Hereditary Hemorrhagic Telangiectasia with Recurrent Epistaxis, Telangiectasia, Hepatic Arteriovenous Malformation, and a Poorly Developed Middle Cerebral Artery in a Patient with a Novel Mutation in the ACVRL1 Gene.

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal-dominant vascular disorder characterized by intractable epistaxis, mucocutaneous telangiectasias, and arteriovenous malformations (AVMs) in multiple organs, including the lungs, liver, gastrointestinal tract, brain, and spinal cord. We herein report a 50-year-old Japanese man with HHT who experienced recurrent epistaxis, telangiectasia in the cornea, apex of the tongue and fingers; hepatic AVM; and a poorly developed main arterial trunk in the right middle cerebral artery. A genetic analysis revealed a novel heterozygous mutation in the activin A receptor-like type 1 gene, with a frameshift mutation in NM_000020.3:c.826_836del (p.Ile276ProfsTer112).

A Microphysiological HHT-on-a-Chip Platform Recapitulates Patient Vascular Lesions.

Hereditary Hemorrhagic Telangiectasia (HHT) is a rare congenital disease in which fragile vascular malformations (VM) - including small telangiectasias and large arteriovenous malformations (AVMs) - focally develop in multiple organs. There are few treatment options and no cure for HHT. Most HHT patients are heterozygous for loss-of-function mutations affecting Endoglin (ENG) or Alk1 (ACVRL1); however, why loss of these genes manifests as VMs remains poorly understood. To complement ongoing work in animal models, we have developed a fully human, cell-based microphysiological model based on our Vascularized Micro-organ (VMO) platform (the HHT-VMO) that recapitulates HHT patient VMs. Using inducible ACVRL1 -knockdown, we control timing and extent of endogenous Alk1 expression in primary human endothelial cells (EC). Resulting HHT-VMO VMs develop over several days. Interestingly, in chimera experiments AVM-like lesions can be comprised of both Alk1-intact and Alk1-deficient EC, suggesting possible cell non-autonomous effects. Single cell RNA sequencing data are consistent with microvessel pruning/regression as contributing to AVM formation, while loss of PDGFB implicates mural cell recruitment. Finally, lesion formation is blocked by the VEGFR inhibitor pazopanib, mirroring positive effects of this drug in patients. In summary, we have developed a novel HHT-on-a-chip model that faithfully reproduces HHT patient lesions and that can be used to better understand HHT disease biology and identify potential new HHT drugs.

Evaluation of Aav Capsids and Delivery Approaches for Hereditary Hemorrhagic Telangiectasia Gene Therapy.

Nosebleeds and intracranial hemorrhage from brain arteriovenous malformations (bAVMs) are among the most devastating symptoms of patients with hereditary hemorrhagic telangiectasis (HHT). All available managements have limitations. We showed that intravenous delivery of soluble FMS-related tyrosine kinase 1 using an adeno-associated viral vector (AAV9-sFLT1) reduced bAVM severity of endoglin deficient mice. However, minor liver inflammation and growth arrest in young mice were observed. To identify AAV variants and delivery methods that can best transduce brain and nasal tissue with an optimal transduction profile, we compared 3 engineered AAV capsids (AAV.cc47, AAV.cc84 and AAV1RX) with AAV9. A single-stranded CBA promoter driven tdTomato transgene was packaged in these capsids and delivered intravenously (i.v.) or intranasally (i.n.) to wild-type mice. A CMV promoter driven Alk1 transgene was packaged into AAV.cc84 and delivered to PdgfbiCre;Alk1 f/f mice through i.v. injection followed by brain AVM induction. Transduced cells in different organs, vessel density and abnormal vessels in the bAVMs, and liver inflammation were analyzed histologically. Liver and kidney function were measured enzymatically. Compared to other viral vectors, AAV.cc84, after i.v. delivery, transduced a high percentage of brain ECs and few hepatocytes; whereas after i.n. delivery, AAV.cc84 transduced ECs and perivascular cells in the brain, and ECs, epithelial cells, and skeletal muscles in the nose with minimum hepatocyte transduction. No changes to liver or kidney function were detected. Delivery of AAV.cc84-Alk1 through i.v. to PdgfbiCre;Alk1 f/f mice reduced bAVM severity. In summary, we propose that AAV.cc84-Alk1 is a promising candidate for developing gene therapy in HHT patients.

Evaluation of AAV Capsids and Delivery Approaches for Hereditary Hemorrhagic Telangiectasia Gene Therapy.

