Diana Fulmer1,2, Katelynn Toomer2, Lilong Guo2, Kelsey Moore2, Janiece Glover2, Reece Moore2, Rebecca Stairley2, Glenn Lobo1,3, Xiaofeng Zuo1, Yujing Dang1, Yanhui Su1, Ben Fogelgren4, Patrick Gerard5, Dongjun Chung6, Mahyar Heydarpour7, Rupak Mukherjee8,9, Simon C Body10, Russell A Norris1,2, Joshua H Lipschutz1,11. 1. Departments of Medicine (D.F., G.L., X.Z., Y.D., Y.S., R.A.N., J.H.L.), Medical University of South Carolina, Charleston. 2. Regenerative Medicine and Cell Biology (D.F., K.T., L.G., K.M., J.G., R. Moore, R.S., R.A.N.), Medical University of South Carolina, Charleston. 3. Ophthalmology (G.L.), Medical University of South Carolina, Charleston. 4. Department of Anatomy, Biochemistry, and Physiology, University of Hawaii at Manoa, Honolulu (B.F.). 5. Department of Mathematical Sciences, Clemson University, SC (P.G.). 6. Public Health Sciences (D.C.), Medical University of South Carolina, Charleston. 7. Department of Anesthesiology, Brigham and Women's Hospital (M.H.), Harvard Medical School, Boston, MA. 8. Surgery (R. Mukherjee), Medical University of South Carolina, Charleston. 9. Departments of Research (R. Mukherjee), Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC. 10. Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center (S.C.B.), Harvard Medical School, Boston, MA. 11. Medicine (J.H.L.), Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC.
Abstract
BACKGROUND: Bicuspid aortic valve (BAV) disease is a congenital defect that affects 0.5% to 1.2% of the population and is associated with comorbidities including ascending aortic dilation and calcific aortic valve stenosis. To date, although a few causal genes have been identified, the genetic basis for the vast majority of BAV cases remains unknown, likely pointing to complex genetic heterogeneity underlying this phenotype. Identifying genetic pathways versus individual gene variants may provide an avenue for uncovering additional BAV causes and consequent comorbidities. METHODS: We performed genome-wide association Discovery and Replication Studies using cohorts of 2131 patients with BAV and 2728 control patients, respectively, which identified primary cilia genes as associated with the BAV phenotype. Genome-wide association study hits were prioritized based on P value and validated through in vivo loss of function and rescue experiments, 3-dimensional immunohistochemistry, histology, and morphometric analyses during aortic valve morphogenesis and in aged animals in multiple species. Consequences of these genetic perturbations on cilia-dependent pathways were analyzed by Western and immunohistochemistry analyses, and assessment of aortic valve and cardiac function were determined by echocardiography. RESULTS: Genome-wide association study hits revealed an association between BAV and genetic variation in human primary cilia. The most associated single-nucleotide polymorphisms were identified in or near genes that are important in regulating ciliogenesis through the exocyst, a shuttling complex that chaperones cilia cargo to the membrane. Genetic dismantling of the exocyst resulted in impaired ciliogenesis, disrupted ciliogenic signaling and a spectrum of cardiac defects in zebrafish, and aortic valve defects including BAV, valvular stenosis, and valvular calcification in murine models. CONCLUSIONS: These data support the exocyst as required for normal ciliogenesis during aortic valve morphogenesis and implicate disruption of ciliogenesis and its downstream pathways as contributory to BAV and associated comorbidities in humans.
BACKGROUND:Bicuspid aortic valve (BAV) disease is a congenital defect that affects 0.5% to 1.2% of the population and is associated with comorbidities including ascending aortic dilation and calcific aortic valve stenosis. To date, although a few causal genes have been identified, the genetic basis for the vast majority of BAV cases remains unknown, likely pointing to complex genetic heterogeneity underlying this phenotype. Identifying genetic pathways versus individual gene variants may provide an avenue for uncovering additional BAV causes and consequent comorbidities. METHODS: We performed genome-wide association Discovery and Replication Studies using cohorts of 2131 patients with BAV and 2728 control patients, respectively, which identified primary cilia genes as associated with the BAV phenotype. Genome-wide association study hits were prioritized based on P value and validated through in vivo loss of function and rescue experiments, 3-dimensional immunohistochemistry, histology, and morphometric analyses during aortic valve morphogenesis and in aged animals in multiple species. Consequences of these genetic perturbations on cilia-dependent pathways were analyzed by Western and immunohistochemistry analyses, and assessment of aortic valve and cardiac function were determined by echocardiography. RESULTS: Genome-wide association study hits revealed an association between BAV and genetic variation in human primary cilia. The most associated single-nucleotide polymorphisms were identified in or near genes that are important in regulating ciliogenesis through the exocyst, a shuttling complex that chaperones cilia cargo to the membrane. Genetic dismantling of the exocyst resulted in impaired ciliogenesis, disrupted ciliogenic signaling and a spectrum of cardiac defects in zebrafish, and aortic valve defects including BAV, valvular stenosis, and valvular calcification in murine models. CONCLUSIONS: These data support the exocyst as required for normal ciliogenesis during aortic valve morphogenesis and implicate disruption of ciliogenesis and its downstream pathways as contributory to BAV and associated comorbidities in humans.
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