Analysis using sperm-FISH of a putative interchromosomal effect in boars carrying reciprocal translocations

The occurrence of interchromosomal effects (ICE) in reciprocal translocation carriers still remains contradictory in the human literature. We used the pig as an animal model to investigate whether the structure of the reciprocal translocations as well as the size and/or type of the chromosomes not involved in the rearrangement may influence the occurrence and the extent of ICE. Analyses of chromosomal sperm content by fluorescence in situ hybridization (FISH) using whole-chromosome painting probes for 7 chromosomes (1, 10, 11, 13, 18, X and Y) were carried out on sperm samples of 2 boars with normal semen parameters carrying different balanced reciprocal translocations: 38, XY, t(3;15)(q27;q13) or 38, XY, t(12;14)(q13;q21). One fertile boar with normal karyotype was also studied as a control. Aneuploidy rates for the 7 chromosomes were estimated by scoring 10,000 to 20,000 spermatozoa for each probe combination. No significant ICE was found except for chromosome 1 in the case of the t(3;15) translocation. Even if statistically significant, this ICE remained very weak and should have very little impact on the reproductive performance of the carrier boar. The size and/or type of chromosomes not involved in the translocation do not seem to have a major influence on the occurrence of ICE. The structure of the translocation could play a role, but complementary studies should be carried out to confirm this assumption.