Scientists have revealed molecular differences between how the African and Asian strains of Zika virus infect neural progenitor cells. The results could provide insights into the Zika virus’ recent emergence as a global health emergency, and also point to inhibitors of the p53 pathway as potential leads for drugs that could protect brain cells from cell death.
The findings, from the Emory/Johns Hopkins/Florida State team that showed this spring that neural progenitor cells are particularly vulnerable to Zika infection (related paper), were published this week in Nucleic Acid Research. The manuscript was also posted on BioRxiv before publication.
Overlap in gene expression changes when neural progenitor cells are infected by African or Asian strains of Zika virus. Diagram from Nucleic Acids Research via Creative Commons.
Zika virus was first discovered in Uganda in the 1940s, and two distinct lineages of Zika diverged sometime in the second half of the 20th century: African and Asian. The strains currently circulating in the Western Hemisphere, which have been linked to microcephaly in infants and Guillain-Barre syndrome in adults, are more closely related to the Asian lineage.
The research team catalogued and compared genes turned on and off by Asian and African strains of Zika virus, as well as dengue virus, in human neural progenitor cells. The authors describe dengue as inducing more robust changes in gene expression than either strain of Zika. Although they show that dengue can infect neural progenitor cells like Zika can, dengue infection does not stunt the cells’ growth or lead to cell death.
“This shows that the differences between Zika and dengue are not at the level of being able to infect neural progenitors, but more about the harm Zika causes when it does infect those cells,” says senior author Peng Jin, PhD, professor of human genetics at Emory University School of Medicine. Read more
Emory neurosurgeon Robert Gross was recently quoted in a Tennessee newspaper article about a clinical trial of cell therapy for stroke. He used cautionary language to set expectations.
“We’re still in the very early exploratory phases of this type of work,” Gross told the Chattanooga Times Free Press. “In these cases, a significant area of the brain has been damaged, and simply putting a deposit of undifferentiated cells into the brain and magically thinking they will rewire the brain as good as new is naive. None of us think that.”
A more preliminary study (just 18 patients) using the same approach at Stanford and University of Pittsburgh was published this summer in Stroke, which says it was the “first reported intracerebral stem cell transplant study for stroke in North America.” The San Diego Union Tribune made an effort to be balanced in how the results were described:
Stroke patients who received genetically modified stem cells significantly recovered their mobility… Outcomes varied, but more than a third experienced significant benefit.
The newspaper articles made us curious about what these cells actually are. They’re mesenchymal stromal cells, engineered with an extra modified Notch gene. That extra gene drives them to make more supportive factors for neurons, but it doesn’t turn them into neurons. Read more
Transgenic Huntington’s disease monkeys display a full spectrum of symptoms resembling the human disease, ranging from motor problems and neurodegeneration to emotional dysregulation and immune system changes, scientists at Yerkes National Primate Research Center, Emory University report.
The results, published online in the journal Brain, Behavior and Immunity, strengthen the case that transgenic Huntington’s disease monkeys could be used to evaluate emerging treatments (such as this) before launching human clinical trials.
“Identifying emotional and immune symptoms in the HD monkeys, along with previous studies demonstrating their cognitive deficits and fine motor problems, suggest the HD monkey model embodies the full array of symptoms similar to human patients with the disease,” says Yerkes research associate Jessica Raper, PhD, lead author of the paper. Read more
It’s sweet, it’s safe, and it looks like it could save neurons. What is it? Trehalose.
Trehalose is a natural sugar.
This natural sugar is used in the food industry as a preservative and flavor enhancer (it’s in Taco Bell’s meat filling). And curiously, medical researchers keep running into trehalose when they’re looking for ways to fight neurodegenerative diseases.
A recent example from Emory’s Department of Pharmacology: Chris Holler, Thomas Kukar and colleagues were looking for drugs that might boost human cells’ production of progranulin (PGRN), a growth factor that keeps neurons healthy. Mutations in the progranulin gene are a common cause of frontotemporal dementia.
The Emory scientists discovered two leads: a class of compounds called mTOR inhibitors — the transplant drug rapamycin is one — and trehalose. The team decided to concentrate on trehalose because it increased PGRN levels in neuronal and non-neuronal cell types, unlike the mTOR inhibitors. Their results were published at the end of June in Molecular Neurodegeneration.
The team confirmed their findings by examining the effects of trehalose on cells derived from patients with progranulin mutations. This paper is the first to include results from Emory’s Laboratory of Translational Cell Biology, which was established in 2012 to facilitate this type of “disease in a dish” approach. Cell biologists Charles Easley, Wilfried Rossoll and Gary Bassell from the LTCB, and neurologists Chad Hales and William Hu from the Center for Neurodegenerative Disease are co-authors.
Emory researchers have identified molecular mechanisms that regulate motivation and persistence in mice. Their findings could have implications for intervention in conditions characterized by behavioral inflexibility, such as drug abuse and depression.
Scientists showedÂ that by manipulating a particular growth factor in one region of the brain, they couldÂ tune up or down a mouseâ€™s tendency to persist in seeking a reward. In humans, this region of the brain is located just behind the eyes and is called the medial orbitofrontal cortex or mOFC.
