Unusual Behavior of the XY Body in Spermatogenesis in Mutagenized Mice

For the first time, it is shown that in hybrid F1 CBA × C57BL/6 mice exposed to the chemical mutagen dipin pachytene spermatocytes are formed with the sex XY chromosomes (XY bodies) lying outside the main nuclei. XY bodies isolated from the main nuclei were also found in the spermatid population. Our quantifications show that in the control and the experiment groups the frequency of occurrence of such genetically abnormal pachytene spermatocytes, the nuclei of which have lost the XY bodies, is 0.22 and 2.9%, respectively, and that of aberrant round spermatids is 0.0 and 2.84%. In spermatogenesis of mutant 129 mouse strain, a similar pattern of XY bodies unusual behavior was revealed, both in the control and in the experiment. In the control and in mutagenized 129 mice, the number of genetically abnormal pachytene spermatocytes was 0.67 and 0.25%, respectively, while the number of aberrant round spermatids was 0.1 and 0.17%. The differences established between the two strains of mice regarding the reaction of XY bodies to the action of dipin might be related to the fact that, in mutagenized 129 mice, the death of genetically damaged developing male germ cells at stages prior to pachytene spermatocytes and round spermatids is higher than in hybrid F1 CBA × C57BL/6 mice.