Summary: Researchers have been awarded a five-year, $3.2 million grant from the U.S. National Institutes of Health’s National Institute of Mental Health. The research targets the precise epigenetic networks within the amygdala that establish long-lasting biological memories of trauma, driving the exaggerated fear responses characteristic of Post-Traumatic Stress Disorder (PTSD).
By auditing histone-modifying proteins, specifically HDAC3, alongside advanced RNA sequencing and CRISPR/Cas9 gene-editing techniques, the inter-university alliance aims to map out, manipulate, and theoretically reverse the molecular mechanics of trauma to pioneer consistent, gender-optimized therapeutic interventions.
Key Facts
- The Unresolved PTSD Crisis: Approximately 7% of individuals in the United States experience PTSD at some point in their lives, a condition marked by long-lasting biological alterations that produce hyper-vigilant fear responses to future stress. Currently, no clinical treatment consistently improves PTSD across all patient demographics.
- The Amygdala’s Epigenetic Markers: Utilizing a highly conserved mammalian mouse model system, the research team is isolating the amygdala, the brain’s anatomical site of fear. The study explores how proteins called histones package DNA strings and undergo temporary epigenetic modifications during trauma. These structural shifts change how accessible critical genes are to cellular machinery without altering the underlying genetic sequence.
- The Primed Molecular Memory Hypothesis: Led by Dr. Janine Kwapis, the team hypothesizes that trauma leaves precise epigenetic marks on fear-memory genes. These marks leave the genes in a hyper-accessible, “ready” state to be expressed ultra-rapidly during subsequent, minor stressful events, causing the survival-based fear response to become pathologically intense and frequent.
- Toggling the HDAC3 Fear Dial: The investigators previously discovered that a specific histone modifier, HDAC3, actively governs memory formation during acute stress. Remarkably, experimentally blocking HDAC3 activity during a mild stressor tricks the brain into remembering the minor event with intense severity, processing it as if it were a massive, lingering trauma.
- A High-Throughput CRISPR Assault: To map out the entire genome-wide system, co-investigator Dr. Istvan Albert will leverage RNA sequencing and ChIP-seq to identify genes over-expressed during stress and pinpoint exactly where histone modifications anchor. The team will then deploy CRISPR/Cas9 gene-editing tools to directly manipulate top candidate genes, aiming to systematically block or erase the exaggerated fear response.
- Unlocking the Gender Prevalence Disparity: Statistically, women are twice as likely to develop PTSD as men, but the biological drivers remain unmapped. Co-investigator Dr. Karyn Frick noted that female mice exhibit an amplified, lingering fear response to mild stressors that leave male mice completely unaffected. The grant will directly investigate whether females require a lower biological threshold of stress to anchor a traumatic molecular memory.
Source: Penn State
Experiencing a traumatic event sometimes produces long-lasting biological changes that can lead to an exaggerated fear response to future stressful events, such as what occurs in individuals with post-traumatic stress disorder (PTSD).
To better understand the regulatory mechanisms in the brain that produce this biological memory and exaggerated fear response, a team of researchers from Penn State and the University of Wisconsin-Milwaukee has been awarded a five-year, $3.2 million grant from the U.S. National Institutes of Health’s National Institute of Mental Health.
According to the researchers, about 7% of people in the United States experience PTSD at some point in their life; however, there is not currently a treatment that consistently improves PTSD in all patients. Additionally, women are about twice as likely to experience PTSD than men, but it is unclear why.
“Fear is an important aspect of survival, but an exaggerated response, such as with PTSD and other anxiety disorders, can cause harm if it interferes with normal functioning,” said Janine Kwapis, Paul Berg Early Career Professor in the Biological Sciences in the Penn State Eberly College of Science and leader of the research team. “We want to know what’s happening during a traumatic event that persistently changes how our brain functions and how that differs between men and women.”
Kwapis and her team are using a mouse-model system to study a part of the brain called the amygdala, which she said is known as the site of fear. While their work is in mice, Kwapis explained that these structures are highly conserved across mammals and can lend important insight into how fear memories are formed in humans.
