Somatic mosaicism in the MAPK pathway in sporadic brain arteriovenous malformation and association with phenotype.

OBJECTIVE: Sporadic brain arteriovenous malformation (BAVM) is a tangled vascular lesion characterized by direct artery-to-vein connections that can cause life-threatening intracerebral hemorrhage (ICH). Recently, somatic mutations in KRAS have been reported in sporadic BAVM, and mutations in other mitogen-activated protein kinase (MAPK) signaling pathway genes have been identified in other vascular malformations. The objectives of this study were to systematically evaluate somatic mutations in MAPK pathway genes in patients with sporadic BAVM lesions and to evaluate the association of somatic mutations with phenotypes of sporadic BAVM severity. METHODS: The authors performed whole-exome sequencing on paired lesion and blood DNA samples from 14 patients with sporadic BAVM, and 295 genes in the MAPK signaling pathway were evaluated to identify genes with somatic mutations in multiple patients with BAVM. Digital droplet polymerase chain reaction was used to validate KRAS G12V and G12D mutations and to assay an additional 56 BAVM samples. RESULTS: The authors identified a total of 24 candidate BAVM-associated somatic variants in 11 MAPK pathway genes. The previously identified KRAS G12V and G12D mutations were the only recurrent mutations. Overall, somatic KRAS G12V was present in 14.5% of BAVM lesions and G12D was present in 31.9%. The authors did not detect a significant association between the presence or allelic burden of KRAS mutation and three BAVM phenotypes: lesion size (maximum diameter), age at diagnosis, and age at ICH. CONCLUSIONS: The authors confirmed the high prevalence of somatic KRAS mutations in sporadic BAVM lesions and identified several candidate somatic variants in other MAPK pathway genes. These somatic variants may contribute to understanding of the etiology of sporadic BAVM and the clinical characteristics of patients with this condition.

Assessing the association of common genetic variants in EPHB4 and RASA1 with phenotype severity in familial cerebral cavernous malformation.

BACKGROUND: To investigate whether common variants in EPHB4 and RASA1 are associated with cerebral cavernous malformation (CCM) disease severity phenotypes, including intracranial hemorrhage (ICH), total and large lesion counts. METHODS: Familial CCM cases enrolled in the Brain Vascular Malformation Consortium were included (n = 338). Total lesions and large lesions (≥5 mm) were counted on MRI; clinical history of ICH at enrollment was assessed by medical records. Samples were genotyped on the Affymetrix Axiom Genome-Wide LAT1 Human Array. We tested the association of seven common variants (three in EPHB4 and four in RASA1) using multivariable logistic regression for ICH (odds ratio, OR) and multivariable linear regression for total and large lesion counts (proportional increase, PI), adjusting for age, sex, and three principal components. Significance was based on Bonferroni adjustment for multiple comparisons (0.05/7 variants = 0.007). RESULTS: EPHB4 variants were not significantly associated with CCM severity phenotypes. One RASA1 intronic variant (rs72783711 A>C) was significantly associated with ICH (OR = 1.82, 95% CI = 1.21-2.37, p = 0.004) and nominally associated with large lesion count (PI = 1.17, 95% CI = 1.03-1.32, p = 0.02). CONCLUSION: A common RASA1 variant may be associated with ICH and large lesion count in familial CCM. EPHB4 variants were not associated with any of the three CCM severity phenotypes.

Cyclo-oxygenase 2, a putative mediator of vessel remodeling, is expressed in the brain AVM vessels and associates with inflammation.

BACKGROUND: Brain arteriovenous malformations (bAVM) may rupture causing disability or death. BAVM vessels are characterized by abnormally high flow that in general triggers expansive vessel remodeling mediated by cyclo-oxygenase-2 (COX2), the target of non-steroidal anti-inflammatory drugs. We investigated whether COX2 is expressed in bAVMs and whether it associates with inflammation and haemorrhage in these lesions. METHODS: Tissue was obtained from surgery of 139 bAVMs and 21 normal Circle of Willis samples. The samples were studied with immunohistochemistry and real-time quantitative polymerase chain reaction (RT-PCR). Clinical data was collected from patient records. RESULTS: COX2 expression was found in 78% (109/139) of the bAVMs and localized to the vessels' lumen or medial layer in 70% (95/135) of the bAVMs. Receptors for prostaglandin E2, a COX2-derived mediator of vascular remodeling, were found in the endothelial and smooth muscle cells and perivascular inflammatory cells of bAVMs. COX2 was expressed by infiltrating inflammatory cells and correlated with the extent of inflammation (r = .231, p = .007, Spearman rank correlation). COX2 expression did not associate with haemorrhage. CONCLUSION: COX2 is induced in bAVMs, and possibly participates in the regulation of vessel wall remodelling and ongoing inflammation. Role of COX2 signalling in the pathobiology and clinical course of bAVMs merits further studies.

