Arteriovenous malformation (AVM) is a fast-flow, congenital vascular anomaly that may arise anywhere in the body. AVMs typically progress, causing destruction of surrounding tissue and, sometimes, cardiac overload. AVMs are difficult to control; they often re-expand after embolization or resection, and pharmacologic therapy is unavailable. We studied extracranial AVMs in order to identify their biological basis. We performed whole-exome sequencing (WES) and whole-genome sequencing (WGS) on AVM tissue from affected individuals. Endothelial cells were separated from non-endothelial cells by immune-affinity purification. We used droplet digital PCR (ddPCR) to confirm mutations found by WES and WGS, to determine whether mutant alleles were enriched in endothelial or non-endothelial cells, and to screen additional AVM specimens. In seven of ten specimens, WES and WGS detected and ddPCR confirmed somatic mutations in mitogen activated protein kinase kinase 1 (MAP2K1), the gene that encodes MAP-extracellular signal-regulated kinase 1 (MEK1). Mutant alleles were enriched in endothelial cells and were not present in blood or saliva. 9 of 15 additional AVM specimens contained mutant MAP2K1 alleles. Mutations were missense or small in-frame deletions that affect amino acid residues within or adjacent to the protein's negative regulatory domain. Several of these mutations have been found in cancers and shown to increase MEK1 activity. In summary, somatic mutations in MAP2K1 are a common cause of extracranial AVM. The likely mechanism is endothelial cell dysfunction due to increased MEK1 activity. MEK1 inhibitors, which are approved to treat several forms of cancer, are potential therapeutic agents for individuals with extracranial AVM.Arteriovenous malformation (AVM) is a congenital vascular anomaly, comprised of abnormal connections between arteries and veins that are missing normal high-resistance capillary beds (Figure 1). 1 Sporadic extracranial AVMs are solitary and may be localized or regional. Rapid blood flow is demonstrable by Doppler ultrasonography. Magnetic resonance imaging reveals signal voids consistent with fast-flow, while angiography shows the early filling of draining veins (Figure 1). With time, arterial to venous shunting causes tissue ischemia that leads to pain, ulceration, bleeding, and destruction of adjacent tissues. Treatment for AVM has been discouraging. Embolization and/or resection are often followed by expansion; there are no drug treatments. 2 The purpose of this study was to identify the genetic basis for sporadic, extracranial AVM in an effort to devise a new therapeutic strategy.The Committee on Clinical Investigation at Boston Children's Hospital approved this study and informed consent was obtained from study participants. Ten AVM specimens that had been collected during a clinically indicated procedure, including matched unaffected tissue specimens from three of the study participants, had DNA extracted using the DNeasy Blood & Tissue Kit (QIAGEN); saliva DNA was extracted using the pr...

Background Capillary malformation is a cutaneous vascular anomaly that is present at birth, darkens over time, and can cause overgrowth of tissues beneath the stain. The lesion is caused by a somatic activating mutation in GNAQ. In a previous study we were unable to identify a GNAQ mutation in patients with a capillary malformation involving an overgrown lower extremity. We hypothesized that mutations in GNA11 or GNA14, genes closely related to GNAQ, also may cause capillary malformations. Methods Human capillary malformation tissue obtained from 8 patients that had tested negative for GNAQ mutations were studied. Lesions involved an extremity (n=7) or trunk (n=1). Droplet digital PCR (ddPCR) was used to detect GNA11 or GNA14 mutant cells (p.Arg183) in the specimens. Single molecule molecular inversion probe sequencing (smMIP-seq) was performed to search for other mutations in GNA11. Mutations were validated by sublconing and sequencing amplimers. Results We found a somatic GNA11 missense mutation (c.547C>T; p.Arg183Cys) in 3 patients with a diffuse capillary malformation of an extremity. Mutant allelic frequencies ranged from 0.3%–5.0%. GNA11 or GNA14 mutations were not found in 5 affected tissues or in unaffected tissues (white blood cell DNA). Conculsions GNA11 mutations are associated with extremity capillary malformations causing overgrowth. Pharmacotherapy that affects GNA11 signaling may prevent the progression of capillary malformations.

BackgroundIntracranial arteriovenous malformation (AVM) is a common cause of primary intracerebral hemorrhage in young adults. Lesions typically are sporadic and contain somatic mutations in KRAS or BRAF. The purpose of this study was to identify somatic mutations in a cohort of participants with brain AVM and to determine if any genotype-phenotype associations exist.MethodsHuman brain AVM specimens (n = 16) were collected during a clinically-indicated procedure and subjected to multiplex targeted sequencing using molecular inversion probe (MIP-seq) for mutations in KRAS, BRAF, HRAS, NRAS, and MAP2K1. Endothelial cells (ECs) were separated from non-ECs by immune-affinity purification. Droplet digital PCR (ddPCR) was used to confirm mutations and to screen for mutations that may have been missed by MIP-seq. Patient and AVM characteristics were recorded.ResultsWe detected somatic mutations in 10 of 16 specimens (63%). Eight had KRAS mutations [G12D (n = 5), G12V (n = 3)] and two had BRAF mutations [V600E (n = 1), Q636X (n = 1)]. We found no difference in age, sex, presenting symptom, AVM location, or AVM size between patients with a confirmed mutation and those without. Nor did we observe differences in these features between patients with KRAS or BRAF mutations. However, two patients with BRAF mutations presented at an older age than other study participants.ConclusionsSomatic mutations in KRAS and, less commonly in BRAF, are found in many but not all intracranial AVM samples. Currently, there are no obvious genotype-phenotype correlations that can be used to predict whether a somatic mutation will be detected and, if so, which gene will be mutated.