Association of common candidate variants with vascular malformations and intracranial hemorrhage in hereditary hemorrhagic telangiectasia

BACKGROUND

Hereditary hemorrhagic telangiectasia (HHT) is caused by mutations in TGFβ/BMP9 pathway genes and characterized by vascular malformations (VM) including arteriovenous malformations (AVM) in lung, liver, and brain, which lead to severe complications including intracranial hemorrhage (ICH) from brain VM. The clinical heterogeneity of HHT suggests a role for genetic modifier effects. Common variants in loci that modify phenotype severity in Tgfb knockout mice were previously reported as associated with lung AVM in HHT. Common variants in candidate genes were reported as associated with sporadic brain AVM and/or ICH. We investigated whether these variants are associated with HHT organ VM or with ICH from brain VM in 752 Caucasian HHT patients enrolled by the Brian Vascular Malformation Consortium.

METHODS

We genotyped 11 candidate variants: four variants reported as associated with lung AVM in HHT (PTPN14 rs2936018, USH2A rs700024, ADAM17 rs12474540, rs10495565), and seven variants reported as associated with sporadic BAVM or ICH (APOE ε2, ANGPTL4 rs11672433, EPHB4 rs314308, IL6 rs1800795, IL1B rs1143627, ITGB8 rs10486391, TNFA rs361525). Association of genotype with any VM, lung AVM, liver VM, brain VM or brain VM ICH was evaluated by multivariate logistic regression adjusted for age, gender, and family clustering.

RESULTS

None of the 11 variants was significantly associated with any phenotype. There was a trend toward association of USH2A rs700024 with ICH (OR = 2.77, 95% CI = 1.13-6.80, p = .026).

CONCLUSION

We did not replicate previously reported associations with HHT lung AVM and variants in Tgfb modifier loci. We also did not find significant associations between variants reported in sporadic brain AVM and VM or ICH in HHT.

Genome-wide association study of sporadic brain arteriovenous malformations

BACKGROUND

The pathogenesis of sporadic brain arteriovenous malformations (BAVMs) remains unknown, but studies suggest a genetic component. We estimated the heritability of sporadic BAVM and performed a genome-wide association study (GWAS) to investigate association of common single nucleotide polymorphisms (SNPs) with risk of sporadic BAVM in the international, multicentre Genetics of Arteriovenous Malformation (GEN-AVM) consortium.

METHODS

The Caucasian discovery cohort included 515 BAVM cases and 1191 controls genotyped using Affymetrix genome-wide SNP arrays. Genotype data were imputed to 1000 Genomes Project data, and well-imputed SNPs (>0.01 minor allele frequency) were analysed for association with BAVM. 57 top BAVM-associated SNPs (51 SNPs with p<10(-05) or p<10(-04) in candidate pathway genes, and 6 candidate BAVM SNPs) were tested in a replication cohort including 608 BAVM cases and 744 controls.

RESULTS

The estimated heritability of BAVM was 17.6% (SE 8.9%, age and sex-adjusted p=0.015). None of the SNPs were significantly associated with BAVM in the replication cohort after correction for multiple testing. 6 SNPs had a nominal p<0.1 in the replication cohort and map to introns in EGFEM1P, SP4 and CDKAL1 or near JAG1 and BNC2. Of the 6 candidate SNPs, 2 in ACVRL1 and MMP3 had a nominal p<0.05 in the replication cohort.

CONCLUSIONS

We performed the first GWAS of sporadic BAVM in the largest BAVM cohort assembled to date. No GWAS SNPs were replicated, suggesting that common SNPs do not contribute strongly to BAVM susceptibility. However, heritability estimates suggest a modest but significant genetic contribution.

Abstract 50: Evaluation of Candidate Polymorphisms for Association With Brain Arteriovenous Malformations and Intracranial Hemorrhage in Hereditary Hemorrhagic Telangiectasia

Introduction: Brain arteriovenous malformations (AVM) are an important cause of intracranial hemorrhage (ICH) in young adults. Most are sporadic, but also occur in inherited diseases such as hereditary hemorrhagic telangiectasia (HHT). ICH presentation of brain AVM in both sporadic and HHT cases is a marker of high ICH risk. In order to investigate whether the same genetic modifiers influence sporadic and HHT brain AVM, we evaluated candidate genetic polymorphisms reported as associated with sporadic brain AVM, with ICH presentation or ICH during clinical course, in HHT patients.