Cytochrome P450 and matrix metalloproteinase genetic modifiers of disease severity in Cerebral Cavernous Malformation type 1.

BACKGROUND: Familial Cerebral Cavernous Malformation type 1 (CCM1) is an autosomal dominant disease caused by mutations in the Krev Interaction Trapped 1 (KRIT1/CCM1) gene, and characterized by multiple brain lesions. CCM lesions manifest across a range of different phenotypes, including wide differences in lesion number, size and susceptibility to intracerebral hemorrhage (ICH). Oxidative stress plays an important role in cerebrovascular disease pathogenesis, raising the possibility that inter-individual variability in genes related to oxidative stress may contribute to the phenotypic differences observed in CCM1 disease. Here, we investigated whether candidate oxidative stress-related cytochrome P450 (CYP) and matrix metalloproteinase (MMP) genetic markers grouped by superfamilies, families or genes, or analyzed individually influence the severity of CCM1 disease. METHODS: Clinical assessment and cerebral susceptibility-weighted magnetic resonance imaging (SWI) were performed to determine total and large (≥5mm in diameter) lesion counts as well as ICH in 188 Hispanic CCM1 patients harboring the founder KRIT1/CCM1 'common Hispanic mutation' (CCM1-CHM). Samples were genotyped on the Affymetrix Axiom Genome-Wide LAT1 Human Array. We analyzed 1,122 genetic markers (both single nucleotide polymorphisms (SNPs) and insertion/deletions) grouped by CYP and MMP superfamily, family or gene for association with total or large lesion count and ICH adjusted for age at enrollment and gender. Genetic markers bearing the associations were then analyzed individually. RESULTS: The CYP superfamily showed a trend toward association with total lesion count (P=0.057) and large lesion count (P=0.088) in contrast to the MMP superfamily. The CYP4 and CYP8 families were associated with either large lesion count or total lesion count (P=0.014), and two other families (CYP46 and the MMP Stromelysins) were associated with ICH (P=0.011 and 0.007, respectively). CYP4F12 rs11085971, CYP8A1 rs5628, CYP46A1 rs10151332, and MMP3 rs117153070 single SNPs, mainly bearing the above-mentioned associations, were also individually associated with CCM1 disease severity. CONCLUSIONS: Overall, our candidate oxidative stress-related genetic markers set approach outlined CYP and MMP families and identified suggestive SNPs that may impact the severity of CCM1 disease, including the development of numerous and large CCM lesions and ICH. These novel genetic risk factors of prognostic value could serve as early objective predictors of disease outcome and might ultimately provide better options for disease prevention and treatment.

Polymorphisms in inflammatory and immune response genes associated with cerebral cavernous malformation type 1 severity.

