Retarded DNA DSB repair kinetics and augmented radiation sensitivity in Wiskott Aldrich syndrome patients

Wiskott-Aldrich Syndrome (WAS), a rare X-linked disorder, features microthrombocytopenia, eczema, immunodeficiency, and elevated malignancy risk due to genomic instability. While prior studies noted DNA repair deficits, the kinetics of ionizing radiation-induced DSB repair in WAS patients remain unclear. This study aimed to characterize DSB repair dynamics and radiation sensitivity in WAS lymphocytes using γH2AX and 53BP1 markers. Lymphocytes from four WAS patients, their carrier mothers, and healthy controls were analyzed. Baseline DSBs were quantified in non-irradiated cells, and repair kinetics assessed post 2 Gy gamma irradiation over 24 h. Immunofluorescence staining for γH2AX (early DSB marker) and 53BP1 (repair facilitator) was performed at multiple time points, with foci quantified via confocal microscopy. Repair half-lives were calculated using exponential decay models. WAS patients exhibited 16-24 fold higher baseline γH2AX and 53BP1 foci than control (mean), indicating spontaneous genomic instability. Post-irradiation, DSB repair in WAS lymphocytes was significantly delayed, with the mean foci repair half-life (T½) in WAS patients being approximately 1.6-fold longer than that of the control (mean). At 24 h post-irradiation, WAS patients retained nearly twice the number of residual foci compared to healthy controls, while carrier mothers mirrored control repair efficiency. This study provides the first evidence of prolonged DSB repair kinetics in WAS patients, emphasising heightened radiosensitivity and genomic instability. These findings suggest tailored radiation strategies in WAS management, particularly for bone marrow transplantation or genotoxic therapies, to mitigate risks and optimize outcomes.