In sexual assault cases, DNA profiling for perpetrator identification requires isolation of pure spermatozoa because evidences are often mixture between the sperm cells and the victim’s cells. Laser microdissection is a powerful tool that directly separates and collects the sperm cells without contamination from another cell. The objectives of this report are to study DNA profiling of laser microdissected spermatozoa for personal identification and to study different factors that may affect the interpretation of DNA profiles from laser microdissected spermatozoa. First, we demonstrated the ability of laser microdissection to identify and genotype spermatozoa. Second, three stains; H&E, eosin and sperm HY-LITER® were evaluated on quality of DNA profiles that derived from laser microdissected spermatozoa. Finally, STR analysis was performed on laser microdissected cell from stained slides that stored in various time. The results showed that at least 150 sperm cells were required to obtain a complete DNA profile, whereas, a partial DNA profile was obtained from 25-75 haploid sperm cells. In staining comparison result, Hematoxylin & Eosin provided the best result of DNA profiles and suitable to apply for laser microdissection. In addition, we obtained complete DNA profiles from stained slide stored for 1 month whereas the stained slide stored for 12 months gave poor DNA profiles. It showed that stained slide storage time had an effect to DNA quality and DNA analysis. In conclusion, laser microdissection is a useful tool to isolate sperm cells and makes a chance to generate genetic profile from low number of sperm cells. However, number of starting sperm cells, staining and duration of storage time are factors that affect the quality of the DNA profile derived from laser microdissected spermatozoa. In addition, to obtain reliable DNA profiles, it is recommended to avoid the factors that may have negative effect on DNA typing process.
Keywords
DNA profile; laser microdissection; spermatozoa; sexual assault