BACKGROUND: Familial cerebral cavernous malformation type 1 (CCM1) is an autosomal dominant disease caused by mutations in the Krev Interaction Trapped 1 (KRIT1/CCM1) gene, and characterized by multiple brain lesions that often result in intracerebral hemorrhage (ICH), seizures, and neurological deficits. Carriers of the same genetic mutation can present with variable symptoms and severity of disease, suggesting the influence of modifier factors. Evidence is emerging that inflammation and immune response play a role in the pathogenesis of CCM. The purpose of this study was to investigate whether common variants in inflammatory and immune response genes influence the severity of familial CCM1 disease, as manifested by ICH and greater brain lesion count. METHODS: Hispanic CCM1 patients (n=188) harboring the founder Q455X 'common Hispanic mutation' (CHM) in the KRIT1 gene were analyzed at baseline. Participants were enrolled between June 2010 and March 2014 either through the Brain Vascular Malformation Consortium (BVMC) study or through the Angioma Alliance organization. Clinical assessment and cerebral susceptibility-weighted magnetic resonance imaging were performed to determine ICH as well as total and large (≥5 mm in diameter) lesion counts. Samples were genotyped on the Affymetrix Axiom Genome-Wide LAT1 Human Array. We analyzed 830 variants in 56 inflammatory and immune response genes for association with ICH and residuals of log-transformed total or large lesion count adjusted for age at enrollment and gender. Variants were analyzed individually or grouped by sub-pathways or whole pathways. RESULTS: At baseline, 30.3% of CCM1-CHM subjects had ICH, with a mean ± standard deviation (SD) of 60.1±115.0 (range 0-713) for total lesions and 4.9±8.7 (range 0-104) for large lesions. The heritability estimates explained by all autosomal variants were 0.20 (SE=0.31), 0.81 (SE=0.17), and 0.48 (SE=0.19), for ICH, total lesion count, and large lesion count, respectively. TGFBR2 rs9823731 was significantly associated with ICH as well as with the total and large lesion counts (p≤0.017). Further, IL-4 rs9327638, CD14 rs778588, IL-6R rs114660934 and MSR1 rs62489577 were associated with two markers of disease severity. Finally, the whole pathway was associated with total lesion count (p=0.005) with TLR-4 rs10759930, CD14 rs778588, IL-6R rs114660934 and IGH rs57767447 mainly bearing this association. Eicosanoid signaling, extracellular pattern recognition, and immune response sub-pathways were also associated with the total lesion count. CONCLUSIONS: These results suggest that polymorphisms in inflammatory and immune response pathways contribute to variability in CCM1 disease severity and might be used as predictors of disease severity. In particular, TGFBR2 rs9823731 was associated with all three markers of CCM1 disease severity tested, suggesting that TGFBR2 might be a key participant in the mechanism underlying CCM1 disease severity and phenotype variability. However, further longitudinal studies in larger sample sizes are needed to confirm these findings.

Expression quantitative trait loci and receptor pharmacology implicate Arg1 and the GABA-A receptor as therapeutic targets in neuroblastoma.

The development of targeted therapeutics for neuroblastoma, the third most common tumor in children, has been limited by a poor understanding of growth signaling mechanisms unique to the peripheral nerve precursors from which tumors arise. In this study, we combined genetics with gene-expression analysis in the peripheral sympathetic nervous system to implicate arginase 1 and GABA signaling in tumor formation in vivo. In human neuroblastoma cells, either blockade of ARG1 or benzodiazepine-mediated activation of GABA-A receptors induced apoptosis and inhibited mitogenic signaling through AKT and MAPK. These results suggest that ARG1 and GABA influence both neural development and neuroblastoma and that benzodiazepines in clinical use may have potential applications for neuroblastoma therapy.

Association of cardiovascular risk factors with disease severity in cerebral cavernous malformation type 1 subjects with the common Hispanic mutation.

BACKGROUND: Cerebral cavernous malformations (CCM) are enlarged vascular lesions affecting 0.1-0.5% of the population worldwide and causing hemorrhagic strokes, seizures, and neurological deficits. Familial CCM type 1 (CCM1) is an autosomal dominant disease caused by mutations in the Krev Interaction Trapped 1 (KRIT1/CCM1) gene, and is characterized by multiple brain lesions whose number and size increase with age. The number of lesions varies widely for unknown reasons, even among carriers of similar ages with the same mutation. The purpose of this study was to investigate whether cardiovascular (CV) risk factors influence potential markers of familial CCM1 disease severity, such as lesion count and history of intracerebral hemorrhage. METHODS: We analyzed baseline data from 185 Hispanic subjects, enrolled in the Brain Vascular Malformation Consortium study between June 2010 and March 2013. All subjects were carriers of the founder Q455X 'Common Hispanic Mutation' (CHM) in the KRIT1 gene, and had a clinical diagnosis of CCM or had an affected first- or second-degree relative with CCM. We performed a cross-sectional study, collecting detailed clinical information of CCM1-CHM subjects and cerebral susceptibility-weighted magnetic resonance imaging to assess lesion count. Linear or logistic regression analysis of log-lesion count or history of intracerebral hemorrhage and CV risk factors (age, gender, obesity, diabetes, hypertension, hyperlipidemia and smoking status) and related quantitative traits (body mass index, glycosylated hemoglobin levels, blood pressure, lipids levels and pack-years of cigarette smoking) was performed accommodating familial clustering. RESULTS: CCM1-CHM subjects were mainly female (63.8%) and symptomatic at presentation (63.2%). Lesion count was highly variable (mean ± SD: 57.7 ± 110.6; range: 0-713); 90% of CCM1-CHM subjects had multiple lesions at enrollment. Age (p < 0.001) was positively correlated with lesion count and male gender (p = 0.035) was associated with a greater number of lesions. Obesity (p = 0.001) and higher body mass index (p = 0.002) were associated with fewer lesions. No association with hypertension was detected, however, systolic blood pressure (p = 0.002) was associated with fewer lesions. No significant association with lesion count was observed for diabetes, hyperlipidemia, smoking status or for related quantitative traits. History of intracerebral hemorrhage was not significantly associated with any CV risk factors, however, we found borderline associations of hemorrhage with obesity (p = 0.062), systolic blood pressure (p = 0.083) and pack-years of cigarette smoking (p = 0.055). After correction for multiple testing, age and obesity remained significantly associated with lesion count in CCM1-CHM subjects. CONCLUSIONS: These results suggest that several CV risk factors explain some of the variability in lesion count in Hispanic CCM1-CHM subjects. Although age, gender, obesity, body mass index and systolic blood pressure may influence familial CCM1 disease severity, further longitudinal studies in larger sample sizes are essential to confirm these findings.

