Novel Variants in ATM Causing Mild Ataxia-Telangiectasia: From Benchside to Bedside and Back Again.
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SUBMITTER: Perez Maturo J
PROVIDER: S-EPMC7396874 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:IntroductionAtaxia telangiectasia is a rare genetic condition with an estimated prevalence of 1 in 40,000-100,000 live births. This condition predominantly affects the nervous and immune systems. It is characterized by progressive ataxia beginning from early childhood. The neurological deficit associated with this condition affects one's balance, coordination, walking, and speech and can be accompanied by chorea, myoclonus, and neuropathy. They may also have ocular telangiectasias and high levels of blood alpha-fetoprotein (AFP). The ataxia telangiectasia mutated gene (ATM) is associated with this condition and codes for the ATM protein which is a phosphatidylinositol 3-kinase. This gene occupies 150 kb on chromosome 11q22-23 and contains 66 exons encoding a 13 kb transcript. ATM is a relatively large protein with a molecular weight of 350 kDa and 3,056 amino acids.MethodsFour patients of Sri Lankan origin presenting with features suggestive of ataxia telangiectasia were referred to our genetics center for specialized genetic counseling and testing. Whole-exome sequencing followed by Sanger sequencing was used to confirm the candidate variants. Protein modeling and genotype to phenotype correlation was performed in the identified variants.ResultsWe observed 6 novel ATM gene variants in four patients with ataxia telangiectasia. The identified variants are as follows: homozygous c.7397C > A (p.Ala2466Glu) and c.510_511delGT (p.Tyr171fs) and compound heterozygous c.5347_5350delGAAA (p.Glu1783fs), c.8137A > T (p.Arg2713 ∗ ) and c.1163A > C (p.Lys388Thr), and c.5227A > C (p.Thr1743Pro). Variant analysis was followed by modeling of the native and altered protein structures.ConclusionWe report novel ATM gene variants that have implications on the molecular diagnosis of ataxia telangiectasia.
| S-EPMC7744220 | biostudies-literature
Project description:Ataxia telangiectasia is a rare neurodegenerative disease caused by biallelic mutations in the ataxia telangiectasia mutated gene. No cure is currently available for these patients but positive effects on neurologic features in AT patients have been achieved by dexamethasone administration through autologous erythrocytes (EryDex) in phase II and phase III clinical trials, leading us to explore the molecular mechanisms behind the drug action. During these investigations, new ATM variants, which originated from alternative splicing of ATM messenger, were discovered, and detected in vivo in the blood of AT patients treated with EryDex. Some of the new ATM variants, alongside an in silico designed one, were characterized and examined in AT fibroblast cell lines. ATM variants were capable of rescuing ATM activity in AT cells, particularly in the nuclear role of DNA DSBs recognition and repair, and in the cytoplasmic role of modulating autophagy, antioxidant capacity and mitochondria functionality, all of the features that are compromised in AT but essential for neuron survival. These outcomes are triggered by the kinase and further functional domains of the tested ATM variants, that are useful for restoring cellular functionality. The in silico designed ATM variant eliciting most of the functionality recover may be exploited in gene therapy or gene delivery for the treatment of AT patients.
| S-EPMC9691487 | biostudies-literature
Project description: Not available
| S-EPMC3885782 | biostudies-literature
Project description:The gene for ataxia-telangiectasia (A-T:MIM: #208900), ATM, spans about 150 kb of genomic DNA and is composed of 62 coding exons. ATM mutations are found along the entire coding sequence of the gene, without evidence of mutational hot spots. Using DNA as the starting material, we used denaturing high performance liquid chromatography (DHPLC) technique to search for ATM gene mutations. Initially, DHPLC was validated in a retrospective study of 16 positive control samples that included 19 known mutations; 100% of mutations were detected. Subsequently, DHPLC was used to screen for mutations a cohort of 22 patients with the classical form of A-T. A total of 27 different mutations were identified on 38 of the 44 alleles, corresponding to a 86% detection rate. Fourteen of the mutations were novel. In addition, 15 different variants and polymorphisms of unknown functional significance were found. The high incidence of new and individual A-T mutations in our cohort of patients demonstrates marked mutational heterogeneity of A-T in Italy and corroborate the efficiency of DHPLC as a method for the mutation screening of A-T patients.
| S-EPMC3862285 | biostudies-literature
Project description: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.
| S-EPMC5833483 | biostudies-literature
Project description:BackgroundAtaxia-telangiectasia (A-T) is a progressive multisystemic neurodegenerative disease. The phenotypic spectrum includes conditions (variant A-T) with mild, late-onset, and atypical clinical presentations characterized by the prevalence of dyskinetic rather than ataxic features.CasesWe describe the clinical presentations of 3 siblings with early-onset truncal ataxia without obvious neurological deterioration or biological markers of classic A-T phenotype. We performed functional and genetic evaluation of 3 siblings with very mild neurological phenotype. Genetic evaluation with a next-generation sequencing panel for genes causative of cerebellar ataxia detected 2 known ATM gene variants, missense c.9023G>A p.(Arg3008His), and leaky splicing c.1066-6T>G variants. Functional studies showed mildly reduced ATM expression and residual kinase activity in the probands compared with healthy controls.ConclusionsThese results suggest the importance of investigating ATM variants even in the presence of clinical and biological atypical cases to ensure specific therapeutic regimens and oncological surveillance in these patients.