Specifically, they are exploring how proteins called histones, which help package long strings of DNA into a more compact form, can temporarily modify certain genes in the brain during stressful events. By changing how tightly they bind to DNA, histones can alter how accessible genes are to the cellular machinery that turns them on or off without changing the gene’s underlying genetic sequence. This kind of temporary change is called an epigenetic modification.
“Our hypothesis is that when that trauma event occurs, there are epigenetic mechanisms that mark genes critical for fear memory, so that those genes are ready to be expressed really rapidly if something else bad happens,” Kwapis said.
“It forms a molecular memory — long-lasting biological changes — with effects that persist well after the fearful event ends. In the case of trauma, that response might be too intense or happen too frequently during subsequent events.”
Kwapis and her research group previously identified that a histone modifier called HDAC3 is active in memory formation during stressful events. By blocking this protein’s activity during a mildly stressful event, she said, it changes the event into one that is remembered very strongly, as if it were more traumatic.
“We want to better understand how this mechanism works and see if there are other epigenetic mechanisms that operate in similar ways.” she said. “If we can characterize this molecular memory for trauma, theoretically we could find a way to manipulate it to lessen or even reverse the effects and, in the best-case scenario, erase PTSD.”
In addition to thoroughly investigating HDAC3, the team will use RNA sequencing to identify genes in the amygdala that are expressed excessively during subsequent stress events. They will also use a technique called ChIP-seq to map areas of the genome that are affected by these histone changes during trauma. After cross-referencing these results, the team will use CRISPR/Cas9 gene-editing techniques to manipulate top candidate genes to try to prevent these exaggerated fear responses.
“It’s likely that many different genes and epigenetic regulators are operating to impact memory formation during stressful events, and we hope to gain a better understanding of how the system works together,” said Istvan Albert, research professor of bioinformatics in the Penn State Department of Biochemistry and Molecular Biology and co-investigator on the grant.
“Once we know how the system works, it could become possible to target specific genes or histones to manipulate the system in ways that may contribute to future therapies for PTSD and other anxiety disorders.”
The research team will also explore why females are more likely to form stronger fear responses. They previously found that female mice show an amplified response to a mild stressor that has no lingering effects in male mice.
“We want to know if it takes less stress for females to develop a stronger fear memory, or if something else is happening that enables this exaggerated response,” said Karyn Frick, distinguished professor of psychology at the University of Wisconsin-Milwaukee, and co-investigator of the grant. “Females and males often have very different responses to the exact same stimulation, but the biological reasons for those differences are still not fully understood.”
The researchers said that their work also has implications for other instances where the brain might overreact, such as anxiety disorders.
“We’re ultimately studying how one experience can impact the brain in a way that has long-lasting changes,” Kwapis said. “How does the brain establish a biological memory, and what are the conditions where that goes from being helpful for survival to being something that interferes with or negatively impacts your life? Starting to answer these questions could have important implications for human health.”
Key Questions Answered:
A: It occurs by creating a physical “molecular memory” through epigenetic changes inside the brain’s fear center, the amygdala. When a traumatic event occurs, specialized proteins called histones change how tightly they wrap around your DNA strands. This structural shift leaves specific fear-response genes completely exposed and uncoiled, acting like a hair-trigger switch that is primed to flash on ultra-rapidly during minor subsequent stressors, blowing normal survival instincts out of proportion.
A: HDAC3 is a crucial histone-modifying protein that acts as an editor for memory formation during stressful situations. In preliminary trials, Penn State researchers discovered that biochemically blocking HDAC3 during a very mild, safe stressor completely alters the brain’s filing system. It causes the brain to burn that minor event into memory with terrifying intensity, treating a small stressor as if it were a catastrophic, life-threatening trauma.
A: Because human epidemiological data shows that women are twice as likely to develop PTSD as men, yet the underlying biological reasons have remained a mystery. In laboratory settings, female mice exhibit an amplified, long-lasting fear response to mild pressures that male mice easily shrug off without any lingering effects. The team is using this grant to determine if the female brain requires a significantly lower stress threshold to permanently mark its genes with trauma.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this genetics, PTSD, and memory research news
Author: Adrienne Berard
Source: Penn State
Contact: Adrienne Berard – Penn State
Image: The image is credited to Neuroscience News
