Gene found to be crucial for formation of certain brain circuitry

Identified using new technique that can speed identification of genes, drug candidates Using a powerful gene-hunting technique for the first time in mammalian brain cells, researchers at Johns Hopkins report they have identified a gene involved in building the circuitry that relays signals through the brain. The gene is a likely player in the aging process in the brain, the researchers say. Additionally, in demonstrating the usefulness of the new method, the discovery paves the way for faster progress toward identifying genes involved in complex mental illnesses such as autism and schizophrenia — as well as potential drugs for such conditions. A summary of the study appears in the Dec. 12 issue of Cell Reports. "We have been looking for a way to sift through large numbers of genes at the same time to see whether they affect processes we're interested in," says Richard Huganir, Ph.D., director of the Johns Hopkins University Solomon H. Snyder Department of Neuroscience and a Howard Hughes Medical Institute investigator, who led the study. "By adapting an automated process to neurons, we were able to go through 800 genes to find one needed for forming synapses — connections — among those cells." Although automated gene-sifting techniques have been used in other areas of biology, Huganir notes, many neuroscience studies instead build on existing knowledge to form a hypothesis about an individual gene's role in the brain. Traditionally, researchers then disable or "knock out" the gene in lab-grown cells or animals to test their hypothesis, a time-consuming and laborious process. In this study, Huganir's group worked to test many genes all at once using plastic plates with dozens of small wells. A robot was used to add precise allotments of cells and nutrients to each well, along with molecules designed to knock out one of the cells' genes — a different one for each well. "The big challenge was getting the neurons, which are very sensitive, to function under these automated conditions," says Kamal Sharma, Ph.D., a research associate in Huganir's group. The team used a trial-and-error approach, adjusting how often the nutrient solution was changed and adding a washing step, and eventually coaxed the cells to thrive in the wells. In addition, Sharma says, they fine-tuned an automated microscope used to take pictures of the circuitry that had formed in the wells and calculated the numbers of synapses formed among the cells. The team screened 800 genes in this way and found big differences in the well of cells with a gene called LRP6 knocked out. LRP6 had previously been identified as a player in a biochemical chain of events known as the Wnt pathway, which controls a range of processes in the brain. Interestingly, Sharma says, the team found that LRP6 was only found on a specific kind of synapse known as an excitatory synapse, suggesting that it enables the Wnt pathway to tailor its effects to just one synapse type. "Changes in excitatory synapses are associated with aging, and changes in the Wnt pathway in later life may accelerate aging in general. However, we do not know what changes take place in the synaptic landscape of the aging brain. Our findings raise intriguing questions: Is the Wnt pathway changing that landscape, and if so, how?" says Sharma. "We're interested in learning more about what other proteins LRP6 interacts with, as well as how it acts in different types of brain cells at different developmental stages of circuit development and refinement." Another likely outcome of the study is wider use of the gene-sifting technique, he says, to explore the genetics of complex mental illnesses. The automated method could also be used to easily test the effects on brain cells of a range of molecules and see which might be drug candidates Continuing Education for Social Workers ### Other authors on the paper are Se-Young Choi, now of Seoul National University School of Dentistry; Yong Zhang, Shunyou Long and Min Li of Johns Hopkins University School of Medicine; and Thomas J.F. Nieland, now of the Broad Institute of Harvard and MIT. This work was supported by grants from the Howard Hughes Medical Institute and the National Institute of Mental Health (grant numbers P50MH084020 and 5U54MH084691). Related stories: Gene Found to Foster Synapse Formation in the Brain http://www.hopkinsmedicine.org/news/media/releases/gene_found_to_foster_synapse_formation_in_the_brain Study Refutes Accepted Model of Memory Formation http://www.hopkinsmedicine.org/news/media/releases/study_refutes_accepted_model_of_memory_formation____ Newly Discovered "Switch" Plays Dual Role in Memory Formation http://m.hopkinsmedicine.org/news/media/releases/newly_discovered_switch_plays_dual_role_in_memory_formation

Aging and gene expression -- possible links to autism and schizophrenia in offspring

