A universal method for DNA extraction from human bone samples at different stages of degradation is not yet available. DNA extraction efficiency and the following possibility to generate good quality genetic profiles may vary depending on the bone preservation conditions and age of the samples. Few studies are available, for example, for bone samples exposed to seawater. To investigate this issue, we studied a selected sample of the migrant victims who died in the April 18th 2015 shipwreck which occurred in the Mediterranean Sea. Samples from the remains of 80 victims were selected for DNA analysis as the personal belongings found on their bodies indicated possible identities and ante mortem information and samples were therefore sought and collected. Since these samples were retrieved from bodies who stayed at a depth of 400 m in seawater for a period variable from three months to one year, we tried to select the most suitable DNA extraction method by using three different commercially available silica-based DNA extraction kits. Bone powder was obtained by drilling femoral/tibial diaphyses from each sample. The extracted DNAs were quantified by qPCR in a previous study and the results compared to macroscopic and microscopic analyses showing a low DNA recovery in more than 80% of the samples together with the presence of well preserved bone tissue. We therefore wished to verify the quality and reliability of the resulting genetic profiles by using three different commercial kits which allowed the overall amplification of up to twenty-one autosomal STRs, a panel of markers suitable for genetic identification. Most of the resulting genetic profiles were partial and affected by PCR artifacts which caused, in some case, interpretation issues. To overcome these problems, the autosomal STR typing coming from the three different amplifications were compared in order to obtain a reliable genetic profile and, in some cases, additional DNA extractions and amplification were performed. The final genetic database available for individual identification resulted in more than 80% of the genetic profiles characterized by ≥ 16 STR markers. This result was obtained only setting up a combined amplification approach, due to the low yield and the degradation rate of the human DNA recovered from the samples. Future research will be needed to fully understand the difficulties to recover reliable genetic profile in front of such morphologically well preserved bone tissues.
The genetic analysis of bone samples exposed to seawater: preliminary results / E. Bertolini, P. Grignani, B. Bertoglio, C. Cattaneo, D. Mazzarelli, C. Previderè. ((Intervento presentato al convegno Fase One Day : symposium in Forensic anthropology tenutosi a Marseilles nel 2018.
The genetic analysis of bone samples exposed to seawater: preliminary results
B. Bertoglio;C. Cattaneo;D. Mazzarelli;
2018
Abstract
A universal method for DNA extraction from human bone samples at different stages of degradation is not yet available. DNA extraction efficiency and the following possibility to generate good quality genetic profiles may vary depending on the bone preservation conditions and age of the samples. Few studies are available, for example, for bone samples exposed to seawater. To investigate this issue, we studied a selected sample of the migrant victims who died in the April 18th 2015 shipwreck which occurred in the Mediterranean Sea. Samples from the remains of 80 victims were selected for DNA analysis as the personal belongings found on their bodies indicated possible identities and ante mortem information and samples were therefore sought and collected. Since these samples were retrieved from bodies who stayed at a depth of 400 m in seawater for a period variable from three months to one year, we tried to select the most suitable DNA extraction method by using three different commercially available silica-based DNA extraction kits. Bone powder was obtained by drilling femoral/tibial diaphyses from each sample. The extracted DNAs were quantified by qPCR in a previous study and the results compared to macroscopic and microscopic analyses showing a low DNA recovery in more than 80% of the samples together with the presence of well preserved bone tissue. We therefore wished to verify the quality and reliability of the resulting genetic profiles by using three different commercial kits which allowed the overall amplification of up to twenty-one autosomal STRs, a panel of markers suitable for genetic identification. Most of the resulting genetic profiles were partial and affected by PCR artifacts which caused, in some case, interpretation issues. To overcome these problems, the autosomal STR typing coming from the three different amplifications were compared in order to obtain a reliable genetic profile and, in some cases, additional DNA extractions and amplification were performed. The final genetic database available for individual identification resulted in more than 80% of the genetic profiles characterized by ≥ 16 STR markers. This result was obtained only setting up a combined amplification approach, due to the low yield and the degradation rate of the human DNA recovered from the samples. Future research will be needed to fully understand the difficulties to recover reliable genetic profile in front of such morphologically well preserved bone tissues.
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