Pathogenesis of ataxia-telangiectasia: the next generation of ATM functions

Metformin and its potential influence on cell fate decision between apoptosis and senescence in cancer, with a special emphasis on glioblastoma

Despite reaching enormous achievements in therapeutic approaches worldwide, GBM still remains the most incurable malignancy among various cancers. It emphasizes the necessity of adjuvant therapies from the perspectives of both patients and healthcare providers. Therefore, most emerging studies have focused on various complementary and adjuvant therapies. Among them, metabolic therapy has received special attention, and metformin has been considered as a treatment in various types of cancer, including GBM. It is clearly evident that reaching efficient approaches without a comprehensive evaluation of the key mechanisms is not possible. Among the studied mechanisms, one of the more challenging ones is the effect of metformin on apoptosis and senescence. Moreover, metformin is well known as an insulin sensitizer. However, if insulin signaling is facilitated in the tumor microenvironment, it may result in tumor growth. Therefore, to partially resolve some paradoxical issues, we conducted a narrative review of related studies to address the following questions as comprehensively as possible: 1) Does the improvement of cellular insulin function resulting from metformin have detrimental or beneficial effects on GBM cells? 2) If these effects are detrimental to GBM cells, which is more important: apoptosis or senescence? 3) What determines the cellular decision between apoptosis and senescence?

Variant ataxia telangiectasia identified during evaluation for short stature

Ataxia telangiectasia (A-T) (OMIM 208900) is an autosomal recessive multisystem disorder characterised by progressive cerebellar ataxia, telangiectasias, immunodeficiency and a predisposition to malignancy. 'Variant' A-T has later onset of neurological symptoms and slower progression compared with the 'classic' form. A woman presented with short stature in late childhood. Karyotype revealed rearrangements involving chromosomes 7 and 14. A chromosomal breakage disorder gene panel demonstrated compound heterozygote mutations in her ATM gene including one mutation c.7271T>G with residual ATM function, confirming the diagnosis of variant A-T. Since diagnosis, she has developed progressive cerebellar ataxia and telangiectasias. Long-standing restrictive and aversive feeding behaviours presented challenges for her management and necessitated gastrostomy.

The ATM Ser49Cys Variant Effects ATM Function as a Regulator of Oncogene-Induced Senescence

An apical component of the cell cycle checkpoint and DNA damage repair response is the ataxia-telangiectasia mutated (ATM) Ser/Thr protein kinase. A variant of ATM, Ser49Cys (rs1800054; minor allele frequency = 0.011), has been associated with an elevated risk of melanoma development; however, the functional consequence of this variant is not defined. ATM-dependent signalling in response to DNA damage has been assessed in a panel of patient-derived lymphoblastoid lines and primary human melanocytic cell strains heterozygous for the ATM Ser49Cys variant allele. The ATM Ser49Cys allele appears functional for acute p53-dependent signalling in response to DNA damage. Expression of the variant allele did reduce the efficacy of oncogene expression in inducing senescence. These findings demonstrate that the ATM 146C>G Ser49Cys allele has little discernible effect on the acute response to DNA damage but has reduced function observed in the chronic response to oncogene over-expression. Analysis of melanoma, naevus and skin colour genomics and GWAS analyses have demonstrated no association of this variant with any of these outcomes. The modest loss of function detected suggest that the variant may act as a modifier of other variants of ATM/p53-dependent signalling.

FGIN-1-27 Mitigates Radiation-induced Mitochondrial Hyperfunction and Cellular Hyperactivation in Cultured Astrocytes

Radiation-induced brain injury (RBI) poses a significant challenge in the context of radiotherapy for intracranial tumors, necessitating a comprehensive understanding of the cellular and molecular mechanisms involved. While prior investigations have underscored the role of astrocyte activation and excessive vascular endothelial growth factor production in microvascular damage associated with RBI, there remains a scarcity of studies examining the impact of radiation on astrocytes, particularly regarding organelles such as mitochondria. Thus, our study aimed to elucidate alterations in astrocyte and mitochondrial functionality following radiation exposure, with a specific focus on evaluating the potential ameliorative effects of translocator protein 18 kDa(TSPO) ligands. In this study, cultured astrocytes were subjected to X-ray irradiation, and their cellular states and mitochondrial functions were examined and compared to control cells. Our findings revealed that radiation-induced astrocytic hyperactivation, transforming them into the neurotoxic A1-type, concomitant with reduced cell proliferation. Additionally, radiation triggered mitochondrial hyperfunction, heightened the mitochondrial membrane potential, and increased oxidative metabolite production. However, following treatment with FGIN-1-27, a TSPO ligand, we observed a restoration of mitochondrial function and a reduction in oxidative metabolite production. Moreover, this intervention mitigated astrocyte hyperactivity, decreased the number of A1-type astrocytes, and restored cell proliferative capacity. In conclusion, our study has unveiled additional manifestations of radiation-induced astrocyte dysfunction and validated that TSPO ligands may serve as a promising therapeutic strategy to mitigate this dysfunction. It has potential clinical implications for the treatment of RBI.

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.

Inhibition of LNC EBLN3P Enhances Radiation-Induced Mitochondrial Damage in Lung Cancer Cells by Targeting the Keap1/Nrf2/HO-1 Axis

Lung cancer remains the leading cause of cancer-related deaths in both women and men, claiming millions of lives worldwide. Radiotherapy is an effective modality for treating early-stage lung cancer; however, it cannot completely eradicate certain tumor cells due to their radioresistance. Radioresistance is commonly observed in conventionally fractionated radiotherapy, which can lead to treatment failure, metastasis, cancer recurrence, and poor prognosis for cancer patients. Identifying the underlying molecular mechanisms of radioresistance in lung cancer can promote the development of effective radiosensitizers, thereby improving patients' life expectancy and curability. In this study, we identified LNC EBLN3P as a regulator of lung cancer cell proliferation and radiosensitivity. The repression of LNC EBLN3P could increase ROS production and mitochondrial injury in NSCLC cells. In addition, knocking down LNC EBLN3P increased the binding of Nrf2 to Keap1, resulting in enhanced Nrf2 degradation, decreased translocation of Nrf2 to the nucleus, reduced expression of antioxidant protein HO-1, weakened cellular antioxidant capacity, and increased radiosensitivity of NSCLC cells. These findings suggest that targeting LNC EBLN3P could be a promising strategy for developing novel radiosensitizers in the context of conventional radiotherapy for NSCLC.

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.

Novel Therapeutic Approaches in Inherited Neuropathies: A Systematic Review

The management of inherited neuropathies relies mostly on the treatment of symptoms. In recent years, a better understanding of the pathogenic mechanisms that underlie neuropathies has allowed for the development of disease-modifying therapies. Here, we systematically review the therapies that have emerged in this field over the last five years. An updated list of diseases with peripheral neuropathy as a clinical feature was created based on panels of genes used clinically to diagnose inherited neuropathy. This list was extended by an analysis of published data by the authors and verified by two experts. A comprehensive search for studies of human patients suffering from one of the diseases in our list yielded 28 studies that assessed neuropathy as a primary or secondary outcome. Although the use of various scales and scoring systems made comparisons difficult, this analysis identified diseases associated with neuropathy for which approved therapies exist. An important finding is that the symptoms and/or biomarkers of neuropathies were assessed only in a minority of cases. Therefore, further investigation of treatment efficacy on neuropathies in future trials must employ objective, consistent methods such as wearable technologies, motor unit indexes, MRI or sonography imaging, or the use of blood biomarkers associated with consistent nerve conduction studies.

