Influence of sex on the meiotic segregation of a t(13;17) Robertsonian translocation: a case study in the pig

Comparison of male versus female meiotic segregation patterns for Robertsonian translocation (RT) carriers with similar genetic background has rarely been reported in mammalian species. The aim of this study was to compare the segregation patterns determined for related males and females carrying a 13;17 RT in an animal model (Sus scrofa domestica L.), using dual colour fluorescence in situ hybridization on decondensed sperm nuclei and metaphases II of in vitro-matured oocytes. In males, no association between the trivalent and the XY body was observed in any of the 90 pachytene nuclei studied, and the rate of unbalanced spermatozoa ranged between 2.96% and 3.83%. Female meiotic segregation analyses were carried out on 83 metaphase II oocytes. The rate of unbalanced gametes was higher in females than in males (28.91% versus 3.21%, P < 0.001). This difference was due to higher rates of diploid gametes (12.04% versus 0.05%) and unbalanced gametes produced by the adjacent segregation (16.86% versus 3.16%). This study is a new scientific contribution to the comparison of segregation patterns in related males and females carrying an identical chromosomal rearrangement. It allows a better understanding of the meiotic behaviour of RTs. It also clearly illustrates the relevance of swine as an animal model for such meiotic studies.