Gender preselection in humans? Flow cytometric separation of X and Y spermatozoa for the prevention of X-linked diseases.

Human X- and Y-chromosome-bearing spermatozoa were separated based on their DNA content, using modified flow cytometric cell sorting technology. The resulting separation purity of the X-bearing from Y-bearing spermatozoa was evaluated using in-situ hybridization with alpha satellite DNA probes for the X- and Y-chromosomes. In the putative X-enriched-sorted populations, an average of 82% of the spermatozoa showed a hybridization signal with the X probe. Similarly, in the Y-sorted population 75% gave a signal with the Y probe. Sorted X- and Y-bearing spermatozoa were found to maintain their viability for several hours after sorting. These results demonstrate that the human sperm sex ratio can be significantly shifted to favour the selection of female-producing (X) spermatozoa or male-producing (Y) spermatozoa when spermatozoa are flow cytometrically sorted on the basis of DNA content. We propose that flow cytometrically sorted human spermatozoa, used in conjunction with in-vitro fertilization or intra-oviductal insemination, could be used by families who are at risk for X-linked diseases to preferentially produce female offspring. Sorted spermatozoa could also be used to pre-select for male offspring if that were medically indicated.