Hepatic fibrosis: a manifestation of the liver disease evolution in patients with Ataxia-telangiectasia

BACKGROUND

Ataxia-telangiectasia (A-T) is a DNA repair disorder characterized by changes in several organs and systems. Advances in clinical protocols have resulted in increased survival of A-T patients, however disease progression is evident, mainly through metabolic and liver changes.

OBJECTIVE

To identify the frequency of significant hepatic fibrosis in A-T patients and to verify the association with metabolic alterations and degree of ataxia.

METHODS

This is a cross-sectional study that included 25 A-T patients aged 5 to 31 years. Anthropometric data, liver, inflammatory, lipid metabolism and glucose biomarkers (oral glucose tolerance test with insulin curve-OGTT) were collected. The Cooperative Ataxia Rating Scale was applied to assess the degree of ataxia. The following were calculated: Homeostasis Model Assessment-Insulin Resistance, Homeostasis Model Assessment-Adiponectin (HOMA-AD), Matsuda index, aspartate aminotransferase (AST): platelet ratio index, nonalcoholic fatty liver disease fibrosis score and BARD score. Liver ultrasonography and transient liver elastography by FibroScan^® were performed.

RESULTS

Significant hepatic fibrosis was observed in 5/25 (20%). Patients in the group with significant hepatic fibrosis were older (p < 0.001), had lower platelet count values (p = 0.027), serum albumin (p = 0.019), HDL-c (p = 0.013) and Matsuda index (p = 0.044); and high values of LDL-c (p = 0.049), AST (p = 0.001), alanine aminotransferase (p = 0.002), gamma-glutamyl transferase (p = 0.001), ferritin (p = 0.001), 120-min glycemia by OGTT (p = 0.049), HOMA-AD (p = 0.016) and degree of ataxia (p = 0.009).

CONCLUSIONS

A non-invasive diagnosis of significant hepatic fibrosis was observed in 20% of A-T patients associated with changes in liver enzymes, ferritin, increased HOMA-AD, and the severity of ataxia in comparison with patients without hepatic fibrosis.

Liver Assessment in Patients with Ataxia-Telangiectasia: Transient Elastography Detects Early Stages of Steatosis and Fibrosis

Background

Ataxia-telangiectasia (A-T) is a rare autosomal-recessive multisystem disorder characterized by pronounced cerebellar ataxia, telangiectasia, cancer predisposition, and altered body composition. Liver diseases with steatosis, fibrosis, and hepatocellular carcinoma are frequent findings in older patients but sensitive noninvasive diagnostic tools are lacking.

Objectives

To determine the sensitivity of transient elastography (TE) as a screening tool for early hepatic tissue changes and serum biomarkers for liver disease.

Methods

Thirty-one A-T patients aged 2 to 25 years were examined prospectively from 2016-2018 by TE. In addition, we evaluated the diagnostic performance of liver biomarkers for steatosis and necroinflammatory activity (SteatoTest and ActiTest, Biopredictive, Paris) compared to TE. For calculation and comparison, patients were divided into two groups (<12, >12 years of age).

Results

TE revealed steatosis in 2/21 (10%) younger patients compared to 9/10 (90%) older patients. Fibrosis was present in 3/10 (30%) older patients as assessed by TE. We found a significant correlation of steatosis with SteatoTest, alpha-fetoprotein (AFP), HbA1c, and triglycerides. Liver stiffness correlated significantly with SteatoTest, ActiTest, HbA1c, and triglycerides.

Conclusion

Liver disease is a common finding in older A-T patients. TE is an objective measure to detect early stages of steatosis and fibrosis. SteatoTest and ActiTest are a good diagnostic assessment for steatosis and necroinflammatory activity in patients with A-T and confirmed the TE results.

Hereditary breast cancer: syndromes, tumour pathology and molecular testing

Hereditary factors account for a significant proportion of breast cancer risk. Approximately 20% of hereditary breast cancers are attributable to pathogenic variants in the highly penetrant BRCA1 and BRCA2 genes. A proportion of the genetic risk is also explained by pathogenic variants in other breast cancer susceptibility genes, including ATM, CHEK2, PALB2, RAD51C, RAD51D and BARD1, as well as genes associated with breast cancer predisposition syndromes - TP53 (Li-Fraumeni syndrome), PTEN (Cowden syndrome), CDH1 (hereditary diffuse gastric cancer), STK11 (Peutz-Jeghers syndrome) and NF1 (neurofibromatosis type 1). Polygenic risk, the cumulative risk from carrying multiple low-penetrance breast cancer susceptibility alleles, is also a well-recognised contributor to risk. This review provides an overview of the established breast cancer susceptibility genes as well as breast cancer predisposition syndromes, highlights distinct genotype-phenotype correlations associated with germline mutation status and discusses molecular testing and therapeutic implications in the context of hereditary breast cancer.

Alternative end-joining originates stable chromosome aberrations induced by etoposide during targeted inhibition of DNA-PKcs in ATM-deficient tumor cells

ATM and DNA-PKcs coordinate the DNA damage response at multiple levels following the exposure to chemotherapy. The Topoisomerase II poison etoposide (ETO) is an effective chemotherapeutic agent that induces DNA double-strand breaks (DSB), but it is responsible from the chromosomal rearrangements frequently found in therapy-related secondary tumors. Targeted inhibition of DNA-PKcs in ATM-defective tumors combined with radio- or chemotherapy has been proposed as relevant therapies. Here, we explored the DNA repair mechanisms and the genetic consequences of targeting the non-oncogenic addiction to DNA-PKcs of ATM-defective tumor cells after exposure to ETO. We demonstrated that chemical inhibition of DNA-PKcs followed by treatment with ETO resulted in the accumulation of chromatid breaks and decreased mitotic index in both A-T cells and ATM-knocked-down (ATM^kd) tumor cells. The HR repair process in DNA-PKcs-inhibited ATM^kd cells amplified the RAD51 foci number, with no correlated increase in sister chromatid exchanges. The analysis of post-mitotic DNA lesions presented an augmented number of persistent unresolved DSB, without alterations in the cell cycle progression. Long-term examination of chromosome aberrations revealed a strikingly high number of chromatid and chromosome exchanges. By using genetic and pharmacological abrogation of PARP-1, we demonstrated that alternative end-joining (alt-EJ) repair pathway is responsible for those chromosome abnormalities generated by limiting c-NHEJ activities during directed inhibition of DNA-PKcs in ATM-deficient cells. Targeting the non-oncogenic addiction to DNA-PKcs of ATM-defective tumors stimulates the DSB repair by alt-EJ, which is liable for the origin of cells carrying stable chromosome aberrations that may eventually restrict the therapeutic strategy.