Advanced paternal age has been associated with greater risk for psychiatric disorders, such as schizophrenia and autism. With an increase in paternal age, there is a greater frequency of certain types of mutations that contribute to these disorders in offspring. Mutations are changes in the genetic code. Recent research, however, looks beyond the genetic code to "epigenetic effects", which do not involve changes in the genes themselves, but rather in how they are expressed to determine one's characteristics. Such epigenetic changes in sperm, related to ageing, have been linked with psychiatric disorders in offspring. Maria Milekic, PhD, reported today, at the American College of Neuropsychopharmacology annual meeting in Hollywood Florida, that old mice have an epigenetic change ‒ a loss of DNA methylation at the locations where the genetic code starts being transcribed. DNA methylation is a biochemical process that plays an important regulatory role in development and disease. The work was done by a research team in the Department of Psychiatry at Columbia University. Offspring of old fathers showed the same deficit in DNA methylation, and they differed in their behavior from the offspring of the young fathers. They showed less exploratory activity and differed in the startle response and in habituation. Two groups, with 10 breeder mice per group, were tested. The breeders were either old (12 month) or young (3 month) males, each bred with two young (3 month) female mice. Then the behavior of the offspring was tested when they were 3 months old. DNA methylation also was tested in the young and old fathers' sperm, and brains of the offspring were tested for DNA methylation as well as gene expression. "We were interested in understanding the mechanism of the paternal age effect", said Dr. Milekic."The risk for schizophrenia increases 2-fold when a father is over 45 years of age, and the risk for autism increases 2-5-fold. It seemed unlikely that mutation alone could account for this. We therefore speculated that DNA methylation could provide an alternative mechanism." Not only did the offspring of the old fathers differ from their counterparts with young fathers in DNA methylation, they also showed significant differences in the expression of genes that have been implicated in autism spectrum disorders and that are known to regulate the development and function of the brain. These findings point to possible factors that can lead to autism spectrum disorders and schizophrenia, and ultimately may lead to more effective therapeutic interventions. With respect to studies in the immediate future, Dr. Milekic said,"We are trying to evaluate changes in different brain regions. Our studies before did not compare brain regions. Most of the genes that have altered expression are in the cerebellum. We are interested in how DNA methylation in the cerebellum is affected by paternal age." Social Worker CEUs ### The work was supported by grants from NIMH and the Simon Foundation to Jay Gingrich, MD, PhD, and a NARSAD Young Investigator Awa rd from the Brain and Behavior Research Foundation to Dr. Milekic.

Gene found to foster synapse formation in the brain

Implications for language development, autism, epilepsy Researchers at Johns Hopkins say they have found that a gene already implicated in human speech disorders and epilepsy is also needed for vocalizations and synapse formation in mice. The finding, they say, adds to scientific understanding of how language develops, as well as the way synapses — the connections among brain cells that enable us to think — are formed. A description of their experiments appears in Science Express on Oct. 31. A group led by Richard Huganir, Ph.D., director of the Solomon H. Snyder Department of Neuroscience and a Howard Hughes Medical Institute investigator, set out to investigate genes involved in synapse formation. Gek-Ming Sia, Ph.D., a research associate in Huganir's laboratory, first screened hundreds of human genes for their effects on lab-grown mouse brain cells. When one gene, SRPX2, was turned up higher than normal, it caused the brain cells to erupt with new synapses, Sia found. When Huganir's team injected fetal mice with an SRPX2-blocking compound, the mice showed fewer synapses than normal mice even as adults, the researchers found. In addition, when SRPX2-deficient mouse pups were separated from their mothers, they did not emit high-pitched distress calls as other pups do, indicating they lacked the rodent equivalent of early language ability. Other researchers' analyses of the human genome have found that mutations in SRPX2 are associated with language disorders and epilepsy, and when Huganir's team injected the human SRPX2 with the same mutations into the fetal mice, they also had deficits in their vocalization as young pups. Another research group at Institut de Neurobiologie de la Méditerranée in France had previously shown that SRPX2 interacts with FoxP2, a gene that has gained wide attention for its apparently crucial role in language ability. Huganir's team confirmed this, showing that FoxP2 controls how much protein the SRPX2 gene makes and may affect language in this way. "FoxP2 is famous for its role in language, but it's actually involved in other functions as well," Huganir comments. "SRPX2 appears to be more specialized to language ability." Huganir suspects that the gene may also be involved in autism, since autistic patients often have language impairments, and the condition has been linked to defects in synapse formation. This study is only the beginning of teasing out how SRPX2 acts on the brain, Sia says. "We'd like to find out what other proteins it acts on, and how exactly it regulates synapses and enables language development." Roger Clem of the Mount Sinai School of Medicine also participated in the study CADC I & II Continuing Education ### This study was supported by the National Institute of Mental Health (grant number P50MH084020) and the National Institute of Neurological Disorders and Stroke (grant number NS050274). Related stories: Study Refutes Accepted Model of Memory Formation Johns Hopkins Scientists Reveal Molecular Sculptor of Memories Johns Hopkins Researchers Discover How to Erase Memory