| S-EPMC9847291 | biostudies-literature
Project description:Ataxia-telangiectasia (A-T) is an infrequent autosomal recessive disorder that involves multiple systems and is characterized by progressive cerebellar ataxia, oculocutaneous telangiectasias, radiosensitivity, immune deficiency with recurrent respiratory infections, and a tendency to develop lymphoid malignancies. A-T is caused by mutations in the ATM gene, with >1,000 mutations reported to date and gradually increasing in number. Patients with A-T have an increased incidence of cancers. The aim of the present study was to retrospectively review the case of a patient who presented at the age of 5 years with cerebellar ataxia without telangiectasia, and was diagnosed with Burkitt leukemia by bone marrow biopsy and molecular testing at the age of 7 years at the Xiangya Hospital of Central South University (Changsha, China). The patient received chemotherapy with the pediatric CCCG-BNHL-2015 regimen (R4 group) and achieved a complete remission after 2 courses. However, recurrent respiratory infections and thrombosis occurred during chemotherapy. The diagnosis of A-T was confirmed by uncovering two variants of the ATM gene, including c.742C>T (p.R248X; rs730881336) in exon 7 and c.6067-c.6068 ins GAGGGAAGAT in exon 41 by whole-exome sequencing. Unfortunately, the patient's parents refused follow-up treatment and he succumbed to recurrent severe infections 4 months after the diagnosis of Burkitt leukemia. The diagnosis of A-T may be challenging, as its phenotype can be incomplete early in the course of the disease. Detailed medical history, characteristic clinical manifestations and increasingly developed exome sequencing techniques may be helpful in diagnosing this rare disease. Management should be based on multidisciplinary guidance and other treatment options must be investigated in the future.
| S-EPMC6200993 | biostudies-literature
Project description:Ataxia-telangiectasia (AT) is an autosomal recessive disorder characterized by progressive ataxia, choreoathetosis and immunodeficiency beginning in early childhood. An 8-year-old girl was referred with a diagnosis of AT. She had gait disturbance and dysarthria for 3years. Multiple cutaneous telangiectases were observed on her face, trunk and limbs. Sequence analysis of the ATM gene revealed a homozygous c.7308-15A>G mutation in IVS49. Human Splicing Finder predicted that the mutation could activate an intronic cryptic acceptor site. We designed primers for amplification of related exons (48-50) from cDNA for evaluating splicing pattern. Sequencing of ATM exons 48-50 revealed a 14-nucleotide insertion from intron 49, between exons 49 and 50, resulting in premature termination of translation at codon 2439. To conclude, we report a novel mutation in a classical AT case, which resulted in an alternatively spliced transcript and was predicted to form a truncated protein or null protein due to nonsense-mediated decay.
| S-EPMC8832216 | biostudies-literature
Project description:While ATM loss of function has long been identified as the genetic cause of ataxia-telangiectasia (A-T), how it leads to selective and progressive degeneration of cerebellar Purkinje and granule neurons remains unclear. ATM expression is enriched in microglia throughout cerebellar development and adulthood. Here, we find evidence of microglial inflammation in the cerebellum of patients with A-T using single-nucleus RNA sequencing. Pseudotime analysis revealed that activation of A-T microglia preceded upregulation of apoptosis-related genes in granule and Purkinje neurons and that microglia exhibited increased neurotoxic cytokine signaling to granule and Purkinje neurons in A-T. To confirm these findings experimentally, we performed transcriptomic profiling of A-T induced pluripotent stem cell (iPSC)-derived microglia, which revealed cell-intrinsic microglial activation of cytokine production and innate immune response pathways compared to controls. Furthermore, A-T microglia co-culture with either control or A-T iPSC-derived neurons was sufficient to induce cytotoxicity. Taken together, these studies reveal that cell-intrinsic microglial activation may promote neurodegeneration in A-T.
| S-EPMC10908398 | biostudies-literature
Project description:Ataxia-telangiectasia (A-T) is a rare autosomal recessive neurodegenerative disorder. It is characterized by early-onset, progressive cerebellar ataxia, oculomotor apraxia, choreoathetosis, conjunctival telangiectasias, immunodeficiency, and an increased risk of malignancy. Although A-T is known to be the most common cause of progressive cerebellar ataxia in childhood, there have been no confirmed cases in Korea. We report the clinical and genetic findings of Korean siblings who presented with limb and truncal ataxia, oculomotor apraxia, choreoathetosis, and telangiectasias of the eyes. Sequence analysis of the ataxia-telangiectasia mutated (ATM) gene revealed a known missense mutation (c.8546G>C; p.Arg2849Pro) and a novel intronic variant of intron 17 (c.2639-19_2639-7del13). Reverse-transcription PCR and sequencing analysis revealed that the c.2639-19_2639-7del13 variant causes a splicing aberration that potentiates skipping exon 18. Because A-T is quite rare in Korea, the diagnosis of A-T in Korean patients can be delayed. We recommend that a diagnosis of A-T should be suspected in Korean patients exhibiting the clinical features of A-T.
| S-EPMC3646200 | biostudies-literature