The John Ritter Research Program got off to a great start this year. Two months into 2016, the group has already published new research identifying two new genes for aortic disease. Your contributions to support the research program are instrumental in making this rapid pace of research possible. A brief description of these papers follows.
1. FOXE3 mutations predispose to thoracic aortic aneurysms and dissections.
Published in: The Journal of Clinical Investigation. 2016 Feb 8. pii: 83778. doi: 10.1172/JCI83778. [Epub ahead of print]
Kuang SQ, Medina-Martinez O, Guo DC, Gong L, Regalado ES, Reynolds CL, Boileau C, Jondeau G, Prakash SK, Kwartler CS, Zhu LY, Peters AM, Duan XY, Bamshad MJ, Shendure J, Nickerson DA, Santos-Cortez RL, Dong X, Leal SM, Majesky MW, Swindell EC, Jamrich M, Milewicz DM.
The ascending thoracic aorta is designed to withstand biomechanical forces from pulsatile blood. Thoracic aortic aneurysms and acute aortic dissections (TAADs) occur as a result of genetically triggered defects in aortic structure and a dysfunctional response to these forces. Here, we describe mutations in the forkhead transcription factor FOXE3 that predispose mutation-bearing individuals to TAAD. We performed exome sequencing of a large family with multiple members with TAADs and identified a rare variant in FOXE3 with an altered amino acid in the DNA-binding domain (p.Asp153His) that segregated with disease in this family. Additional pathogenic FOXE3 variants were identified in unrelated TAAD families. In mice, Foxe3 deficiency reduced smooth muscle cell (SMC) density and impaired SMC differentiation in the ascending aorta. Foxe3 expression was induced in aortic SMCs after transverse aortic constriction, and Foxe3 deficiency increased SMC apoptosis and ascending aortic rupture with increased aortic pressure. These phenotypes were rescued by inhibiting p53 activity, either by administration of a p53 inhibitor (pifithrin-α), or by crossing Foxe3-/- mice with p53-/- mice. Our data demonstrate that FOXE3 mutations lead to a reduced number of aortic SMCs during development and increased SMC apoptosis in the ascending aorta in response to increased biomechanical forces, thus defining an additional molecular pathway that leads to familial thoracic aortic disease.
2. LOX Mutations Predispose to Thoracic Aortic Aneurysms and Dissections.
Published in: Circulation Research. 2016 Jan 12. pii: CIRCRESAHA.115.307130. [Epub ahead of print]
Guo D, Regalado ES, Gong L, Duan X, Santos-Cortez RL, Arnaud P, Ren Z, Cai B, Hostetler EM, Moran R, Liang D, Estrera AL, Safi HJ, Leal SM, Bamshad MJ, Shendure J, Nickerson DA, Jondeau G, Boileau C, Milewicz DM.
RATIONALE: Mutations in several genes have been identified that are responsible for approximately 25% of families with familial thoracic aortic aneurysms and dissections (TAAD). However, the causative gene remains unknown in 75% of families.
OBJECTIVE: To identify the causative mutation in families with autosomal dominant inheritance of TAAD.
METHODS AND RESULTS: Exome sequencing was used to identify the mutation responsible for a large family with TAAD. A heterozygous rare variant, c.839G>T (p.Ser280Arg), was identified in LOX, encoding a lysyl oxidase, that segregated with disease in the family. Sanger and exome sequencing was performed to investigate mutations in candidate genes in an additional 410 probands from unrelated families. Additional LOX rare variants that segregated with disease in families were identified, including c.125G>A (p.Trp42*), c.604G>T (p.Gly202*), c.743C>T (p.Thr248Ile), c.800A>C (p.Gln267Pro), and c.1044T>A (p.Ser348Arg). The altered amino acids cause haploinsufficiency for LOX or are located at a highly conserved LOX catalytic domain, which is relatively invariant in the population. Expression of the LOX variants p.Ser280Arg and p.Ser348Arg had significantly lower lysyl oxidase activity when compared with the wild type protein. Individuals with LOX variants had fusiform enlargement of the root and ascending thoracic aorta, leading to ascending aortic dissections.
CONCLUSIONS: These data, along with previous studies showing the deficiency of LOX in mice or inhibition of lysyl oxidases in turkeys and rats causes aortic dissections, support the conclusion that rare genetic variants in LOX predispose to thoracic aortic disease.
ACTA2 mutations are responsible for disease in approximately 20% of families with thoracic aortic aneurysms and dissections(TAAD). Dr. Milewicz directs the John Ritter Research Program and her research group identified ACTA2 as a gene that causes TAAD in 2009. The Milewicz group has now published an analysis of clinical data collected from a large group of people (close to 300) who have ACTA2 mutations. This information is important in medical management of patients with ACTA2 mutations. The publication can be accessed by clicking on the article “Aortic Disease Presentation and Outcome Associated with ACTA2 Mutations” available here.
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Your generosity helps us support families with aortic disease, identify new genes and pathways that cause this condition, and develop guidelines to improve the survival of patients. This year your support helped researchers from the John Ritter Research Program publish a total of 21 papers in peer reviewed journals, listed below. Thank you for your support.
1. MFAP5 Loss‐of‐Function Mutations Underscore the Involvement of Matrix Alteration in the Pathogenesis of Familial Thoracic Aortic Aneurysms and Dissections. Am J Hum Genet. 2014 Dec 4;95(6):736‐43.
2. Myh11(R247C/R247C) mutations increase thoracic aorta vulnerability to intramural damage despite a general biomechanical adaptivity. J Biomech. 2014 Nov 1. pii: S0021‐9290(14)00552‐1.
