Paternally inherited chromosomal structural aberrations detected in mouse first-cleavage zygote metaphases by multicolour fluorescence in situ hybridization painting

We describe a fluorescence in situ hybridization (FISH) procedure for assessing zygotic risk of paternal exposure to endogenous or exogenous agents. The procedure employs multicolour FISH with chromosome-specific DNA painting probes plus DAPI staining for detecting both balanced and unbalanced chromosomal aberrations in mouse first-cleavage (1-CI) zygote metaphases, Four composite probes specific for chromosomes 1, 2, 3 or X, each labelled with biotin, plus a composite probe specific for chromosome Y labelled with digoxigenin, were used. We applied this method to evaluate the effects of paternal exposure to acrylamide, a model germ cell clastogen. First-cleavage zygote metaphases, collected from untreated females mated to males whose sperm or late spermatids were treated with acrylamide, were scored for the induction of structural aberrations using both chromosome painting (PAINT analysis) and DAPI analysis. Structural chromosomal aberrations were observed in the sperm-derived, but not in the egg-derived, pronuclei. While 59.4% of the zygotes had structural aberrations by DAPI analysis, 94.1% of the same zygotes had structural aberrations by PAINT analysis (P<0.001), illustrating the increased sensitivity for detecting translocations and insertions obtained by adding chromosome painting. These findings show that FISH painting of mouse 1-CI zygotes when used in conjunction with DAPI analysis is a powerful model for investigating the cytogenetic defects transmitted from father to offspring.