Identification of spermatozoa using a novel 3-plex MSRE-PCR assay for forensic examination of sexual assaults
Journal
International Journal of Legal Medicine
Date Issued
2020
Author(s)
Liu K.-L.
Tsai L.-C.
Lin Y.-C.
Huang N.-E.
Yang L.-J.
Linacre A.
Hsieh H.-M.
Abstract
Identification of semen and then spermatozoa is essential to verify that sexual activity has occurred in alleged cases of sexual assault. Microscopic examination commonly used for spermatozoa identification is however time-consuming and can often lead to false-negative results for samples with deformed and, or, limited number of spermatozoa. To address this limitation, we report on a novel 3-plex MSRE-PCR (methylation-sensitive restriction enzyme-PCR) assay to specifically identify spermatozoa. This assay is comprised of 3 markers: a digestive control marker (DC), sperm-specific marker (SP), and Y chromosome marker (SRY). A total of 214 samples from 10 body fluids or tissues were analyzed. Specificity testing showed that all the normal semen samples were unambiguously identified as being sperm-positive, and no other body fluid (or tissues) showed a sperm-specific signal in the electropherogram. Testing for sensitivity showed that 0.1 ng of DNA from a semen extract was sufficient to identify the presence of spermatozoa by this assay. Mixture analyses illustrated the sensitivity of the assay when the vaginal/semen DNA ratio (80/0.1) was under 800 or the menstrual blood/semen DNA ratio (5/0.1) was under 50, the trace amounts (approximately 0.1 ng) of DNA from semen can still be identified by this 3-plex MSRE-PCR assay. This assay was also applied to the identification of 31 non-probative forensic samples from 18 sexual assault cases. The case studies showed that the 3-plex MSRE-PCR assay was an improvement in the sensitivity of spermatozoa detection. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
Subjects
Methylation-sensitive restriction enzyme-PCR (MSRE-PCR); Sex-determining region Y (SRY); Sexual assault; Spermatozoa identification
Other Subjects
biological marker; DNA; adult; bodily secretions; body fluid; chemistry; DNA methylation; female; forensic medicine; human; isolation and purification; male; middle aged; polymerase chain reaction; procedures; restriction mapping; sensitivity and specificity; sexual crime; sperm; spermatozoon; young adult; Adult; Biomarkers; Bodily Secretions; Body Fluids; DNA; DNA Methylation; Female; Forensic Medicine; Humans; Male; Middle Aged; Polymerase Chain Reaction; Restriction Mapping; Semen; Sensitivity and Specificity; Sex Offenses; Spermatozoa; Young Adult
Type
journal article