BACKGROUND:

Ataxia Telangiectasia (AT) is a rare incurable genetic disease, caused by biallelic mutations in the Ataxia Telangiectasia-Mutated (ATM) gene. Treatment with glucocorticoid analogues has been shown to improve the neurological symptoms that characterize this syndrome. Nevertheless, the molecular mechanism underlying the glucocorticoid action in AT patients is not yet understood. Recently, we have demonstrated that Dexamethasone treatment may partly restore ATM activity in AT lymphoblastoid cells by a new ATM transcript, namely ATMdexa1.

RESULTS:

In the present study, the new ATMdexa1 transcript was also identified in vivo, specifically in the PMBCs of AT patients treated with intra-erythrocyte Dexamethasone (EryDex). In these patients it was also possible to isolate new "ATMdexa1 variants" originating from canonical and non-canonical splicing, each containing the coding sequence for the ATM kinase domain. The expression of the ATMdexa1 transcript family was directly related to treatment and higher expression levels of the transcript in patients' blood correlated with a positive response to Dexamethasone therapy. Neither untreated AT patients nor untreated healthy volunteers possessed detectable levels of the transcripts. ATMdexa1 transcript expression was found to be elevated 8 days after the drug infusion, while it decreased 21 days after treatment.

CONCLUSIONS:

For the first time, the expression of ATM splicing variants, similar to those previously observed in vitro, has been found in the PBMCs of patients treated with EryDex. These findings show a correlation between the expression of ATMdexa1 transcripts and the clinical response to low dose dexamethasone administration.

Ataxia-telangiectasia (A-T) is a devastating human recessive disorder characterized by progressive cerebellar ataxia, immunodeficiency, chromosomal instability, and cancer susceptibility. The European Workshop on Ataxia-Telangiectasia 2011 in Frankfurt focused on status quo of patient care and future clinical research directions. In Europe, approximately 600 patients are registered and many national websites have been established. During the meeting, guidelines of patient care were discussed and all participants agreed to build up an European A-T research network in near future to bring basic research and new therapies into clinical applications.

Ataxia-telangiectasia (A-T) is characterized by neuronal degeneration, cancer, diabetes, immune deficiency, and increased sensitivity to ionizing radiation. A-T is attributed to the deficiency of the protein kinase coded by the ATM (ataxia-telangiectasia mutated) gene. ATM is a sensor of DNA double-strand breaks (DSBs) and signals to cell cycle checkpoints and the DNA repair machinery. ATM phosphorylates numerous substrates and activates many cell-signaling pathways. There has been considerable debate about whether a defective DNA damage response is causative of the neurological aspects of the disease. In proliferating cells, ATM is localized mainly in the nucleus; however, in postmitotic cells such as neurons, ATM is mostly cytoplasmic. Recent studies reveal an increasing number of roles for ATM in the cytoplasm, including activation by oxidative stress. ATM associates with organelles including mitochondria and peroxisomes, both sources of reactive oxygen species (ROS), which have been implicated in neurodegenerative diseases and aging. ATM is also associated with synaptic vesicles and has a role in regulating cellular homeostasis and autophagy. The cytoplasmic roles of ATM provide a new perspective on the neurodegenerative process in A-T. This review will examine the expanding roles of ATM in cellular homeostasis and relate these functions to the complex A-T phenotype. Developmental Dynamics 247:33-46, 2018.

© 2017 Wiley Periodicals, Inc.

Ataxia-Telangiectasia (A-T) is a prototypical genomic instability disorder with multi-organ deficiency and it is caused by the defective function of a single gene, ATM (Ataxia-Telangiectasia Mutated). Radiosensitivity, among the pleiotropic symptoms of A-T, reflects the basic physiological functions of ATM protein in the double strand break (DSB)-induced DNA damage response (DDR) and also restrains A-T patients from the conventional radiation therapy for their lymphoid malignancy. In this chapter, we describe two methods that have been developed in our lab to assess the radiosensitivity of A-T patients: (1) Colony Survival Assay (CSA) and (2) Flow Cytometry of phospho-SMC1 (FC-pSMC1). The establishment of these more rapid and reliable functional assays to measure the radiosensitivity, exemplified by A-T, would facilitate the diagnosis of other genomic instability genetic disorders as well as help the treatment options for most radiosensitive patients.

