September 11, 2001 is the day that will live in infamy for my generation. On that beautiful late summer day, I was at my desk working on the Fall issue of Neural Notes magazine when a colleague learned of the first plane hitting the World Trade Center. As the morning wore on, we learned quickly that it wasn’t just one plane, and it wasn’t just the World Trade Center.
Information was sparse. The world wide web was incredibly slow, and social media wasn’t much of a thing—nothing more than a few listservs for the life sciences. Someone managed to find a TV with a rabbit-eared, foil-covered antenna, and we gathered in the cafeteria of Promega headquarters—our shock growing as more footage became available. At Promega, conversation immediately turned to how we could bring our DNA forensic analysis expertise to help and support the authorities with the identification of victims and cataloguing of reference samples.
Just as the internet and social media have evolved into faster and more powerful means of communication—no longer do we rely on TVs with antennas for breaking news—the technology that is used to identify victims of a tragedy from partial remains like bone fragments and teeth has also evolved to be faster and more powerful.
Teeth and Bones: Then and Now
“Bones tell me the story of a person’s life—how old they were, what their gender was, their ancestral background.” Kathy Reichs
Many stories, both fact and fiction, start with a discovery of bones from a burial site or other scene. Bones can be recovered from harsh environments, having been exposed to extreme heat, time, acidic soils, swamps, chemicals, animal activities, water, or fires and explosions. These exposures degrade the sample and make recovering DNA from the cells deep within the bone matrix difficult.
The rapid advancement of next-generation sequencing technology, also known as massively parallel sequencing (MPS), has revolutionized many areas of applied research. One such area, the analysis of mitochondrial DNA (mtDNA) in forensic applications, has traditionally used another method—Sanger sequencing followed by capillary electrophoresis (CE).
Although MPS can provide a wealth of information, its initial adoption in forensic workflows continues to be slow. However, the barriers to adoption of the technology have been lowered in recent years, as exemplified by the number of abstracts discussing the use of MPS presented at the 29th International Symposium for Human Identification (ISHI 29), held in September 2018. Compared to Sanger sequencing, MPS can provide more data on minute variations in the human genome, particularly for the analysis of mtDNA and single-nucleotide polymorphisms (SNPs). It is especially powerful for analyzing mixture samples or those where the DNA is highly degraded, such as in human remains. Continue reading “Harnessing the Power of Massively Parallel Sequencing in Forensic Analysis”
Today’s post was written by guest blogger Anupama Gopalakrishnan, Global Product Manager for the Genetic Identity group at Promega.
Next-generation sequencing (NGS), or massively parallel sequencing (MPS), is a powerful tool for genomic research. This high-throughput technology is fast and accessible—you can acquire a robust data set from a single run. While NGS systems are widely used in evolutionary biology and genetics, there is a window of opportunity for adoption of this technology in the forensic sciences.
Currently, the gold standard is capillary electrophoresis (CE)-based technologies to analyze short tandem repeats (STR). These systems continue to evolve with increasing sensitivity, robustness and inhibitor tolerance by the introduction of probabilistic genotyping in data analysis—all with a combined goal of extracting maximum identity information from low quantity challenging samples. However, obtaining profiles from these samples and the interpretation of mixture samples continue to pose challenges.
MPS systems enable simultaneous analysis of forensically relevant genetic markers to improve efficiency, capacity and resolution—with the ability to generate results on nearly 10-fold more genetic loci than the current technology. What samples would truly benefit from MPS? Mixture samples, undoubtedly. The benefit of MPS is also exemplified in cases where the samples are highly degraded or the only samples available are teeth, bones and hairs without a follicle. By adding a sequencing component to the allele length component of CE technology, MPS resolves the current greatest challenges in forensic DNA analysis—namely identifying allele sharing between contributors and PCR artifacts, such as stutter. Additionally, single nucleotide polymorphisms in flanking sequence of the repeat sequence can identify additional alleles contributing to discrimination power. For example, sequencing of Y chromosome loci can help distinguish between mixed male samples from the same paternal lineage and therefore, provide valuable information in decoding mixtures that contain more than one male contributor. Also, since MPS technology is not limited by real-estate, all primers in a MPS system can target small loci maximizing the probability of obtaining a usable profile from degraded DNA typical of challenging samples.
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