Christina talks about analysis of mitochondrial DNA from archaeological and cold case bone samples
March 18, 2021
The Young Investigator Community is a forum for young forensic researchers and graduate students to share their achievements and aspirations with peers, friends and colleagues. Each new Investigator blog is a personal introduction to one of these talented researchers. Read on as they share what first drew them to forensic science and explain what sustains their passionate commitment to their work.
This new Investigator blog introduces Christina Amory, a researcher in the lab led by Professor Walther Parson at the Institute for Legal Medicine, Medical University of Innsbruck. This active group of scientists has published more than 400 peer-reviewed articles in the forensic and medical genetics field and is internationally recognized as a leader in forensic mitochondrial DNA (mtDNA) analysis.
Christina Amory 1. Tell us about your background and how you became interested in forensic science?
After completing my compulsory high school with an emphasis on natural sciences in a small village in Tyrol, I decided to study biology in Innsbruck. I was interested in different fields during my studies and decided after my bachelor's degree to focus on microbiology. I graduated from Innsbruck University with an M.Sc. in microbiology. I enjoyed working in this field for my thesis, but I developed an even stronger passion for human genetics. This led me to apply to the Institute for Legal Medicine in Innsbruck. I started working at the Institute in a research project focusing on validating and implementing mitogenome sequencing using massive parallel sequencing (MPS). From this initial work, I had the opportunity to get involved in human identification projects using MPS including some high-profile cases. The exciting nature of these projects was what confirmed my interest for forensic genetics.
2. Can you provide a summary of the project you are working on?
My main project has been developing methodologies for sequencing mitochondrial (mt)DNA from forensically relevant samples. In a lineage study, we analyzed more than 500 full mitogenome sequences from diverse phylogenetic backgrounds and tissues typically analyzed in the forensic field. We validated this method in combination with other Institutes and this forms the scientific basis for our accreditation for mitochondrial DNA MPS methods, just recently certified (Jan 2021). The project will develop further in the future as my interest has evolved now to focus on more difficult samples.
We see that PCR-based methods have limitations, particularly when extremely degraded specimens are under investigation. Non-PCR methods are clearly advantageous in this respect. So, I have been looking into primer extension capture (PEC) assays that were optimized for forensic usage in our laboratory. More recently, we have observed that hybridization capture methods perform very similarly to PEC in terms of sensitivity but offer the advantage of covering the entire mitogenome. Our PEC method currently focuses on the mitochondrial control region. I am excited to be carrying out further experiments with my colleagues to better understand the pros and cons of the individual methods.
On the other hand, these molecular genetic methods are already shown to be reliable tools. I was able to contribute to several projects in archeology including excavation of a Viking mass grave and analysis of early medieval burials, as well as assist with forensic cold cases. We learn a lot from the field of ancient DNA where samples are typically present in minute amounts, the DNA is highly degraded, and chemically modified by environmental conditions.
Most recently, I have been involved in a high-profile case relating to famous historic individuals. I hope I will be able to talk about details soon.
3. Please describe your typical day in the lab.
As my passion and main task now revolves around ancient DNA, I will describe a typical day in the bone lab where I have improved and adapted steps in the challenging DNA workflow.
Since preventing contamination is critical, I usually start in the bone lab by gowning up for the day. The next step always involves decontaminating the whole bone preparation area. This includes the UV irradiation of all the instruments which will be used for the next steps.
After the photo documentation and weighing of the samples, I start with a mechanical cleaning of the bones, followed by the bone powder generation step. For this, I use dentist drills that allow me to create the small amounts of fine powder used for the DNA extraction.
Once the samples have been extracted, I perform DNA quantitation. This is when I get my first DNA-based feedback. The quant values provide crucial information for the choice of downstream genotyping/haplotyping methods used for the identification process.
4. What do you find most interesting about your project? Have you seen any surprising results?
I love the fact that each bone behaves differently in the lab and you never know what you will be able to get out of it. Therefore, each investigation is always very exciting and each analysis interesting. Moreover, every bone sample is related to a different case with its own story. I learned to observe characteristics of the samples during preparation and connect these to the DNA yield and genotyping outcome. This helps to triage methods and samples and streamlines the performance of cases in our lab. We continue to gain experience and confidence, both important add-ons to the scientific endeavor.
5. What are the benefits of your project?
We continue to have a very high success rate with even the most challenging samples. I personally continue to learn and gather experience. This is crucial for staying on top of scientific developments but also benefits the stakeholders involved in the cases. It is very satisfying to go home knowing that you have done your best to aid identification in a case. And if the data we generate can provide evidence to solve a case, it makes it even better.
6. What are the major challenges faced while working on your project and how do you overcome them?
The biggest obstacles I am confronted with are of a technical nature. I am happy that I have the time and resources to focus on these, as this makes my work challenging and interesting. I am providing a couple of issues as examples.
For the DNA extraction: Risk of potential contaminations, this requires extreme care in the lab including systematic decontamination of the equipment and instruments.
Nature of the samples: The samples often contain only small amounts of very degraded DNA and thus, require the use of dedicated and optimized methods.
Downstream applications: The quantification, amplification and analysis methods used for human identification with full mtDNA genome data needed to be specifically developed to deal with challenging cases.
7. Which QIAGEN products do you use and what do you like about the products?
In my opinion, QIAGEN has a long and important history in the field of DNA extraction. Their products are known for consistent and reliable results. especially for challenging samples. I am particularly pleased with the performance of the MinElute PCR Purification Kit that represents a crucial step in our DNA extraction protocol of bone samples. The purification is quick and easy but more importantly, the resulting DNA is clean in most of the cases. This is particularly important for MPS technologies that are more sensitive to inhibitors.
8. Outside of forensic science, what are your hobbies?
I enjoy the Tyrolean Alps for hiking, running and skiing but I also like travelling and diving in exotic waters. On the weekends I like to go to concerts and spend time with my husband and friends, who share the same special music taste, but I also appreciate quiet evenings with good food and a glass of wine.