X-ray-induced simple, pseudosimple and complex exchanges involving two distinctly painted chromosomes

Area of Science:

• Cytogenetics
• Radiation Biology
• Molecular Biology

Background:

• Chromosome aberrations are key indicators of DNA damage from ionizing radiation.
• Distinguishing between simple and complex exchanges is crucial for understanding radiation effects.
• Fluorescence in situ hybridization (FISH) painting allows visualization of specific chromosome rearrangements.

Purpose of the Study:

• To characterize simple, pseudosimple, and complex chromosome exchanges induced by X-rays.
• To determine the number of breaks and chromosomes involved in complex exchanges.
• To assess the frequency of non-reciprocal exchanges using two-color FISH painting.

Main Methods:

• Human primary fibroblasts were irradiated with 250kV X-rays (2, 4, 6 Gy).
• FISH painting was performed using probes for chromosomes 1, 2, and pancentromeric regions.
• Analysis focused on two-paint exchanges to identify complexity and rejoining patterns.

Main Results:

• 78 two-paint exchanges were observed, with 35 simple and 43 complex.
• 23 complex exchanges included pseudosimple aberrations.
• Over 50% of complex exchanges involved non-reciprocal rejoining events.

Conclusions:

• Non-reciprocal rejoining in complex exchanges supports a multi-break-end interaction model.
• Distinct dose-response curves for simple (linear) and complex (curvilinear) exchanges were identified.
• Findings align with previous data on single-painted exchanges, accounting for pseudosimple events.