Genetic Profiling from different tissues subjected to the process of embalming

TRABAJO LIBRE SOMETIDO EN LAS XV JORNADAS LATINOAMERICANAS DE GÉNETICA FORENSE DE LA SLAGF BOLIVIA 2025

Abstract

Objective: To obtain genetics profiles of different tissues from two individuals embalmed approximately eight months earlier.
Introduction: Embalming techniques aim at the temporary preservation of tissues after death by applying chemical substances, either through the blood vessels; filling the thoracic and abdominal cavities; or by directly soak up body parts. These chemical substances damage the integrity of genetic material, such as formaldehyde, a substance widely used in mortuary science, wich can cause cross-linking of nucleic acids and proteins, hydrolyze phosphodiester bonds and methylate nitrogenous bases. Another example are dyes, known as polymerase chain reaction (PCR) inhibitors, wich impede DNA analysis. Obtaining genetic material from challenging samples for human identification in administration of justice requiinlres methodologies that optimize every stage of analysis, including the quantity and type of sample, supplies, and processing time.
Methods: From two individuals embalmed around eight months earlier, 33 samples were selected: visibly putrefied muscle tissue, cartilage, compact bone, spongy bone and yellow bone marrow (from long bones) embedded in QIAcard FTA cards. The cards were washed with QIAcard FTA Wash Buffer, while tissue, cartilage and bone samples were treated with the reagents from QIAquick Gel Extraction Kit and PrepFiler® BTA Forensic DNA Extraction Kit (using the AutoMate Express™ Forensic DNA Extraction System). Genomic amplification was performed with PCR using the PowerPlex® Fusion 6C System; and alleles were identified by capillary electrophoresis via the Genetic Analyzer 3500. Finally, these data were analyzed using GeneMapper ID-X software.
Results: Yellow bone marrow samples embedded in QIAcard FTA cards were the most efficient in DNA recovery, followed by bone and muscle samples extracted using magnetic beads and silica membranes. Cartilage was the most affected by DNA degradation due to direct exposure to the chemicals used in the embalming process. A total of 16 complete profiles, 10 partial profiles and 7 null profiles were obtained, enabling the identification of both individuals in a short period of time.
Discussion and conclusion: Using these methodologies, genetic profiles were obtained from different embalmed tissues, sufficient for the individuals identification. However, the bone marrow, composed mainly of fat and stem cells, that was embedded in the QIAcard FTA card, enabled faster DNA extraction and purification process compared with muscle tissue, cartilage and bone tissue samples (compact and spongy), which took longer time of sampling and extraction process, demonstrating that an adequate sampling strategy is key to obtaining results, optimizing the standardization of protocols and the laboratory´s forensic kits.