Nosebleeds and intracranial hemorrhage from brain arteriovenous malformations (bAVMs) are among the most devastating symptoms of patients with hereditary hemorrhagic telangiectasis (HHT). All available managements have limitations. We showed that intravenous (i.v.) delivery of soluble Feline McDonough Sarcoma (FMS)-related tyrosine kinase 1 using an adeno-associated viral vector (AAV9-sFLT1) reduced bAVM severity of endoglin deficient mice. However, minor liver inflammation and growth arrest in young mice were observed. To identify AAV variants and delivery methods that can best transduce brain and nasal tissue with an optimal transduction profile, we compared 3 engineered AAV capsids (AAV.cc47, AAV.cc84, and AAV1RX) with AAV9. A single-stranded CBA promoter driven tdTomato transgene was packaged in these capsids and delivered i.v. or intranasally (i.n.) to wild-type mice. A CMV promoter driven Alk1 transgene was packaged into AAV.cc84 and delivered to PdgfbiCre;Alk1f/f mice through i.v. followed by bAVM induction. Transduced cells in organs, vessel density, abnormal vessels in the bAVMs, and liver inflammation were analyzed histologically. Liver and kidney function were measured enzymatically. Compared to other viral vectors, AAV.cc84, after i.v. delivery, transduced a high percentage of brain endothelial cells (ECs) and few hepatocytes; whereas after i.n. delivery, AAV.cc84 transduced ECs and perivascular cells in the brain, and ECs, epithelial cells, and muscles in the nose with minimum hepatocyte transduction. No changes to liver or kidney function were detected. The delivery of AAV.cc84-Alk1 through i.v. to PdgfbiCre;Alk1f/f mice reduced bAVM severity. In summary, we propose that AAV.cc84-Alk1 is a promising candidate for developing gene therapy in HHT patients.

The importance of synthetic pharmacotherapy for recessive cerebellar ataxias.

INTRODUCTION: The last decade has witnessed major breakthroughs in identifying novel genetic causes of hereditary ataxias, deepening our understanding of disease mechanisms, and developing therapies for these debilitating disorders. AREAS COVERED: This article reviews the currently approved and most promising candidate pharmacotherapies in relation to the known disease mechanisms of the most prevalent autosomal recessive ataxias. Omaveloxolone is an Nrf2 activator that increases antioxidant defense and was recently approved for treatment of Friedreich ataxia. Its therapeutic effect is modest, and further research is needed to find synergistic treatments that would halt or reverse disease progression. Promising approaches include upregulation of frataxin expression by epigenetic mechanisms, direct protein replacement, and gene replacement therapy. For ataxia-telangiectasia, promising approaches include splice-switching antisense oligonucleotides and small molecules targeting oxidative stress, inflammation, and mitochondrial function. Rare recessive ataxias for which disease-modifying therapies exist are also reviewed, emphasizing recently approved therapies. Evidence supporting the use of riluzole and acetyl-leucine in recessive ataxias is discussed. EXPERT OPINION: Advances in genetic therapies for other neurogenetic conditions have paved the way to implement feasible approaches with potential dramatic benefits. Particularly, as we develop effective treatments for these conditions, we may need to combine therapies, consider newborn testing for pre-symptomatic treatment, and optimize non-pharmacological approaches.

Ataxia-Telangiectasia Mutated (ATM) gene signaling pathways in human cancers and their therapeutic implications.

Cancer is a multifaceted disease driven by abnormal cell growth and poses a significant global health threat. The multifactorial causes, differences in individual susceptibility to therapeutic drugs, and induced drug resistance pose major challenges in addressing cancers effectively. One of the most important aspects in making cancers highly heterogeneous in their physiology lies in the genes involved and the changes occurring to some of these genes in malignant conditions. The Genetic factors have been implicated in the oncogenesis, progression, responses to treatment, and metastasis. One such gene that plays a key role in human cancers is the mutated form of the Ataxia-telangiectasia gene (ATM). ATM gene located on chromosome 11q23, plays a vital role in maintaining genomic stability. Understanding the genetic basis of A-T is crucial for diagnosis, management, and treatment. Breast cancer, lung cancer, prostate cancer, and gastric cancer exhibit varying relationships with the ATM gene and influence their pathways. Targeting the ATM pathway proves promising for enhancing treatment effectiveness, especially in conjunction with DNA damage response pathways. Analyzing the therapeutic consequences of ATM mutations, especially in these cancer types facilitates the approaches for early detection, intervention, development of personalized treatment approaches, and improved patient outcomes. This review emphasizes the role of the ATM gene in various cancers, highlighting its impact on DNA repair pathways and therapeutic responses.

