rs564398 — CDKN2B-AS1

ANRIL and the 9p21 Beta-Cell Clock

The region of chromosome 9 known as 9p21 harbors one of the most consistently replicated type 2 diabetes risk signals in the human genome. rs564398 sits within CDKN2B-AS1 (ANRIL)¹¹ CDKN2B-AS1 (ANRIL)
ANRIL stands for "antisense non-coding RNA in the INK4 locus" — a long non-coding RNA transcribed in the opposite direction from the CDKN2A and CDKN2B protein-coding genes at 9p21. lncRNAs regulate nearby gene expression through chromatin remodeling and other epigenetic mechanisms. — a long non-coding RNA that modulates expression of the adjacent tumor suppressor genes CDKN2A (p16) and CDKN2B (p15). These inhibitors act as brakes on cell division, and in pancreatic beta cells they control how readily the insulin-producing mass can renew itself.

rs564398 is a secondary signal at this locus, independent of but weaker than the primary variant rs10811661 (~200 kb away). The T risk allele carries a per-allele T2D odds ratio of approximately 1.08, compared to ~1.24 for the primary signal. Both act through the same broad mechanism — reducing glucose-stimulated beta-cell proliferative capacity — but may tag distinct regulatory elements within the locus.

The Mechanism

The 9p21 locus regulates how effectively pancreatic beta cells can replicate in response to metabolic demand. Unlike T2D variants that impair acute insulin secretion per cell (e.g., TCF7L2 or SLC30A8), rs564398 acts at the level of beta-cell mass maintenance²² beta-cell mass maintenance
Beta cells must periodically replace themselves as they age or are damaged by metabolic stress. The total number of functional beta cells declines over decades if renewal capacity is impaired, eventually reducing the pancreas's ability to secrete enough insulin..

A functional study by Kong et al. 2018³³ Kong et al. 2018
Kong Y et al. CDKN2A/B T2D Genome-Wide Association Study Risk SNPs Impact Locus Gene Expression and Proliferation in Human Islets. Diabetes 2018. PMID:29432124 measured BrdU incorporation (a direct index of cell division) in 43 human islet preparations cultured at high versus normal glucose concentrations. Islets carrying one or two T risk alleles at rs564398 showed significantly lower glucose-stimulated proliferation than CC homozygous islets — directly linking the variant to impaired beta-cell renewal under metabolic challenge. Notably, rs564398 did not alter expression of p14, p15, p16, or MTAP in islets, suggesting its mechanism operates through ANRIL at a regulatory level distinct from simple CDKN2A/B transcript abundance.

The Evidence

The T risk allele at rs564398 was first reported as a T2D susceptibility signal in the landmark WTCCC GWAS⁴⁴ WTCCC GWAS
Zeggini et al. Replication of genome-wide association signals in UK samples reveals risk loci for type 2 diabetes. Science 2007. PMID:17463249, where it reached genome-wide significance with OR 1.13 (95% CI 1.08–1.19, p = 1×10⁻⁶). This was one of the largest initial T2D GWAS, covering ~1,900 cases from the WTCCC plus replication in ~3,700 additional cases.

The Cugino et al. 2012 meta-analysis⁵⁵ Cugino et al. 2012 meta-analysis
Cugino et al. Type 2 diabetes and polymorphisms on chromosome 9p21: a meta-analysis. Nutr Metab Cardiovasc Dis 2012. PMID:21315566 of 22 chromosome 9p21 studies quantified the rs564398 signal at OR 1.08 (95% CI 1.05–1.12) with a population attributable risk of 6% — roughly half the PAR of the primary rs10811661 signal (15%). A further meta-analysis⁶⁶ further meta-analysis
Peng et al. The relationship between five widely-evaluated variants in CDKN2A/B and CDKAL1 genes and the risk of type 2 diabetes: a meta-analysis. Gene 2013. PMID:24012816 of 16 studies (20,029 cases, 24,419 controls) found a significant association in Caucasians (OR 1.19, p=0.012) but not in Asians (OR 1.01, p=0.868), with marked ethnic heterogeneity at this SNP.

The C allele frequency varies substantially across populations — ~41% in Europeans, ~34% globally, ~13% in East Asians, and ~7% in Africans. This population stratification mirrors the primary 9p21 signal and may partially explain the stronger T2D associations observed in European cohorts.

Practical Actions

Because the 9p21 locus reduces beta-cell renewal capacity rather than impairing acute insulin secretion, the relevant intervention strategy centers on reducing cumulative metabolic demand on a beta-cell pool that has limited ability to self-replenish. This means:

• Keeping postprandial glucose excursions small by choosing low-glycemic-load carbohydrates (legumes, lentils, non-starchy vegetables) reduces the secretory burden on each individual beta cell.
• Periodic fasting glucose and HbA1c monitoring allows detection of gradually declining beta-cell reserve before frank diabetes develops.
• Minimizing direct beta-cell stressors (excess fructose, saturated fat overload) is specifically relevant when renewal capacity is genetically constrained.

Interactions

rs564398 and the primary 9p21 SNP rs10811661 are approximately 104 kb apart and are not in complete linkage disequilibrium — they may represent independent regulatory signals within the locus. Carrying risk alleles at both SNPs could compound the impairment of beta-cell renewal through distinct regulatory elements within ANRIL and flanking chromatin.

Beyond the 9p21 locus, the 9p21 beta-cell mass signal acts through a mechanism completely distinct from the TCF7L2 pathway (rs7903146), which impairs incretin-stimulated insulin secretion per cell. Individuals carrying risk alleles at both loci face additive T2D susceptibility from two independent mechanisms: reduced beta-cell mass (9p21) and reduced per-cell insulin output (TCF7L2).

The ANRIL locus also carries well-established cardiovascular disease associations; rs564398 has been linked to coronary artery disease risk in a Turkish cohort, particularly in females, highlighting the pleiotropic role of this genomic region.