Meiotic outcome in two carriers of Y autosome reciprocal translocations: selective elimination of certain segregants

Abstract

Background: Reciprocal Y autosome translocations are rare but frequently associated with male infertility. We report on the meiotic outcome in embryos fathered by two males with the karyotypes 46,X,t(Y;4)(q12;p15.32) and 46,X,t(Y;16)(q12;q13). The two couples underwent preimplantation genetic diagnosis (PGD) enabling determination of the segregation types that were compatible with fertilization and preimplantation embryo development. Both PGD and follow up analysis were carried out via fluorescence in situ hybridization (FISH) or array comparative genomic hybridization (aCGH) allowing the meiotic segregation types to be determined in a total of 27 embryos. Results: Interestingly, it was seen that the number of female embryos resulting from alternate segregation with the chromosome combination of X and the autosome from the carrier gamete differed from the corresponding balanced males with derivative Y and the derivative autosome by a ratio of 7:1 in each case (P = 0.003) while from the adjacent-1 mode of segregation, the unbalanced male embryos with the combination of der Y and the autosome were seen in all embryos from couple A and in couple B with the exception of one embryo only that had the other chromosome combination of X and derivative autosome (P = 0.011). In both cases the deficit groups have in common the der autosome chromosome that includes the segment Yq12 to qter. Conclusion: The most likely explanation may be that this chromosome is associated with the X chromosome at PAR2 (pseudoautosomal region 2) in the sex-body leading to inactivation of genes on the autosomal segment that are required for the meiotic process and that this has led to degeneration of this class of spermatocytes during meiosis.