Increased Risk for Infections and Allergic Disease in Hereditary Hemorrhagic Telangiectasia.

Background/Objectives: Hereditary hemorrhagic telangiectasia (HHT) is a rare disorder characterized by dilated blood vessels. Different immunological changes have been described in these patients. In this study, the predisposition of patients with HHT to infections and allergic diseases was assessed. Methods: Patients with HHT completed an online survey in English or German. Their data were compared to non-affected partners or friends. Results: A total of 430 out of 588 respondents with HHT answered our questions about infections and allergies. Patients with HHT suffered significantly more often from various types of allergies than their partners, especially type I allergies (n = 226/276, 82%), and had a higher risk for sinusitis, urinary tract infections, pulmonary infections, and abscesses. A total of 38% of the patients took antibiotics prior to dental or surgical procedures (n = 57/152), and, in 10% of these patients, pulmonary arteriovenous malformations (PAVMs) were not detected. On the other hand, 51% of patients with PAVM did not report a prophylactic antibiotic intake (n = 40/79). The patients who needed iron supplementations suffered more often from sepsis (OR: 9.00, 95%CI: 0.92-88.16). Conclusions: Compared to their non-affected controls, patients with HHT showed an increased risk for infections in different organs and allergic diseases. There is a need for campaigns raising greater awareness recommending prophylactic antibiotic intake in patients with PAVM.

Hepatic manifestations of hereditary haemorrhagic telangiectasia.

Hereditary haemorrhagic telangiectasia is a genetic condition of abnormal blood vessel formation resulting from an imbalance of pro- and anti-angiogenic products of the transforming growth factor ß/bone morphogenetic protein signalling pathway which contributes to vascular remodelling and maintenance. Hepatic vascular malformations are common although less frequently symptomatic, but may result in high-output cardiac failure, portal hypertension and biliary ischaemia. Whilst the understanding of the genetic and cell signalling pathways that are the hallmark of hereditary haemorrhagic telangiectasia have been clarified, there remain challenges in therapy for these patients. Only patients with symptomatic hepatic vascular malformations require treatment, with most (63%) responding to first-line medical therapy. For non-responders, bevacizumab is effective in reducing cardiac output in those with heart failure secondary to hepatic vascular malformations as well as other manifestations of the disease. Although liver transplantation is the only curative option, optimal timing is critical. Novel anti-angiogenetic drugs and those that target aberrant cell signalling pathway are being explored.

Ataxia Telangiectasia patient-derived neuronal and brain organoid models reveal mitochondrial dysfunction and oxidative stress.

Ataxia Telangiectasia (AT) is a rare disorder caused by mutations in the ATM gene and results in progressive neurodegeneration for reasons that remain poorly understood. In addition to its central role in nuclear DNA repair, ATM operates outside the nucleus to regulate metabolism, redox homeostasis and mitochondrial function. However, a systematic investigation into how and when loss of ATM affects these parameters in relevant human neuronal models of AT was lacking. We therefore used cortical neurons and brain organoids from AT-patient iPSC and gene corrected isogenic controls to reveal levels of mitochondrial dysfunction, oxidative stress, and senescence that vary with developmental maturity. Transcriptome analyses identified disruptions in regulatory networks related to mitochondrial function and maintenance, including alterations in the PARP/SIRT signalling axis and dysregulation of key mitophagy and mitochondrial fission-fusion processes. We further show that antioxidants reduce ROS and restore neurite branching in AT neuronal cultures, and ameliorate impaired neuronal activity in AT brain organoids. We conclude that progressive mitochondrial dysfunction and aberrant ROS production are important contributors to neurodegeneration in AT and are strongly linked to ATM's role in mitochondrial homeostasis regulation.

Reduced levels of MRE11 cause disease phenotypes distinct from ataxia telangiectasia-like disorder.

