In 2016, a team of researchers led by scientists at Lawrence Livermore National Laboratory developed a new biological identification method that exploits information encoded in proteins. At the time, they thought it could have multiple applications. Nearly two years later, they turned out to be right.
In September 2016, Livermore scientists announced they had developed a way to use protein markers from human hair to identify people and link individuals to evidence. Now they’ve found a second way to use protein markers from human tissue for identification – this time from bones. Their work is described in a paper published online by “Forensic Science International”, an Amsterdam-based journal.
Proteins are long molecular chains formed from amino acids – the basic building blocks of life. DNA is the pattern or template the body uses to produce proteins. In the research, the protein markers used by the scientists have been variants in the proteins resulting from amino acid substitutions that stem from DNA mutations and are known as single amino acid polymorphisms (SAPs).Using the process developed at Livermore, proteins are first extracted from a bone sample and broken down into shorter amino acid chains, called peptides. The researchers then use liquid chromatograph-mass spectrometry to separate, detect and quantify the peptide sequences. Results are compared to a protein sequence database to identify known SAPs present in the sample. Given data on the frequencies of each corresponding DNA mutation, the researchers can derive identifying information and determine the biogeographic origin of the person who provided a sample.
In the new study, the team examined rib bone samples from 10 recently deceased individuals – five male and five female – of European-American ancestry, finding a total of 35 different protein markers. The researchers found enough markers to provide a unique pattern for an individual that would distinguish that person in ranges of from 1 in 6 people to 1 in 42,000 people. Although rib bone samples were used in the study, it is believed that any type of human bone could be used for identifying people or linking them to evidence.
The new protein marker technology addresses a 2009 National Research Council report on forensic science that detailed the weaknesses of many current approaches and reported an urgent need for new forensic methods. Speaking about this latest breakthrough, Livermore’s Katelyn Mason, the paper’s lead author notes that this is the first manuscript to describe the detection and validation of protein markers from human bones and that the results show this approach can provide a powerful new tool for forensic science. Brad Hart, the director of Livermore’s Forensic Science Centre and a co-author of the paper says that one of the most exciting aspects of the research is that it seeks to provide a completely new objective methodology for human identification and that expanding the proteomic approach to include bone tissue promises greater potential for determining the identity of remains recovered from challenging environments and circumstances.
There is inherently less genetic variability in proteins present in bone compared to human hair and therefore for purposes of identifying people or linking them to evidence, hair proteins are more valuable. Nonetheless, there are situations where bone tissue may be all that is available and for those cases there may be no other way to the identify human remains. One possible important application for using protein markers from human bones could therefore be to help determine the identity of partial remains from catastrophic events, such as plane crashes and fires.
The work to use protein markers from human hair has come a long way since the breakthrough was announced in 2016. Using current sample sizes, the researchers say they are now able to find enough distinctive markers to provide a unique pattern for an individual that would distinguish that person among a population of 1 billion people.
In addition to Katelyn Mason, Brad Hart, and Deon Anex from Livermore, other co-authors of the paper are Glendon Parker, who previously worked at Livermore and is now an adjunct associate professor in the University of California, Davis’ Environmental Toxicology Department; and Todd Grey, who is retired from the Utah Office of the Medical Examiner.