DNA Methylation and Ischemic Stroke Risk: An Epigenome-Wide Association Study.

BACKGROUND: Ischemic stroke (IS) risk heritability is partly explained by genetics. Other heritable factors, such as epigenetics, could explain an unknown proportion of the IS risk. The objective of this study is to evaluate DNA methylation association with IS using epigenome-wide association studies (EWAS). METHODS: We performed a two-stage EWAS comprising 1,156 subjects. Differentially methylated positions (DMPs) and differentially methylated regions (DMRs) were assessed using the Infinium 450K and EPIC BeadChip in the discovery cohort (252 IS and 43 controls). Significant DMPs were replicated in an independent cohort (618 IS and 243 controls). Stroke subtype associations were also evaluated. Differentially methylated cell-type (DMCT) was analyzed in the replicated CpG sites using EpiDISH. We additionally performed pathway enrichment analysis and causality analysis with Mendelian randomization for the replicated CpG sites. RESULTS: A total of 957 CpG sites were epigenome-wide-significant (p ≤ 10-7) in the discovery cohort, being CpG sites in the top signals (logFC = 0.058, p = 2.35 × 10-22; logFC = 0.035, p = 3.22 × 10-22, respectively). ZFHX3 and MAP3K1 were among the most significant DMRs. In addition, 697 CpG sites were replicated considering Bonferroni-corrected p-values (p < 5.22 × 10-5). All the replicated DMPs were associated with risk of cardioembolic, atherothrombotic, and undetermined stroke. The DMCT analysis demonstrated that the significant associations were driven by natural killer cells. The pathway enrichment analysis showed overrepresentation of genes belonging to certain pathways including oxidative stress. ZFHX3 and MAP3K1 methylation was causally associated with specific stroke-subtype risk. CONCLUSION: Specific DNA methylation pattern is causally associated with IS risk. These results could be useful for specifically predicting stroke occurrence and could potentially be evaluated as therapeutic targets.

Evolutionary diversification of the canonical Wnt signaling effector TCF/LEF in chordates.

Wnt signaling is essential during animal development and regeneration, but also plays an important role in diseases such as cancer and diabetes. The canonical Wnt signaling pathway is one of the most conserved signaling cascades in the animal kingdom, with the T-cell factor/lymphoid enhancer factor (TCF/LEF) proteins being the major mediators of Wnt/ß-catenin-regulated gene expression. In comparison with invertebrates, vertebrates possess a high diversity of TCF/LEF family genes, implicating this as a possible key change to Wnt signaling at the evolutionary origin of vertebrates. However, the precise nature of this diversification is only poorly understood. The aim of this study is to clarify orthology, paralogy, and isoform relationships within the TCF/LEF gene family within chordates via in silico comparative study of TCF/LEF gene structure, molecular phylogeny, and gene synteny. Our results support the notion that the four TCF/LEF paralog subfamilies in jawed vertebrates (gnathostomes) evolved via the two rounds of whole-genome duplications that occurred during early vertebrate evolution. Importantly, gene structure comparisons and synteny analysis of jawless vertebrate (cyclostome) TCFs suggest that a TCF7L2-like form of gene structure is a close proxy for the ancestral vertebrate structure. In conclusion, we propose a detailed evolutionary path based on a new pre-whole-genome duplication vertebrate TCF gene model. This ancestor gene model highlights the chordate and vertebrate innovations of TCF/LEF gene structure, providing the foundation for understanding the role of Wnt/ß-catenin signaling in vertebrate evolution.

Genome-wide transcriptome study in skin biopsies reveals an association of E2F4 with cadasil and cognitive impairment.