3. RNF213 rare variants in an ethnically diverse population with Moyamoya disease. Stroke. 2014 Nov;45(11):3200‐7.
4. Use of genetics for personalized management of heritable thoracic aortic disease: How do we get there? J Thorac Cardiovasc Surg.2014 Aug 5. pii: S0022‐5223(14)01043‐5.
5. A roadmap to investigate the genetic basis of bicuspid aortic valve and its complications: insights from the International BAVCon (Bicuspid Aortic Valve Consortium). J Am Coll Cardiol. 2014 Aug 26;64(8):832‐9.
6. Aortic dilatation with bicuspid aortic valve. N Engl J Med. 2014 Aug 14;371(7):683.
7. Bicuspid aortic valve: identifying knowledge gaps and rising to the challenge from the International Bicuspid Aortic Valve Consortium (BAVCon). Circulation. 2014 Jun 24;129(25):2691‐704.
8. Essential Hypertension vs. Secondary Hypertension Among Children. Am J Hypertens. 2015 Jan;28(1):73‐80.
9. Cell biology. Dysfunctional mechanosensing in aneurysms. Science. 2014 May 2;344(6183):477‐9.
10. Clinical and biochemical profiles suggest fibromuscular dysplasia is a systemic disease with altered TGF‐β expression and connective tissue features. FASEB J. 2014 Aug;28(8):3313‐24.
11. Overexpression of smooth muscle myosin heavy chain leads to activation of the unfolded protein response and autophagic turnover of thick filament‐associated proteins in vascular smooth muscle cells. J Biol Chem. 2014 May 16;289(20):14075‐88.
12. Aortic Valve Operative Outcomes in Marfan Patients Study Group. Early and 1‐year outcomes of aortic root surgery in patients with Marfan syndrome: a prospective, multicenter, comparative study. J Thorac Cardiovasc Surg. 2014 Jun;147(6):1758‐66, 1767.e1‐4.
13. Molecular diagnosis in vascular Ehlers‐Danlos syndrome predicts pattern of arterial involvement and outcomes. J Vasc Surg. 2014 Jul;60(1):160‐9.
14. Vascular Ehlers‐Danlos syndrome: exploring the role of inflammation in arterial disease. Circ Cardiovasc Genet. 2014 Feb;7(1):5‐7.
15. Surgical treatment of bicuspid aortic valve disease: knowledge gaps and research perspectives. J Thorac Cardiovasc Surg. 2014 Jun;147(6):1749‐57, 1757.e1.
16. Abnormal muscle mechanosignaling triggers cardiomyopathy in mice with Marfan syndrome. J Clin Invest. 2014 Mar 3;124(3):1329‐39.
17. Advanced atherosclerosis is associated with increased medial degeneration in sporadic ascending aortic aneurysms. Atherosclerosis. 2014 Feb;232(2):361‐8.
18. IL‐6 regulates extracellular matrix remodeling associated with aortic dilation in a fibrillin‐1 hypomorphic mgR/mgR mouse model of severe Marfan syndrome. J Am Heart Assoc. 2014 Jan 21;3(1):e000476.
19. Acute aortic dissections with pregnancy in women with ACTA2 mutations. Am J Med Genet A. 2014 Jan;164A(1):106‐12.
20. Successes and challenges of using whole exome sequencing to identify novel genes underlying an inherited predisposition for thoracic aortic aneurysms and acute aortic dissections. Trends Cardiovasc Med. 2014 Feb;24(2):53‐60.
21. Single‐nucleotide polymorphism array genotyping is equivalent to metaphase cytogenetics for diagnosis of Turner syndrome. Genet Med. 2014 Jan;16(1):53‐9.
HOUSTON – (Aug. 7, 2013) – A multi-institutional team led by Dianna Milewicz, M.D., Ph.D., of The University of Texas Health Science Center at Houston (UTHealth) has found a recurrent genetic mutation that has been linked to deadly thoracic aortic dissections in family members as young as 17 years of age.
The gene known as PRKG1 makes a protein called cGMP-dependent kinase, type I. The PRKG1 mutation alters the function of the protein and causes the muscle cells in the wall of the aorta to respond incorrectly to pulsatile blood flow from the heart, and the change in this one protein ultimately causes thoracic aortic aneurysm and acute aortic dissection. The mutation was identified in four families, including three in the United States. The majority of the affected family members suffered acute aortic dissections at young ages (17 to 51 years). (more…)
Gene Defect for New Syndrome Discovered – Systemic Complications Include Life-threatening Thoracic Aortic Disease
HOUSTON – (July 9, 2012) – Research teams from The University of Texas Health Science Center at Houston (UTHealth) and Paris, France have discovered a gene defect linked to a cluster of systemic complications, including life-threatening thoracic aortic disease and intracranial aneurysms. The new syndrome is similar, but distinct from known syndromes such as Marfan and Loeys-Dietz syndrome. (more…)
Dianna Milewicz, M.D., Ph.D. director of the John Ritter Research Program, and her team of researchers at UTHealth, along with researchers at Baylor College of Medicine, published the discovery of common genetic variants which predispose individuals to thoracic aortic aneurysms and dissection (TAAD) in the absence of a family history of the disease (called sporadic TAAD) or a genetic syndrome which causes TAAD. The variants are located in the same region on chromosome 15 as the FBN1 gene; changes (mutations) in FBN1 cause Marfan syndrome. The researchers hope an increased understanding of how mutations and variants in FBN1 lead to thoracic aortic disease will ultimately result in effective treatments for individuals with sporadic TAAD.
Dianna Milewicz, M.D., Ph.D. and director of the John Ritter Research Program, and her team of researchers at UTHealth published the discovery of new gene that, when altered, causes aortic disease to run in families. This gene joins four other genes that Dr. Milewicz and her team discovered which can account for aortic disease in approximately 20% of families. (more…)