Metaphase and interphase mapping by FISH: improvement of chromosome banding and signal resolution in interphase nuclei by means of iterative deconvolution.

FISH images obtained with conventional epifluorescence microscopes are always blurred by glare and out of focus light emissions. In order to restore high contrast images, a procedure based on a modelling of the optical system in the microscope was developed and used for the processing of images acquired with a cooled CCD camera mounted on a fluorescence microscope. This procedure was tested on images of both mouse and human chromosomes stained with DAP1 and on images of interphase nuclei hybridized with pairs of cosmid probes. This method improves the definition and the sharpness of the DAPI G-banding and thus facilitates and speeds up the identification of chromosomes. When performed on images of interphase cell nuclei, this procedure allows the discrimination of fluorescent signals which appear partially overlapping on raw images. This significant improvement of spatial resolution is of particular interest for ordering sets of probes on DNA fibers.