New image analysis methods for 3D visualization and assessment of mapping distance for chromosomes in interphase nuclei

Confocal microscopy (Meridian Instruments, Inc.) images of interphase nuclei with portions or entire chromosomes singley- or doubly-labeled by fluorescence in situ hybridization were analyzed with newly-developed software on an 80486 PC equipped with an autostereoscopic display (Dimension Technologies, Inc.). The computer display is hologram-like with the ability to address points in 3D space using the associated mouse. Software was developed which allowed for reduction of background by a 19 voxel (3x3x3 voxel cube without corner voxels) median filtering algorithm followed by rendering of a 3D surface and skeleton figure of a chromosome. Visualization at multiple viewing angles by animation allows approximate coordinate locations to be obtained with a 3D mouse to guide the process thereby reducing significantly the required calculation times. Two biological applications under development include (1) correct counting of a given chromosome's copy number using centromere/chromosome-specific probes, and (2) visualization of painted chromosomes and subregion-specific probes at different locations on that chromosome for physical mapping. In either application, real-world distances within each confocal plane and between planes are calculable to give physical mapping distances in three dimensions and along the chromosome.