A genome-wide investigation of copy number variation in patients with sporadic brain arteriovenous malformation.

BACKGROUND: Brain arteriovenous malformations (BAVM) are clusters of abnormal blood vessels, with shunting of blood from the arterial to venous circulation and a high risk of rupture and intracranial hemorrhage. Most BAVMs are sporadic, but also occur in patients with Hereditary Hemorrhagic Telangiectasia, a Mendelian disorder caused by mutations in genes in the transforming growth factor beta (TGFß) signaling pathway. METHODS: To investigate whether copy number variations (CNVs) contribute to risk of sporadic BAVM, we performed a genome-wide association study in 371 sporadic BAVM cases and 563 healthy controls, all Caucasian. Cases and controls were genotyped using the Affymetrix 6.0 array. CNVs were called using the PennCNV and Birdsuite algorithms and analyzed via segment-based and gene-based approaches. Common and rare CNVs were evaluated for association with BAVM. RESULTS: A CNV region on 1p36.13, containing the neuroblastoma breakpoint family, member 1 gene (NBPF1), was significantly enriched with duplications in BAVM cases compared to controls (P = 2.2×10(-9)); NBPF1 was also significantly associated with BAVM in gene-based analysis using both PennCNV and Birdsuite. We experimentally validated the 1p36.13 duplication; however, the association did not replicate in an independent cohort of 184 sporadic BAVM cases and 182 controls (OR = 0.81, P = 0.8). Rare CNV analysis did not identify genes significantly associated with BAVM. CONCLUSION: We did not identify common CNVs associated with sporadic BAVM that replicated in an independent cohort. Replication in larger cohorts is required to elucidate the possible role of common or rare CNVs in BAVM pathogenesis.

Brain-derived neurotrophic factor Val66Met polymorphism predicts worse functional outcome after surgery in patients with unruptured brain arteriovenous malformation.

BACKGROUND AND PURPOSE: The Val66Met polymorphism of brain-derived neurotrophic factor is associated with decreased brain-derived neurotrophic factor secretion and poor outcome after acute neurological injury. We hypothesized that the Met allele is associated with worsening of functional outcome after brain arteriovenous malformation resection. METHODS: Three hundred forty-one surgically treated patients with brain arteriovenous malformation with outcome data were genotyped for Val66Met. Outcome was change in modified Rankin Scale preoperatively versus postoperatively, dichotomized into poor (change >0) or good outcome (change ≤0). Likelihood ratio tests for interactions and logistic regression analysis were performed. RESULTS: A significant interaction (P=0.03) of Val66Met genotype and hemorrhagic presentation existed; thus, ruptured and unruptured patients were considered separately. The Met allele was associated with increased risk of poor outcome among patients presenting unruptured (OR, 2.15; 95% CI, 1.02-4.55; P=0.045) but not ruptured (OR, 0.54; 95% CI, 0.19-1.53; P=0.25), adjusting for covariates. CONCLUSIONS: The Val66Met polymorphism is associated with worsened surgical outcome in patients with unruptured brain arteriovenous malformation, a group that currently has no good risk predictors. Further studies replicating these findings are needed.

