Syndicate content

Archive - Mar 26, 2015

Rockefeller Scientists Use “Amazing” CRISPR-Cas9 Technique to Modify and Study Key Genes of Aedes aegypti Mosquito, Carrier of Chikungunya, Yellow Fever, and Dengue; Technique Is “Revolutionizing Biology,” Group Leader Vosshall Says

Traditionally, to understand how a gene functions, a scientist would breed an organism that lacks that gene - "knocking it out" - then ask how the organism has changed. Are its senses affected? Its behavior? Can it even survive? Thanks to the recent advance of gene editing technology, this gold standard genetic experiment has become much more accessible in a wide variety of organisms. Now, researchers at Rockefeller University have harnessed an increasingly popular molecular technique known as CRISPR-Cas9 editing (originally identified in bacteria as a natural defense mechanism that bacteria possess to recognize and disable viruses and plasmids by cutting up their genetic material) in an important and understudied species: the mosquito, Aedes aegypti (photo), which infects hundreds of millions of people annually with the viral diseases chikungunya, yellow fever, and dengue. Rockefeller researchers led by postdoctoral fellow Dr. Benjamin J. Matthews adapted the CRISPR-Cas9 system to Ae. aegypti and were able to efficiently generate targeted mutations and insertions in a number of genes. The immediate goal of this project, says Dr. Matthews, is to learn more about how different genes help the species operate so efficiently as a disease vector, and create new ways to control it. "To understand how the female mosquito actually transmits disease," says Dr. Matthews, "you have to learn how she finds humans to bite, and how she chooses a source of water to lay her eggs. Once you have that information, techniques for intervention will come."

Honey Bees Appear to Use Independent RNAi and Methylation Pathways in Anti-Viral Defense

Honey bees use different sets of genes, regulated by two distinct mechanisms, to fight off viruses, bacteria, and gut parasites, according to researchers at Penn State, the Georgia Institute of Technology, and the University of California, Davis. The findings may help scientists develop honey bee treatments that are tailored to specific types of infections. "Our results indicate that different sets of genes are used in immune responses to viruses versus other pathogens, and these anti-viral genes are regulated by two very distinct processes -- expression and DNA methylation," said David Galbraith, a graduate student in entomology at Penn State. The results were published online on March 26, 2015 in the open-access journal PLOS Pathogens. The article is titled “Parallel Epigenomic and Transcriptomic Responses to Viral Infection in Honey Bees (Apis mellifera).” According to Dr. Christina Grozinger, Director of the Penn State Center for Pollinator Research, beekeepers lose an average of 30 percent of their colonies every winter and an average of 25 percent in the summer. "Honey bees have more than 20 types of viruses, and several of them have been linked to losses of honey bee colonies," she said. "Yet, beekeepers currently do not have any commercially available methods to reduce viral infections." With a goal of uncovering which genes increase or decrease their activity in response to the presence of viruses, the researchers measured expression levels of all genes in the honey bee genome in both infected and uninfected bees. They found that the RNAi pathway had increased activity and, therefore, is likely an important anti-viral immune pathway in bees.

Young Girl Nearly Dies from Flu Infection Because of Mutations in Both Homologous Copies of IRF7 Gene for Interferon Amplification

Nobody likes getting the flu, but for some people, fluids and rest aren't enough. A small number of children who catch the influenza virus fall so ill they end up in the hospital -- perhaps needing ventilators to breathe -- even while their family and friends recover easily. New research by Rockefeller University scientists, published online on March 26, 2015 in Science, helps explain why: rare genetic mutations. The article is titled “Life-Threatening influenza and Impaired Interferon Amplification in Human IRF7 Deficiency.” The researchers scrutinized blood and tissue samples from a young girl who, at the age of two-and-a-half, developed acute respiratory distress syndrome after catching the flu, and ended up fighting for her life in the hospital. Years after her ordeal, which she survived, scientists led by Rockefeller’s Dr. Jean-Laurent Casanova discovered that it could be explained by rare mutations she carries that prevented her from producing a protein, interferon, that helps fight off the virus. "This is the first example of a common, isolated, and life-threatening infection of childhood that is shown to be also a genetic disease," says Dr. Casanova. The good news from these results, however, is that clinicians have a new treatment option for children who mysteriously develop severe cases of the flu. "This finding suggests that one could treat severe flu of childhood with interferon, which is commercially available," says Dr. Casanova, who is Professor and Head of the St. Giles Laboratory of Human Genetics of Infectious Disease at Rockefeller, as well as a Howard Hughes Medical Institute (HHMI) investigator. The fact that a child's genes could affect the severity of her illness wasn't a surprise to the members of Casanova's lab, who have been studying this phenomenon for decades.