The MRE11/RAD50/NBS1 (MRN) complex plays critical roles in cellular responses to DNA double-strand breaks. MRN is involved in end binding and processing, and it also induces cell cycle checkpoints by activating the ataxia-telangiectasia mutated (ATM) protein kinase. Hypomorphic pathogenic variants in the MRE11, RAD50, or NBS1 genes cause autosomal recessive genome instability syndromes featuring variable degrees of dwarfism, neurological defects, anemia, and cancer predisposition. Disease-associated MRN alleles include missense and nonsense variants, and many cause reduced protein levels of the entire MRN complex. However, the dramatic variability in the disease manifestation of MRN pathogenic variants is not understood. We sought to determine if low protein levels are a significant contributor to disease sequelae and therefore generated a transgenic murine model expressing MRE11 at low levels. These mice display dramatic phenotypes including small body size, severe anemia, and impaired DNA repair. We demonstrate that, distinct from ataxia telangiectasia-like disorder caused by MRE11 pathogenic missense or nonsense variants, mice and cultured cells expressing low MRE11 levels do not display the anticipated defects in ATM activation. Our findings indicate that ATM signaling can be supported by very low levels of the MRN complex and imply that defective ATM activation results from perturbation of MRN function caused by specific hypomorphic disease mutations. These distinct phenotypic outcomes underline the importance of understanding the impact of specific pathogenic MRE11 variants, which may help direct appropriate early surveillance for patients with these complicated disorders in a clinical setting.

Case report: Compound heterozygous variants detected by next-generation sequencing in a Tunisian child with ataxia-telangiectasia.

Ataxia-telangiectasia (A-T) is an autosomal recessive primary immunodeficiency disorder (PID) caused by biallelic mutations occurring in the serine/threonine protein kinase (ATM) gene. The major role of nuclear ATM is the coordination of cell signaling pathways in response to DNA double-strand breaks, oxidative stress, and cell cycle checkpoints. Defects in ATM functions lead to A-T syndrome with phenotypic heterogeneity. Our study reports the case of a Tunisian girl with A-T syndrome carrying a compound heterozygous mutation c.[3894dupT]; p.(Ala1299Cysfs3;rs587781823), with a splice acceptor variant: c.[5763-2A>C;rs876659489] in the ATM gene that was identified by next-generation sequencing (NGS). Further genetic analysis of the family showed that the mother carried the c.[5763-2A>C] splice acceptor variant, while the father harbored the c.[3894dupT] variant in the heterozygous state. Molecular analysis provides the opportunity for accurate diagnosis and timely management in A-T patients with chronic progressive disease, especially infections and the risk of malignancies. This study characterizes for the first time the identification of compound heterozygous ATM pathogenic variants by NGS in a Tunisian A-T patient. Our study outlines the importance of molecular genetic testing for A-T patients, which is required for earlier detection and reducing the burden of disease in the future, using the patients' families.

Ataxia-telangiectasia in Latin America: clinical features, immunodeficiency, and mortality in a multicenter study.

Ataxia-telangiectasia (AT) is a rare genetic disorder leading to neurological defects, telangiectasias, and immunodeficiency. We aimed to study the clinical and immunological features of Latin American patients with AT and analyze factors associated with mortality. Referral centers from 9 Latin American countries participated in this retrospective cohort study, and 218 patients were included. Median (IQR) ages at symptom onset and diagnosis were 1.0 (1.0-2.0)  and 5.0 (3.0-8.0) years, respectively. Most patients presented recurrent airway infections, which was significantly associated with IgA deficiency. IgA deficiency was observed in 60.8% of patients and IgG deficiency in 28.6%. T- and B-lymphopenias were also present in most cases. Mean survival was 24.2 years, and Kaplan-Meier 20-year-survival rate was 52.6%, with higher mortality associated with female gender and low IgG levels. These findings suggest that immunologic status should be investigated in all patients with AT.

New insights into ATR inhibition in muscle invasive bladder cancer: The role of apolipoprotein B mRNA editing catalytic subunit 3B.

Background: Apolipoprotein B mRNA editing catalytic polypeptide (APOBEC), an endogenous mutator, induces DNA damage and activates the ataxia telangiectasia and Rad3-related (ATR)-checkpoint kinase 1 (Chk1) pathway. Although cisplatin-based therapy is the mainstay for muscle-invasive bladder cancer (MIBC), it has a poor survival rate. Therefore, this study aimed to evaluate the efficacy of an ATR inhibitor combined with cisplatin in the treatment of APOBEC catalytic subunit 3B (APOBEC3B) expressing MIBC. Methods: Immunohistochemical staining was performed to analyze an association between APOBEC3B and ATR in patients with MIBC. The APOBEC3B expression in MIBC cell lines was assessed using real-time polymerase chain reaction and western blot analysis. Western blot analysis was performed to confirm differences in phosphorylated Chk1 (pChk1) expression according to the APOBEC3B expression. Cell viability and apoptosis analyses were performed to examine the anti-tumor activity of ATR inhibitors combined with cisplatin. Conclusion: There was a significant association between APOBEC3B and ATR expression in the tumor tissues obtained from patients with MIBC. Cells with higher APOBEC3B expression showed higher pChk1 expression than cells expressing low APOBEC3B levels. Combination treatment of ATR inhibitor and cisplatin inhibited cell growth in MIBC cells with a higher APOBEC3B expression. Compared to cisplatin single treatment, combination treatment induced more apoptotic cell death in the cells with higher APOBEC3B expression. Conclusion: Our study shows that APOBEC3B's higher expression status can enhance the sensitivity of MIBC to cisplatin upon ATR inhibition. This result provides new insight into appropriate patient selection for the effective application of ATR inhibitors in MIBC.

