Enhanced Recovery of Spermatozoa and Comprehensive Lysis of Epithelial Cells From Sexual Assault Samples Having a Low Cell Counts or Aged Up to One Year

• NCJ Number: 246744
• Journal: Forensic Science International: Genetics Volume: 8 Issue: 1 Dated: January 2014 Pages: 84-89
• Author(s): Jenny A. Lounsbury; Shanti M. Nambiar; Anne Karlsson; Helina Cunniffe; Jessica V. Norris; Jerome P. Ferrance; James P. Landers
• Date Published: January 2014
• Length: 6 pages
• Publication Format: Article
• Publication Type: Report (Study/Research)
• Language: English
• Country: United States of America

Annotation

Differential extraction DE is the most common method for processing sexual assault samples, allowing for the simultaneous recovery of sperm and epithelial cells from the swab with the separation of sperm cells from epithelial cell DNA by exploiting the differences in the cell membrane susceptibility to detergents.

Abstract

Differential extraction DE is the most common method for processing sexual assault samples, allowing for the simultaneous recovery of sperm and epithelial cells from the swab with the separation of sperm cells from epithelial cell DNA by exploiting the differences in the cell membrane susceptibility to detergents. However, sperm cell recovery when using DE is generally 40-50% 1, which can reduce the probability of obtaining a STR profile of the semen contributor, especially if the sample is aged or has a low number of sperm cells. Here, we present a novel buffer, containing SDS and ProK that, when used as an initial incubation buffer, enhances sperm cell recovery to as high as 90%, representing a 200-300% increase over conventional DE buffer. Adjusting the incubation time and temperature provided high, reproducible sperm cell yields. Sample vortexing and replacement of SDS with sodium octyl sulfate SOS, another sulfate-based anionic detergent, did not provide any further enhancement of the sperm cell recoveries. Furthermore, the one-step buffer provided up to a 300% increase in recovery over the conventional DE buffer when used on samples aged up to one year. STR analysis of samples containing 500 or more sperm cells treated with this buffer showed comparable results i.e., full STR profiles; 16 of 16 loci to those obtained using a conventional DE buffer. Finally, when the sample contained only 400 sperm cells recovered in 100ìL volume, then extracted, substantially more STR loci 14 of 16 were generated using the novel buffer in comparison to the conventional DE buffer 4 of 16 loci. This work demonstrates that this buffer may be useful as an alternative for the initial sample incubation step in differential extraction, particularly for aged or samples known to have a low number of sperm cells.