Separation of sperm from mixed samples using ultra-high-speed cell sorter followed by DNA typing

DNA typing of samples obtained from crime scenes can be used to identify suspects. However, samples obtained from sex crimes are often mixtures, and it is difficult to separate these for DNA typing. We extracted sperm from mixed samples using an ultra-high-speed cell sorter and examined whether DNA typing was possible. Propidium iodide was able to react with semen, allowing sperm nuclei to be sorted with the cell sorter. DNA typing was performed using the sorted sperm. The utility of anti-sperm antibody for cell sorting was compared with that of anti-sperm surface protein SP17, and anti-sperm antibody was found to be more suitable. Thus, semen reacted with anti-sperm antibody and with propidium iodide, thereby allowing sperm with nuclei to be collected. DNA typing could then be performed using the sorted sperm.