EPIDIDYMAL SPERM ANEUPLOIDIES IN 3 STRAINS OF RATS DETECTED BY MULTICOLOR FLUORESCENCE IN-SITU HYBRIDIZATION

A multicolor fluorescence in situ hybridization (FISH) method was deve loped to detect aneuploidy and diploidy in epididymal sperm of rats us ing DNA probes specific for chromosomes 4 and Y. Fourteen healthy youn g-adult rats from three strains were evaluated: inbred Fisher 344/N/eh s, outbred Sprague-Dawley, and outbred WU Wistar/CPB. The hybridizatio n efficiency of the FISH procedure was >99.9%, the sex-ratio in sperm was similar to 1 as expected, and there was no significant variation a mong two independent scorers. No significant variations were detected within or among strains in the frequencies of sperm disomy for chromos ome 4 (1-6.5 per 10,000 cells per animal) or the Y chromosome (0-2.5 p er 10,000 cells per animal). There was a trend toward increased variat ion among Wister rats. The frequencies of sperm-carrying hyper- and hy pohaploidy for chromosome 4 were similar, suggesting a symmetrical mec hanism of chromosome gain and loss during meiosis. The frequencies of Y-Y-4-4 sperm, which represent genomic meiosis II errors, did not diff er significantly across strains (0.1-0.7 per 10,000 cells per strain). This FISH method for detecting aneuploidy in rat epididymal sperm pro vides a promising interspecies biomarker of male germ cell aneuploidy and introduces the rot as on animal model for investigating the herita ble risk to offspring associated with paternal genotype, physiology, a nd exposure to environmental mutagens. There appear to be no significa nt differences among young healthy rats, mice, and men in the baseline frequencies of sperm with Y chromosomal disomy, the only chromosome f or which data currently exists for all three species. (C) 1998 Wiley-L iss, Inc.