CADASIL is a small vessel disease caused by mutations in NOTCH3 that lead to an odd number of cysteines in the EGF-like repeat domain, causing protein misfolding and aggregation. The main symptoms are migraine, psychiatric disturbances, recurrent strokes and dementia, being executive function characteristically impaired. The molecular pathways altered by this receptor aggregation need to be studied further. A genome-wide transcriptome study (four cases paired with three healthy siblings) was carried out, in addition to a qRT-PCR for validation purposes (ten new cases and eight new controls). To study the expression profile by cell type of the significant mRNAs found, we performed an in situ hybridization (ISH) (nine cases and eight controls) and a research in the Single-nuclei Brain RNA-seq expression browser (SNBREB). Pathway analysis enrichment was carried out with Gene Ontology and Reactome. Neuropsychological tests were performed in five of the qRT-PCR cases. The two most significant differentially expressed mRNAs (BANP, p-value = 7.23 × 10-4 and PDCD6IP, p-value = 8.36 × 10-4) were selected for the validation study by qRT-PCR. Additionally, we selected two more mRNAs (CAMK2G, p-value = 4.52 × 10-3 and E2F4, p-value = 4.77 × 10-3) due to their association with ischemic neuronal death. E2F4 showed differential expression in the genome-wide transcriptome study and in the qRT-PCR (p = 1.23 × 10-3), and it was upregulated in CADASIL cases. Furthermore, higher E2F4 expression was associated with worse executive function (p = 2.04 × 10-2) and attention and information processing speed (IPS) (p = 8.73 × 10-2). In situ hibridization showed E2F4 expression in endothelial and vascular smooth vessel cells. In silico studies indicated that E2F4 is also expressed in brain endothelial cells. Among the most significant pathways analyzed, there was an enrichment of vascular development, cell adhesion and vesicular machinery terms and autophagy process. E2F4 is more highly expressed in the skin biopsy of CADASIL patients compared to controls, and its expression is present in endothelial cells and VSMCs. Further studies are needed to understand whether E2F4 could be useful as a biomarker, to monitor the disease or be used as a therapeutic target.

Early Neurological Change After Ischemic Stroke Is Associated With 90-Day Outcome.

BACKGROUND AND PURPOSE: Large-scale observational studies of acute ischemic stroke (AIS) promise to reveal mechanisms underlying cerebral ischemia. However, meaningful quantitative phenotypes attainable in large patient populations are needed. We characterize a dynamic metric of AIS instability, defined by change in National Institutes of Health Stroke Scale score (NIHSS) from baseline to 24 hours baseline to 24 hours (NIHSSbaseline - NIHSS24hours = ΔNIHSS6-24h), to examine its relevance to AIS mechanisms and long-term outcomes. METHODS: Patients with NIHSS prospectively recorded within 6 hours after onset and then 24 hours later were enrolled in the GENISIS study (Genetics of Early Neurological Instability After Ischemic Stroke). Stepwise linear regression determined variables that independently influenced ΔNIHSS6-24h. In a subcohort of tPA (alteplase)-treated patients with large vessel occlusion, the influence of early sustained recanalization and hemorrhagic transformation on ΔNIHSS6-24h was examined. Finally, the association of ΔNIHSS6-24h with 90-day favorable outcomes (modified Rankin Scale score 0-2) was assessed. Independent analysis was performed using data from the 2 NINDS-tPA stroke trials (National Institute of Neurological Disorders and Stroke rt-PA). RESULTS: For 2555 patients with AIS, median baseline NIHSS was 9 (interquartile range, 4-16), and median ΔNIHSS6-24h was 2 (interquartile range, 0-5). In a multivariable model, baseline NIHSS, tPA-treatment, age, glucose, site, and systolic blood pressure independently predicted ΔNIHSS6-24h (R2=0.15). In the large vessel occlusion subcohort, early sustained recanalization and hemorrhagic transformation increased the explained variance (R2=0.27), but much of the variance remained unexplained. ΔNIHSS6-24h had a significant and independent association with 90-day favorable outcome. For the subjects in the 2 NINDS-tPA trials, ΔNIHSS3-24h was similarly associated with 90-day outcomes. CONCLUSIONS: The dynamic phenotype, ΔNIHSS6-24h, captures both explained and unexplained mechanisms involved in AIS and is significantly and independently associated with long-term outcomes. Thus, ΔNIHSS6-24h promises to be an easily obtainable and meaningful quantitative phenotype for large-scale genomic studies of AIS.

DNA methylation of MMPs and TIMPs in atherothrombosis process in carotid plaques and blood tissues.

