In Cerebellar Atrophy of 12-Month-Old ATM-Null Mice, Transcriptome Upregulations Concern Most Neurotransmission and Neuropeptide Pathways, While Downregulations Affect Prominently Itpr1, Usp2 and Non-Coding RNA

The autosomal recessive disorder Ataxia-Telangiectasia is caused by a dysfunction of the stress response protein, ATM. In the nucleus of proliferating cells, ATM senses DNA double-strand breaks and coordinates their repair. This role explains T-cell dysfunction and tumour risk. However, it remains unclear whether this function is relevant for postmitotic neurons and underlies cerebellar atrophy, since ATM is cytoplasmic in postmitotic neurons. Here, we used ATM-null mice that survived early immune deficits via bone-marrow transplantation, and that reached initial neurodegeneration stages at 12 months of age. Global cerebellar transcriptomics demonstrated that ATM depletion triggered upregulations in most neurotransmission and neuropeptide systems. Downregulated transcripts were found for the ATM interactome component Usp2, many non-coding RNAs, ataxia genes Itpr1, Grid2, immediate early genes and immunity factors. Allelic splice changes affected prominently the neuropeptide machinery, e.g., Oprm1. Validation experiments with stressors were performed in human neuroblastoma cells, where ATM was localised only to cytoplasm, similar to the brain. Effect confirmation in SH-SY5Y cells occurred after ATM depletion and osmotic stress better than nutrient/oxidative stress, but not after ATM kinase inhibition or DNA stressor bleomycin. Overall, we provide pioneer observations from a faithful A-T mouse model, which suggest general changes in synaptic and dense-core vesicle stress adaptation.

Ataxia-telangiectasia clinical trial landscape and the obstacles to overcome

INTRODUCTION

Ataxia telangiectasia (A-T) is a life-limiting autosomal recessive disease characterized by cerebellar degeneration, ocular telangiectasias, and sinopulmonary disease. Since there is no cure for A-T, the standard of care is primarily supportive.

AREAS COVERED

We review clinical trials available in PubMed from 1990 to 2023 focused on lessening A-T disease burden. These approaches include genetic interventions, such as antisense oligonucleotides, designed to ameliorate disease progression in patients with select mutations. These approaches also include pharmacologic treatments that target oxidative stress, inflammation, and mitochondrial exhaustion, to attenuate neurological progression in A-T. Finally, we discuss the use of biological immunotherapies for the treatment of malignancies and granulomatous disease, along with other supportive therapies being used for the treatment of pulmonary disease and metabolic syndrome.

EXPERT OPINION

Barriers to successful genetic and pharmacologic interventions in A-T include the need for personalized treatment approaches based on patient-specific ATM mutations and phenotypes, lack of an animal model for the neurologic phenotype, and extreme rarity of disease making large-scale randomized trials difficult to perform. Ongoing efforts are needed to diagnose patients earlier, discover more effective therapies, and include more individuals in clinical trials, with the goal to lessen disease burden and to find a cure for patients with A-T.

The incidence and type of cancer in patients with ataxia-telangiectasia via a retrospective single-centre study

Ataxia-telangiectasia (A-T) is a hereditary immune system disorder with neurodegeneration. Its first neurologic symptoms include ataxic gait in early childhood, with slowly progressive cerebellar ataxia, oculomotor apraxia, oculocutaneous telangiectasia, and progressive muscle weakness. Neonatal screening for severe T-cell deficiency was recently found to diagnose A-T patients with a significantly reduced naïve T-cell pool. Our study includes 69 A-T patients between 8 January 2002 and 1 December 2019. Nineteen cases of cancer were diagnosed in 17 patients (25%), with a median overall survival [OS; 95% cumulative indcidence (CI)] of 26·9 years for the entire cohort. The 15-year OS of 82·5% (72-95%) was significantly decreased among A-T patients with malignancies, who had a median OS of 2·11 years, with a two-year-estimated OS of 50·7% (31-82%). Haematological malignancies were the major causes of death within the initial years of life with a 15 times increased risk for death [HR (95% CI): 6·9 (3·1-15.2), P < 0·001] upon malignancy diagnosis. Male patients with A-T are at a higher cancer risk than their female counterparts. This manuscript highlights the need for cancer surveillance and prevention, as well as optimal treatment in this cohort.