Gene Variants Implicated in Extreme Weight Gain Associated with Antipsychotics

Gene Variants Implicated in Extreme Weight Gain Associated with Antipsychotics Source: JupiterExtreme weight gain associated with taking an antipsychotic medication may be linked to certain genetic variants, according to a study published in the September 2012 issue of the Archives of General Psychiatry. Background Antipsychotic medications, especially those known as “second generation” or “atypical” antipsychotics, generally are the first-line of treatment for schizophrenia and other serious mental disorders. They are effective in treating psychotic symptoms, but they are also associated with serious metabolic side effects that can result in substantial weight gain, and other cardiovascular problems.Some people appear to be more susceptible to severe weight gain than others, but it is difficult to predict who is most at risk. To date, there have been few genetic studies of weight gain associated with antipsychotics, in part because it is difficult to control such variables as prior exposure to the medications, and because patients often stop taking the medications prematurely.Anil Malhotra M.D., of the Feinstein Institute for Medical Research, and colleagues set out to identify any common gene variants associated with antipsychotic-induced weight gain in a group of patients who had never taken the medications before and who were carefully monitored to ensure they continued to take the medication over the study period. The initial study included a cohort of 139 pediatric patients who were prescribed a second-generation antipsychotic. Patients were examined over a period of 12 weeks to assess weight and metabolic effects of the medications.To compare and confirm their results, the researchers also conducted similar assessments of three small cohorts with adult patients taking second generation antipsychotics. Results of the Study The researchers found markers in a gene called the melanocortin 4 receptor (MC4R) that were associated with severe weight gain in people taking second generation antipsychotics. The MC4R region overlaps somewhat with another region previously identified as being associated with obesity in the general population. In addition, the results were replicated in the three independent cohorts. Significance In many genetic studies involving obesity, thousands of participants are needed to achieve statistically significant results and to overcome the many environmental factors that can influence a person’s weight. In this study, the critical environmental factor predisposing patients to weight gain was only antipsychotic medication use over a short period of time, thus allowing more control over other variables that could have confounded results. Therefore, even though the study only included 139 individuals, the researchers were able to detect results that implicated specific gene variants.The results also have potential clinical implications. Patients with the identified gene variants that would predispose them to severe weight gain while taking an antipsychotic could be directed to alternative treatments, especially those who do not have a psychotic disorder LPC Continuing Education Although particular gene variants were implicated, the study’s sample size was small. Further research with larger samples is needed to extend the findings. LPC CEUs Reference Malhotra A, et al. Association between common variants near the melanocortin 4 receptor gene and severe antipsychotic drug-induced weight gain. Arch Gen. Psychiatry. 2012 Sep. 69(9):904-912.

Genetic Switch Involved in Depression

The activity of a single gene sets in motion some of the brain changes seen in depression, according to a new study. The finding suggests a promising target for potential therapies. People with major depressive disorder, or major depression, have feelings of sadness, loss, anger or frustration that interfere with daily life for weeks or longer. The symptoms of depression also include memory loss and trouble thinking. Past studies have found that people with major depression have brains that are physically different from those of non-depressed people. The depressed brain has a smaller prefrontal cortex, a region at the front of the brain that handles emotion and complicated thought. The area also has fewer and smaller neurons (nerve cells) in the depressed brain. To gain insight into the neural mechanisms at work, a group led by Dr. Ronald Duman of Yale University began with data collected in a previous study. They had done a comparison of postmortem brains from 15 depressed people and 15 non-depressed people who were matched in age, ethnicity and gender. Using DNA microarray chips to analyze the activity of 20,000 genes, the researchers had found numerous genes that were expressed (turned on and off) differently in the brains of depressed people. For the new study, the team focused specifically on genes related to synapses, the place where signals pass from one neuron to another. The work was funded in part by NIH’s National Institute of Mental Health (NIMH) and National Center for Research Resources (NCRR). The findings were published in the September 2012 issue of Nature Medicine. Analysis revealed that about 30% of the genes with significantly lower expression in the depressed brains related to some aspect of synapse function. Further experiments found significantly reduced expression for 5 particular genes in the prefrontal cortex of depressed people. The scientists searched for transcription factors—proteins that bind to the DNA of other genes to turn them on or off—that were capable of regulating the 5 genes. They found one called GATA1 that is expressed significantly more in the brains of people with major depressive disorder. Expression of the Gata1 gene in the prefrontal cortex was also higher in a rat model of depression. Raising expression of Gata1 in cultured rat neurons decreased the expression of synapse-related genes. It also decreased the number of connections between neurons, supporting the idea that higher Gata1 expression can lead to the changes seen in depressed brains. The researchers next tested the gene in rats and found that putting extra copies of Gata1 into their brains made them behave as if they were depressed MHC Ceus “We show that circuits normally involved in emotion, as well as cognition, are disrupted when this single transcription factor is activated,” Duman explains. These findings may point toward a new target for treatment. “We hope that by enhancing synaptic connections, either with novel medications or behavioral interventions, we can develop more effective antidepressant therapies,” says Duman. — by Helen Fields Related Links: Depression: http://www.nimh.nih.gov/health/topics/depression/index.shtml More Young Neurons Equals Better Brain Function: http://www.nih.gov/researchmatters/april2011/ 04112011brainfunction.htm Brain Basics: Know Your Brain: http://www.ninds.nih.gov/disorders/brain_basics/know_your_brain.htm Reference: Nat Med. 2012 Aug 12. [Epub ahead of print] PMID: 22885997.