Ataxia-telangiectasia is a chronic progressive disorder affecting the nervous and immune systems, caused by a genetic defect in the ATM protein. Clasmatodendrosis, a distinct form of astroglial death, has rarely been reported in ataxia-telangiectasia. Neuropathology of our patient disclosed diffuse edema of the cerebral and cerebellar white matter with prominent clasmatodendrosis, implicating ATM in the regulation of astroglial cell death.

Ataxia-telangiectasia is a rare, neurodegenerative, and multisystem disease, characterized by cerebellar ataxia, oculocutaneous telangiectasia, immunodeficiency, progressive respiratory failure, and an increased risk of malignancies. It demands specialized care tailored to the individual patient's needs. Besides the classic ataxia-telangiectasia phenotype, a variant phenotype exists with partly overlapping but some distinctive disease characteristics. This guideline summarizes frequently encountered medical problems in the disease course of patients with classic and variant ataxia-telangiectasia, in the domains of neurology, immunology and infectious diseases, pulmonology, anaesthetic and perioperative risk, oncology, endocrinology, and nutrition. Furthermore, it provides a practical guide with evidence- and expert-based recommendations for the follow-up and treatment of all these different clinical topics.

Recent developments in sequencing technologies led to the discovery of a novel form of genomic instability, termed chromothripsis. This catastrophic genomic event, involved in tumorigenesis, is characterized by tens to hundreds of simultaneously acquired locally clustered rearrangements on one chromosome. We hypothesized that leukemias developing in individuals with Ataxia Telangiectasia, who are born with two mutated copies of the ATM gene, an essential guardian of genome stability, would show a higher prevalence of chromothripsis due to the associated defect in DNA double-strand break repair. Using whole-genome sequencing, fluorescence in situ hybridization and RNA sequencing, we characterized the genomic landscape of Acute Lymphoblastic Leukemia (ALL) arising in patients with Ataxia Telangiectasia. We detected a high frequency of chromothriptic events in these tumors, specifically on acrocentric chromosomes, as compared with tumors from individuals with other types of DNA repair syndromes (27 cases total, 10 with Ataxia Telangiectasia). Our data suggest that the genomic landscape of Ataxia Telangiectasia ALL is clearly distinct from that of sporadic ALL. Mechanistically, short telomeres and compromised DNA damage response in cells of Ataxia Telangiectasia patients may be linked with frequent chromothripsis. Furthermore, we show that ATM loss is associated with increased chromothripsis prevalence in additional tumor entities.

BACKGROUND:

Ataxia telangiectasia (AT) is a primary immunodeficiency associated with recurrent infections. We aimed to investigate clinical and immunological classification in AT patients who suffer from a different spectrum of humoral immune defects.

METHODS:

AT patients were categorized according to the ability of class switching and patients with hyper IgM (HIgM) profile were defined as class switching defect (CSD).

RESULTS:

Serum immunoglobulin profile in 66 AT patients showed normal immunoglobulin level (22.8%), IgA deficiency (37.9%) and hypogammaglobulinemia (18.1%) in the majority of patients, while 21.2% had HIgM profile revealing CSD. CSD does not affect the frequency of infections, however, the frequency of lymphoproliferation (p < 0.001), and autoimmunity (p = 0.004) were significantly higher in this group. Neurologic symptoms in CSD patients are mild or appear after recurrent infections, therefore these patients were usually misdiagnosed as HIgM syndrome.

CONCLUSIONS:

Although most of AT patients have reduced IgA levels or normal immunoglobulin levels, but a fraction of these patients may show CSD ensuing HIgM-profile. CSD poses affected individuals at higher risk of non-infectious complications.