â€œWhen we make decisions, we often need to gauge the value of a reward before we can see it — for example, will lunch at a certain restaurant be better than lunch at another, or worth the cost,â€ says Shannon Gourley, PhD, assistant professor of pediatrics and psychiatry at Emory University School of Medicine. â€œWe think the mOFC is important for calculating value, particularly when we have to imagine the reward, as opposed to having it right in front of us.â€
The results were published WednesdayÂ inÂ Journal of Neuroscience.
Shannon Gourley, PhD
Being able to appropriately determine the value of a perceived reward is critical in goal-directed decision making, a component of drug-seeking and addiction-related behaviors. While scientists already suspected that the medial orbitofrontal cortex was important for this type of learning and decision-making, the specific genes and growth factors were not as well-understood.
The researchers focused on brain-derived neurotrophic factor (BDNF), a protein that supports the survival and growth of neurons in the brain. BDNF is known to play key roles in long-term potentiation and neuronal remodeling, both important in learning and memory tasks. Variations in the human gene that encodes BDNF have been linked with several psychiatric disorders.
Emory’s Alzheimer’s Disease Research Center recently announced a grant that will support studies on the connections between blood pressure regulation and Alzheimer’s disease. It focuses on the roles of the renin-angiotensin system, the targets of common blood pressure medications, and endothelial cells, which line blood vessels.
Research on that theme is already underway at Emory. Malu Tansey is leading a large project funded by the National Institute on Aging ($3.4 million) with a similar title: “Inflammation and Renin-Angiotensin System Dysfunction as Risk Factors for Alzheimer’s Disease.” Co-investigators are Felicia Goldstein and Lary Walker at Emory and Christopher Norris at the University of Kentucky.
Both studies build on evidence that molecules that control blood pressure and inflammation also drive progression of Alzheimer’s disease, including work by Emory’s Whitney Wharton and Ihab Hajjar. They had found in an observational study that people who take medications targeting the renin-angiotensin system have a lower risk of progressing from mild cognitive impairment to Alzheimer’s.
Wharton is gearing up to test that idea more directly in an interventional study with the generic angiotensin receptor blocker telmisartan. This study is part of a Part the Cloud initiative supported by the Alzheimer’s Association.
Tansey’s project has started bearing fruit in an animal model of Alzheimer’s, according to this Keystone meeting report from Alzforum. Last summer, her graduate student Kathryn Macpherson described initial findings on the effects of an anti-inflammatory (anti-TNF) agent, which also has positive effects in a Parkinson’s model, and her plans to investigate the effects of high-sugar, high-fat diet.
Emory researchers were part of a recent advance in understanding how the Zika virus harms the developing brain. The research was published March 4 inÂ Cell Stem Cell.Â
Emory geneticist Peng Jin and his colleagues were part of a rapidly assembled research team, including scientists from Johns Hopkins and Florida State University, that showed the Zika virus can infect neural progenitor cells critical for brain development.
The research suggests a potential explanation for the cases of microcephaly seen in Latin America during the Zika outbreak. While it does not prove the direct link between Zika and microcephaly, it is a first step that shows where the virus may be doing the most damage.
The team showed that the Zika virus infects a type of neural stem cell that gives rise to the brainâ€™s cerebral cortex. The researchers used neural progenitor cells, formed from induced pluripotent stem cells (iPSCs). The scientists showed that the virus infects neural progenitor cells more readily than iPSCs or immature neurons.
Zhexing Wen, PhD
The role of Jin’s lab was to analyze how the patterns of gene activity in neuronal cells were altered by Zika infection. Jin reports the team is continuing to examine the differences between the effects of Zika and other related viruses such as dengue and West Nile.
In addition, Lab Land recently learned that one of the scientists from Johns Hopkins, Zhexing Wen, was recruited to Emory as faculty and will start in June. His research won’t be all about Zika — in Guo-li Ming’s lab, Wen gained experience using iPSCs to model complex brain disorders such as schizophrenia. Read more
Adult mice don’t need the gene that, when mutated in humans, causes the inherited neurodegenerative disorder Huntington’s disease.Â The finding suggests that treatment strategies for Huntington’s that aim to shut off the huntingtin gene in adults — now in early clinical stages — could be safe.
The results were publishedÂ Monday, March 7 inÂ PNAS.
How HD gene silencing is supposed to work. The Emory study didn’t test this approach directly, but the Emory studyÂ has implications for what types of side effects HD gene silencingÂ may have in humans. Image from HDBuzz.net via Creative Commons.
Huntington’s disease is caused by a gene encoding a toxic protein (mutant huntingtin) that causes brain cells to die. Symptoms commonly appear in mid-life and include uncontrolled movements, balance problems, mood swings and cognitive decline. A juvenile form of Huntington’s disease also can appear during the teenage years.
Researchers led by Xiao-Jiang Li, MD, PhD and Shihua Li, MD, at Emory University School of Medicine, used genetically engineered mice in which the huntingtin gene can be deleted, triggered only when the mice are given the drug tamoxifen. Note: these mice don’t produce toxic mutant huntingtin protein.
When the huntingtin gene is deleted at an age older than four months, these mice appeared to stay healthy, despite having lost their huntingtin genes in cells all over their bodies. They maintained their body weight and could complete tests of movement and grip strength as well as control mice.Â In contrast with adults, engineered mice younger than four months old whose huntingtin gene was deleted developed lethal pancreatitis.