UCLA study uncovers new tools for targeting genes linked to autism

Findings could lead to future therapeutic targets UCLA researchers have combined two tools – gene expression and the use of peripheral blood -- to expand scientists' arsenal of methods for pinpointing genes that play a role in autism. Published in the June 21 online edition of the American Journal of Human Genetics, the findings could help scientists zero in on genes that offer future therapeutic targets for the disorder. "Technological advances now allow us to rapidly sequence the genome and uncover dozens of rare mutations," explained principal investigator Dr. Daniel Geschwind, the Gordon and Virginia MacDonald Distinguished Professor of Human Genetics and a professor of neurology at the David Geffen School of Medicine at UCLA. "But just because a particular genetic mutation is rare doesn't mean it's actually causing disease. We used a new approach to tease out potential precursors of autism from the occasional genetic glitch." Geschwind and his colleagues studied DNA contained in blood samples from 244 families with one healthy child and one child on the autism spectrum. The team used a hybrid method that blended tests that read the order of DNA bases with those that analyze gene expression, the process by which genes make cellular proteins. "Monitoring gene expression provides us with another line of data to inform our understanding of how autism develops," said Geschwind, who is also director of the Center for Autism Research and Treatment at the Semel Institute for Neuroscience and Behavior at UCLA. "Integrating this method with the sequencing of DNA bases expands our ability to find mutations leading to the disease." Gene expression offers a molecular signpost pointing scientists in the right direction by narrowing the field and highlighting specific areas of the genome. For example, if a gene is expressed at substantially higher or lower levels in a patient, researchers will review the patient's DNA to check if that gene has changed. "We found that we can use gene expression to help understand whether a rare mutation is causing disease or playing a role in disease development," said Geschwind. "A true mutation will alter a gene's sequence, modifying the protein or RNA it produces -- or preventing the gene from producing them entirely. "A gene mutation accompanied by a change in expression clues us to a hot spot on the genome and directs us where to look next," he added. "Not all mutations will influence gene expression, but this approach improves our ability to pinpoint those that do." The researchers used the combined method to prioritize gene targets that merit closer investigation, potentially explaining why one person develops autism and their sibling does not. Their search turned up new regions in the genome where genetic variations showed strong links to autism and altered expression patterns. Genes in these regions were more likely to be mutated in the autistic children than in their unaffected siblings. "When we looked at genes associated with nervous-system function we found significantly more genes were expressed at higher or lower levels in the children diagnosed with autism than we did in their siblings unaffected by the disorder," said Geschwind. Finally, the research team discovered that the DNA contained in peripheral blood can help shed light on diseases of the central nervous system. Brain cells and genes related to synaptic function are expressed in the blood, offering a window into gene expression. "Brain tissue from people with autism is not readily available for study, and some people are reluctant to use non-neural tissue in psychiatric disease," explained Geschwind. "But our study demonstrates that even peripheral blood can expand our knowledge of neurological disease." The team's next step will be to replicate their findings in a larger population. ### Autism is a complex brain disorder that strikes in early childhood. The condition disrupts a child's ability to communicate and develop social relationships and is often accompanied by acute behavioral challenges. Autism spectrum disorders are diagnosed in one in 110 children in the United States, affecting four times as many boys as girls. Diagnoses have expanded tenfold in the last decade. The research was supported by grants from the Simons Foundation, the National Institute of Mental Health (5R01 MH081754-04), the Wellcome Trust and Autism Speaks. Geschwind's coauthors included first author Rui Luo, Irina Voineagu, Lambertus Klei, Chaochao Cai, Jing Ou, Jennifer Lowe and Matthew State of UCLA; Stephan Sanders of Yale University; Ni Huang and Matthew Hurles of the Wellcome Trust Sanger Institute; and Su Chu and Bernie Devlin of Carnegie Mellon University. The UCLA Center for Autism Research and Treatment provides diagnosis, family counseling, clinical trials and treatment for patients with autism. UCLA is one of eight centers in the National Institutes of Health–funded Studies to Advance Autism Research and Treatment network and one of 10 original Collaborative Programs for Excellence in Autism social worker ceus

Genetic manipulation boosts growth of brain cells linked to learning, enhances antidepressants

DALLAS -- UT Southwestern Medical Center investigators have identified a genetic manipulation that increases the development of neurons in the brain during aging and enhances the effect of antidepressant drugs.

The research finds that deleting the Nf1 gene in mice results in long-lasting improvements in neurogenesis, which in turn makes those in the test group more sensitive to the effects of antidepressants.