Methods: We genotyped 8 polymorphisms ( APOE E2/3/4 [rs7412, rs429358], ANGPTL rs116724, EPHB4 rs314308, IL6 -174G>C [rs1800795], IL1B -31T>C [rs1143627], ITGB8 rs10486391, TNF -238G>A[rs361525]) in 753 Caucasian HHT patients enrolled by the Brian Vascular Malformation Consortium (BVMC). Genotypes were collapsed into risk allele carriers vs. other for analysis, as published for sporadic AVM. APOE E2/3/4 haplotypes were assigned based on genotypes of the 2 APOE polymorphisms. Association of genotype with phenotype was evaluated by multivariable logistic regression adjusted for age, gender and accounting for family clustering. We used a nominal significance threshold of p=0.05, requiring the same direction of effect as in sporadic brain AVM (odds ratio for risk genotype [OR]>1).

Results: Among 753 HHT patients, 155 (21%) had brain AVM, of whom 26 (17%) presented with ICH. Two additional brain AVM patients had ICH during follow-up. None of the 7 variants (6 single nucleotide polymorphisms and APOE haplotype) were significantly associated with brain AVM (OR=0.6-1.3), with ICH presentation of brain AVM (OR=0.4-1.9), or with any brain AVM ICH in HHT patients (OR=0.5-2.1).

Conclusions: Common genetic variants previously reported to be associated with sporadic brain AVM were not associated with brain AVM nor with ICH in the BVMC HHT cohort, suggesting different genetic modifiers may influence sporadic and HHT brain AVM. However, the number of ICH cases in the cohort is small, so the confidence intervals are wide and we cannot rule out clinically important associations. The BVMC is enrolling additional HHT patients to expand the cohort and increase power for association analyses.

Association between Venous Angioarchitectural Features of Sporadic Brain Arteriovenous Malformations and Intracranial Hemorrhage

BACKGROUND AND PURPOSE

Intracranial hemorrhage is the most serious outcome for brain arteriovenous malformations. This study examines associations between venous characteristics of these lesions and intracranial hemorrhage.

MATERIALS AND METHODS

Statistical analysis was performed on a prospectively maintained data base of brain AVMs evaluated at an academic medical center. DSA, CT, and MR imaging studies were evaluated to classify lesion side, drainage pattern, venous stenosis, number of draining veins, venous ectasia, and venous reflux. Logistic regression analyses were performed to identify the association of these angiographic features with intracranial hemorrhage of any age at initial presentation.

RESULTS

Exclusively deep drainage (OR, 3.42; 95% CI, 1.87-6.26; P < .001) and a single draining vein (OR, 1.98; 95% CI, 1.26-3.08; P = .002) were associated with hemorrhage, whereas venous ectasia (OR, 0.52; 95% CI, 0.34-0.78; P = .002) was inversely associated with hemorrhage.

CONCLUSIONS

Analysis of venous characteristics of brain AVMs may help determine their prognosis and thereby identify lesions most appropriate for treatment.

The ACVRL1 c.314-35A>G polymorphism is associated with organ vascular malformations in hereditary hemorrhagic telangiectasia patients with ENG mutations, but not in patients with ACVRL1 mutations

Hereditary hemorrhagic telangiectasia (HHT) is characterized by vascular malformations (VMs) and caused by mutations in TGFβ/BMP9 pathway genes, most commonly ENG or ACVRL1. Patients with HHT have diverse manifestations related to skin and mucosal telangiectases and organ VMs, including arteriovenous malformations (AVM). The clinical heterogeneity of HHT suggests a role for genetic modifiers. We hypothesized that the ACVRL1 c.314-35A>G and ENG c.207G>A polymorphisms, previously associated with sporadic brain AVM, are associated with organ VM in HHT. We genotyped these variants in 716 patients with HHT and evaluated association of genotype with presence of any organ VM, and specifically with brain VM, liver VM and pulmonary AVM, by multivariate logistic regression analyses stratified by HHT mutation. Among all patients with HHT, neither polymorphism was significantly associated with presence of any organ VM; ACVRL1 c.314-35A>G showed a trend toward association with pulmonary AVM (OR = 1.48, P = 0.062). ACVRL1 c.314-35A>G was significantly associated with any VM among patients with HHT with ENG (OR = 2.66, P = 0.022), but not ACVRL1 (OR = 0.79, P = 0.52) mutations. ACVRL1 c.314-35A>G was also associated with pulmonary AVM and liver VM among ENG mutation heterozygotes. There were no significant associations between ENG c.207G>A and any VM phenotype. These results suggest that common polymorphisms in HHT genes other than the mutated gene modulate phenotype severity of HHT disease, specifically presence of organ VM.

