Watch any episode of “CSI” and a character will use the forensic DNA profile to identify a criminal. A new San Francisco State University study suggests that these forensic profiles may indirectly reveal medical information – perhaps even that of crime victims – contrary to what the legal field has believed for nearly 30 years. The findings could have ethical and legal implications.
“The central assumption in choosing those [forensic] markers was that there would be no information on individuals other than identification. Our article challenges this hypothesis, “said lead author Mayra Bañuelos (BS, ’19), who began working on the project as a San Francisco state student and is now a PhD student at Brown University.
Law enforcement agencies use the Combined DNA Index System (CODIS), a system that organizes criminal justice DNA databases that uses specific genetic markers to identify individuals. National, state and local crime labs contribute to these databases and provide profiles from samples collected from crime scene evidence, convicted offenders, arrested for felonies, missing persons and more. Law officials can use the database to try to match samples found in a survey to profiles already stored in the database.
CODIS profiles are made up of genetic variants of an individual as a set of short tandem repeats (STRs), DNA sequences that repeat at various frequencies between individuals. Since the 1990s, 20 STRs have been chosen for forensic CODIS profiling precisely because they were believed not to convey medical information. If these profiles contained trait information, there could be medical privacy concerns.
“But this hypothesis hasn’t been the subject of much investigation in a long time, and we now know a lot more about the genome than we did then,” explained Rori Rohlfs, an associate professor of biology at the SF State, who led this project.
Even the assumption that only criminals are sampled is not entirely correct. “It actually also includes victims of crimes and people who may have been at the crime scene. You have these huge databases that include a lot of people who aren’t necessarily criminals,” Banuelos said. “I also believe that the accessibility of these databases varies a lot by jurisdiction.”
The researchers explained that other papers found associations between other STR (non-CODIS) and disease or gene expression. With this in mind, the SF State team wanted to understand the relationship between CODIS STR markers and gene expression.
Rohfls’ laboratory used publicly available data (1000 Genome Project) and genetic models to study the relationship between CODIS markers and gene expression. Of the 20 CODIS markers, they found six associations between CODIS markers and the gene expression of neighboring genes in the white blood cell lines of more than 400 unrelated individuals in the database.
“In some genes, the change in gene expression has been associated with medical conditions,” Bañuelos explained, citing previous research. “[In this study,] we indirectly know that there is an association between these CODIS genotypes and some changes in the genes that can lead to the disease. “
The authors noted three gene associations (CSF1R, LARS2, KDSR) that were particularly interesting. Previous literature shows that mutations and changes in CSF1R gene expression can be linked to psychiatric conditions (depression and schizophrenia). Mutations and gene expression changes in other genes have been linked to Perrault syndrome, MELAS syndrome, severe skin and platelet conditions, and more, the scientists note. PNAS (Proceedings of the National Academy of Sciences) paper. If CODIS markers can be linked to the expression of genes related to disease and health, it means that the data in the CODIS database could compromise an individual’s medical privacy.
“Our article is in some ways like the tip of the iceberg,” Rohlfs said, admitting she was surprised to find associations in a relatively small sample size. The project itself simply started out as a university exploration project. Eight of the 11 authors were, like Bañuelos, college students at SF State when the project began.
“Raises the question: if we did a broader one [genetic] study, would we find even more information that would be revealed by the CODIS profiles? “asked Rohlfs.
Bañuelos and Rohlfs are curious about what they would find if they looked at a larger dataset of more diverse populations – their current dataset is predominantly European. Their analysis was also limited to white blood cells. What relationships would they find if they looked into other fabrics?
These are important lines of investigation because the current dataset does not represent the general population. Additionally, Latin and African American communities are overrepresented in these CODIS databases, Bañuelos explained.
Further studies are needed to better clarify the relationship between CODIS and medical information. However, the researchers point out that if CODIS profiles contain medical information, there could be important implications.
“Self [these CODIS profiles] contain medical information, so their treatment should be consistent with how we protect medical information in the United States. We should have policies governing the seizure, storage and sharing of these profiles, ”Rohlfs added.