"The significant implication of this work is that enhancing neurogenesis sensitizes mice to antidepressants – meaning they needed lower doses of the drugs to affect 'mood' – and also appears to have anti-depressive and anti-anxiety effects of its own that continue over time," said Dr. Luis Parada, director of the Kent Waldrep Center for Basic Research on Nerve Growth and Regeneration and senior author of the study published in the Journal of Neuroscience.

Just as in people, mice produce new neurons throughout adulthood, although the rate declines with age and stress, said Dr. Parada, chairman of developmental biology at UT Southwestern. Studies have shown that learning, exercise, electroconvulsive therapy and some antidepressants can increase neurogenesis. The steps in the process are well known but the cellular mechanisms behind those steps are not.

"In neurogenesis, stem cells in the brain's hippocampus give rise to neuronal precursor cells that eventually become young neurons, which continue on to become full-fledged neurons that integrate into the brain's synapses," said Dr. Parada, an elected member of the prestigious National Academy of Sciences, its Institute of Medicine, and the American Academy of Arts and Sciences.

The researchers used a sophisticated process to delete the gene that codes for the Nf1 protein only in the brains of mice, while production in other tissues continued normally. After showing that mice lacking Nf1 protein in the brain had greater neurogenesis than controls, the researchers administered behavioral tests designed to mimic situations that would spark a subdued mood or anxiety, such as observing grooming behavior in response to a small splash of sugar water.

The researchers found that the test group mice formed more neurons over time compared to controls, and that young mice lacking the Nf1 protein required much lower amounts of anti-depressants to counteract the effects of stress. Behavioral differences between the groups persisted at three months, six months and nine months. "Older mice lacking the protein responded as if they had been taking antidepressants all their lives," said Dr. Parada.

"In summary, this work suggests that activating neural precursor cells could directly improve depression- and anxiety-like behaviors, and it provides a proof-of-principle regarding the feasibility of regulating behavior via direct manipulation of adult neurogenesis," Dr. Parada said.

Dr. Parada's laboratory has published a series of studies that link the Nf1 gene – best known for mutations that cause tumors to grow around nerves – to wide-ranging effects in several major tissues. For instance, in one study researchers identified ways that the body's immune system promotes the growth of tumors, and in another study, they described how loss of the Nf1 protein in the circulatory system leads to hypertension and congenital heart disease social worker ceus

The current study's lead author is former graduate student Dr. Yun Li, now a postdoctoral researcher at the Massachusetts Institute of Technology. Other co-authors include Yanjiao Li, a research associate of developmental biology, Dr. Renée McKay, assistant professor of developmental biology, both of UT Southwestern, and Dr. Dieter Riethmacher of the University of Southampton in the United Kingdom.

The study was supported by the National Institutes of Health's National Institute of Neurological Disorders and Stroke, and National Institute of Mental Health. Dr. Parada is an American Cancer Society Research Professor.

This news release is available on our World Wide Web home page at www.utsouthwestern.edu/home/news/index.html

To automatically receive news releases from UT Southwestern via email, subscribe at www.utsouthwestern.edu/receivenews

Scripps Research Institute Team Wrests Partial Control of a Memory

News Release

The work advances understanding of how memories form and offers new insight into disorders such as schizophrenia and post traumatic stress disorder

LA JOLLA, CA – March 22, 2012 – Scripps Research Institute scientists and their colleagues have successfully harnessed neurons in mouse brains, allowing them to at least partially control a specific memory. Though just an initial step, the researchers hope such work will eventually lead to better understanding of how memories form in the brain, and possibly even to ways to weaken harmful thoughts for those with conditions such as schizophrenia and post traumatic stress disorder.

The results are reported in the March 23, 2012 issue of the journal Science.

Researchers have known for decades that stimulating various regions of the brain can trigger behaviors and even memories. But understanding the way these brain functions develop and occur normally—effectively how we become who we are—has been a much more complex goal.

“The question we’re ultimately interested in is: How does the activity of the brain represent the world?” said Scripps Research neuroscientist Mark Mayford, who led the new study. “Understanding all this will help us understand what goes wrong in situations where you have inappropriate perceptions. It can also tell us where the brain changes with learning.”

On-Off Switches and a Hybrid Memory

As a first step toward that end, the team set out to manipulate specific memories by inserting two genes into mice. One gene produces receptors that researchers can chemically trigger to activate a neuron. They tied this gene to a natural gene that turns on only in active neurons, such as those involved in a particular memory as it forms, or as the memory is recalled. In other words, this technique allows the researchers to install on-off switches on only the neurons involved in the formation of specific memories.

For the study’s main experiment, the team triggered the “on” switch in neurons active as mice were learning about a new environment, Box A, with distinct colors, smells and textures continuing education for counselors

Next the team placed the mice in a second distinct environment—Box B—after giving them the chemical that would turn on the neurons associated with the memory for Box A. The researchers found the mice behaved as if they were forming a sort of hybrid memory that was part Box A and part Box B. The chemical switch needed to be turned on while the mice were in Box B for them to demonstrate signs of recognition. Alone neither being in Box B nor the chemical switch was effective in producing memory recall.