Abstract W P417: A Common Variant in a TGFβ Modifier Locus Is Associated with Intracranial Hemorrhage Presentation of Brain Arteriovenous Malformation in Hereditary Hemorrhagic Telangiectasia

Introduction: Hereditary hemorrhagic telangiectasia (HHT) is caused by mutations in TGFβ/BMP9 pathway genes, most commonly ENG or ALK1. HHT patients have arteriovenous malformations (AVM) in brain, lung and liver, leading to severe complications including intracranial hemorrhage (ICH) from brain AVM. ICH presentation of brain AVM in HHT is a marker of high ICH risk. The clinical heterogeneity of HHT suggests a potential role for genetic modifier effects. Common genetic variants in loci that modify phenotype severity in Tgfb knockout mice have been reported to be associated with pulmonary AVM in HHT. We sought to replicate these associations and investigate whether these variants are also associated with brain AVM and ICH presentation of brain AVM in HHT patients.

Methods: We genotyped 3 variants (PTPN14 rs2936018, USH2A rs700024 and ADAM17 rs10495565) in 665 Caucasian HHT patients enrolled by the Brian Vascular Malformation Consortium (BVMC). Association of genotype with pulmonary AVM, brain AVM and ICH presentation was evaluated by multivariate logistic regression adjusted for age, gender and family clustering, and also stratified by HHT mutation (ALK1 or ENG).

Results: Of 665 Caucasian HHT patients analyzed, 51% had pulmonary AVM and 20% had brain AVM, of whom 17% presented with ICH. None of the 3 SNPs was significantly associated with pulmonary or brain AVM. Among 130 brain AVM patients, USH2A rs700024 was associated with ICH presentation (OR=3.34, 95% CI=1.22-9.15, p=0.019). The effect size was similar in HHT patients with ALK1 and ENG mutations, but only reached statistical significance among the latter (OR=6.77, p=0.014).

Conclusions: A common variant in USH2A, rs700024, previously reported to be associated with pulmonary AVM in HHT, was associated with ICH presentation of brain AVM, but not with brain or pulmonary AVM, in the BVMC HHT cohort. Association of the same USH2A variant with different HHT severity phenotypes in different cohorts suggests that it may act as a genetic modifier of HHT phenotype severity in concert with other genetic and environmental factors. Once validated, such genetic modifiers may improve our understanding of the phenotypic heterogeneity of HHT and aid in ICH risk prediction in HHT brain AVM.

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 (TGFβ) 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.

Accumulation of multipotent progenitors with a basal differentiation bias during aging of human mammary epithelia

Women older than 50 years account for 75% of new breast cancer diagnoses, and the majority of these tumors are of a luminal subtype. Although age-associated changes, including endocrine profiles and alterations within the breast microenvironment, increase cancer risk, an understanding of the cellular and molecular mechanisms that underlies these observations is lacking. In this study, we generated a large collection of normal human mammary epithelial cell strains from women ages 16 to 91 years, derived from primary tissues, to investigate the molecular changes that occur in aging breast cells. We found that in finite lifespan cultured and uncultured epithelial cells, aging is associated with a reduction of myoepithelial cells and an increase in luminal cells that express keratin 14 and integrin-α6, a phenotype that is usually expressed exclusively in myoepithelial cells in women younger than 30 years. Changes to the luminal lineage resulted from age-dependent expansion of defective multipotent progenitors that gave rise to incompletely differentiated luminal or myoepithelial cells. The aging process therefore results in both a shift in the balance of luminal/myoepithelial lineages and to changes in the functional spectrum of multipotent progenitors, which together increase the potential for malignant transformation. Together, our findings provide a cellular basis to explain the observed vulnerability to breast cancer that increases with age.