Study of the occurrence of interchromosomal effect in spermatozoa of chromosomal rearrangement carriers by fluorescence in-situ hybridization and primed in-situ labelling techniques

The possibility that a chromosomal rearrangement might disturb the meiotic behaviour of chromosomes not involved in the rearrangement and favour non-d isjunction is a controversial issue in human cytogenetics. Using two-colour fluorescence in-situ hybridization and primed in-situ labelling techniques , we have investigated the segregation pattern of 10 chromosomes (chromosom es 1, 4, 9, 13, 15, 16, 20, 21, X and Y) in spermatozoa from nine carriers of balanced structural rearrangements and three normal men. The patients we re divided into two groups according to their semen parameters. In rearrang ement carriers and normal subjects, sex chromosomes and chromosome 21 displ ayed a higher rate of disomy than the other chromosomes. No evidence for th e occurrence of interchromosomal effect was found in the spermatozoa of fer tile rearrangement carriers, but significant variations were observed for a ll chromosomes tested in the group of infertile translocation carriers, sug gesting a direct correlation between poor quality spermatozoa and increased aneuploidy rate in this group. In fertile carriers of chromosomal rearrang ements, the occurrence of non-disjunction of chromosomes not involved in th e rearrangement might therefore be considered as fortuitous, whereas in inf ertile carriers, the risk for interchromosomal effect appears to be real an d should be taken into consideration in the genetic counselling of infertil e couples with a male partner carrying a chromosomal rearrangement.