“We know from studies in both animals and humans that memories are not formed in isolation but are built up over years incorporating previously learned information,” Mayford said. “This study suggests that one way the brain performs this feat is to use the activity pattern of nerve cells from old memories and merge this with the activity produced during a new learning session.”

Future Manipulation of the Past

The team is now making progress toward more precise control that will allow the scientists to turn one memory on and off at will so effectively that a mouse will in fact perceive itself to be in Box A when it’s in Box B.

Once the processes are better understood, Mayford has ideas about how researchers might eventually target the perception process through drug treatment to deal with certain mental diseases such as schizophrenia and post traumatic stress disorder. With such problems, patients’ brains are producing false perceptions or disabling fears. But drug treatments might target the neurons involved when a patient thinks about such fear, to turn off the neurons involved and interfere with the disruptive thought patterns.

In addition to Mayford, other authors of the paper, “Generation of a Synthetic Memory Trace,” are Aleena Garner, Sang Youl Hwang, and Karsten Baumgaertel from Scripps Research, David Rowland and Cliff Kentros from the University of Oregon, Eugene, and Bryan Roth from the University of North Carolina (UNC), Chapel Hill.

This work is supported by the National Institute of Mental Health, the National Institute on Drug Abuse, the California Institute for Regenerative Medicine, and the Michael Hooker Distinguished Chair in Pharmacology at UNC.

About The Scripps Research Institute

The Scripps Research Institute is one of the world's largest independent, non-profit biomedical research organizations. Scripps Research is internationally recognized for its discoveries in immunology, molecular and cellular biology, chemistry, neuroscience, and vaccine development, as well as for its insights into autoimmune, cardiovascular, and infectious disease. Headquartered in La Jolla, California, the institute also includes a campus in Jupiter, Florida, where scientists focus on drug discovery and technology development in addition to basic biomedical science. Scripps Research currently employs about 3,000 scientists, staff, postdoctoral fellows, and graduate students on its two campuses. The institute's graduate program, which awards Ph.D. degrees in biology and chemistry, is ranked among the top ten such programs in the nation. For more information, see www.scripps.edu.

# # #

For information:
Office of Communications
Tel: 858-784-8134
Fax: 858-784-8136
press@scripps.edu

Suspect Gene Variants Boost PTSD Risk after Mass Shooting

Profile of Risk Emerging for Trauma-triggered Molecular Scars

College students exposed to a mass shooting were 20-30 percent more likely to later develop post traumatic stress disorder (PTSD) symptoms if they harbored a risk version of a gene, NIMH-funded researchers have discovered. This boost in risk, traced to common variants of the gene that controls recycling of serotonin, was comparable to the risk conferred by close proximity to the shooting – for example, being in the room with the shooter versus just being on campus.

The discovery is the latest of several recently reported that collectively profile heightened biological vulnerability to developing PTSD following trauma – and the molecular scars it leaves in the brain.

For example, early this year, researchers linked high levels of a stress-triggered, estrogen-related hormone to PTSD symptoms in women, with certain versions of the hormone receptor’s gene conferring higher risk. A PET scan study in September traced increased PTSD symptoms to heightened levels of a serotonin receptor. Both studies suggest potential new drug targets for treating the disorder. Evidence is also mounting that trauma – particularly if experienced very early in life – can adversely alter the set-points of gene expression in brain stress circuits and compromise immune and inflammatory system function continuing education for counselors

Gene-by-environment – caught in the act

By chance, researchers at Northern Illinois University (NIU) had already collected data on students’ PTSD symptoms prior to the 2008 murder-suicide that killed six on the Dekalb, Illinois campus.*

“This provided a rare opportunity to pinpoint not just a correlation but a cause – to document that such a tragedy can conspire with a risk gene to produce the disorder,” explained Kerry Ressler, M.D., Ph.D., of Emory University.

NIMH grantees Ressler, NIU’s Holly Orcutt, Ph.D., and colleagues, report on discovery of this gene-by-environment interaction online September 5th 2011 in the Archives of General Psychiatry.

Previous efforts to confirm such an interaction in PTSD had been confounded by lack of data on individuals’ pre-trauma symptoms. Any pre-existing symptoms must be taken into account to establish a common baseline – so that new symptoms that develop can confidently be pegged to the traumatic event.

By chance, before the tragedy, Orcutt’s team had prospectively surveyed PTSD symptoms in more than a thousand NIU undergraduate women, as part of a longitudinal study on predictors of sexual victimization, which can trigger the disorder. Within a few weeks after the tragedy, they seized the opportunity and – with help from a NIMH RAPID grant – conducted follow-up surveys, using the same measures, in subsets of the original sample – and then again after several months – to track symptom changes. Ressler’s team ultimately analyzed saliva samples from 235 women for gene type.

