Molecular cytogenetic diagnostics in sperm

Among other factors contributing to male infertility, chromosomal anomalies are a frequent finding. Investigating 440 males with reduced sperm counts (< 20 x 10(6)/mL) we found 19 males with chromosome abnormalities (aneuploidies and translocations). This frequency of chromosomal aberrations (4.3%) is much higher than in the normal population. We were able to investigate sperm nuclei from seven out of these 19 men with molecular cytogenetic methods. There were two carriers of Robertsonian translocations, two had a constitutional reciprocal translocation and three were XYY males. In addition, one other man with a long history of infertility and a marker chromosome 15 was included. Using fluorescence in-situ hybridization, it was possible to investigate a great number of sperm nuclei in each case. Each translocation case showed a specific mode of chromosomal segregation; confirming the dependence on chromosomes involved and the individual segregation pattern in each patient. The well known elimination of the supernumerary Y-chromosome in XYY males during meiosis was confirmed in our study. Molecular cytogenetic investigations in sperm provide a more reliable risk estimate with respect to the possible injection of chromosomally unbalanced sperm during intracytoplasmatic sperm injection and can be valuable in genetic counselling.