232015Mar

Genetic markers of PTSD linked to immune system reponse


A new study of blood samples from US Marines has identified genetic markers associated with post-traumatic stress disorder that are also linked to the immune system response. The research team – from the US and UK – says the discovery could lead to new diagnostic techniques and treatments for the condition, as well as predict which individuals are most at risk for the disorder.

Post-traumatic stress disorder (PTSD) is a mental health condition that can occur after experiencing a terrifying event or situation. Violent assaults, accidents, natural or human-caused disasters and military combat are some common triggers of PTSD.

It is estimated that around 6.8% of Americans will develop PTSD at some point in their lives. These individuals may have recurrent, distressing memories of the terrifying ordeal they have been through, sleep problems, severe anxiety and depression, and they may even have suicidal thoughts.

Previous studies have aimed to uncover genetic markers of PTSD by investigating differences in gene expression between people with the disorder and those without it. But the team involved in this latest research decided to adopt a “systems-level approach,” which involved using whole transcriptome RNA sequencing on blood samples of US Marines with and without PTSD.

“By comparing US Marines who develop PTSD symptoms to those who do not, we can measure differences in genes, but also take into consideration the dynamic relationships between and among them, their connectivity,” explains senior author Michael S. Breen, of the University of Southampton in the UK.

“Because PTSD is thought to be such a complex disorder,” he adds, “measuring these dynamic relationships is crucial to better understanding the PTSD pathology.”

Markers of PTSD linked to innate immune system and interferon signaling

For their study, the results of which are published in the journal Molecular Psychiatry, the researchers took blood samples from 188 US Marines before and after they were deployed to conflict zones.

Using whole transcriptome RNA sequencing to analyze the blood samples, the team identified groups of genes that regulate the innate immune system and interferon signaling that were also linked to PTSD.

The innate immune system is the body’s first line of defense against pathogens, and interferon signaling is the release of signaling proteins (interferons) by host cells in response to pathogens.

Interestingly, the researchers identified these innate immunity and interferon signaling gene groups both before and following development of PTSD among the participants.

The researchers replicated their findings in a separate analysis of blood samples from 96 US Marines.

Principal Investigator Dr. Dewleen G. Baker, of the Veteran Affairs San Diego Healthcare System, CA, and the University of California-San Diego, says the findings raise an important question: what is triggering interferon signaling prior to the development of PTSD?

“The answer could be any number of factors,” Baker speculates, “ranging from a simple explanation of increased anticipatory stress prior to deployment or more complex scenarios where individuals may have a higher viral load. It’s a question for future studies.”

The researchers hope the design of their study will encourage other researchers to adopt a similar approach when looking to identify genetic markers of PTSD. Co-senior author Christopher H. Woelk, PhD, of the University of Southampton and UC-San Diego, adds:

“Since our causal (pre-deployment) and consequential (post-deployment) discoveries are based upon peripheral blood samples, these results suggest that identifying individuals at risk for PTSD development may be achievable through high-throughput profiling of molecular data.”

The researchers explain that adopting this approach could lead to the creation of a blood panel of biomarkers that could help identify which individuals are at risk of PTSD. What is more, they say the molecular information from blood samples could be used to develop personalized prevention and treatment strategies for the disorder.

In January, Medical News Today reported on a study by researchers from the University of California-Los Angeles, in which they claim to have identified two gene variants that may affect the likelihood of developing PTSD.

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