Identification of a rare BMP pathway mutation in a non-syndromic human brain arteriovenous malformation via exome sequencing

• Published in: Human genome variation Vol. 5; no. 1; p. 18001
• Main Authors: Walcott, Brian P, Winkler, Ethan A, Zhou, Sirui, Birk, Harjus, Guo, Diana, Koch, Matthew J, Stapleton, Christopher J, Spiegelman, Dan, Dionne-Laporte, Alexandre, Dion, Patrick A, Kahle, Kristopher T, Rouleau, Guy A, Lawton, Michael T
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 08.03.2018; Springer Nature B.V; Nature Publishing Group
• Subjects: 631/208/2489/144; 692/308/2056; 692/699/375/1370/534; Biomedical and Life Sciences; Biomedicine; Brain; Gene Expression; Gene Function; Gene Therapy; Human Genetics; Molecular Medicine; Mutation; Proteins
• ISSN: 2054-345X; 2054-345X
• DOI: 10.1038/hgv.2018.1

Brain arteriovenous malformations (AVMs) are abnormal connections between arteries and veins that can result in hemorrhagic stroke. A genetic basis for AVMs is suspected, and we investigated potential mutations in a 14-year-old girl who developed a recurrent brain AVM. Whole-exome sequencing (WES) of AVM lesion tissue and blood was performed accompanied by in silico modeling, protein expression observation in lesion tissue and zebrafish modeling. A stop-gain mutation (c.C739T:p.R247X) in the gene SMAD family member 9 ( SMAD9 ) was discovered. In the human brain tissue, immunofluorescent staining demonstrated a vascular predominance of SMAD9 at the protein level. Vascular SMAD9 was markedly reduced in AVM peri-nidal blood vessels, which was accompanied by a decrease in phosphorylated SMAD4, a downstream effector protein of the bone morphogenic protein signaling pathway. Zebrafish modeling ( Tg kdrl:eGFP ) of the morpholino splice site and translation-blocking knockdown of SMAD9 resulted in abnormal cerebral artery-to-vein connections with morphologic similarities to human AVMs. Orthogonal trajectories of evidence established a relationship between the candidate mutation discovered in SMAD9 via WES and the clinical phenotype. Replication in similar rare cases of recurrent AVM, or even more broadly sporadic AVM, may be informative in building a more comprehensive understanding of AVM pathogenesis. Stroke: Untangling genetic causes Disordered growth of abnormal blood vessels in the brain, leading to hemorrhagic stroke, can be caused by a rare genetic mutation. Brain arteriovenous malformations (AVMs), in which blood vessels in the brain form tangles that are prone to rupture, are a significant cause of stroke in both adults and children. The causes of AVMs remain poorly understood. Brian Walcott at the University of Southern California and co-workers searched for a potential genetic cause underlying a recurring AVM in a 14-year old girl. Genetic analysis identified a mutation in the SMAD9 gene, which resulted in decreased production of its protein. When the researchers modeled the same mutation in microscopic zebrafish, their blood vessels showed vascular development patterns with striking similarities to human AVMs. This research may help improve our understanding of how AVMs develop.