Ataxia-telangiectasia (AT) is a neurodegenerative disorder characterized by ataxia, telangiectasia, and immunodeficiency. An increased risk of malignancies and respiratory diseases dramatically reduce life expectancy. To better counsel families, develop individual follow-up programs, and select patients for therapeutic trials, more knowledge is needed on factors influencing survival. This retrospective cohort study of 61 AT patients shows that classical AT patients had a shorter survival than variant patients (HR 5.9, 95%CI 2.0-17.7), especially once a malignancy was diagnosed (HR 2.5, 95%CI 1.1-5.5, compared to classical AT patients without malignancy). Patients with the hyper IgM phenotype with hypogammaglobulinemia (AT-HIGM) and patients with an IgG₂ deficiency showed decreased survival compared to patients with normal IgG (HR 9.2, 95%CI 3.2-26.5) and patients with normal IgG₂ levels (HR 7.8, 95%CI 1.7-36.2), respectively. If high risk treatment trials will become available for AT, those patients with factors indicating the poorest prognosis might be considered for inclusion first.

Ataxia-telangiectasia (A-T) is an autosomal recessive chromosome breakage disorder caused by mutations in the ATM gene. Typically, it presents in early childhood with progressive cerebellar dysfunction along with immunodeficiency and oculocutaneous telangiectasia. An increased risk of malignancy is also associated with the syndrome and, rarely, may be the presenting feature in small children. We describe a 17-year-old boy with slurred speech, mild motor delays and learning disability diagnosed with atypical A-T in the setting of T-cell acute lymphoblastic leukemia. Suspicion for A-T was raised after review of a peripheral blood karyotype demonstrating rearrangements involving chromosomes 7 and/or 14. The diagnosis was confirmed after molecular testing identified a novel homozygous missense variant in ATM (c.5585T>A; p.Leu1862His) that resulted in protein instability and abolished serine/threonine protein kinase activity. To our knowledge, this is the first report of concurrent A-T and lymphoid malignancy diagnoses in an older child or adult with only mild neurological disease. Our experience suggests that screening for the disorder should be considered in any individual with lymphoid malignancy and neurological findings, especially as radiation and certain chemotherapy protocols are contraindicated in A-T.

BACKGROUND:

Ataxia telangiectasia (AT) is a genetically based multisystemic disorder. We aimed to make a comprehensive evaluation of multisystem involvement in AT by describing clinical features and outcome of 91 patients.

METHODS:

Medical records of the patients who were diagnosed and followed by a multidisciplinary approach during a 27-year period (1988-2015) were reviewed retrospectively.

RESULTS:

Forty six female and 45 male patients with a mean follow-up period of 39.13±4.28 months were evaluated. The mean age at the time of symptom onset and diagnosis were 15.4±1.09 months and 73.61±4.11 months, respectively. Neurological abnormalities were progressive truncal ataxia, nystagmus, dysarthria, oculomotor apraxia and choreoathetosis. Thirty one patients (34.1%) became dependent on wheelchair at a mean age of 12.1±2.8 years. Eleven patients (12.1%) became bedridden by a mean age of 14.7±1.8 years. Cranial magnetic resonance imaging revealed pathological findings in 47/66 patients. Abnormal immunological parameters were determined in 51/91 patients: immunoglobulin (Ig)A deficiency (n=38), lymphopenia (n=30), IgG (n=15) and IgG₂ (n=11) deficiency. Occurrence of recurrent sinopulmonary infections (n=45) and bronchiectasis (n=22) were found to be more common in patients with impaired immunological parameters (P=0.029 and P=0.023, respectively). Malignancy developed in 5 patients, being mostly lymphoreticular in origin and resulted in death of 4 patients.

CONCLUSIONS:

AT is a long lasting disease with multisystem involvement necessitating multidisciplinary follow up, as described in our cohort. Early diagnosis of malignancy and supportive treatments regarding pulmonary and neurological health may prolong survival and increase the quality of life.