Mitochondrial DNA sequence variation and risk of pancreatic cancer.

Although the mitochondrial genome exhibits high mutation rates, common mitochondrial DNA (mtDNA) variation has not been consistently associated with pancreatic cancer. Here, we comprehensively examined mitochondrial genomic variation by sequencing the mtDNA of participants (cases = 286, controls = 283) in a San Francisco Bay Area pancreatic cancer case-control study. Five common variants were associated with pancreatic cancer at nominal statistical significance (P < 0.05) with the strongest finding for mt5460g in the ND2 gene [OR = 3.9; 95% confidence interval (CI), 1.5-10; P = 0.004] which encodes an A331T substitution. Haplogroup K was nominally associated with reduced pancreatic cancer risk (OR = 0.32; 95% CI, 0.13-0.76; P = 0.01) when compared with the most common haplogroup, H. A total of 19 haplogroup-specific rare variants yielded nominal statistically significant associations (P < 0.05) with pancreatic cancer risk, with the majority observed in genes involved in oxidative phosphorylation. Weighted-sum statistics were used to identify an aggregate effect of variants in the 22 mitochondrial tRNAs on pancreatic cancer risk (P = 0.02). While the burden of singleton variants in the HV2 and 12S RNA regions was three times higher among European haplogroup N cases than controls, the prevalence of singleton variants in ND4 and ND5 was two to three times higher among African haplogroup L cases than in controls. Together, the results of this study provide evidence that aggregated common and rare variants and the accumulation of singleton variants are important contributors to pancreatic cancer risk.

Angiopoietin-like 4 (ANGPTL4) gene polymorphisms and risk of brain arteriovenous malformations.

BACKGROUND: Brain arteriovenous malformations (BAVM) are high-flow vascular lesions prone to intracranial hemorrhage (ICH). Abnormal angiogenesis is a key characteristic of BAVM tissue. Angiopoietin-like 4 (ANGPTL4), a secreted glycoprotein, is thought to be involved in angiogenesis and required for proper postnatal blood vessel partitioning. We investigated whether common single nucleotide polymorphisms (SNPs) in ANGPTL4 were associated with risk of BAVM or ICH. METHODS AND RESULTS: We conducted a case-control study of 216 Caucasian BAVM cases and 246 healthy controls, and a secondary case-only analysis, comparing 83 ruptured (ICH) with 133 unruptured BAVM cases at presentation. Four tagSNPs in ANGPTL4 captured variation over a 10-kb region (rs2278236, rs1044250, rs11672433, and rs1808536) and were tested for association with BAVM or ICH. The minor allele (A) of rs11672433 (exon 6, Pro389Pro) was associated with an increased risk of BAVM (p = 0.006), which persisted after adjusting for multiple comparisons (p = 0.03). After adjustments for age and sex, carriers of the minor allele (A) remained at higher risk for BAVM compared to noncarriers (odds ratio, OR = 1.56; 95% confidence interval, CI = 1.01-2.41; p = 0.046) and risk of BAVM was increased with increasing copy of the minor A allele (OR = 1.49, 95% CI = 1.03-2.15; p(trend) = 0.03). Five common haplotypes (frequency >1%) were inferred; overall haplotype distribution differed between BAVM cases and controls (χ(2) = 12.2, d.f. = 4, p = 0.02). Neither SNPs (p > 0.05) nor haplotype distribution (χ(2) = 1.1, d.f. = 4, p = 0.89) were associated with risk of ICH among BAVM cases. CONCLUSION: A synonymous SNP in ANGPTL4 and haplotypes carrying it are associated with risk of BAVM but not with ICH presentation in BAVM cases.

Differences in presentation and progression between severe FIC1 and BSEP deficiencies.

