Stains of ejaculated pre and post-vasectomy: Purity and sufficient quantity of recovered DNA after 10 years of storage

Abstract

Vasectomy is a widely used method of contraception. The absence of spermatozoa in the ejaculate of azoospermic individuals increases the difficulty of extracting DNA for analysis, especially if the biological samples are in the form of spots and stored for years. The aim of this study is to evaluate the possibility of obtaining autosomal and Y-STR profiles from stains containing the ejaculate of individuals pre and post-vasectomy, stored in cotton fabric for a period of 10 years. Samples from 28 (twenty eight) individuals: semen pre-vasectomy and seminal fluid (post-vasectomy) stains, stored from 2004 to 2014 at room temperature were used. Three cutouts of 1.5 cm in diameter (punch) were taken from central region of each spot. It was used the QIAamp DNA Mini kit (Qiagen) to extract DNA with an adapted protocol followed by quantification by Nanodrop equipment. Genetic profiles were obtained using ESI17PowerPlex R (Promega). Capillary electrophoresis was performed on the ABI PRISM 3500XL DNA Analyzer. The DNA extraction was successful in all punch analyzed, and its concentration ranged from 1.1ng/uL to 23.3ng/uL in the pre-vasectomy and from 0.8ng/uL to 7 ng/uL in postvasectomy punch. The samples had suitable purity, reflecting the presence of few contaminants. Currently, the techniques of DNA amplification are extremely sensitive and capable of assessing human DNA in small quantities generating partial or full profiles, trespassing situations such as long storage periods in cotton fabric. These data can be used as a benchmark for forensic analysis in cases of semen analysis. IntroductionThe need to obtain genetic profiles to be added to DNA databank is a recent reality in Brazil, since only in 2012 the legislative started to regulate the creation and the use of the National Bank of Genetic Profiles (NBGP), which counts with CODIS technology [1]. It is well known that because of the nature of the crime, sexual assault tends to leave traces that allow the identification of the perpetrator in about 50% of cases [2], and due to the possibility of additional offenses by the criminal, it is recommended to insert the genetic profiles generated in DNA banks [3]. In parallel, there are situations where the only materials available for analysis are traces, such as semen stains on the victim's clothing. The absence of spermatozoa in the ejaculate of azoospermic individuals increases the difficulty of extracting DNA for profile analysis, especially if the biological samples are impregnated on fabric and stored for years. With the launch of NBGP, the analysis of cases without suspects lead to the necessity of generating autosomal genetic profiles for sex offenders. The aim of this study was to evaluate the possibility of obtaining autosomal and Y-STR profiles from ejaculate stains of 28 pre and post-vasectomy individuals stored for 10 years in cotton fabrics.