Molecular analysis of the chromosomal equipment in spermatozoa of a 46, XY, t(7;8) (q11.21;cen) carrier by using fluorescence in situ hybridization.
The meiotic segregation of a balanced reciprocal translocation (7;8) (q11.21;cen) was analysed by interphase fluorescence in situ hybridization (FISH) on carrier spermatozoa. A dual interphase FISH technique was applied to 34,527 decondensed sperm heads with chromosome-7- and chromosome-8-specific alpha-satellite probes. Analysis with such probes was possible according to the cytogenetic characteristics of these translocation breakpoints, which implied a centromeric breakpoint. The majority of the analysed nuclei (56.70%) showed normal (30.40%) or balanced (26.30%) chromosomal equipment resulting from alternate segregation during meiosis. A total of 14,935 spermatozoa (43.26%) was unbalanced with a predominance of gametes resulting from adjacent-I (25.10%) or adjacent-II (11.10%) segregation; such gametes could produce partial mono- or trisomies at term. The frequency of analysed cells resulting from a 3:1 segregation, which could induce complete mono- and trisomies at term, was 7.06%; 0.04% of scored cells were diploid. The same dual-FISH technique was carried out either with chromosome-15- and chromosome-18-specific probes or with gonosome-specific probes, in order to detect a possible interchromosomal effect. A significant increase of disomic 18 spermatozoa was observed in the carrier. Such studies are not yet frequent. Multicolour-FISH seems a rapid and accurate tool for direct analyses of spermatogenetic segregation mechanisms in a carrier of balanced chromosomal abnormalities and provides interesting information for characterizing the possible risks for the offspring.
Mercier
S
S
Laboratoire Histologie-Embryologie-Cytogénétique, UPRESA CNRS 6025, Faculté de Médecine, Besançon, France.
Morel
F
F
Fellman
F
F
Roux
C
C
Bresson
J L
JL
D000328:Adult; D002503:Centromere / Q000235:genetics; D002871:Chromosome Banding; D002884:Chromosomes, Human, Pair 15 / Q000235:genetics; D002887:Chromosomes, Human, Pair 18 / Q000235:genetics; D002897:Chromosomes, Human, Pair 7 / Q000235:genetics*; D002898:Chromosomes, Human, Pair 8 / Q000235:genetics*; D006579:Heterozygote; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008540:Meiosis / Q000235:genetics; D013094:Spermatozoa; D014178:Translocation, Genetic / Q000235:genetics*; D014960:X Chromosome / Q000235:genetics; D014998:Y Chromosome / Q000235:genetics