Genetic basis of the circle of Willis characteristics in the healthy and intracranial aneurysm population.

Rupture of an intracranial aneurysm (IA) can result in aneurysmal subarachnoid hemorrhage (ASAH), a severe and often fatal form of stroke. The configuration of the intracranial arteries - collectively known as the circle of Willis (CoW) - influences the risk of IA development and rupture. Although CoW variation is known to be heritable, its genetic underpinnings and contribution to IA remain poorly understood. Here, we aimed to investigate the genetic architecture of CoW variation and its potential link with IA. Using a semi-automated detection tool, we characterized the diameters, bifurcation angles, and presence of arterial segments of the CoW in 1078 participants from a population-based cohort and 682 IA patients. Composite traits capturing variation in all CoW characteristics were generated through principal component analysis. We conducted a genome-wide association study (GWAS) on these composite traits and identified four loci with suggestively significant associations. Lead single-nucleotide polymorphisms (SNPs) were located in or near the genes DPYSL2, CSMD3, TRPC6, and PKD1L2. Notably, PKD1L2 is closely related to PKD1, a gene implicated in autosomal dominant polycystic kidney disease, a connective tissue disorder that increases IA susceptibility. We observed statistically significant SNP-based heritability for the second principal component of CoW variation (heritability estimate = 0.95, standard error = 0.25). All lead SNPs demonstrated nominal association (p < 0.05) with multiple CoW characteristics and other vascular traits. Our findings highlight a substantial genetic contribution to CoW morphology and offer new insights into the molecular mechanisms underlying CoW variation and its role in IA pathogenesis.