Meiotic segregation of a t(7;8)(q11.21;cen) translocation in two carrier brothers

To determine the meiotic segregation of a t(7;8)(q11.21;cen) translocation in two carrier brothers.Analysis of sperm nuclei by fluorescence in situ hybridization (FISH).Franche-Comté University Fertility Center in Besançon, France.Two oligospermic brothers with a (7;8) translocation.Dual FISH for chromosomes 7 and 8, and multicolor FISH for chromosomes X, Y, 15, and 18 were performed.Meiotic segregation differences between both brothers and controls.In dual FISH 7-8, a total of 34527 (older brother) and 10023 (younger brother) spermatozoa were analyzed. The frequencies of alternate, adjacent 1, adjacent 2, and 3:1 segregations and diploidies were 56.7%, 25.1%, 11.1%, 7.06%, and 0.04%, respectively, in the older brother and 62.84%, 17.61%, 12.8%, 6.47%, and 0.28% in the younger. Also, the disomy rates of some chromosomes not implicated in the translocation would suggest a possible interchromosomal effect.The similar segregation profiles for the same translocation, compared with those very divergent profiles of the other cases of studied translocations that were published in the literature, confirm that the risks of meiotic imbalances vary primarily according to the characteristics of the chromosomes involved in the rearrangement and the breakpoint position.