BACKGROUND AND PURPOSE: Polymorphisms and serum levels of Matrix Metalloproteinases (MMP) and Tissue Inhibitor of Metalloproteinases (TIMP) have been studied with regard to atheromatous plaques and ischemic stroke, while no studies of DNA methylation (DNAm) patterns of MMP or TIMP have been performed to that end. Here, we evaluate DNAm levels of the MMP and TIMP gene families in human carotid plaques and blood samples of atherothrombotic stroke patients. METHODS: We profiled the DNAm status of stable and ulcerated atherosclerotic plaques obtained as pair sets from three patients who underwent carotid endarterectomy surgery. We selected 415 CpG sites, mapping into MMPs and TIMPs genes for further study. Secondly, the statistically associated CpG sites were analyzed in blood samples from two separate atherothrombotic stroke cohorts (total sample size = 307), ischemic stroke-cohort 1 (ISC-1): 37 atherothrombotic patients and 6 controls, ischemic stroke-cohort 2 (ISC-2): 80 atherothrombotic patients and 184 controls. DNAm levels from plaque tissue and blood samples were evaluated using a high-density microarray Infinium, HumanMethylation450 BeadChip and Infinium MethylationEPIC BeadChip. RESULTS: Three CpG sites were statistically significantly associated with unstable plaque portions; cg02969624, q-value = 0.035 (TIMP2), and cg04316754, q-value = 0.037 (MMP24) were hypermethylated, while cg24211657 q-value = 0.035 (TIMP2) was hypomethylated. Association of cg04316754 (MMP24) methylation levels with atherothrombotic risk was also observed in blood tissue: ISC-1 p-values = 0.03, ISC-2 p-value = 1.9 × 10-04. CONCLUSIONS: The results suggest different DNAm status of MMP24 between stable and unstable atherothrombotic carotid plaques, and between atherothrombotic stroke and controls in blood samples.

Clinical Variables and Genetic Risk Factors Associated with the Acute Outcome of Ischemic Stroke: A Systematic Review.

Stroke is a complex disease and one of the main causes of morbidity and mortality among the adult population. A huge variety of factors is known to influence patient outcome, including demographic variables, comorbidities or genetics. In this review, we expound what is known about the influence of clinical variables and related genetic risk factors on ischemic stroke outcome, focusing on acute and subacute outcome (within 24 to 48 hours after stroke and until day 10, respectively), as they are the first indicators of stroke damage. We searched the PubMed data base for articles that investigated the interaction between clinical variables or genetic factors and acute or subacute stroke outcome. A total of 61 studies were finally included in this review. Regarding the data collected, the variables consistently associated with acute stroke outcome are: glucose levels, blood pressure, presence of atrial fibrillation, prior statin treatment, stroke severity, type of acute treatment performed, severe neurological complications, leukocyte levels, and genetic risk factors. Further research and international efforts are required in this field, which should include genome-wide association studies.

Genome-Wide Association Study of White Blood Cell Counts in Patients With Ischemic Stroke.

Background and Purpose- Immune cells play a key role in the first 24h poststroke (acute phase), being associated with stroke outcome. We aimed to find genetic risk factors associated with leukocyte counts during the acute phase of stroke. Methods- Ischemic stroke patients with leukocyte counts data during the first 24h were included. Genome-wide association study and gene expression studies were performed. Results- Our genome-wide association study, which included 2064 (Discovery) and 407 (Replication) patients, revealed a new locus (14q24.3) associated with leukocyte counts. After Joint analysis (n=2471) 5 more polymorphisms reached genome-wide significance (P<5×10-8). The 14q24.3 locus was associated with acute stroke outcome (rs112809786, P=0.036) and with ACOT1 and PTGR2 gene expression. Previous polymorphisms associated with leukocyte counts in general-population did not show any significance in our study. Conclusions- We have found the first locus associated with leukocyte counts in ischemic stroke, also associated with acute outcome. Genetic analysis of acute endophenotypes could be useful to find the genetic factors associated with stroke outcome. Our findings suggested a different modulation of immune cells in stroke compared with healthy conditions.

PATJ Low Frequency Variants Are Associated With Worse Ischemic Stroke Functional Outcome.

RATIONALE: Ischemic stroke is among the leading causes of adult disability. Part of the variability in functional outcome after stroke has been attributed to genetic factors but no locus has been consistently associated with stroke outcome. OBJECTIVE: Our aim was to identify genetic loci influencing the recovery process using accurate phenotyping to produce the largest GWAS (genome-wide association study) in ischemic stroke recovery to date. METHODS AND RESULTS: A 12-cohort, 2-phase (discovery-replication and joint) meta-analysis of GWAS included anterior-territory and previously independent ischemic stroke cases. Functional outcome was recorded using 3-month modified Rankin Scale. Analyses were adjusted for confounders such as discharge National Institutes of Health Stroke Scale. A gene-based burden test was performed. The discovery phase (n=1225) was followed by open (n=2482) and stringent joint-analyses (n=1791). Those cohorts with modified Rankin Scale recorded at time points other than 3-month or incomplete data on previous functional status were excluded in the stringent analyses. Novel variants in PATJ (Pals1-associated tight junction) gene were associated with worse functional outcome at 3-month after stroke. The top variant was rs76221407 (G allele, ß=0.40, P=1.70×10-9). CONCLUSIONS: Our results identify a set of common variants in PATJ gene associated with 3-month functional outcome at genome-wide significance level. Future studies should examine the role of PATJ in stroke recovery and consider stringent phenotyping to enrich the information captured to unveil additional stroke outcome loci.

