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Published on: June 18, 2021
ANGPT1 methylation and delayed cerebral ischemia in aneurysmal subarachnoid hemorrhage patients
Dongjing Liu1, Annie I Arockiaraj2, John R Shaffer2,3
1Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
Insights
This study investigated DNA methylation in delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (aSAH). Results did not consistently link ANGPT1 methylation to DCI risk, suggesting further research in larger cohorts is needed.
Area of Science:
- Neuroscience
- Genetics
- Epigenetics
Background:
- Delayed cerebral ischemia (DCI) is a significant cause of mortality and disability following aneurysmal subarachnoid hemorrhage (aSAH).
- Understanding DCI pathogenesis, risk factors, and biomarkers is crucial for early detection and improved patient outcomes.
- DNA methylation's role in DCI risk was investigated using epigenome-wide association studies (EWAS).
Purpose of the Study:
- To explore the association between DNA methylation patterns and the risk of developing delayed cerebral ischemia (DCI) in patients with aneurysmal subarachnoid hemorrhage (aSAH).
- To identify potential DNA methylation biomarkers for early DCI detection and prognosis.
Main Methods:
- An epigenome-wide association study (EWAS) was conducted on 68 patients within 48 hours of aSAH, analyzing DNA methylation at approximately 450,000 CpG sites.
- A replication cohort of 175 patients was used to validate findings for top CpG sites identified in the discovery phase.
- Blood samples were collected for DNA methylation profiling.
Main Results:
- No epigenome-wide significant CpGs were identified in the discovery EWAS.
- The top signal, cg18031596, associated with the ANGPT1 gene, showed mixed results in the replication cohort, with some CpG sites passing Bonferroni correction but others showing opposite effect directions.
- Pooled analysis indicated a potential association, but the replication attempt failed to demonstrate a consistent effect of ANGPT1 methylation on DCI risk.
Conclusions:
- The study did not establish a significant and consistent link between ANGPT1 methylation and DCI risk across two cohorts.
- Despite the failure to replicate, the functional relevance of ANGPT1 warrants further investigation in larger aSAH cohorts.
- Future research with larger sample sizes is recommended to definitively determine the role of ANGPT1 methylation in DCI occurrence.
Background:
Delayed cerebral ischemia (DCI) is a common secondary complication and an important cause of disability and mortality among patients who survive aneurysmal subarachnoid hemorrhage (aSAH). Knowledge on DCI pathogenesis, risk factors, and biomarkers are essential for early detection and improved prognosis. To investigate the role of DNA methylation in DCI risk, we conducted an epigenome-wide association study (EWAS) in 68 patients followed up to 1 year after the initial aneurysm rupture. Blood samples were collected within 48 h post hemorrhage and used for DNA methylation profiling at ~ 450k CpG sites. A separate cohort of 175 patients was sequenced for the top CpG sites from the discovery analysis for a replication of the EWAS findings.
Results:
EWAS did not identify any epigenome-wide significant CpGs. The top signal, cg18031596, was annotated to ANGPT1, a gene with critical functions in angiogenesis after vascular injury. Post hoc power calculations indicated a well-powered discovery analysis for cg18031596. Analysis of the replication cohort showed that four out of the five CpG sites sequenced at the ANGPT1 locus passed a Bonferroni-adjusted significance threshold. In a pooled analysis of the entire sample, three out of five yielded a significant p-value, and the top association signal (p-value = 0.004) was seen for a CpG that was not originally measured in the discovery EWAS. However, four ANGPT1 CpG sites had an opposite effect direction in the replication analysis compared to the discovery EWAS, marking a failure of replication. We carefully examined this observed flip in directions and propose several possible explanations in addition to that it was a random chance that ANGPT1 ranked at the top in the discovery EWAS.
Conclusions:
We failed to demonstrate a significant and consistent effect of ANGPT1 methylation in DCI risk in two cohorts. Though the replication attempt to weaken the overall support of this gene, given its relevant function and top rank of significance in the EWAS, our results call for future studies of larger aSAH cohorts to determine its relevance for the occurrence of DCI.