BACKGROUND & AIMS: Progressive familial intrahepatic cholestasis (PFIC) with normal serum levels of gamma-glutamyltranspeptidase can result from mutations in ATP8B1 (encoding familial intrahepatic cholestasis 1 [FIC1]) or ABCB11 (encoding bile salt export pump [BSEP]). We evaluated clinical and laboratory features of disease in patients diagnosed with PFIC, who carried mutations in ATP8B1 (FIC1 deficiency) or ABCB11 (BSEP deficiency). Our goal was to identify features that distinguish presentation and course of these two disorders, thus facilitating diagnosis and elucidating the differing consequences of ATP8B1 and ABCB11 mutations. METHODS: A retrospective multi-center study was conducted, using questionnaires and chart review. Available clinical and biochemical data from 145 PFIC patients with mutations in either ATP8B1 (61 "FIC1 patients") or ABCB11 (84 "BSEP patients") were evaluated. RESULTS: At presentation, serum aminotransferase and bile salt levels were higher in BSEP patients; serum alkaline phosphatase values were higher, and serum albumin values were lower, in FIC1 patients. Elevated white blood cell counts, and giant or multinucleate cells at liver biopsy, were more common in BSEP patients. BSEP patients more often had gallstones and portal hypertension. Diarrhea, pancreatic disease, rickets, pneumonia, abnormal sweat tests, hearing impairment, and poor growth were more common in FIC1 patients. Among BSEP patients, the course of disease was less rapidly progressive in patients bearing the D482G mutation. CONCLUSIONS: Severe forms of FIC1 and BSEP deficiency differed. BSEP patients manifested more severe hepatobiliary disease, while FIC1 patients showed greater evidence of extrahepatic disease.

Glucocorticoid receptor gene, low-grade inflammation, and heart failure: the Heart and Soul study.

CONTEXT: A common haplotype of the glucocorticoid receptor (GR) gene has been associated with increased susceptibility to coronary heart disease (CHD). Whether this haplotype predisposes to heart failure (HF) is unknown. OBJECTIVE: The objective of the study was to determine whether GR haplotype 3 is associated with HF and whether this association is explained by low-grade inflammation (C-reactive protein). DESIGN: In a prospective cohort study, participants were genotyped for common GR gene polymorphisms (ER22/23EK, BclI C/G, N363S, 9beta A/G). Haplotype analyses were conducted. SETTING: The study was conducted at one university medical center, two Veterans Affairs medical centers, and nine public health clinics. PATIENTS: Patients included 526 white outpatients with stable CHD. MAIN OUTCOME MEASURES: Echocardiographic evidence of ventricular dysfunction, self-reported heart failure, and subsequent hospitalization for heart failure were measured. RESULTS: After adjusting for age, sex, smoking, and body mass index, participants with two copies of haplotype 3 were more likely than those with 0 or 1 copy to report heart failure [hazard ratio (HR) 4.15, 95% confidence interval (CI) 1.5-11.3, P < 0.01], have systolic dysfunction (left ventricular ejection fraction <50%) (HR 3.0, 95% CI 0.9-9.9, P = 0.07), and be hospitalized for HF during a mean follow-up of 6 yr (HR 3.0, 95% CI 1.3-7.0, P = 0.01). These associations were attenuated after adjustment for higher C-reactive protein levels in patients with two copies of haplotype 3. CONCLUSIONS: We found that the GR gene haplotype 3 was associated with prevalent HF, systolic dysfunction, and subsequent HF hospitalization in patients with CHD. This association was partly mediated by low-grade inflammation.

Strain background modifies phenotypes in the ATP8B1-deficient mouse.

BACKGROUND: Mutations in ATP8B1 (FIC1) underlie cases of cholestatic disease, ranging from chronic and progressive (progressive familial intrahepatic cholestasis) to intermittent (benign recurrent intrahepatic cholestasis). The ATP8B1-deficient mouse serves as an animal model of human ATP8B1 deficiency. METHODOLOGY/PRINCIPAL FINDINGS: We investigated the effect of genetic background on phenotypes of ATP8B1-deficient and wild-type mice, using C57Bl/6 (B6), 129, and (B6-129) F1 strain backgrounds. B6 background resulted in greater abnormalities in ATP8B1-deficient mice than did 129 and/or F1 background. ATP8B1-deficient pups of B6 background gained less weight. In adult ATP8B1-deficient mice at baseline, those of B6 background had lower serum cholesterol levels, higher serum alkaline phosphatase levels, and larger livers. After challenge with cholate-supplemented diet, these mice exhibited higher serum alkaline phosphatase and bilirubin levels, greater weight loss and larger livers. ATP8B1-deficient phenotypes in mice of F1 and 129 backgrounds are usually similar, suggesting that susceptibility to manifestations of ATP8B1 deficiency may be recessive. We also detected differences in hepatobiliary phenotypes between wild-type mice of differing strains. CONCLUSIONS/SIGNIFICANCE: Our results indicate that the ATP8B1-deficient mouse in a B6 background may be a better model of human ATP8B1 deficiency and highlight the importance of informed background strain selection for mouse models of liver disease.