Computational gene expression analysis reveals distinct molecular subgroups of T-cell prolymphocytic leukemia

T-cell prolymphocytic leukemia (T-PLL) is a rare blood cancer with poor prognosis. Overexpression of the proto-oncogene TCL1A and missense mutations of the tumor suppressor ATM are putative main drivers of T-PLL development, but so far only little is known about the existence of T-PLL gene expression subtypes. We performed an in-depth computational reanalysis of 68 gene expression profiles of one of the largest currently existing T-PLL patient cohorts. Hierarchical clustering combined with bootstrapping revealed three robust T-PLL gene expression subgroups. Additional comparative analyses revealed similarities and differences of these subgroups at the level of individual genes, signaling and metabolic pathways, and associated gene regulatory networks. Differences were mainly reflected at the transcriptomic level, whereas gene copy number profiles of the three subgroups were much more similar to each other, except for few characteristic differences like duplications of parts of the chromosomes 7, 8, 14, and 22. At the network level, most of the 41 predicted potential major regulators showed subgroup-specific expression levels that differed at least in comparison to one other subgroup. Functional annotations suggest that these regulators contribute to differences between the subgroups by altering processes like immune responses, angiogenesis, cellular respiration, cell proliferation, apoptosis, or migration. Most of these regulators are known from other cancers and several of them have been reported in relation to leukemia (e.g. AHSP, CXCL8, CXCR2, ELANE, FFAR2, G0S2, GIMAP2, IL1RN, LCN2, MBTD1, PPP1R15A). The existence of the three revealed T-PLL subgroups was further validated by a classification of T-PLL patients from two other smaller cohorts. Overall, our study contributes to an improved stratification of T-PLL and the observed subgroup-specific molecular characteristics could help to develop urgently needed targeted treatment strategies.

Discovery of Therapeutics Targeting Oxidative Stress in Autosomal Recessive Cerebellar Ataxia: A Systematic Review

Autosomal recessive cerebellar ataxias (ARCAs) are a heterogeneous group of rare neurodegenerative inherited disorders. The resulting motor incoordination and progressive functional disabilities lead to reduced lifespan. There is currently no cure for ARCAs, likely attributed to the lack of understanding of the multifaceted roles of antioxidant defense and the underlying mechanisms. This systematic review aims to evaluate the extant literature on the current developments of therapeutic strategies that target oxidative stress for the management of ARCAs. We searched PubMed, Web of Science, and Science Direct Scopus for relevant peer-reviewed articles published from 1 January 2016 onwards. A total of 28 preclinical studies fulfilled the eligibility criteria for inclusion in this systematic review. We first evaluated the altered cellular processes, abnormal signaling cascades, and disrupted protein quality control underlying the pathogenesis of ARCA. We then examined the current potential therapeutic strategies for ARCAs, including aromatic, organic and pharmacological compounds, gene therapy, natural products, and nanotechnology, as well as their associated antioxidant pathways and modes of action. We then discussed their potential as antioxidant therapeutics for ARCAs, with the long-term view toward their possible translation to clinical practice. In conclusion, our current understanding is that these antioxidant therapies show promise in improving or halting the progression of ARCAs. Tailoring the therapies to specific disease stages could greatly facilitate the management of ARCAs.

Atypical Ataxia Presentation in Variant Ataxia Telangiectasia: Iranian Case-Series and Review of the Literature

Ataxia-telangiectasia (AT) is a rare autosomal recessive neurodegenerative multisystem disorder. A minority of AT patients can present late-onset atypical presentations due to unknown mechanisms. The demographic, clinical, immunological and genetic data were collected by direct interview and examining the Iranian AT patients with late-onset manifestations. We also conducted a systematic literature review for reported atypical AT patients. We identified three Iranian AT patients (3/249, 1.2% of total registry) with later age at ataxia onset and slower neurologic progression despite elevated alpha-fetoprotein levels, history of respiratory infections, and immunological features of the syndrome. Of note, all patients developed autoimmunity in which a decrease of naïve T cells and regulatory T cells were observed. The literature searches also summarized data from 73 variant AT patients with atypical presentation indicating biallelic mild mutations mainly lead to an atypical phenotype with an increased risk of cancer. Variant AT patients present with milder phenotype or atypical form of classical symptoms causing under- or mis- diagnosis. Although missense mutations are more frequent, an atypical presentation can be associated with deleterious mutations due to unknown modifying factors.

Molecular Features and Clinical Management of Hereditary Pancreatic Cancer Syndromes and Familial Pancreatic Cancer

Hereditary pancreatic cancers are caused by several inherited genes. Familial pancreatic cancer is defined as pancreatic cancer arising in a patient with at least two first-degree relatives with pancreatic cancer in the absence of an identified genetic cause. Hereditary pancreatic cancer syndromes and familial pancreatic cancers account for about 10% of pancreatic cancer cases. Germline mutations in BRCA1, BRCA2, ATM, PALB2, CDKN2A, STK11, and TP53 and mismatch repair genes (MLH1, MSH2, MSH6, PMS2, and EPCAM) are among the well-known inherited susceptibility genes. Currently available targeted medications include poly (ADP-ribose) polymerase inhibitors (PARP) for cases with mutant BRCA and immune checkpoint inhibitors for cases with mismatch repair deficiency. Loss of heterozygosity of hereditary pancreatic cancer susceptibility genes such as BRCA1/2 plays a key role in carcinogenesis and sensitivity to PARP inhibitors. Signature 3 identified by whole genome sequencing is also associated with homologous recombination deficiency and sensitivity to targeted therapies. In this review, we summarize molecular features and treatments of hereditary pancreatic cancer syndromes and surveillance procedures for unaffected high-risk cases. We also review transgenic murine models to gain a better understanding of carcinogenesis in hereditary pancreatic cancer.

O-GlcNAcylation in Chronic Lymphocytic Leukemia and Other Blood Cancers

In the past decade, aberrant O-GlcNAcylation has emerged as a new hallmark of cancer. O-GlcNAcylation is a post-translational modification that results when the amino-sugar β-D-N-acetylglucosamine (GlcNAc) is made in the hexosamine biosynthesis pathway (HBP) and covalently attached to serine and threonine residues in intracellular proteins by the glycosyltransferase O-GlcNAc transferase (OGT). O-GlcNAc moieties reflect the metabolic state of a cell and are removed by O-GlcNAcase (OGA). O-GlcNAcylation affects signaling pathways and protein expression by cross-talk with kinases and proteasomes and changes gene expression by altering protein interactions, localization, and complex formation. The HBP and O-GlcNAcylation are also recognized to mediate survival of cells in harsh conditions. Consequently, O-GlcNAcylation can affect many of the cellular processes that are relevant for cancer and is generally thought to promote tumor growth, disease progression, and immune escape. However, recent studies suggest a more nuanced view with O-GlcNAcylation acting as a tumor promoter or suppressor depending on the stage of disease or the genetic abnormalities, proliferative status, and state of the p53 axis in the cancer cell. Clinically relevant HBP and OGA inhibitors are already available and OGT inhibitors are in development to modulate O-GlcNAcylation as a potentially novel cancer treatment. Here recent studies that implicate O-GlcNAcylation in oncogenic properties of blood cancers are reviewed, focusing on chronic lymphocytic leukemia and effects on signal transduction and stress resistance in the cancer microenvironment. Therapeutic strategies for targeting the HBP and O-GlcNAcylation are also discussed.

