ANEUPLOID EPIDIDYMAL SPERM DETECTED IN CHROMOSOMALLY NORMAL AND ROBERTSONIAN TRANSLOCATION-BEARING MICE USING A NEW 3-CHROMOSOME FISH METHOD

We present a new method to detect epididymal sperm aneuploidy (ESA) in mice using simultaneous fluorescence in situ hybridization (FISH) wit h DNA probes specific for mouse chromosomes X, Y and 8. The method was applied to Robertsonian (Rb) translocation (8.14) heterozygotes and h omozygotes as well as the chromosomally normal B6C3F1. The sex ratios of sperm did not differ from the expected 1:1 and the hybridization ef ficiencies were similar to 99.7% for over 60 000 sperm analyzed. Mice heterozygous for Rb (8.14) produced about tenfold higher rates of sper m with chromosome 8 hyperhaploidy than did Rb (8.14) homozygotes or ch romosomally normal mice, while frequencies of sperm with hyperhaploidi es for chromosomes X and Y were unaffected in all three lines of mice. Hyperhaploid frequencies obtained with the ESA method were consistent with those of the previous testicular FISH method and were validated by published data obtained by conventional cytogenetic analyses (meiot ic metaphase II and first cleavage). Thus, the mouse three-chromosome ESA assay together with the previously developed aneuploidy assay for human sperm constitute a promising pair of interspecific biomarkers fo r comparative studies of the genetic and physiologic mechanisms of the induction and persistence of aneuploidy in male germ cells.