DETECTION OF SEX CHROMOSOMAL ANEUPLOIDIES X-X, Y-Y, AND X-Y IN HUMAN SPERM USING 2-CHROMOSOME FLUORESCENCE IN-SITU HYBRIDIZATION

Sex chromosome aneuploidy is the most common numerical chromosomal abn ormality in humans at birth and a substantial portion of these abnorma lities involve paternal chromosomes. An efficient method is presented for using air-dried smears of human semen to detect the number of X an d Y chromosomes in sperm chromatin using two-chromosome fluorescence i n situ hybridization. Air-dried semen smears were pre-treated with dit hiothreitol and 3,4-diiodosalicylate salt to decondense the sperm chro matin and then were hybridized with repetitive sequence DNA probes tha t had been generated by PCR and differentially labeled. Hybridizations with X and Y specific probes showed the expected ratio of 50%X:50%Y b earing sperm. Sperm carrying extra fluorescence domains representing d isomy for the X or Y chromosomes occurred at frequencies of similar to 4 per 10,000 sperm each. Cells carrying both X and Y fluorescence dom ains occurred at a frequency of similar to 6/10,000. Thus, the overall frequency of sperm that carried an extra sex chromosome was 1.4/1,000 . The frequencies of sperm carrying sex chromosome aneuploidies determ ined by hybridization did not differ statistically from those reported from the same laboratory using the human-sperm/hamster-egg cytogeneti c technique. Multi-chromosome fluorescence in situ hybridization to sp erm is a promising method for assessing sex-ratio alterations in human semen and for determining the fraction of sperm carrying sex or other chromosome aneuploidies which may be transmissible to offspring. (C) 1994 Wiley-Liss, Inc.