Previous studies had linked PTSD to a version of the gene that codes for the serotonin transporter (SERT), the protein on neurons that recycles the chemical messenger serotonin back into the cell after it is secreted into the synapse. So the researchers focused their genetic analysis on this variation, noting that it is “the most commonly described polymorphism in the psychiatric genetics literature.”

For example, this same site of genetic variation has also been linked to increased risk for anxiety - and, in some studies, increased risk for depression following stressful life events, although the latter findings remain controversial. Some hypothesize that these implicated variants may have less to do with conferring disease risk, per se, than with increased sensitivity to environmental influences more generally.**

Antidepressant medications, serotonin selective reuptake inhibitors (SSRIs), work by blocking SERT, thereby enhancing serotonin activity. SSRIs are the main medication treatment for PTSD.

Everyone inherits two copies of the SERT gene, one from each parent. So people can inherit one or two copies of risk-associated versions that are common in the population. Carrying any combination of these risk versions had been associated with increased risk for PTSD in 8 out of 9 previous studies.

The new study more definitively connects the dots between the environmental trigger and these risk gene types. Among 204 women without prior symptoms, 20 percent of those who showed acute symptoms within a few weeks after the shooting had developed PTSD symptoms when surveyed several months later. Proximity to the shooting and the risk gene types were about equally predictive of increased risk among this group.

These results come at a time of ferment in the field over confidence in gene-by-environment findings. A recent analysis by NIMH grantees of more than 100 such studies over the past decade uncovered what they call “publication bias.” They found that positive new findings were more likely to get published, while direct replications – which tend be less likely to confirm positive new findings – were under-reported. The net effect: an unintentional bias toward false positive reports. Notably, the researchers singled out as a prime example of this bias the scientific literature on serotonin transporter gene-by-environment interactions.

“How we measure environment may be at least as important as how we measure genetics, but to date, little effort has been focused on that,” noted Ressler. “We think that performing prospective studies in populations with shared trauma may be one way to 'hold constant' the environment variable, thus allowing for more clarity in the role of genetics.”

PTSD symptoms of NIU undergraduate women with a risk-associated serotonin transporter gene type (s/s, lG/lG, s/lG) increased 20-30 percent more than in classmates with a protective gene type after the 2008 campus shootings (Time 2). The increased risk was comparable to that conferred by close proximity to the shooting.
Source: Kerry Ressler, M.D., Ph.D., Emory University

Why Women are More Vulnerable

Earlier this year, Ressler and colleagues reported findings that may help to explain why women are twice as likely as men to develop PTSD. They linked PTSD symptoms in women to higher blood levels of what has been dubbed the “master regulator” of the stress response, a hormone called PACAP (pituitary adenyl cyclase-activating peptide).

PTSD symptoms were 5-fold higher in women with above average PACAP levels, compared to women with below average levels. Also in women only, a certain version of the gene that codes for PACAP’s receptor, PAC-1, conferred increased vulnerability. Experiments in rodents confirmed that this variable part of the PAC-1 gene is regulated, in part, by the female hormone estrogen.

This suggests that heightened vulnerability to PTSD in females may be traceable to this brain system critical to proper stress circuit function. Genetic variation in a different pathway may similarly be linked to increased risk for PTSD in men, say the researchers.

Females with higher-than-average levels of the stress-managing hormone PACAP had 5 times more PTSD symptoms than females with lower-than-average levels. By contrast, PACAP levels were unrelated to PTSD symptoms in males. Since the PACAP system is shaped, in part, by the female hormone estrogen, these differences could help to explain why women are twice as likely as men to develop the disorder.
Source: Kerry Ressler, M.D., Ph.D., Emory University

PACAP, “master regulator” of the stress response.
Source: Lee Eiden, Ph.D., NIMH Section on Molecular Neuroscience

Molecular scars

The Emory researchers also found increased methylation – epigenetic regulation of gene expression in response to the environment – in the part of Pac1 associated with PTSD in both women and men. Adverse experiences can induce molecules called methyl groups to attach to DNA and block genes from turning on. This results in enduring changes in the proteins the genes express. These molecular scars can weaken the brain’s defenses against PTSD.

Indeed, methylation increases pervasively in PTSD, according to Ressler and colleagues. Notably, they pinpointed such increases in several genes implicated in inflammatory and immune system abnormalities that go along with PTSD. They also saw abnormalities in immune system chemical messengers, called cytokines. Increased blood levels of one such cytokine TNF-alpha, known to trigger stress response symptoms, correlated with a history of child abuse and cumulative life stresses.

