Oxidative Damage Induced Telomere Mediated Genomic Instability in Cells from Ataxia Telangiectasia Patients

Prarthana Srikanth; Amit Roy Chowdhury; Grace Kah Mun Low; Radha Saraswathy; Akira Fujimori; Birendranath Banerjee; Wilner Martinez-Lopez; M Prakash Hande

doi:10.14293/genint.13.1.003

Oxidative Damage Induced Telomere Mediated Genomic Instability in Cells from Ataxia Telangiectasia Patients

Genome Integr. 2022 Dec 21:13:2. doi: 10.14293/genint.13.1.003. eCollection 2022.

Authors

Prarthana Srikanth^{1

2}, Amit Roy Chowdhury³, Grace Kah Mun Low¹, Radha Saraswathy², Akira Fujimori⁴, Birendranath Banerjee^{1

3}, Wilner Martinez-Lopez^{2

5

6}, M Prakash Hande^{1

2

7}

Affiliations

¹ Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
² Department of Biomedical Sciences, School of Biosciences and Technology, Vellore Institute of Technology, Vellore, India.
³ inDNA Center for Research and Innovation in Molecular Diagnostics, inDNA Life Sciences Private Limited, Bhubaneswar, India.
⁴ Molecular and Cellular Radiation Biology Group, Department of Charged Particle Therapy Research Institute for Quantum Medical Science Chiba, Japan.
⁵ Genetics Department and Biodosimetry Services, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay.
⁶ Associate Unit on Genomic Stability, Faculty of Medicine, University of the Republic (UdelaR), Montevideo, Uruguay.
⁷ Department of Applied Zoology, Mangalore University, Mangalore, India.

Abstract

Our cellular genome is susceptible to cytotoxic lesions which include single strand breaks and double strand breaks among other lesions. Ataxia telangiectasia mutated (ATM) protein was one of the first DNA damage sensor proteins to be discovered as being involved in DNA repair and as well as in telomere maintenance. Telomeres help maintain the stability of our chromosomes by protecting the ends from degradation. Cells from ataxia telangiectasia (AT) patients lack ATM and accumulate chromosomal alterations. AT patients display heightened susceptibility to cancer. In this study, cells from AT patients (called as AT ^-/- and AT ^+/- cells) were characterized for genome stability status and it was observed that AT ^-/- cells show considerable telomere attrition. Furthermore, DNA damage and genomic instability were compared between normal (AT ^+/+ cells) and AT ^-/- cells exhibiting increased frequencies of spontaneous DNA damage and genomic instability markers. Both AT ^-/- and AT ^+/- cells were sensitive to sodium arsenite (1.5 and 3.0 μg/ml) and ionizing radiation-induced (2 Gy, gamma rays) oxidative stress. Interestingly, telomeric fragments were detected in the comet tails as revealed by comet-fluorescence in situ hybridization analysis, suggestive of telomeric instability in AT ^-/- cells upon exposure to sodium arsenite or radiation. Besides, there was an increase in the number of chromosome alterations in AT ^-/- cells following arsenite treatment or irradiation. In addition, complex chromosome aberrations were detected by multicolor fluorescence in situ hybridization in AT ^-/- cells in comparison to AT ^+/- and normal cells. Telomere attrition and chromosome alterations were detected even at lower doses of sodium arsenite. Peptide nucleic acid - FISH analysis revealed defective chromosome segregation in cells lacking ATM proteins. The data obtained in this study substantiates the role of ATM in telomere stability under oxidative stress.

Keywords: Ataxia Telangiectasia Mutated; DNA Repair Deficiency; Genome Instability; Oxidative Damage; Telomere Dynamics.