We report, to the best of our knowledge, the first case of a child with typical ataxia telangiectasia (A-T) who developed juvenile idiopathic arthritis (JIA). The patient was a 15-year-old boy with A-T who presented with noninfectious polyarthritis. A-T is a rare, autosomal recessive disorder characterized by cerebellar atrophy, oculocutaneous telangiectasia, immunodeficiency, radiosensitivity, and predisposition to cancer. The gene responsible for A-T is the A-T mutated (ATM) gene. Clinical manifestations of the disorder are the result of lacking ATM protein, which is involved in DNA repair, apoptosis, various checkpoints in the cell cycle, gene regulation, translation, initiation, and telomere maintenance. There are a few articles that describe deficiency of the DNA repair enzyme, ATM, in rheumatoid arthritis, but the connection between the absence of ATM protein and JIA has not been presented or studied yet. JIA is a heterogeneous group of diseases characterized by arthritis of unknown origin with onset before the age of 16 years. It is the most common childhood chronic rheumatic disease and causes significant disability. Because immunodeficiency can be part of A-T, infectious arthritis can occur, but chronic autoimmune arthritis in these patients is rare. We report a rare case of a 15-year-old boy with A-T and JIA. This case shows a possible relationship between altered function of ATM protein and the pathogenesis of JIA.

BACKGROUND:

Our previous studies of Alzheimer's disease (AD) suggested that glutamine broadly improves cellular readiness to respond to stress and acts as a neuroprotectant both in vitro and in AD mouse models. We now expand our studies to a second neurodegenerative disease, ataxia-telangiectasia (A-T). Unlike AD, where clinically significant cognitive decline does not typically occur before age 65, A-T symptoms appear in early childhood and are caused exclusively by mutations in the ATM (A-T mutated) gene.

RESULTS:

Genetically ATM-deficient mice and wild type littermates were maintained with or without 4 % glutamine in their drinking water for several weeks. In ATM mutants, glutamine supplementation restored serum glutamine and glucose levels and reduced body weight loss. Lost neurophysiological function assessed through the magnitude of hippocampal long term potentiation was significantly restored. Glutamine supplemented mice also showed reduced thymus pathology and, remarkably, a full one-third extension of lifespan. In vitro assays revealed that ATM-deficient cells are more sensitive to glutamine deprivation, while supra-molar glutamine (8 mM) partially rescued the reduction of BDNF expression and HDAC4 nuclear translocation of genetically mutant Atm(-/-) neurons. Analysis of microarray data suggested that glutamine metabolism is significantly altered in human A-T brains as well.

CONCLUSION:

Glutamine is a powerful part of an organism's internal environment. Changes in its concentrations can have a huge impact on the function of all organ systems, especially the brain. Glutamine supplementation thus bears consideration as a therapeutic strategy for the treatment of human A-T and perhaps other neurodegenerative diseases.

Rare pleiotropic genetic disorders, Ataxia-telangiectasia (A-T), Bloom syndrome (BS) and Nijmegen breakage syndrome (NBS) are characterised by immunodeficiency, extreme radiosensitivity, higher cancer susceptibility, premature aging, neurodegeneration and insulin resistance. Some of these functional abnormalities can be explained by aberrant DNA damage response and chromosomal instability. It has been suggested that one possible common denominator of these conditions could be chronic oxidative stress caused by endogenous ROS overproduction and impairment of mitochondrial homeostasis. Recent studies indicate new, alternative sources of oxidative stress in A-T, BS and NBS cells, including NADPH oxidase 4 (NOX4), oxidised low-density lipoprotein (ox-LDL) or Poly (ADP-ribose) polymerases (PARP). Mitochondrial abnormalities such as changes in the ultrastructure and function of mitochondria, excess mROS production as well as mitochondrial damage have also been reported in A-T, BS and NBS cells. A-T, BS and NBS cells are inextricably linked to high levels of reactive oxygen species (ROS), and thereby, chronic oxidative stress may be a major phenotypic hallmark in these diseases. Due to the presence of mitochondrial disturbances, A-T, BS and NBS may be considered mitochondrial diseases. Excess activity of antioxidant enzymes and an insufficient amount of low molecular weight antioxidants indicate new pharmacological strategies for patients suffering from the aforementioned diseases. However, at the current stage of research we are unable to ascertain if antioxidants and free radical scavengers can improve the condition or prolong the survival time of A-T, BS and NBS patients. Therefore, it is necessary to conduct experimental studies in a human model.