Jiménez‐Conde, Jordi

Background: Intracerebral hemorrhage (ICH) is the stroke subtype with the worst prognosis and has no established acute treatment. ICH is classified as lobar and non-lobar based on the location of the hemorrhage, with genetic variation contributing to risk of both subtypes. We report the first genome wide association study (GWAS) of this condition. Methods: The discovery phase included GWAS data (Illumina 610 or Affymetrix 6.0) from 6 ICH studies that enrolled subjects of European ancestry in the US and Europe. Cases were classified as lobar or non-lobar ICH based on head CT. ICH-free controls were selected from ambulatory clinics or by random digit dialing. Standard quality controls filters were applied and principal component analysis was used to account for population structure. Unobserved genotypes were inferred by imputation to 1000 genomes references panels. Association testing was carried out using logistic regression, assuming additive effects, and including age, gender and principal components in the model. Meta-analyses were completed using the inverse normal method, weighting by sample size. Replication of signals with p<1x10E-6 was pursued in an independent multi-ethnic study utilizing direct genotyping. Results: The discovery phase included 1545 cases (664 lobar and 881 non-lobar) and 1481 controls, and tested 5,358,103 SNPs. Two loci were identified: for lobar ICH, an intergenic region located on chromosome 12q21.1 (rs11179580: minor allele frequency [MAF] 0.22, OR 1.54, 95% CI 1.33 - 1.84; p = 6.7x10E-8); and for non-lobar ICH, a region on chromosome 1q22 encompassing the PMF1 and SLC25A44 genes (rs2984613: MAF 0.31, OR 1.45, 95% CI 1.2 - 1.64; p = 8.9x10E-9). Replication included 1256 cases (329 whites, 506 blacks and 421 Hispanics) and 760 controls (237 whites, 346 blacks and 177 Hispanics) and confirmed both loci: 12q21.1 (p = 0.037, meta-analysis p = 2.3x10E-8) and 1q22 (p = 3.0x10E-4, meta-analysis p = 2.2x10E-11). Conclusions: Two new susceptibility loci for ICH were identified, both showing location-specificity. These results confirm the presence of biological heterogeneity across ICH subtypes and highlight that different genetic risk factors may contribute to the small vessel diseases that underlie each ICH subtype.

Introduction: Even though neuroinflammation is increasingly recognized as an essential contributor to ischemic brain injury, the exact underlying mechanisms remain unclear. Higher expression of the vascular cell adhesion molecule 1 (VCAM-1) increases leukocyte-brain endothelium interaction and has been associated with larger infarct size following acute ischemic stroke (AIS). The activation of the TGF-β signaling pathways can down-regulate VCAM-1 expression and ameliorate deleterious tissue outcome during neuroinflammation. Hypothesis: We sought to investigate whether genetic variation in the TGF-beta pathway and adhesion molecule genes is associated with acute stroke lesion size. Methods: We completed genome-wide association (GWA) testing and diffusion-weighted imaging lesion volume (DWIv) analysis in a discovery cohort of 532 AIS patients of European ancestry enrolled within 48 hours of symptom onset. An independent European ancestry cohort of 724 AIS patients with GWA data and automated DWIv served as replication cohort. GWA testing per SNP was performed using linear regression modeling of natural log-transformed DWIv adjusted for age, sex and relevant principal components. We selected 42 inflammatory genes in the TGF-beta pathway for a gene-based analysis using VEGAS (Versatile Gene-based -Association Study) software. A pre-specified discovery phase Bonferroni-corrected threshold was set at p<0.001. In the replication phase, 14 SNPs overlapping were tested at the Bonferroni-corrected p-value threshold of p<0.004. Results: Of all genes in the TGF-beta pathway, VCAM1 (p=0.0006) was significantly associated with DWIv in the discovery AIS cohort (age: 66 ± 14.9 years, sex: 63.4% male, DWIv: 2.2cm 3 (IQR: 0.6-11.7cm 3 )). A single SNP within the VCAM1 gene boundaries (rs3176876 (BETA=0.2341, p=0.003)) was significantly associated with DWIv in the replication AIS cohort (age: 65 ± 14.1 years, sex: 68.6% male, DWIv: 4cm 3 (IQR: 1.3-17.2cm 3 )). Conclusion: The genetic variant rs3176876 in the VCAM1 gene is associated with larger infarct lesion size measured on brain MRI of AIS patients. These findings suggest genetic contribution to the pro-inflammatory mechanisms in acute cerebral ischemia and warrant further investigation.