Diatom bloom-derived biotoxins cause aberrant development and gene expression in the appendicularian chordate Oikopleura dioica.

Investigating environmental hazards than could affect appendicularians is of prime ecological interest because they are among the most abundant components of the mesozooplankton. This work shows that embryo development of the appendicularian Oikopleura dioica is compromised by diatom bloom-derived biotoxins, even at concentrations in the same range as those measured after blooms. Developmental gene expression analysis of biotoxin-treated embryos uncovers an aberrant golf ball-like phenotype affecting morphogenesis, midline convergence, and tail elongation. Biotoxins induce a rapid upregulation of defensome genes, and considerable delay and silencing of zygotic transcription of developmental genes. Upon a possible future intensification of blooms associated with ocean warming and acidification, our work puts an alert on the potential impact that an increase of biotoxins may have on marine food webs, and points to defensome genes as molecular biosensors that marine ecologists could use to monitor the genetic stress of natural populations exposed to microalgal blooms.

Coelimination and Survival in Gene Network Evolution: Dismantling the RA-Signaling in a Chordate.

The bloom of genomics is revealing gene loss as a pervasive evolutionary force generating genetic diversity that shapes the evolution of species. Outside bacteria and yeast, however, the understanding of the process of gene loss remains elusive, especially in the evolution of animal species. Here, using the dismantling of the retinoic acid metabolic gene network (RA-MGN) in the chordate Oikopleura dioica as a case study, we combine approaches of comparative genomics, phylogenetics, biochemistry, and developmental biology to investigate the mutational robustness associated to biased patterns of gene loss. We demonstrate the absence of alternative pathways for RA-synthesis in O. dioica, which suggests that gene losses of RA-MGN were not compensated by mutational robustness, but occurred in a scenario of regressive evolution. In addition, the lack of drastic phenotypic changes associated to the loss of RA-signaling provides an example of the inverse paradox of Evo-Devo. This work illustrates how the identification of patterns of gene coelimination-in our case five losses (Rdh10, Rdh16, Bco1, Aldh1a, and Cyp26)-is a useful strategy to recognize gene network modules associated to distinct functions. Our work also illustrates how the identification of survival genes helps to recognize neofunctionalization events and ancestral functions. Thus, the survival and extensive duplication of Cco and RdhE2 in O. dioica correlated with the acquisition of complex compartmentalization of expression domains in the digestive system and a process of enzymatic neofunctionalization of the Cco, while the surviving Aldh8 could be related to its ancestral housekeeping role against toxic aldehydes.

Oikopleura dioica culturing made easy: a low-cost facility for an emerging animal model in EvoDevo.

The genome sequencing and the development of RNAi knockdown technologies in the urochordate Oikopleura dioica are making this organism an attractive emergent model in the field of EvoDevo. To succeed as a new animal model, however, an organism needs to be easily and affordably cultured in the laboratory. Nowadays, there are only two facilities in the world capable to indefinitely maintain Oikopleura dioica, one in the SARS institute (Bergen, Norway) and the other in the Osaka University (Japan). Here, we describe the setup of a new facility in the University of Barcelona (Spain) in which we have modified previously published husbandry protocols to optimize the weekly production of thousands of embryos and hundreds of mature animals using the minimum amount of space, human resources, and technical equipment. This optimization includes novel protocols of cryopreservation and solid cultures for long-term maintenance of microalgal stocks-Chaetoceros calcitrans, Isochrysis sp., Rhinomonas reticulate, and Synechococcus sp.-needed for Oikopleura dioica feeding. Our culture system maintains partially inbred lines healthy with similar characteristics to wild animals, and it is easily expandable to satisfy on demand the needs of any laboratory that may wish to use Oikopleura dioica as a model organism.