contributing to both atherosclerotic plaque formation (CAD) and the focal arterial wall weakening that predisposes to aneurysm formation.

Critically, rs1333040 is located in a distinct region of the ANRIL gene (between introns 7 and 15) from the more well-known rs1333049 variant, and the two SNPs tag partly different regulatory elements and risk effects. The rs1333040-T risk allele appears particularly relevant to intracranial aneurysm pathophysiology³³ intracranial aneurysm pathophysiology
The T allele region of ANRIL may affect arterial wall matrix metalloproteinase activity and extracellular matrix remodeling, an arterial vulnerability mechanism distinct from atherosclerosis.

The Evidence

The strongest evidence for rs1333040 comes from intracranial aneurysm genetics. Hashikata et al. 2010⁴⁴ Hashikata et al. 2010
Stroke 2010; 96 familial IA subjects and 419 sporadic IA cases vs 408 controls confirmed that the T allele is associated with both familial IA (transmission disequilibrium test, p=0.002) and sporadic IA (OR 1.28; 95% CI 1.04–1.57). A larger analysis by Nakaoka et al. 2010⁵⁵ Nakaoka et al. 2010
Stroke 2010, Japanese population reported a per-allele OR of 1.43 (95% CI 1.24–1.66), with stronger effects at posterior communicating artery aneurysm sites (OR 1.69). A landmark meta-analysis of over 116,000 individuals⁶⁶ meta-analysis of over 116,000 individuals
Alg et al. Neurology 2013; 32,887 IA cases and 83,683 controls across 61 studies confirmed rs1333040 with a pooled OR of 1.24 (95% CI 1.20–1.29), among the most robustly replicated IA associations in the literature.

For coronary artery disease, multiple meta-analyses confirm the rs1333040 association. Hu et al. 2019⁷⁷ Hu et al. 2019
Bioscience Reports; meta-analysis of 19 studies on ANRIL polymorphisms and CAD found significant associations under dominant, recessive, and allelic models (all p<0.0001). Additionally, Fracassi et al. 2019⁸⁸ Fracassi et al. 2019
Eur Heart J Acute Cardiovasc Care; 133 STEMI patients found that TT homozygotes had significantly higher rates of coronary microvascular obstruction after myocardial infarction (p=0.03–0.04), a complication linked to worse outcomes.

Smoking substantially amplifies the 9p21 risk. Deka et al. 2010⁹⁹ Deka et al. 2010
Stroke; familial IA cohort demonstrated a multiplicative relationship between rs1333040 risk alleles and smoking for intracranial aneurysm risk — carriers who smoke face compounded vascular risk beyond either factor alone.

Practical Actions

The T allele at rs1333040 increases arterial disease risk through mechanisms related to vascular wall integrity and smooth muscle cell regulation. For TT homozygotes, the priority is protecting arterial health from all angles: controlling blood pressure is particularly critical because hypertension is the most potent modifiable risk factor for intracranial aneurysm rupture, and blood pressure control also directly reduces CAD events. Smoking cessation is urgent — the smoking-by-genotype interaction at this locus makes rs1333040 TT one of the clearest examples of gene-environment amplification in vascular disease.

A family history of intracranial aneurysm in first-degree relatives, combined with TT genotype, warrants discussion with a neurologist about screening brain imaging. The 9p21 locus also shows dietary modifiability: the prudent diet pattern (abundant vegetables, fruits, legumes) shown to attenuate 9p21-related CAD risk with sibling variants likely applies across 9p21, though direct diet-interaction studies for rs1333040 specifically are limited.

Interactions

rs1333040 is in partial linkage disequilibrium with other 9p21 variants including rs1333049 (the strongest CAD-associated variant at this locus) and rs4977574 and rs10757278. These variants tag partly distinct functional effects within ANRIL and may compound each other's influence. The rs1333040-T allele is particularly enriched in the intracranial aneurysm risk signature, while rs1333049-C and rs4977574-G are more heavily weighted toward coronary artery disease. Carriers of risk alleles at multiple 9p21 variants face cumulative arterial risk across the vascular system.