DETECTION OF CHROMOSOMES AND ESTIMATION OF ANEUPLOIDY IN HUMAN SPERMATOZOA USING FLUORESCENCE IN-SITU HYBRIDIZATION

The development and application of fluorescence in-situ hybridization (FISH) has opened the way for comprehensive studies on numerical chrom osome abnormalities in human spermatozoa. FISH can be rapidly applied to large numbers of spermatozoa and thus overcomes the major limitatio n of karyotyping spermatozoa after penetration of zona-free hamster oo cytes, The simultaneous hybridization of two or more chromosome-specif ic probes to spermatozoa and subsequent detection of the bound probes using different fluorescent detection systems enables two or more chro mosomes to be localized simultaneously in the same spermatozoon and pr ovides a technique for undertaking reasonable estimates of aneuploidy. The most commonly used probes are those which bind to the centromeric region of specific chromosomes. Most studies to date have concentrate d on estimating aneuploidy in spermatozoa from normospermic men, altho ugh reports are beginning to appear on aneuploidy in spermatozoa from subfertile and infertile men. Multi-probe FISH studies have generally reported disomy (hyperhaploidy) estimates of 0.05-0.2% per chromosome, There is preliminary evidence that some chromosomes such as X, Y and 21 are predisposed towards higher rates of non-disjunction during sper matogenesis, There are also suggestions of inter-donor variability in aneuploidy frequencies for specific chromosomes, although this require s confirmation in larger studies, While FISH is clearly a powerful tec hnique that has many applications in reproductive medicine, it must al so be realized that it does have limitations and the technology itself is still evolving and has yet to be fully validated on spermatozoa.