Reduced expression of integrin alphavbeta8 is associated with brain arteriovenous malformation pathogenesis.

Brain arteriovenous malformations (BAVMs) are a rare but potentially devastating hemorrhagic disease. Transforming growth factor-beta signaling is required for proper vessel development, and defective transforming growth factor-beta superfamily signaling has been implicated in BAVM pathogenesis. We hypothesized that expression of the transforming growth factor-beta activating integrin, alphavbeta8, is reduced in BAVMs and that decreased beta8 expression leads to defective neoangiogenesis. We determined that beta8 protein expression in perivascular astrocytes was reduced in human BAVM lesional tissue compared with controls and that the angiogenic response to focal vascular endothelial growth factor stimulation in adult mouse brains with local Cre-mediated deletion of itgb8 and smad4 led to vascular dysplasia in newly formed blood vessels. In addition, common genetic variants in ITGB8 were associated with BAVM susceptibility, and ITGB8 genotypes associated with increased risk of BAVMs correlated with decreased beta8 immunostaining in BAVM tissue. These three lines of evidence from human studies and a mouse model suggest that reduced expression of integrin beta8 may be involved in the pathogenesis of sporadic BAVMs.

Association of TGFBR2 polymorphism with risk of sudden cardiac arrest in patients with coronary artery disease.

BACKGROUND: Transforming growth factor ss (TGFss) signaling has been shown to promote myocardial fibrosis and remodeling with coronary artery disease (CAD), and previous studies show a major role for fibrosis in the initiation of malignant ventricular arrhythmias (VA) and sudden cardiac arrest (SCA). Common single nucleotide polymorphisms (SNPs) in TGFss pathway genes may be associated with SCA. OBJECTIVE: We examined the association of common SNPs among 12 candidate genes in the TGFss pathway with the risk of SCA. METHODS: SNPs (n = 617) were genotyped in a case-control study comparing 89 patients with CAD and SCA caused by VA to 520 healthy control subjects. RESULTS: Nineteen SNPs among 5 genes (TGFB2, TGFBR2, SMAD1, SMAD3, SMAD6) were associated with SCA after adjustment for age and sex. After permutation analysis to account for multiple testing, a single SNP in TGFBR2 (rs9838682) was associated with SCA (odds ratio: 1.66, 95% confidence interval: 1.08 to 2.54, P = .02). CONCLUSION: We show an association between a common TGFBR2 polymorphism and risk of SCA caused by VA in the setting of CAD. If validated, these findings support the role of genetic variation in TGFss signaling in SCA susceptibility.

EPHB4 gene polymorphisms and risk of intracranial hemorrhage in patients with brain arteriovenous malformations.

BACKGROUND: Brain arteriovenous malformations (BAVMs) are a tangle of abnormal vessels directly shunting blood from the arterial to venous circulation and an important cause of intracranial hemorrhage (ICH). EphB4 is involved in arterial-venous determination during embryogenesis; altered signaling could lead to vascular instability resulting in ICH. We investigated the association of single-nucleotide polymorphisms (SNPs) and haplotypes in EPHB4 with risk of ICH at clinical presentation in patients with BAVM. METHODS AND RESULTS: Eight haplotype-tagging SNPs spanning approximately 29 kb were tested for association with ICH presentation in 146 white patients with BAVM (phase I: 56 ICH, 90 non-ICH) using allelic, haplotypic, and principal components analysis. Associated SNPs were then genotyped in 102 additional cases (phase II: 37 ICH, 65 non-ICH), and data were combined for multivariable logistic regression. Minor alleles of 2 SNPs were associated with reduced risk of ICH presentation (rs314313_C, P=0.005; rs314308_T, P=0.0004). Overall, haplotypes were also significantly associated with ICH presentation (chi(2)=17.24, 6 df, P=0.008); 2 haplotypes containing the rs314308 T allele (GCCTGGGT, P=0.003; GTCTGGGC, P=0.036) were associated with reduced risk. In principal components analysis, 2 components explained 91% of the variance and complemented haplotype results by implicating 4 SNPs at the 5' end, including rs314308 and rs314313. These 2 SNPs were replicated in the phase II cohort, and combined data resulted in greater significance (rs314313, P=0.0007; rs314308, P=0.00008). SNP association with ICH presentation persisted after adjusting for age, sex, BAVM size, and deep venous drainage. CONCLUSIONS: EPHB4 polymorphisms are associated with risk of ICH presentation in patients with BAVM, warranting further study.