Dysfunction of cerebellar microglia in Ataxia-telangiectasia

Ataxia-telangiectasia (A-T) is a multisystem autosomal recessive disease caused by mutations in the ATM gene and characterized by cerebellar atrophy, progressive ataxia, immunodeficiency, male and female sterility, radiosensitivity, cancer predisposition, growth retardation, insulin-resistant diabetes, and premature aging. ATM phosphorylates more than 1500 target proteins, which are involved in cell cycle control, DNA repair, apoptosis, modulation of chromatin structure, and other cytoplasmic as well as mitochondrial processes. In our quest to better understand the mechanisms by which ATM deficiency causes cerebellar degeneration, we hypothesized that specific vulnerabilities of cerebellar microglia underlie the etiology of A-T. Our hypothesis is based on the recent finding that dysfunction of glial cells affect a variety of process leading to impaired neuronal functionality (Song et al., 2019). Whereas astrocytes and neurons descend from the neural tube, microglia originate from the hematopoietic system, invade the brain at early embryonic stage, and become the innate immune cells of the central nervous system and important participants in development of synaptic plasticity. Here we demonstrate that microglia derived from Atm^-/- mouse cerebellum display accelerated cell migration and are severely impaired in phagocytosis, secretion of neurotrophic factors, and mitochondrial activity, suggestive of apoptotic processes. Interestingly, no microglial impairment was detected in Atm-deficient cerebral cortex, and Atm deficiency had less impact on astroglia than microglia. Collectively, our findings validate the roles of glial cells in cerebellar attrition in A-T.

Role of Mitochondria in Radiation Responses: Epigenetic, Metabolic, and Signaling Impacts

Until recently, radiation effects have been considered to be mainly due to nuclear DNA damage and their management by repair mechanisms. However, molecular biology studies reveal that the outcomes of exposures to ionizing radiation (IR) highly depend on activation and regulation through other molecular components of organelles that determine cell survival and proliferation capacities. As typical epigenetic-regulated organelles and central power stations of cells, mitochondria play an important pivotal role in those responses. They direct cellular metabolism, energy supply and homeostasis as well as radiation-induced signaling, cell death, and immunological responses. This review is focused on how energy, dose and quality of IR affect mitochondria-dependent epigenetic and functional control at the cellular and tissue level. Low-dose radiation effects on mitochondria appear to be associated with epigenetic and non-targeted effects involved in genomic instability and adaptive responses, whereas high-dose radiation effects (>1 Gy) concern therapeutic effects of radiation and long-term outcomes involving mitochondria-mediated innate and adaptive immune responses. Both effects depend on radiation quality. For example, the increased efficacy of high linear energy transfer particle radiotherapy, e.g., C-ion radiotherapy, relies on the reduction of anastasis, enhanced mitochondria-mediated apoptosis and immunogenic (antitumor) responses.

Simple Measurement of IgA Predicts Immunity and Mortality in Ataxia-Telangiectasia

Patients with ataxia-telangiectasia (A-T) suffer from progressive cerebellar ataxia, immunodeficiency, respiratory failure, and cancer susceptibility. From a clinical point of view, A-T patients with IgA deficiency show more symptoms and may have a poorer prognosis. In this study, we analyzed mortality and immunity data of 659 A-T patients with regard to IgA deficiency collected from the European Society for Immunodeficiencies (ESID) registry and from 66 patients with classical A-T who attended at the Frankfurt Goethe-University between 2012 and 2018. We studied peripheral B- and T-cell subsets and T-cell repertoire of the Frankfurt cohort and survival rates of all A-T patients in the ESID registry. Patients with A-T have significant alterations in their lymphocyte phenotypes. All subsets (CD3, CD4, CD8, CD19, CD4/CD45RA, and CD8/CD45RA) were significantly diminished compared to standard values. Patients with IgA deficiency (n = 35) had significantly lower lymphocyte counts compared to A-T patients without IgA deficiency (n = 31) due to a further decrease of naïve CD4 T-cells, central memory CD4 cells, and regulatory T-cells. Although both patient groups showed affected TCR-ß repertoires compared to controls, no differences could be detected between patients with and without IgA deficiency. Overall survival of patients with IgA deficiency was significantly diminished. For the first time, our data show that patients with IgA deficiency have significantly lower lymphocyte counts and subsets, which are accompanied with reduced survival, compared to A-T patients without IgA deficiency. IgA, a simple surrogate marker, is indicating the poorest prognosis for classical A-T patients. Both non-interventional clinical trials were registered at clinicaltrials.gov 2012 (Susceptibility to infections in ataxia-telangiectasia; NCT02345135) and 2017 (Susceptibility to Infections, tumor risk and liver disease in patients with ataxia-telangiectasia; NCT03357978)

Cellular functions of the protein kinase ATM and their relevance to human disease

The protein kinase ataxia telangiectasia mutated (ATM) is a master regulator of double-strand DNA break (DSB) signalling and stress responses. For three decades, ATM has been investigated extensively to elucidate its roles in the DNA damage response (DDR) and in the pathogenesis of ataxia telangiectasia (A-T), a human neurodegenerative disease caused by loss of ATM. Although hundreds of proteins have been identified as ATM phosphorylation targets and many important roles for this kinase have been identified, it is still unclear how ATM deficiency leads to the early-onset cerebellar degeneration that is common in all individuals with A-T. Recent studies suggest the existence of links between ATM deficiency and other cerebellum-specific neurological disorders, as well as the existence of broader similarities with more common neurodegenerative disorders. In this Review, we discuss recent structural insights into ATM regulation, and possible aetiologies of A-T phenotypes, including reactive oxygen species, mitochondrial dysfunction, alterations in transcription, R-loop metabolism and alternative splicing, defects in cellular proteostasis and metabolism, and potential pathogenic roles for hyper-poly(ADP-ribosyl)ation.

Correction of ATM mutations in iPS cells from two ataxia-telangiectasia patients restores DNA damage and oxidative stress responses

Patients with ataxia-telangiectasia (A-T) lack a functional ATM kinase protein and exhibit defective repair of DNA double-stranded breaks and response to oxidative stress. We show that CRISPR/Cas9-assisted gene correction combined with piggyBac (PB) transposon-mediated excision of the selection cassette enables seamless restoration of functional ATM alleles in induced pluripotent stem cells from an A-T patient carrying compound heterozygous exonic missense/frameshift mutations, and from a patient with a homozygous splicing acceptor mutation of an internal coding exon. We show that the correction of one allele restores expression of ~ 50% of full-length ATM protein and ameliorates DNA damage-induced activation (auto-phosphorylation) of ATM and phosphorylation of its downstream targets, KAP-1 and H2AX. Restoration of ATM function also normalizes radiosensitivity, mitochondrial ROS production and oxidative-stress-induced apoptosis levels in A-T iPSC lines, demonstrating that restoration of a single ATM allele is sufficient to rescue key ATM functions. Our data further show that despite the absence of a functional ATM kinase, homology-directed repair and seamless correction of a pathogenic ATM mutation is possible. The isogenic pairs of A-T and gene-corrected iPSCs described here constitute valuable tools for elucidating the role of ATM in ageing and A-T pathogenesis.