Early trauma may deplete resilience molecule

In September, a NIMH-funded brain imaging study reported that levels of a type of serotonin receptor (1B) were markedly lower in stress circuits of PTSD patients than in others exposed to trauma. This protein on neurons, to which the neurotransmitter binds, plays a pivotal role in stress resilience and antidepressant effect. By contrast, PET scans revealed that people who had experienced trauma but didn’t develop PTSD had only slightly fewer receptors than healthy controls.

NIMH grantee Alexander Neumeister, M.D., of Mount Sinai School of Medicine, and colleagues, traced both the severity of symptoms and the depleted receptors largely to the age at which trauma was first experienced. The earlier the age and the more subsequent trauma exposures, the fewer receptors expressed and the more severe the PTSD symptoms and overlap with depression. The dearth of receptors likely reflects such features of patients’ trauma histories, with those who develop PTSD also having other genetic or environmental vulnerabilities, say the researchers.

Patients with PTSD (right) had significantly fewer serotonin 1B receptors (yellow & red areas) in their brain stress circuits than healthy controls (left). PET scan images show destinations of a radioactive tracer that binds to serotonin 1B receptors. Front of brain is at bottom.
Source: Alexander Neumeister, M.D., Mount Sinai School of Medicine

Possible Uses: Risk profile and treatment targets?

Such epigenetic and genetic signatures of PTSD proneness in blood and brain, together with behavioral measures, may collectively prove useful in profiling a patient’s risk for developing the disorder. Molecules such as PACAP and the serotonin 1B receptor may also hold promise as potential targets of new drugs aimed at correcting specific abnormalities in the affected brain pathways, suggest the researchers.


NIMH RAPID grant helps salvage science from tragedy
2/14/08 Mass shooting on NIU campus
2/19/08 NIU researcher Holly Orcutt, Ph.D., contacts NIMH to discuss how to make the most of her prospectively collected data on PTSD and other parameters to learn from the tragedy.
3/26/08 Orcutt submits a concept for a follow-up study under the NIMH Rapid Assessment Post Impact of Disaster (RAPID) research program announcement – a unique time sensitive mechanism for expediting funding of research grants in response to emergency situations.
5/17/08 Grant application submitted.
6/18/08 Application undergoes peer review.
9/18/08 Grant awarded to NIU and Orcutt.

References

Acute and Posttraumatic Stress Symptoms in a Prospective Gene x Environment Study of a University Campus Shooting. Mercer KB, Orcutt HK, Quinn JF, Fitzgerald CA, Conneely KN, Barfield RT, Gillespie CF, Ressler KJ. Arch Gen Psychiatry. 2011 Sep 5. [Epub ahead of print]
PMID:21893641

A Critical Review of the First 10 Years of Candidate Gene-by-Environment Interaction Research in Psychiatry. Duncan LE, Keller MC. Am J Psychiatry. 2011 Sep 2. [Epub ahead of print]
PMID: 21890791

Post-traumatic stress disorder is associated with PACAP and the PAC1 receptor.
Ressler KJ, Mercer KB, Bradley B, Jovanovic T, Mahan A, Kerley K, Norrholm SD, Kilaru V, Smith AK, Myers AJ, Ramirez M, Engel A, Hammack SE, Toufexis D, Braas KM, Binder EB, May V.Nature. 2011 Feb 24;470(7335):492-7. Erratum in: Nature. 2011 Sep 1;477(7362):120.
PMID:21350482

PACAP: a master regulator of neuroendocrine stress circuits and the cellular stress response.
Stroth N, Holighaus Y, Ait-Ali D, Eiden LE. Ann N Y Acad Sci. 2011 Mar;1220:49-59. doi: 10.1111/j.1749-6632.2011.05904.x. Review. PMID:21388403

The Effect of Early Trauma Exposure on Serotonin Type 1B Receptor Expression Revealed by Reduced Selective Radioligand Binding. Murrough JW, Czermak C, Henry S, Nabulsi N, Gallezot JD, Gueorguieva R, Planeta-Wilson B, Krystal JH, Neumaier JF, Huang Y, Ding YS, Carson RE, Neumeister A. Arch Gen Psychiatry. 2011 Sep;68(9):892-900. PMID:21893657

Differential immune system DNA methylation and cytokine regulation in post-traumatic stress disorder. Smith AK, Conneely KN, Kilaru V, Mercer KB, Weiss TE, Bradley B, Tang Y, Gillespie CF, Cubells JF, Ressler KJ. Am J Med Genet B Neuropsychiatr Genet. 2011 Sep;156(6):700-8. doi: 10.1002/ajmg.b.31212. Epub 2011 Jun 28. PMID:21714072

Psychiatry: A molecular shield from trauma. Stein MB. Nature. 2011 Feb 24;470(7335):468-9. No abstract available. PMID:21350472

*http://en.wikipedia.org/wiki/Northern_Illinois_University_shooting

** http://www.theatlantic.com/magazine/archive/2009/12/the-science-of-success/7761/