Advances in Computer Analysis of Radiation-Induced Changes in the Human Genome

Abstract

Radiation-induced chromosomal aberrations can be detected using fluorescence in situ hybridization (FISH). Additional to numerical and structural aberrations changes in spatial arrangement of chromosomes can be detected by appropriate DNA-probes. Using FISH, both metaphase spreads as well as interphase nuclei can be analyzed, the latter being important for non-dividing cells.

The analysis of FISH-stained microscopic slides can be done either manually or by means of a computer. The second approach is obviously preferable as the analysis is quicker, more precise, not biased and can be automated. Moreover, the computer can work overnight and process large amounts of data. The possibility to analyze a lot of images (i.e. numerous metaphase spreads or interphase nuclei) is of great value for studies scoring rare events such as aberrations induced by environmental radiation. If, as for low doses, the percentage of damaged cells is very low a lot of data is needed for proper statistical scoring.

The computer-aided analysis of FISH-stained slides can be divided into three main parts: (i) search for the object (e.g. finding the metaphase spreads or interphase nuclei on the slide), (ii) capture of the image (the image must be recorded using a suitable CCD camera, digitized and saved into the computer memory), (iii) image analysis (computer must find the metaphase spreads or interphase nuclei, FISH-signals on them and evaluate the data).

This paper describes the automation of these three tasks and, subsequently, the whole process of FISH-stained slide analysis. The paper concentrates on the system developed in Brno based on a motorized Leica DMRXA microscope, a cooled CCD camera, a PC computer which drives both the microscope and the camera, and ownsoftware for image acquisition and analysis. The system was already successfully used in several studies of radiation-induced changes in the human genome.