Nanoparticle Delivery of FL2 Inactivator (siRNA) Cuts Wound-Healing Time in Half

An experimental therapy developed by researchers at Albert Einstein College of Medicine of Yeshiva University in New York City cut in half the time it takes to heal wounds compared to no treatment at all. Details of the therapy, which was successfully tested in mice, were published on March 10, 2015, online in the Journal of Investigative Dermatology. The title of the article is “Fidgetin-like 2: A Novel Microtubule-Based Regulator of Wound Healing." "We envision that our nanoparticle therapy could be used to speed the healing of all sorts of wounds, including everyday cuts and burns, surgical incisions, and chronic skin ulcers, which are a particular problem in the elderly and people with diabetes," said study co-leader David J. Sharp, Ph.D., Professor of Physiology & Biophysics at Einstein. Dr. Sharp and his colleagues had earlier discovered that an enzyme called fidgetin-like 2 (FL2) puts the brakes on skin cells as they migrate towards wounds to heal them. They reasoned that the healing cells could reach their destination faster if their levels of FL2 could be reduced. So the scientists developed a drug that inactivates the gene that makes FL2 and then put the drug in tiny gel capsules called nanoparticles and applied the nanoparticles to wounds on mice. The treated wounds healed much faster than untreated wounds. FL2 belongs to the fidgetin family of enzymes, which play varying roles in cellular development and function. To learn more about FL2's role in humans, Dr. Sharp suppressed FL2's activity in human cells in tissue culture. When those cells were placed on a standard wound assay (for measuring properties like cell migration and proliferation), they moved unusually fast. "This suggested that if we could find a way to target FL2 in humans, we might have a new way to promote wound healing," said Dr. Sharp.

Skin Microbiome May Offer Answers to Protecting Threatened Frogs from Lethal Fungus

A team of scientists including Virginia Tech researchers is one step closer to understanding how bacteria on a frog's skin affects the frog’s likelihood of contracting disease. A frog-killing fungus known as Batrachochytrium dendrobatidis, or Bd, has already led to the decline of more than 200 amphibian species, including the now-extinct-in-the-wild Panamanian golden frog. In a recent study, the research team attempted to apply beneficial bacteria found on the skin of various Bd-resistant wild Panamanian frog species to Panamanian golden frogs in captivity, to see if this would stimulate a defense against the disease. They found that, while the treatment with beneficial bacteria was not successful due to its inability to stick to the skin, there were some frogs that survived exposure to the fungus. These survivors actually had unique bacterial communities on their skin before the experiments started. The results were published online on March 18, 2015 in an open-access article in the Proceedings of the Royal Society B. The title of the article is “Composition of Symbiotic Bacteria Predicts Survival in Panamanian Golden Frogs Infected with a Lethal Fungus.” The next step is to explore these new bacterial communities. "We were disappointed that the treatment didn't work, but glad to have discovered new information about the relationship between these symbiotic microbial communities and amphibian disease resistance," said Dr. Lisa Belden, an Associate Professor of Biological Sciences in the College of Science, a Fralin Life Science Institute affiliate, and a faculty member with the new Global Change Center at Virginia Tech. "Every bit of information gets us closer to getting these frogs back into nature."

NEJM Report Reviews Global Spread of Mosquito-Borne Chikungunya Virus

The mosquito-borne chikungunya virus (image of virus particles) has been the subject of increasing attention as it spreads throughout South America, Central America, the Caribbean and Mexico. This painful and potentially debilitating disease is predicted to soon spread to the U.S. The University of Texas Medical Branch (UTMB) at Galveston's Scott Weaver, Ph.D., globally recognized for his expertise in mosquito-borne diseases, has been studying chikungunya virus for more than 15 years. Dr. Weaver and fellow infectious disease expert Dr. Marc Lecuit of the Institut Pasteur in Paris have summarized currently available information on this disease in the March 26, 2015 issue of the New England Journal of Medicine. Since chikungunya was first identified in 1952 in present-day Tanzania, the virus has been confirmed in other African countries, Asia, the South Pacific, and Europe. In December 2013, the first locally acquired case of chikungunya in the Americas was reported in the Caribbean. Since then, chikungunya has been identified in 44 countries or territories throughout the Americas with more than 1.3 million suspected cases reported to the Pan American Health Organization from affected areas. Symptoms appear about three days after being bitten by an infected mosquito. The most common symptoms and signs are fever and severe joint pain, and may include headache, arthritis, muscle pain, weakness, and rash. Some patients will feel better within a week but others develop longer-term joint pain that can last weeks to years. Death is rare, but can occur. People at increased risk for severe disease include young children, older adults, and people with medical conditions such as diabetes or heart disease.