Genome instability and lymphoma

Lymphoma is one of the most common malignant tumor of the hematologic system. The genome instability is not only an important molecular basis for the development of lymphoma, but also has important value in the diagnosis and prognosis of lymphoma. There are 2 types of genome instability: Microsatellite instability (MSI/MIN) at gene level and chromosomal instability at chromosome level. Through the study on genes associated with lymphoma, the unstable genes associated with lymphoma could be found, meanwhile the mechanism of its occurrence and development of lymphoma could be explored, and the important basis of molecular biology could also be provided in the field of current hot lymphoma precision medical research.

Ataxia Telangiectasia Mutated Protein Kinase: A Potential Master Puppeteer of Oxidative Stress-Induced Metabolic Recycling

Ataxia Telangiectasia Mutated protein kinase (ATM) has recently come to the fore as a regulatory protein fulfilling many roles in the fine balancing act of metabolic homeostasis. Best known for its role as a transducer of DNA damage repair, the activity of ATM in the cytosol is enjoying increasing attention, where it plays a central role in general cellular recycling (macroautophagy) as well as the targeted clearance (selective autophagy) of damaged mitochondria and peroxisomes in response to oxidative stress, independently of the DNA damage response. The importance of ATM activation by oxidative stress has also recently been highlighted in the clearance of protein aggregates, where the expression of a functional ATM construct that cannot be activated by oxidative stress resulted in widespread accumulation of protein aggregates. This review will discuss the role of ATM in general autophagy, mitophagy, and pexophagy as well as aggrephagy and crosstalk between oxidative stress as an activator of ATM and its potential role as a master regulator of these processes.

SIRT3, a metabolic target linked to ataxia-telangiectasia mutated (ATM) gene deficiency in diffuse large B-cell lymphoma

Inactivation of Ataxia-telangiectasia mutated (ATM) gene results in an increased risk to develop cancer. We show that ATM deficiency in diffuse large B-cell lymphoma (DLBCL) significantly induce mitochondrial deacetylase sirtuin-3 (SIRT3) activity, disrupted mitochondrial structure, decreased mitochondrial respiration, and compromised TCA flux compared with DLBCL cells expressing wild type (WT)-ATM. This corresponded to enrichment of glutamate receptor and glutamine pathways in ATM deficient background compared to WT-ATM DLBCL cells. ATM^−/− DLBCL cells have decreased apoptosis in contrast to radiosensitive non-cancerous A-T cells. In vivo studies using gain and loss of SIRT3 expression showed that SIRT3 promotes growth of ATM CRISPR knockout DLBCL xenografts compared to wild-type ATM control xenografts. Importantly, screening of DLBCL patient samples identified SIRT3 as a putative therapeutic target, and validated an inverse relationship between ATM and SIRT3 expression. Our data predicts SIRT3 as an important therapeutic target for DLBCL patients with ATM null phenotype.

A Collaborative Effort to Define Classification Criteria for ATM Variants in Hereditary Cancer Patients

BACKGROUND

Gene panel testing by massive parallel sequencing has increased the diagnostic yield but also the number of variants of uncertain significance. Clinical interpretation of genomic data requires expertise for each gene and disease. Heterozygous ATM pathogenic variants increase the risk of cancer, particularly breast cancer. For this reason, ATM is included in most hereditary cancer panels. It is a large gene, showing a high number of variants, most of them of uncertain significance. Hence, we initiated a collaborative effort to improve and standardize variant classification for the ATM gene.

METHODS

Six independent laboratories collected information from 766 ATM variant carriers harboring 283 different variants. Data were submitted in a consensus template form, variant nomenclature and clinical information were curated, and monthly team conferences were established to review and adapt American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) criteria to ATM, which were used to classify 50 representative variants.

RESULTS

Amid 283 different variants, 99 appeared more than once, 35 had differences in classification among laboratories. Refinement of ACMG/AMP criteria to ATM involved specification for twenty-one criteria and adjustment of strength for fourteen others. Afterwards, 50 variants carried by 254 index cases were classified with the established framework resulting in a consensus classification for all of them and a reduction in the number of variants of uncertain significance from 58% to 42%.

CONCLUSIONS

Our results highlight the relevance of data sharing and data curation by multidisciplinary experts to achieve improved variant classification that will eventually improve clinical management.

Effects of Neurological Disorders on Bone Health

Neurological diseases, particularly in the context of aging, have serious impacts on quality of life and can negatively affect bone health. The brain-bone axis is critically important for skeletal metabolism, sensory innervation, and endocrine cross-talk between these organs. This review discusses current evidence for the cellular and molecular mechanisms by which various neurological disease categories, including autoimmune, developmental, dementia-related, movement, neuromuscular, stroke, trauma, and psychological, impart changes in bone homeostasis and mass, as well as fracture risk. Likewise, how bone may affect neurological function is discussed. Gaining a better understanding of brain-bone interactions, particularly in patients with underlying neurological disorders, may lead to development of novel therapies and discovery of shared risk factors, as well as highlight the need for broad, whole-health clinical approaches toward treatment.

Cutaneous and systemic granulomatosis in ataxia-telangiectasia: a clinico-pathological study

Introduction

The development of granulomas is a well-recognized manifestation of immunodeficiency in ataxia-telangiectasia (A-T), resulting from lymphocyte developmental abnormalities, impaired immunosurveillance, and inappropriate innate immune response-driven inflammation.

Aim

To better understand pathological and immunological phenomena involved in development of cutaneous and visceral granulomatosis observable in patients with ataxia-telangiectasia.

Material and methods

We retrospectively reviewed medical records of eight A-T children, aged from 2 to 13 years, with regard to clinical, immunological and histopathological features of cutaneous and visceral granulomatosis.

Results

In four out of eight A-T patients studied, cutaneous granulomas clinically presented as skin nodules and ulcerated erythematous plaques disseminated on the face, and on trauma-prone areas of upper and lower extremities. Visceral granulomatosis had a severe clinical course and involved the lungs, the spleen, the liver and the larynx. Histologically, cutaneous and laryngeal granulomas showed extensive cellular infiltrations containing T lymphocytes with predominating CD8+ phenotype and with CD68+ histiocytes. The immunological profile with the hyper-IgM phenotype, markedly reduced numbers of B and naive CD4+ and CD8+ T cells with predominating IgM-only memory B cells and skewed repertoire of a T cell receptor was observable in patients with skin and visceral granulomatosis.

Conclusions

In the setting of combined immunodeficiency in A-T, cutaneous and systemic granulomatosis reflects a granulomatous reaction pattern, as a result of inappropriate immune regulation.

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.

Heart failure and diabetes: role of ATM

Heart failure is a leading cause of death in the United States. Diabetes, also known as diabetes mellitus (DM), exponentially increases the risk of heart failure. The increase in oxidative stress and metabolic dysfunction caused by DM can lead to DNA damage and the development of diabetic cardiomyopathy. Ataxia telangiectasia mutated kinase (ATM) is a DNA damage response protein with a primary nuclear function to regulate cell cycle progression in response to double-strand DNA breaks, acts as a redox sensor, and facilitates DNA repair. ATM deficiency associates with the development of insulin resistance and DM. Consequently, patients with Ataxia telangiectasia, a rare autosomal recessive disorder, have an increased risk of developing heart failure. The main objective of this review is to summarize the shared metabolic and cardiac abnormalities associated with DM and ATM deficiency, with a focus on the development of heart failure.

Impaired ATM activation in B cells is associated with bone resorption in rheumatoid arthritis

Patients with rheumatoid arthritis (RA) may display atypical CD21^-/lo B cells in their blood, but the implication of this observation remains unclear. We report here that the group of patients with RA and elevated frequencies of CD21^-/lo B cells shows decreased ataxia telangiectasia-mutated (ATM) expression and activation in B cells compared with other patients with RA and healthy donor controls. In agreement with ATM involvement in the regulation of V(D)J recombination, patients with RA who show defective ATM function displayed a skewed B cell receptor (BCR) Igκ repertoire, which resembled that of patients with ataxia telangiectasia (AT). This repertoire was characterized by increased Jκ1 and decreased upstream Vκ gene segment usage, suggesting improper secondary recombination processes and selection. In addition, altered ATM function in B cells was associated with decreased osteoprotegerin and increased receptor activator of nuclear factor κB ligand (RANKL) production. These changes favor bone loss and correlated with a higher prevalence of erosive disease in patients with RA who show impaired ATM function. Using a humanized mouse model, we also show that ATM inhibition in vivo induces an altered Igκ repertoire and RANKL production by immature B cells in the bone marrow, leading to decreased bone density. We conclude that dysregulated ATM function in B cells promotes bone erosion and the emergence of circulating CD21^-/lo B cells, thereby contributing to RA pathophysiology.

The cerebellar degeneration in ataxia-telangiectasia: A case for genome instability

Research on the molecular pathology of genome instability disorders has advanced our understanding of the complex mechanisms that safeguard genome stability and cellular homeostasis at large. Once the culprit genes and their protein products are identified, an ongoing dialogue develops between the research lab and the clinic in an effort to link specific disease symptoms to the functions of the proteins that are missing in the patients. Ataxi A-T elangiectasia (A-T) is a prominent example of this process. A-T's hallmarks are progressive cerebellar degeneration, immunodeficiency, chronic lung disease, cancer predisposition, endocrine abnormalities, segmental premature aging, chromosomal instability and radiation sensitivity. The disease is caused by absence of the powerful protein kinase, ATM, best known as the mobilizer of the broad signaling network induced by double-strand breaks (DSBs) in the DNA. In parallel, ATM also functions in the maintenance of the cellular redox balance, mitochondrial function and turnover and many other metabolic circuits. An ongoing discussion in the A-T field revolves around the question of which ATM function is the one whose absence is responsible for the most debilitating aspect of A-T - the cerebellar degeneration. This review suggests that it is the absence of a comprehensive role of ATM in responding to ongoing DNA damage induced mainly by endogenous agents. It is the ensuing deterioration and eventual loss of cerebellar Purkinje cells, which are very vulnerable to ATM absence due to a unique combination of physiological features, which kindles the cerebellar decay in A-T.

Altered Cerebrospinal Fluid (CSF) in Children with Ataxia Telangiectasia

Ataxia telangiectasia (A-T) is a devastating multi-system disorder characterized by progressive cerebellar ataxia and immunodeficiency. The neurological decline may be caused by multiple factors of which ongoing inflammation and oxidative stress may play a dominant role. The objective of the present investigation was to determine cerebrospinal fluid (CSF) proteins and possible low-grade inflammation and its relation to age and neurological deterioration. In the present study, we investigated 15 patients with A-T from 2 to 16 years. Our investigation included blood and CSF tests, clinical neurological examination, A-T score, and MRI findings. The albumin ratio (AR) was analyzed to determine the blood-brain-barrier function. In addition, inflammatory cytokines (IL-1α, IL-6, IL-8, IL-12 p40, IL-17A, IFN-γ, TNF-α) were measured by the multiplex cytometric bead array. We compared the results with those from an age-matched control group. Three of the A-T patients were analyzed separately (one after resection of a cerebral meningioma, one after radiation and chemotherapy due to leukemia, one after stem cell transplantation). Patient had significantly more moderate and severe side effects due to CSF puncture (vomiting, headache, need for anti-emetic drugs) compared with healthy controls. Total protein, albumin, and the AR increased with age indicating a disturbed blood barrier function in older children. There were no differences for cytokines in serum and CSF with the exception of IL-2, which was significantly higher in controls in serum. The AR is significantly altered in A-T patients, but low-grade inflammation is not detectable in serum and CSF.

Functional Confirmation of DNA Repair Defect in Ataxia Telangiectasia (AT) Infants Identified by Newborn Screening for Severe Combined Immunodeficiency (NBS SCID)

BACKGROUND

The introduction of newborn screening for severe combined immunodeficiencies (NBS SCID) in 2010 was a significant public health milestone. Although SCID was the primary target, several other conditions associated with severe T-cell lymphopenia have subsequently been identified as secondary targets. The differential diagnosis in infants with an abnormal T-cell receptor excision circle result on NBS SCID who do not meet criteria for typical SCID is often broad, and often the evaluation of these conditions requires immunological and functional testing, in conjunction with genetic analysis, to obtain an accurate diagnosis and develop an appropriate management and treatment plan.

OBJECTIVE

We describe here 3 infants identified by NBS SCID, who required additional workup as they did not have a typical SCID phenotype and meet the relevant diagnostic criteria. Genetic testing identified pathogenic variants in ATM in all 3 patients, and the pathogenicity of the variants was confirmed by a functional flow cytometry assay.

METHODS

The patients underwent immunological and genetic workup to identify an underlying cause of their abnormal NBS SCID. Ataxia telangiectasia (AT) was suspected based on clinical and family history, and immunological analyses. The diagnosis was confirmed in all patients with a rapid functional flow cytometric assay and genetic testing.

RESULTS

A rapid functional flow cytometry assay was used as a diagnostic and confirmatory tool, in conjunction with genetic testing, to make a diagnosis of AT. Experimental validation of the causal relationship between genotype and phenotype allowed for expeditious diagnosis, which facilitated early discussions with families regarding prognosis, treatment, and management.

CONCLUSIONS

Even with increased rapidity and access to genetic results, functional testing is required for clinical diagnosis in infants identified by NBS SCID who do not fit into the classic categories or have novel genetic variants to confirm the diagnosis. Consideration should be given to the use of functional assays as an essential component of an integrated evaluation to characterize the genetics and mechanisms of inborn errors of immunity.

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.

Molecular crosstalk between cancer and neurodegenerative diseases

The progression of cancers and neurodegenerative disorders is largely defined by a set of molecular determinants that are either complementarily deregulated, or share remarkably overlapping functional pathways. A large number of such molecules have been demonstrated to be involved in the progression of both diseases. In this review, we particularly discuss our current knowledge on p53, cyclin D, cyclin E, cyclin F, Pin1 and protein phosphatase 2A, and their implications in the shared or distinct pathways that lead to cancers or neurodegenerative diseases. In addition, we focus on the inter-dependent regulation of brain cancers and neurodegeneration, mediated by intercellular communication between tumor and neuronal cells in the brain through the extracellular microenvironment. Finally, we shed light on the therapeutic perspectives for the treatment of both cancer and neurodegenerative disorders.

Protective Mechanisms Against DNA Replication Stress in the Nervous System

The precise replication of DNA and the successful segregation of chromosomes are essential for the faithful transmission of genetic information during the cell cycle. Alterations in the dynamics of genome replication, also referred to as DNA replication stress, may lead to DNA damage and, consequently, mutations and chromosomal rearrangements. Extensive research has revealed that DNA replication stress drives genome instability during tumorigenesis. Over decades, genetic studies of inherited syndromes have established a connection between the mutations in genes required for proper DNA repair/DNA damage responses and neurological diseases. It is becoming clear that both the prevention and the responses to replication stress are particularly important for nervous system development and function. The accurate regulation of cell proliferation is key for the expansion of progenitor pools during central nervous system (CNS) development, adult neurogenesis, and regeneration. Moreover, DNA replication stress in glial cells regulates CNS tumorigenesis and plays a role in neurodegenerative diseases such as ataxia telangiectasia (A-T). Here, we review how replication stress generation and replication stress response (RSR) contribute to the CNS development, homeostasis, and disease. Both cell-autonomous mechanisms, as well as the evidence of RSR-mediated alterations of the cellular microenvironment in the nervous system, were discussed.

Granulomatous Liver Disease in Ataxia-Telangiectasia With the Hyper-IgM Phenotype: A Case Report

Ataxia-telangiectasia (A-T) is an autosomal recessive disorder characterized by neurodegeneration, combined immunodeficiency, and oculocutaneous telangiectasia. The hyper-IgM phenotype of A-T, correlating with a class-switch recombination defect, IgG and IgA deficiency, T helper and B cell lymphopenia, immune dysregulation, proinflammatory immune response, autoimmune disease, and a high risk of lymphomagenesis. Progressive liver disease is a hallmark of classical A-T with the hyper-IgM phenotype and manifests as non-alcoholic hepatic steatosis and fibrosis. We report a case of a 17-year-old male A-T patient, in whom a progressive granulomatous liver disease with portal hypertension, has led to massive splenomegaly and hypersplenism, metabolic liver insufficiency, bleeding from esophageal varices and pancytopenia. In this patient, an unusual severe disease course with a highly variable constellation of A-T symptomatology includes granulomatous skin, visceral, and internal organs disease with liver involvement. The liver disease is associated with the hyper-IgM immunophenotype and escalating neurodegeneration, creating a vicious circle of immune deficiency, permanent systemic inflammatory response, and organ-specific immunopathology.

Ataxia Telangiectasia Diagnosed on Newborn Screening-Case Cohort of 5 Years' Experience

Ataxia telangiectasia (AT) is a genetic condition caused by mutations involving ATM (Ataxia Telangiectasia Mutated). This gene is responsible for the expression of a DNA double stranded break repair kinase, the ATM protein kinase. The syndrome encompasses combined immunodeficiency and various degrees of neurological abnormalities and increased risk of malignancy. Typically, patients present early in life with delay in neurological milestones, but very infrequently, with life threatening infections typical of a profound T cell deficiency. It would therefore be unexpected to identify this condition immediately after birth using T cell receptor excision circle (TREC)-based newborn screening (NBS) for SCID. We sought to evaluate the frequency of AT detected by NBS, and to assess immunity as well as the genetic aberrations associated with this early presentation. Here, we describe the clinical, laboratory, and genetic features of patients diagnosed with AT through the Ontario NBS program for SCID, and followed in our center since its inception in 2013. Four patients were diagnosed with AT as a result of low TRECs on NBS. In each case, whole exome sequencing was diagnostic. All of our patients had compound heterozygous mutations involving the FRAP-ATM-TRRAP (FAT) domain of the ATM gene, which appears critical for kinase activity and is highly sensitive to mutagenesis. Our patients presented with profound lymphopenia involving both B and T cells. The ratio of naïve/memory CD45+RA/RO T cells population was variable. T cell repertoire showed decreased T cell diversity. Two out of four patients had decreased specific antibody response to vaccination and hypogammaglobulinemia requiring IVIG replacement. In two patients, profound decreased responses to phytohemagglutinin stimulation was observed. In the other two patients, the initial robust response declined with time. In summary, the rate of detection of AT through NBS had been surprisingly high at our center. One case was identified per year, while the total rate for SCID has been five new cases per year. This early detection may allow for better prospective evaluation of AT shortly after birth, and may assist in formulating early and more effective interventions both for the neurological as well as the immune abnormalities in this syndrome.

GSE4 peptide suppresses oxidative and telomere deficiencies in ataxia telangiectasia patient cells

Ataxia telangiectasia (AT) is a genetic disease caused by mutations in the ATM gene but the mechanisms underlying AT are not completely understood. Key functions of the ATM protein are to sense and regulate cellular redox status and to transduce DNA double-strand break signals to downstream effectors. ATM-deficient cells show increased ROS accumulation, activation of p38 protein kinase, and increased levels of DNA damage. GSE24.2 peptide and a short derivative GSE4 peptide corresponding to an internal domain of Dyskerin have proved to induce telomerase activity, decrease oxidative stress, and protect from DNA damage in dyskeratosis congenita (DC) cells. We have found that expression of GSE24.2 and GSE4 in human AT fibroblast is able to decrease DNA damage, detected by γ-H2A.X and 53BP1 foci. However, GSE24.2/GSE4 expression does not improve double-strand break signaling and repair caused by the lack of ATM activity. In contrast, they cause a decrease in 8-oxoguanine and OGG1-derived lesions, particularly at telomeres and mitochondrial DNA, as well as in reactive oxygen species, in parallel with increased expression of SOD1. These cells also showed lower levels of IL6 and decreased p38 phosphorylation, decreased senescence and increased ability to divide for longer times. Additionally, these cells are more resistant to treatment with H202 and the radiomimetic-drug bleomycin. Finally, we found shorter telomere length (TL) in AT cells, lower levels of TERT expression, and telomerase activity that were also partially reverted by GSE4. These observations suggest that GSE4 may be considered as a new therapy for the treatment of AT that counteracts the cellular effects of high ROS levels generated in AT cells and in addition increases telomerase activity contributing to increased cell proliferation.

Diversity of ATM gene variants: a population-based genome data analysis for precision medicine

BACKGROUND

Ataxia-telangiectasia (AT) is a rare autosomal recessive disorder that causes deficiency or dysfunction of the ataxia-telangiectasia mutated (ATM) protein. Not only AT patients, but also certain ATM heterozygous mutation carriers show a significantly reduced life expectancy due to cancer and ischemic heart disease; in particular, female carriers having particular alleles have an increased risk of breast cancer. The frequency of such risk heterozygotes at a population level remains to be fully determined, and evidence-based preventive medical guidelines have not yet been established.

