In-vitro decondensation of human spermatozoa for fluorescence in-situ hybridization

In order to enhance the efficiency of fluorescence in-situ hybridization (FISH) on human interphase spermatozoa, a simple method for partial decondensation of human spermatozoa chromatin is described. The spermatozoa were washed once in 0.01 M Tris and decondensed using 10 mM dithiothreitol in 0.05 M Tris for 10-50 min, before being spread onto clean slides. Sperm samples were observed every 10 min under a phase-contrast microscope in order to modify the duration of the decondensation process. Using several centromeric or YAC probes in multicolour FISH, high hybridization rates were obtained.