Survival and Functional Immune Reconstitution After Haploidentical Stem Cell Transplantation in Atm-Deficient Mice

Hematopoietic stem cell transplantation (HSCT) has been proposed as a promising therapeutic opportunity to improve immunity and prevent hematologic malignancies in Ataxia-telangiectasia (A-T). However, experience in the transplantation strategy for A-T patients is still scarce. The aim of this study was to investigate whether different approaches of HSCT are feasible in regard to graft versus host response and sufficient concerning functional immune reconstitution. Atm-deficient mice were treated with a clinically relevant non-myeloablative host-conditioning regimen and transplanted with CD90.2-depleted, green fluorescent protein (GFP)-expressing, and ataxia telangiectasia mutated (ATM)-competent bone marrow donor cells in a syngeneic, haploidentical or allogeneic setting. Like syngeneic HSCT, haploidentical HSCT, but not allogeneic HSCT extended the lifespan of Atm-deficient mice through the reduction of thymic tumors and normalized T-cell numbers. Donor-derived splenocytes isolated from transplanted Atm-deficient mice filled the gap of cell loss in the naïve T-cell population and raised CD4 cell functionality up to wild-type level. Interestingly, HSCT using heterozygous donor cells let to a significantly improved survival of Atm-deficient mice and increased CD4 cell numbers as well as CD4 cell functionality equivalent to HSCT using with wild-type donor cells. Our data provided evidence that haploidentical HSCT could be a feasible strategy for A-T, possibly even if the donor is heterozygous for ATM. However, this basic research cannot substitute any research in humans.

Neurofilament Light Chain Is a Biomarker of Neurodegeneration in Ataxia Telangiectasia

Ataxia telangiectasia (A-T) is a progressive and life-limiting disease associated with cerebellar ataxia due to progressive cerebellar degeneration. In addition to ataxia, which is described in detail, the presence of chorea, dystonia, oculomotor apraxia, athetosis, parkinsonism, and myoclonia are typical manifestations of the disease. The study aimed to evaluate the specificity and sensitivity of neurofilament light chain (NfL) as a biomarker of neurodegeneration in relation to SARA score. In this prospective trial, one visit of 42 A-T patients aged 1.3–25.6 years (mean 11.6 ± 7.3 years) was performed, in which NfL was determined from serum by ELISA. Additionally, a neurological examination of the patients was performed. Blood was collected from 19 healthy volunteers ≥ 12 years of age. We found significantly increased levels of NfL in patients with A-T compared to healthy controls (21.5 ± 3.6 pg/mL vs. 9.3 ± 0.49 pg/mL, p ≤ 0.01). There was a significant correlation of NfL with age, AFP, and SARA. NfL is a new potential progression biomarker in blood for neurodegeneration in A-T which increases with age.

Bone Marrow Transplantation as Therapy for Ataxia-Telangiectasia: A Systematic Review

Ataxia-Telangiectasia (A-T) is a rare autosomal recessive disorder, first reported in 1926, caused by a deficiency of ATM (Ataxia-Telangiectasia Mutated) protein. The disease is characterized by progressive cerebellar neurodegeneration, immunodeficiency, leukemia, and lymphoma cancer predisposition. Immunoglobulin replacement, antioxidants, neuroprotective factors, growth, and anti-inflammatory hormones are commonly used for A-T treatment, but, to date, there is no known cure. Bone marrow transplantation (BMT) is a successful therapy for several forms of diseases and it is a valid approach for tumors, hemoglobinopathies, autoimmune diseases, inherited disorders of metabolism, and other pathologies. Some case reports of A-T patients have shown that BMT is becoming a good option, as a correct engraftment of healthy cells can restore some aspects of immunologic capacity. However, due to a high risk of mortality as a result of a clinical and cellular hypersensitivity to ionizing radiation and radiomimetic drugs, a specific non-myeloablative conditioning is required before BMT. Although BMT might be considered as one promising therapy for the treatment of immunological defects and cancer prevention in selected A-T patients, the therapy is currently not recommended or recognized and the eligibility of A-T patients for BMT is a point to deepen and deliberate.

Diabetes in Patients With Ataxia Telangiectasia: A National Cohort Study

Background: Ataxia telangiectasia (A-T) is a rare autosomal-recessive multisystem disorder characterized by pronounced cerebellar ataxia, telangiectasia, cancer predisposition and altered body composition. In addition, evidence is rising for endocrine dysfunction. Objectives: To determine the evolution of diabetes and its prevalence in a larger A-T cohort. Methods: A retrospective analysis of the patient charts of 39 subjects from the Frankfurt A-T cohort was performed between August 2002 and 2018 concerning HbA1c and oral glucose tolerance (OGTT). The median follow-up period was 4 years (1-16 years). In addition, in 31 A-T patients aged 1 to 38 years HbA1c and fasting glucose were studied prospectively from 2018 to 2019. Results: In the retrospective analysis, we could demonstrate a longitudinal increase of HbA1c. The prospective analysis showed a significant increase of HbA1c and fasting glucose with age (r = 0.79, p ≤ 0.0001). OGTT has a good sensitivity for insulin resistance screening, whereas HbA1c can be used to evaluate individual courses and therapy response. Seven out of 39 (17.9%) patients suffered from diabetes. Metformin did not always lead to sufficient diabetes control; one patient was treated successfully with repaglinide. Conclusion: Diabetes is a common finding in older A-T patients and often starts in puberty. Our data clearly demonstrate the need for an annual diabetes screening in patients > 12 years.

Tracking of Infused Mesenchymal Stem Cells in Injured Pulmonary Tissue in Atm-Deficient Mice

Pulmonary failure is the main cause of morbidity and mortality in the human chromosomal instability syndrome Ataxia-telangiectasia (A-T). Major phenotypes include recurrent respiratory tract infections and bronchiectasis, aspiration, respiratory muscle abnormalities, interstitial lung disease, and pulmonary fibrosis. At present, no effective pulmonary therapy for A-T exists. Cell therapy using adipose-derived mesenchymal stromal/stem cells (ASCs) might be a promising approach for tissue regeneration. The aim of the present project was to investigate whether ASCs migrate into the injured lung parenchyma of Atm-deficient mice as an indication of incipient tissue damage during A-T. Therefore, ASCs isolated from luciferase transgenic mice (mASCs) were intravenously transplanted into Atm-deficient and wild-type mice. Retention kinetics of the cells were monitored using in vivo bioluminescence imaging (BLI) and completed by subsequent verification using quantitative real-time polymerase chain reaction (qRT-PCR). The in vivo imaging and the qPCR results demonstrated migration accompanied by a significantly longer retention time of transplanted mASCs in the lung parenchyma of Atm-deficient mice compared to wild type mice. In conclusion, our study suggests incipient damage in the lung parenchyma of Atm-deficient mice. In addition, our data further demonstrate that a combination of luciferase-based PCR together with BLI is a pivotal tool for tracking mASCs after transplantation in models of inflammatory lung diseases such as A-T.

Hematopoietic Stem Cell Transplantation Restores Naïve T-Cell Populations in Atm-Deficient Mice and in Preemptively Treated Patients With Ataxia-Telangiectasia

Background: Ataxia-telangiectasia (A-T) is a multisystem disorder with progressive cerebellar ataxia, immunodeficiency, chromosomal instability, and increased cancer susceptibility. Cellular immunodeficiency is based on naïve CD4⁺ and CD8⁺ T-cell lymphopenia. Hematopoietic stem cell transplantation (HSCT) offers a potential to cure immunodeficiency and cancer due to restoration of the lymphopoietic system. The aim of this investigation was to analyze the effect of HSCT on naïve CD4⁺ as well as CD8⁺ T-cell numbers in A-T.

Methods: We analyzed total numbers of peripheral naïve (CD45RA⁺CD62L⁺) and memory (CD45RO⁺CD62L⁻) CD4⁺ and CD8⁺ T-cells of 32 A-T patients. Naïve (CD62L^highCD44^low) and memory (CD62L^lowCD44^high) T-cells were also measured in Atm-deficient mice before and after HSCT with GFP-expressing bone marrow derived hematopoietic stem cells. In addition, we analyzed T-cells in the peripheral blood of two A-T patients after HLA-identic allogeneic HSCT.

Results: Like in humans, naïve CD4⁺ as well as naïve CD8⁺ lymphocytes were decreased in Atm-deficient mice. HSCT significantly inhibited thymic lymphomas and increased survival time in these animals. Donor cell chimerism increased up to more than 50% 6 months after HSCT accompanied by a significant increase of naïve CD4 and CD8 T-cell subpopulations, but not of memory T-cells. This finding was also identified in the blood of the A-T patients after HSCT.

Conclusion: HSCT seems to be a feasible strategy to overcome immunodeficiency and might be a conceivable strategy to avoid T-cell driven cancer in A-T at higher risk for malignancy. Naïve CD4 and CD8 T-cells counts are suitable markers for monitoring immune reconstitution post-HSCT. However, risks and benefits of HSCT in A-T have to be properly weighted.

ATM activity in T cells is critical for immune surveillance of lymphoma in vivo

The proximal DNA damage response kinase ATM is frequently inactivated in human malignancies. Germline mutations in the ATM gene cause Ataxia-telangiectasia (A-T), characterized by cerebellar ataxia and cancer predisposition. Whether ATM deficiency impacts on tumor initiation or also on the maintenance of the malignant state is unclear. Here, we show that Atm reactivation in initially Atm-deficient B- and T cell lymphomas induces tumor regression. We further find a reduced T cell abundance in B cell lymphomas from Atm-defective mice and A-T patients. Using T cell-specific Atm-knockout models, as well as allogeneic transplantation experiments, we pinpoint impaired immune surveillance as a contributor to cancer predisposition and development. Moreover, we demonstrate that Atm-deficient T cells display impaired proliferation capacity upon stimulation, due to replication stress. Altogether, our data indicate that T cell-specific restoration of ATM activity or allogeneic hematopoietic stem cell transplantation may prevent lymphomagenesis in A-T patients.

Ataxia-telangiectasia: A review of clinical features and molecular pathology

Ataxia-telangiectasia (A-T) is an autosomal recessive primary immunodeficiency (PID) disease that is caused by mutations in ataxia-telangiectasia mutated (ATM) gene encoding a serine/threonine protein kinase. A-T patients represent a broad range of clinical manifestations including progressive cerebellar ataxia, oculocutaneous telangiectasia, variable immunodeficiency, radiosensitivity, susceptibility to malignancies, and increased metabolic diseases. This congenital disorder has phenotypic heterogeneity, and the severity of symptoms varies in different patients based on severity of mutations and disease progression. The principal role of nuclear ATM is the coordination of cellular signaling pathways in response to DNA double-strand breaks, oxidative stress, and cell cycle checkpoint. The pathogenesis of A-T is not limited to the role of ATM in the DNA damage response (DDR) pathway, and it has other functions mainly in the hematopoietic cells and neurons. ATM adjusts the functions of organelles such as mitochondria and peroxisomes and also regulates angiogenesis and glucose metabolisms. However, ATM has other functions in the cells (especially cell viability) that need further investigations. In this review, we described functions of ATM in the nucleus and cytoplasm, and also its association with some disorder formation such as neurologic, immunologic, vascular, pulmonary, metabolic, and dermatologic complications.

Hematopoietic Stem Cell Transplantation for DNA Double Strand Breakage Repair Disorders

The ubiquitous presence of enzymes required for repair of DNA double strand breaks renders patients with defects in these pathways susceptible to immunodeficiency, an increased risk of infection, autoimmunity, bone marrow failure and malignancies, which are commonly associated with Epstein Barr virus (EBV) infection. Treatment of malignancies is particularly difficult, as the nature of the systemic defect means that patients are sensitive to chemotherapy and radiotherapy. Increasing numbers of patients with Nijmegen Breakage syndrome, Ligase 4 deficiency and Cernunnos-XLF deficiency have been successfully transplanted. Best results are obtained with the use of reduced intensity conditioning. Patients with ataxia-telangiectasia have particularly poor outcomes and the best treatment approach for these patients is still to be determined.