Surgical treatment of brain arteriovenous malformations in patients with hereditary hemorrhagic telangiectasia: a single-center experience.

OBJECTIVE: Hereditary hemorrhagic telangiectasia (HHT) is an autosomal-dominant disorder characterized by multiple vascular malformations. Brain arteriovenous malformations (bAVMs) are a significant manifestation of HHT. The surgical management of these lesions in patients with HHT remains debated, with limited literature on postoperative outcomes. The goal of this study was to evaluate the safety and efficacy of surgical treatment for bAVMs in patients with HHT and propose a treatment rationale based on a single-center experience. METHODS: This retrospective review included 20 patients diagnosed with HHT who underwent resection of 23 bAVMs at the Stanford University Medical Center between January 2007 and September 2023. Data were also collected on bAVMs treated conservatively, with embolization, or with radiosurgery at the authors' institution, for comparison. RESULTS: There were 16 Spetzler-Martin (SM) grade I, 6 SM grade II, and 1 SM grade IV bAVM. Six of the bAVMs presented with neurological symptoms (3 with hemorrhage and 3 with focal neurological deficits), while the rest were detected on routine screening. Complete excision was angiographically confirmed in all patients, with a mean overall hospital stay of 2.1 days and a mean follow-up of 36 months. Postoperative complications were limited to transient mild weakness in 2 patients, 1 of whom also had transient speech deficits, and visual field deficits in 3 patients, 2 of whom improved on long-term follow-up. CONCLUSIONS: In this most extensive surgical series published to date, resection of bAVMs in patients with HHT showed favorable outcomes with a low complication rate, suggesting that the benefits of surgery outweigh the risks, especially considering the potential cumulative lifetime risk of hemorrhage. MR arterial spin labeling was found to be the most sensitive noninvasive measure of detecting bAVMs in patients with HHT.

Endothelial-to-Mesenchymal Transition in an Hereditary Hemorrhagic Telangiectasia-like Pediatric Case of Multiple Pulmonary Arteriovenous Malformations.

Pulmonary arteriovenous malformations (PAVMs) are vascular anomalies resulting in abnormal connections between pulmonary arteries and veins. In 80% of cases, PAVMs are present from birth, but clinical manifestations are rarely seen in childhood. These congenital malformations are typically associated with Hereditary Hemorrhagic Telangiectasia (HHT), a rare disease that affects 1 in 5000/8000 individuals. HHT disease is frequently caused by mutations in genes involved in the TGF-ß pathway. However, approximately 15% of patients do not have a genetic diagnosis and, among the genetically diagnosed, more than 33% do not meet the Curaçao criteria. This makes clinical diagnosis even more challenging in the pediatric age group. Here, we introduce an 8-year-old patient bearing a severe phenotype of multiple diffuse PAVMs caused by an unknown mutation which ended in lung transplantation. Phenotypically, the case under study follows a molecular pattern which is HHT-like. Therefore, molecular- biological and cellular-functional analyses have been performed in primary endothelial cells (ECs) isolated from the explanted lung. The findings revealed a loss of functionality in lung endothelial tissue and a stimulation of endothelial-to-mesenchymal transition. Understanding the molecular basis of this transition could potentially offer new therapeutic strategies to delay lung transplantation in severe cases.

ACR Appropriateness Criteria® Pulmonary Arteriovenous Malformation (PAVM): 2023 Update.

Pulmonary arteriovenous malformations (PAVMs) occur in 30% to 50% of patients with hereditary hemorrhagic telangiectasia. Clinical presentations vary from asymptomatic disease to complications resulting from the right to left shunting of blood through the PAVM such as paradoxical stroke, brain abscesses, hypoxemia, and cardiac failure. Radiology plays an important role both in the diagnosis and treatment of PAVM. Based on different clinical scenarios, the appropriate imaging study has been reviewed and is presented in this document. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.