METHODS

Using the 3.5KJPNv2 allele frequency panel of Japanese Multi Omics Reference Panel v201902, which shows single-nucleotide variant (SNV) and insertion/deletion (INDEL) allele frequencies from 3552 Japanese healthy individuals, we investigated the diversity of ATM gene variants.

RESULTS

We detected 2845 (2370 SNV and 475 INDEL) variants in the ATM gene, including 1338 (1160 SNV and 178 INDEL) novel variants. Also, we found a stop-gained SNV (NC_000008.11:g.108115650G > A (p.Trp266*)) and a disruptive-inframe-deletion (NC_000008.11:g. 108181014AAGAAAAGTATGGATGATCAAG/A (p.Ala1945_Phe1952delinsVal) and two frameshift INDELs (NC_000008.11:g.108119714CAA/C (p.Glu376fs) and NC_000008.11:g.108203577CTTATA/C (p.Ile2629fs)), which would be novel variants predicted to lead to loss of ATM functionality.

CONCLUSION

The combination of population-based biobanking and human genomics provided a novel insight of diversity of ATM gene variants at a population level. For the advancement of precision medicine, such approach will be useful to predict novel pathogenic/likely pathogenic variants in the ATM gene and to establish preventive medical guidelines for certain ATM heterozygotes pertaining to their risk of particular diseases.

Activation of NRF2 by dexamethasone in ataxia telangiectasia cells involves KEAP1 inhibition but not the inhibition of p38

Oxidative stress has been shown to play a crucial role in the pathophysiology of the neurodegenerative disease Ataxia Telangiectasia. We have recently demonstrated that Dexamethasone treatment is able to counteract the oxidative state by promoting nuclear factor erythroid 2-related factor 2 (NRF2) nuclear accumulation. However, substantial gaps remain in our knowledge of the underlying molecular mechanism(s) according to which Dexamethasone acts as an NRF2 inducer. Herein we investigate the possible effects of the drug on the main NRF2 activation pathways by initially focusing on key kinases known to differently affect NRF2 activation. Neither AKT nor ERK1/2, known to be NRF2-activating kinases, were found to be activated upon Dexamethasone treatment, thus excluding their involvement in the transcription factor nuclear shift. Likewise, GSK3 inactivating kinase was not inhibited, thus ruling out its role in NRF2 activation. On the other hand, p38 MAPK, another NRF2-inhibitory kinase, was indeed switched-off in Ataxia Telangiectasia cells by Dexamethasone-mediated induction of DUSP1 phosphatase, and therefore it appeared that it might account for NRF2 triggering. However, this mechanism was excluded by the use of a selective p38 inhibitor, which failed to cause a significant NRF2 nuclear shift and target gene induction. Finally, dexamethasone effects on the classical oxidative pathway orchestrated by KEAP1 were addressed. Dexamethasone was found to decrease the expression of the inhibitor KEAP1 at both mRNA and protein levels and to induce the shift from the reduced to the oxidized form of KEAP1, thus favouring NRF2 translocation into the nucleus. Furthermore, preliminary data revealed very low levels of the negative regulator Fyn in Ataxia Telangiectasia cells, which might account for the prolonged NRF2-activated gene expression.

Ataxia-Telangiectasia Mutated is located in cardiac mitochondria and impacts oxidative phosphorylation

The absence of Ataxia-Telangiectasia mutated protein kinase (ATM) is associated with neurological, metabolic and cardiovascular defects. The protein has been associated with mitochondria and its absence results in mitochondrial dysfunction. Furthermore, it can be activated in the cytosol by mitochondrial oxidative stress and mediates a cellular anti-oxidant response through the pentose phosphate pathway (PPP). However, the precise location and function of ATM within mitochondria and its role in oxidative phosphorylation is still unknown. We show that ATM is found endogenously within cardiac myocyte mitochondria under normoxic conditions and is consistently associated with the inner mitochondrial membrane. Acute ex vivo inhibition of ATM protein kinase significantly decreased mitochondrial electron transfer chain complex I-mediated oxidative phosphorylation rate but did not decrease coupling efficiency or oxygen consumption rate during β-oxidation. Chemical inhibition of ATM in rat cardiomyoblast cells (H9c2) significantly decreased the excited-state autofluorescence lifetime of enzyme-bound reduced NADH and its phosphorylated form, NADPH (NAD(P)H; 2.77 ± 0.26 ns compared to 2.57 ± 0.14 ns in KU60019-treated cells). This suggests an interaction between ATM and the electron transfer chain in the mitochondria, and hence may have an important role in oxidative phosphorylation in terminally differentiated cells such as cardiomyocytes.

Bioinformatics analysis of four proteins of Leishmania donovani to guide epitopes vaccine design and drug targets selection

Visceral leishmaniasis (VL) is a serious and widespread parasitic disease caused by Leishmania donovani complex. The threat of this fatal disease continues due to the lack of ideal drugs or vaccines. In this study, we selected Amastin, CaNA2, Kmp-11 and PDI proteins of Leishmania donovani for study, which are VL vaccine candidates or possible drug targets. Eleven bioinformatics tools were used to analyze different aspects of these proteins, including amino acid composition, topology, signal peptide, secondary structure, surface properties, phosphorylation sites and kinases, protein binding sites, 3D homology modeling, B cell epitopes, MHC class Ⅰ and Ⅱ epitopes and protein-protein interactions. Finally, the functionally related amino acid sites and dominant epitopes of these proteins were founded. Some possible relationships between protein structure, phosphorylation sites, protein binding sites and epitopes were also discovered. High flexibility and random coils regions of protein have a tendency to be phosphorylated, bind proteins and present epitopes. Since some phosphorylation sites and their kinases are involved in Leishmania invasion and survival in host cells, they may be potential drug targets. Bioinformatics analysis helps us better understand protein function and find dominant epitopes to guide drug design and vaccine development.

ATM deficiency promotes progression of CRPC by enhancing Warburg effect

ATM is a well-known master regulator of double strand break (DSB) DNA repair and the defective DNA repair has been therapeutically exploited to develop PARP inhibitors based on the synthetic lethality strategy. ATM mutation is found with increased prevalence in advanced metastatic castration-resistant prostate cancer (mCRPC). However, the molecular mechanisms underlying ATM mutation-driving disease progression are still largely unknown. Here, we report that ATM mutation contributes to the CRPC progression through a metabolic rather than DNA repair mechanism. We showed that ATM deficiency generated by CRISPR/Cas9 editing promoted CRPC cell proliferation and xenograft tumor growth. ATM deficiency altered cellular metabolism and enhanced Warburg effect in CRPC cells. We demonstrated that ATM deficiency shunted the glucose flux to aerobic glycolysis by upregulating LDHA expression, which generated more lactate and produced less mitochondrial ROS to promote CRPC cell growth. Inhibition of LDHA by siRNA or inhibitor FX11 generated less lactate and accumulated more ROS in ATM-deficient CRPC cells and therefore potentiated the cell death of ATM-deficient CRPC cells. These findings suggest a new therapeutic strategy for ATM-mutant CRPC patients by targeting LDHA-mediated glycolysis metabolism, which might be effective for the PARP inhibitor resistant mCRPC tumors.