Pre-emptive Allogeneic Hematopoietic Stem Cell Transplantation in Ataxia Telangiectasia

Ataxia telangiectasia (A-T) is a primary immunodeficiency with mutations in the gene encoding the A-T mutated (ATM) protein that interacts with immune, hematopoietic, and endocrine targets resulting in broad multi-systemic clinical manifestations with a devastating outcome. Apart from a progressive neurodegenerative disorder, A-T leads to significantly increased susceptibility to malignancies. It is a matter of discussion whether pre-emptive allogeneic hematopoietic stem cell transplantation (alloHSCT) using a reduced intensity conditioning regimen would be an option to restore immune-competence and prevent malignancy, as shown in animal models, because conventional treatment protocols of malignant diseases using radio- and/or chemotherapy have a high rate of therapy-related morbidity and mortality in these patients. We present the course of the disease, including immune reconstitution and neurological outcome following pre-emptive alloHSCT in a 4-year-old boy with A-T on a 6 year follow-up. Our manuscript provides a proof-of-concept of alloHSCT as an individual pre-emptive treatment strategy from which some A-T patients might benefit.

Atm reactivation reverses ataxia telangiectasia phenotypes in vivo

Hereditary deficiencies in DNA damage signaling are invariably associated with cancer predisposition, immunodeficiency, radiation sensitivity, gonadal abnormalities, premature aging, and tissue degeneration. ATM kinase has been established as a central player in DNA double-strand break repair and its deficiency causes ataxia telangiectasia, a rare, multi-system disease with no cure. So ATM represents a highly attractive target for the development of novel types of gene therapy or transplantation strategies. Atm tamoxifen-inducible mouse models were generated to explore whether Atm reconstitution is able to restore Atm function in an Atm-deficient background. Body weight, immunodeficiency, spermatogenesis, and radioresistance were recovered in transgenic mice within 1 month from Atm induction. Notably, life span was doubled after Atm restoration, mice were protected from thymoma and no cerebellar defects were observed. Atm signaling was functional after DNA damage in vivo and in vitro. In summary, we propose a new Atm mouse model to investigate novel therapeutic strategies for ATM activation in ataxia telangiectasia disease.

In vivo imaging system for explants analysis-A new approach for assessment of cell transplantation effects in large animal models

Introduction

Despite spectacular progress in cellular transplantology, there are still many concerns about the fate of transplanted cells. More preclinical studies are needed, especially on large animal models, to bridge the translational gap between basic research and the clinic. Herein, we propose a novel approach in analysis of cell transplantation effects in large animals explants using in vivo imaging system (IVIS®) or similar equipment.

Material and methods

In the in vitro experiment cells labeled with fluorescent membrane dyes: DID (far red) or PKH26 (orange) were visualized with IVIS®. The correlation between the fluorescence signal and cell number with or without addition of minced muscle tissue was calculated. In the ex vivo study urethras obtained from goats after intraurethral cells (n = 9) or PBS (n = 4) injections were divided into 0.5 cm cross-slices and analyzed by using IVIS®. Automatic algorithm followed or not by manual setup was used to separate specific dye signal from tissue autofluorescence. The results were verified by systematic microscopic analysis of standard 10 μm specimens prepared from slices before and after immunohistochemical staining. Comparison of obtained data was performed using diagnostic test function.

Results

Fluorescence signal strength in IVIS® was directly proportional to the number of cells regardless of the dye used and detectable for minimum 0.25x10⁶ of cells. DID-derived signal was much less affected by the background signal in comparison to PKH26 in in vitro test. Using the IVIS® to scan explants in defined arrangement resulted in precise localization of DID but not PKH26 positive spots. Microscopic analysis of histological specimens confirmed the specificity (89%) and sensitivity (80%) of IVIS® assessment relative to DID dye. The procedure enabled successful immunohistochemical staining of specimens derived from analyzed slices.

Conclusions

The IVIS® system under appropriate conditions of visualization and analysis can be used as a method for ex vivo evaluation of cell transplantation effects. Presented protocol allows for evaluation of cell delivery precision rate, enables semi-quantitative assessment of signal, preselects material for further analysis without interfering with the tissue properties. Far red dyes are appropriate fluorophores to cell labeling for this application.

Low-dose irradiation prior to bone marrow transplantation results in ATM activation and increased lethality in Atm-deficient mice

Ataxia telangiectasia is a genetic instability syndrome characterized by neurodegeneration, immunodeficiency, severe bronchial complications, hypersensitivity to radiotherapy and an elevated risk of malignancies. Repopulation with ATM-competent bone marrow-derived cells (BMDCs) significantly prolonged the lifespan and improved the phenotype of Atm-deficient mice. The aim of the present study was to promote BMDC engraftment after bone marrow transplantation using low-dose irradiation (IR) as a co-conditioning strategy. Atm-deficient mice were transplanted with green fluorescent protein-expressing, ATM-positive BMDCs using a clinically relevant non-myeloablative host-conditioning regimen together with TBI (0.2-2.0 Gy). IR significantly improved the engraftment of BMDCs into the bone marrow, blood, spleen and lung in a dose-dependent manner, but not into the cerebellum. However, with increasing doses, IR lethality increased even after low-dose IR. Analysis of the bronchoalveolar lavage fluid and lung histochemistry revealed a significant enhancement in the number of inflammatory cells and oxidative damage. A delay in the resolution of γ-H2AX-expression points to an insufficient double-strand break repair capacity following IR with 0.5 Gy in Atm-deficient splenocytes. Our results demonstrate that even low-dose IR results in ATM activation. In the absence of ATM, low-dose IR leads to increased inflammation, oxidative stress and lethality in the Atm-deficient mouse model.

Radiation-sensitive severe combined immunodeficiency: The arguments for and against conditioning before hematopoietic cell transplantation--what to do?

Defects in DNA cross-link repair 1C (DCLRE1C), protein kinase DNA activated catalytic polypeptide (PRKDC), ligase 4 (LIG4), NHEJ1, and NBS1 involving the nonhomologous end-joining (NHEJ) DNA repair pathway result in radiation-sensitive severe combined immunodeficiency (SCID). Results of hematopoietic cell transplantation for radiation-sensitive SCID suggest that minimizing exposure to alkylating agents and ionizing radiation is important for optimizing survival and minimizing late effects. However, use of preconditioning with alkylating agents is associated with a greater likelihood of full T- and B-cell reconstitution compared with no conditioning or immunosuppression alone. A reduced-intensity regimen using fludarabine and low-dose cyclophosphamide might be effective for patients with LIG4, NHEJ1, and NBS1 defects, although more data are needed to confirm these findings and characterize late effects. For patients with mutations in DCLRE1C (Artemis-deficient SCID), there is no optimal approach that uses standard dose-alkylating agents without significant late effects. Until nonchemotherapy agents, such as anti-CD45 or anti-CD117, become available, options include minimizing exposure to alkylators, such as single-agent low-dose targeted busulfan, or achieving T-cell reconstitution, followed several years later with a conditioning regimen to restore B-cell immunity. Gene therapy for these disorders will eventually remove the issues of rejection and graft-versus-host disease. Prospective multicenter studies are needed to evaluate these approaches in this rare but highly vulnerable patient population.

ATM signalling and cancer

ATM, the protein kinase mutated in the rare human disease ataxia telangiectasia (A-T), has been the focus of intense scrutiny over the past two decades. Initially this was because of the unusual radiosensitive phenotype of cells from A-T patients, and latterly because investigating ATM signalling has yielded valuable insights into the DNA damage response, redox signalling and cancer. With the recent explosion in genomic data, ATM alterations have been revealed both in the germline as a predisposing factor for cancer and as somatic changes in tumours themselves. Here we review these findings, as well as advances in the understanding of ATM signalling mechanisms in cancer and ATM inhibition as a strategy for cancer treatment.

Altered mucosal immune response after acute lung injury in a murine model of Ataxia Telangiectasia

Background

Ataxia telangiectasia (A-T) is a rare but devastating and progressive disorder characterized by cerebellar dysfunction, lymphoreticular malignancies and recurrent sinopulmonary infections. In A-T, disease of the respiratory system causes significant morbidity and is a frequent cause of death.

Methods

We used a self-limited murine model of hydrochloric acid-induced acute lung injury (ALI) to determine the inflammatory answer due to mucosal injury in Atm (A-T mutated)- deficient mice (Atm^-/-).

Results

ATM deficiency increased peak lung inflammation as demonstrated by bronchoalveolar lavage fluid (BALF) neutrophils and lymphocytes and increased levels of BALF pro-inflammatory cytokines (e.g. IL-6, TNF). Furthermore, bronchial epithelial damage after ALI was increased in Atm^-/- mice. ATM deficiency increased airway resistance and tissue compliance before ALI was performed.

Conclusions

Together, these findings indicate that ATM plays a key role in inflammatory response after airway mucosal injury.