Association of common genetic variation in the insulin/IGF1 signaling pathway with human longevity.

The insulin/IGF1 signaling pathways affect lifespan in several model organisms, including worms, flies and mice. To investigate whether common genetic variation in this pathway influences lifespan in humans, we genotyped 291 common variants in 30 genes encoding proteins in the insulin/IGF1 signaling pathway in a cohort of elderly Caucasian women selected from the Study of Osteoporotic Fractures (SOF). The cohort included 293 long-lived cases (lifespan > or = 92 years (y), mean +/- standard deviation (SD) = 95.3 +/- 2.2y) and 603 average-lifespan controls (lifespan < or = 79y, mean = 75.7 +/- 2.6y). Variants were selected for genotyping using a haplotype-tagging approach. We found a modest excess of variants nominally associated with longevity. Nominally significant variants were then replicated in two additional Caucasian cohorts including both males and females: the Cardiovascular Health Study and Ashkenazi Jewish Centenarians. An intronic single nucleotide polymorphism in AKT1, rs3803304, was significantly associated with lifespan in a meta-analysis across the three cohorts (OR = 0.78 95%CI = 0.68-0.89, adjusted P = 0.043); two intronic single nucleotide polymorphisms in FOXO3A demonstrated a significant lifespan association among women only (rs1935949, OR = 1.35, 95%CI = 1.15-1.57, adjusted P = 0.0093). These results demonstrate that common variants in several genes in the insulin/IGF1 pathway are associated with human lifespan.

Inflammation and stress-related candidate genes, plasma interleukin-6 levels, and longevity in older adults.

Interleukin-6 (IL-6) is an inflammatory cytokine that influences the development of inflammatory and aging-related disorders and ultimately longevity. In order to study the influence of variants in genes that regulate inflammatory response on IL-6 levels and longevity, we screened a panel of 477 tag SNPs across 87 candidate genes in >5000 older participants from the population-based Cardiovascular Health Study (CHS). Baseline plasma IL-6 concentration was first confirmed as a strong predictor of all-cause mortality. Functional alleles of the IL6R and PARP1 genes were significantly associated with 15%-20% higher baseline IL-6 concentration per copy among CHS European-American (EA) participants (all p<10(-4)). In a case/control analysis nested within this EA cohort, the minor allele of PARP1 rs1805415 was nominally associated with decreased longevity (p=0.001), but there was no evidence of association between IL6R genotype and longevity. The PARP1 rs1805415--longevity association was subsequently replicated in one of two independent case/control studies. In a pooled analysis of all three studies, the "risk" of longevity associated with the minor allele of PARP1 rs1805415 was 0.79 (95%CI 0.62-1.02; p=0.07). These findings warrant further study of the potential role of PARP1 genotype in inflammatory and aging-related phenotypes.

Brain arteriovenous malformation biology relevant to hemorrhage and implication for therapeutic development.

Brain arteriovenous malformations cause intracranial hemorrhage. Molecular characterization of lesional tissue implicates angiogenic (vascular endothelial growth factor, ANG-2, matrix metalloproteinase-9) and inflammatory (cytokines and chemokines) pathways, but the pathogenesis remain obscure and medical therapy is lacking. Macrophage and neutrophil invasion has also been observed in the absence of prior intracranial hemorrhage. Common polymorphisms in interleukin-1beta and activin receptor-like kinase-1 are associated with arteriovenous malformation susceptibility, and polymorphisms in interleukin-1beta, interleukin-6, tumor necrosis factor-alpha and APOE are associated with arteriovenous malformation rupture. These observations suggest that even without a complete understanding of the determinants of arteriovenous malformation development, the recent discoveries of downstream derangements in vascular function and integrity may offer potential targets for therapy development. Furthermore, biomarkers can be established for assessing intracranial hemorrhage risk. Finally, these data will aid in development of model systems for mechanistic testing by development of surrogate phenotypes (microvascular dysplasia) and/or models recapitulating the clinical syndrome of recurrent spontaneous intracranial hemorrhage.