Carbapenem-Resistant Common Bacteria Threaten Global Spread

Antibiotic resistance is poised to spread globally among bacteria frequently implicated in respiratory and urinary infections in hospital settings, according to new research from Washington University School of Medicine in St. Louis, Missouri. The study shows that two genes that confer resistance against a particularly strong class of antibiotics can be shared easily among a family of bacteria responsible for a significant portion of hospital-associated infections. Drug-resistant germs in the same family of bacteria recently infected several patients at two Los Angeles hospitals. The infections have been linked to medical scopes believed to have been contaminated with bacteria that can resist carbapenems, potent antibiotics that are supposed to be used only in gravely ill patients or those infected by resistant bacteria. "Carbapenems are one of our last resorts for treating bacterial infections, what we use when nothing else works," said senior author Gautam Dantas, Ph.D., Associate Professor of Pathology and Immunology at Washington University. "Given what we know now, I don't think it's overstating the case to say that for certain types of infections, we may be looking at the start of the post-antibiotic era, a time when most of the antibiotics we rely on to treat bacterial infections are no longer effective." Dr. Dantas and other experts recommend strictly limiting the usage of carbapenems to cases in which no other treatments can help. The study, conducted by researchers at Washington University, Barnes-Jewish Hospital, and the National University of Sciences and Technology in Pakistan, is currently available online in an open-access article in the June 2015 issue of Emerging Infectious Diseases (http://wwwnc.cdc.gov/eid/article/21/6/14-1504_article).

MRI Measurement of Hippocampus Atrophy Likely to Become “Gold Standard” for Measuring Earliest Signs of Alzheimer’s Disease

After six years of painstaking research, a UCLA-led team has validated the first standardized protocol for measuring one of the earliest signs of Alzheimer’s disease: the atrophy of the part of the brain known as the hippocampus. The finding marks the final step in an international consortium’s successful effort to develop a unified and reliable approach to assessing signs of Alzheimer’s-related neurodegeneration through structural imaging tests, a staple in the diagnosis and monitoring of the disease. The study was published in the February 2015 issue of the journal Alzheimer’s and Dementia. Using brain tissue of deceased Alzheimer’s disease patients, a group headed by Liana Apostolova (photo), M.D., Director of the Neuroimaging Laboratory at the Mary S. Easton Center for Alzheimer’s Disease Research at UCLA, confirmed that the newly agreed-upon method for measuring hippocampal atrophy in structural MRI tests correlates with the pathologic changes that are known to be hallmarks of the disease — the progressive development of amyloid plaques and neurofibrillary tangles in the brain. “This hippocampal protocol will now become the gold standard in the field, adopted by many, if not all, research groups across the globe in their study of Alzheimer’s disease,” said Dr. Apostolova, who was invited to play a key role in the consortium because of her reputation as one of the world’s leading experts in hippocampal structural anatomy and atrophy. “It will serve as a powerful tool in clinical trials for measuring the efficacy of new drugs in slowing or halting disease progression.” The brain is the least accessible and most challenging organ to study in the human body; as a result, Alzheimer’s disease can be diagnosed definitively only by examining brain tissue after death.

Isogenic iPSCs Used to Dissect 7q Deletion and Identify Candidate Genes for MDS Blood Cancer

Induced pluripotent stem cells (iPSCs), adult cells that have been reprogrammed back to an embryonic stem cell-like state, may better model the genetic contributions to each patient's particular disease. In a process called cellular reprogramming, researchers at the Icahn School of Medicine at Mount Sinai in New York City have taken mature blood cells from patients with myelodysplastic syndrome (MDS) and reprogrammed them back into iPSCs to study the genetic origins of this rare blood cancer. The results were published online on March 23, 2015 in Nature Biotechnology. The title of the article is “Functional Analysis of a Chromosomal Deletion Associated with Myelodysplastic Syndromes Using Isogenic Human Induced Pluripotent Stem Cells.” In MDS, genetic mutations in the bone marrow stem cell cause the number and quality of blood-forming cells to decline irreversibly, further impairing blood production. Patients with MDS can develop severe anemia and in some cases a leukemia also known as AML (acute myeloid leukemia). But which genetic mutations are the critical ones causing this disease? In this study, researchers took cells from patients with blood cancer MDS and turned them into stem cells to study the deletions of one copy of the long arm of human chromosome 7 (7q) that are often associated with this disease. "With this approach, we were able to pinpoint a region on chromosome 7 that is critical and were able to identify candidate genes residing there that may cause this disease," said lead researcher Eirini Papapetrou (photo), M.D., Ph.D., Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai.