This technique, which can be performed using a simple light microscope, could allow neuroscientists to visualize the activity of circuits within the brain and link them to specific behaviors, says Edward Boyden, the Y. Eva Tan Professor in Neurotechnology and a professor of biological engineering and of brain and cognitive sciences at MIT.

“If you want to study a behavior, or a disease, you need to image the activity of populations of neurons because they work together in a network,” says Boyden, who is also a member of MIT’s McGovern Institute for Brain Research, Media Lab, and Koch Institute for Integrative Cancer Research.

Using this voltage-sensing molecule, the researchers showed that they could record electrical activity from many more neurons than has been possible with any existing, fully genetically encoded, fluorescent voltage probe.

Boyden and Xue Han, an associate professor of biomedical engineering at Boston University, are the senior authors of the study, which appears in the Oct. 9 online edition of Nature. The lead authors of the paper are MIT postdoc Kiryl Piatkevich, BU graduate student Seth Bensussen, and BU research scientist Hua-an Tseng.

Seeing connections

Neurons compute using rapid electrical impulses, which underlie our thoughts, behavior, and perception of the world. Traditional methods for measuring this electrical activity require inserting an electrode into the brain, a process that is labor-intensive and usually allows researchers to record from only one neuron at a time. Multielectrode arrays allow the monitoring of electrical activity from many neurons at once, but they don’t sample densely enough to get all the neurons within a given volume. Calcium imaging does allow such dense sampling, but it measures calcium, an indirect and slow measure of neural electrical activity.

In 2018, Boyden’s team developed an alternative way to monitor electrical activity by labeling neurons with a fluorescent probe. Using a technique known as directed protein evolution, his group engineered a molecule called Archon1 that can be genetically inserted into neurons, where it becomes embedded in the cell membrane. When a neuron’s electrical activity increases, the molecule becomes brighter, and this fluorescence can be seen with a standard light microscope.

In the 2018 paper, Boyden and his colleagues showed that they could use the molecule to image electrical activity in the brains of transparent worms and zebrafish embryos, and also in mouse brain slices. In the new study, they wanted to try to use it in living, awake mice as they engaged in a specific behavior.

To do that, the researchers had to modify the probe so that it would go to a subregion of the neuron membrane. They found that when the molecule inserts itself throughout the entire cell membrane, the resulting images are blurry because the axons and dendrites that extend from neurons also fluoresce. To overcome that, the researchers attached a small peptide that guides the probe specifically to membranes of the cell bodies of neurons. They called this modified protein SomArchon.

“With SomArchon, you can see each cell as a distinct sphere,” Boyden says. “Rather than having one cell’s light blurring all its neighbors, each cell can speak by itself loudly and clearly, uncontaminated by its neighbors.”

The researchers used this probe to image activity in a part of the brain called the striatum, which is involved in planning movement, as mice ran on a ball. They were able to monitor activity in several neurons simultaneously and correlate each one’s activity with the mice’s movement. Some neurons’ activity went up when the mice were running, some went down, and others showed no significant change.

“Over the years, my lab has tried many different versions of voltage sensors, and none of them have worked in living mammalian brains until this one,” Han says.

Using this fluorescent probe, the researchers were able to obtain measurements similar to those recorded by an electrical probe, which can pick up activity on a very rapid timescale. This makes the measurements more informative than existing techniques such as imaging calcium, which neuroscientists often use as a proxy for electrical activity.

“We want to record electrical activity on a millisecond timescale,” Han says. “The timescale and activity patterns that we get from calcium imaging are very different. We really don’t know exactly how these calcium changes are related to electrical dynamics.”

With the new voltage sensor, it is also possible to measure very small fluctuations in activity that occur even when a neuron is not firing a spike. This could help neuroscientists study how small fluctuations impact a neuron’s overall behavior, which has previously been very difficult in living brains, Han says.

Mapping circuits

The researchers also showed that this imaging technique can be combined with optogenetics — a technique developed by the Boyden lab and collaborators that allows researchers to turn neurons on and off with light by engineering them to express light-sensitive proteins. In this case, the researchers activated certain neurons with light and then measured the resulting electrical activity in these neurons.

This imaging technology could also be combined with expansion microscopy, a technique that Boyden’s lab developed to expand brain tissue before imaging it, make it easier to see the anatomical connections between neurons in high resolution.

“One of my dream experiments is to image all the activity in a brain, and then use expansion microscopy to find the wiring between those neurons,” Boyden says. “Then can we predict how neural computations emerge from the wiring.”

Such wiring diagrams could allow researchers to pinpoint circuit abnormalities that underlie brain disorders, and may also help researchers to design artificial intelligence that more closely mimics the human brain, Boyden says.

The MIT portion of the research was funded by Edward and Kay Poitras, the National Institutes of Health, including a Director’s Pioneer Award, Charles Hieken, John Doerr, the National Science Foundation, the HHMI-Simons Faculty Scholars Program, the Human Frontier Science Program, and the U.S. Army Research Office.

Eating processed foods such as breads, cereals and sodas is associated with negative health effects, including insulin resistance and obesity.

Reporting Oct. 9 in the journal Cell Host & Microbe, scientists have identified a specific human gut bacterial strain that breaks down the chemical fructoselysine, and turns it into harmless byproducts. Fructoselysine is in a class of chemicals called Maillard Reaction Products, which are formed during food processing. Some of these chemicals have been linked to harmful health effects. These findings raise the prospect that it may be possible to use such knowledge of the gut microbiome to help develop healthier, more nutritious processed foods.

The study was conducted in mice that were raised under sterile conditions, given known collections of human gut microbes and fed diets containing processed food ingredients.

“This study gives us a deeper view of how components of our modern diets are metabolized by gut microbes, including the breakdown of components that may be unhealthy for us,” said Jeffrey I. Gordon, MD, the Dr. Robert J. Glaser Distinguished University Professor and director of the Edison Family Center for Genome Sciences & Systems Biology. “We now have a way to identify these human gut microbes and how they metabolize harmful food chemicals into innocuous byproducts.”

Human gut microbial communities see foods as collections of chemicals. Some of these chemical compounds have beneficial effects on the communities of microbes living in the gut as well as on human health. For example, Gordon’s past work has shown that the gut microbiome plays a vital role in a baby’s early development, with healthy gut microbes contributing to healthy growth, immune function, and bone and brain development. But modern food processing can generate chemicals that may be detrimental to health. Such chemicals have been associated with inflammation linked to diabetes and heart disease. The researchers are interested in understanding the complex interactions between human gut microbes and the chemicals that are commonly consumed as part of a typical American diet.

In the new study, the researchers showed that a specific bacterium called Collinsella intestinalis breaks down the chemical fructoselysine into components that are harmless.

“Fructoselysine is common in processed food, including ultra-pasteurized milk, pasta, chocolate and cereals,” said first author Ashley R. Wolf, PhD, a postdoctoral researcher in Gordon’s lab. “High amounts of fructoselysine and similar chemicals in the blood have been linked to diseases of aging, such as diabetes and atherosclerosis.”

When fed a diet containing high amounts of fructoselysine, mice harboring Collinsella intestinalis in their gut microbial communities showed an increase in the abundance of this bacteria as well as an increase in the gut microbial communities’ ability to break down fructoselysine into harmless byproducts.

“This specific bacterial strain thrives in these circumstances,” Gordon said. “And as it increases in abundance, fructoselysine is metabolized more efficiently.”

He added, “The new tools and knowledge gained from this initial study could be used to develop healthier, more nutritious foods as well as design potential strategies to identify and harness certain types of gut bacteria shown to process potentially harmful chemicals into innocuous ones. A corollary is that they may help us distinguish between consumers whose gut microbial communities are either vulnerable or resistant to the effects of certain products introduced during food processing.”

Emphasizing the complexity of this task, Gordon, Wolf and their colleagues also showed that close cousins of Collinsella intestinalis did not respond to fructoselysine in the same way. These bacterial cousins, whose genomes vary somewhat, do not thrive in a fructoselysine-rich environment. The researchers said future studies are required before scientists will be able to identify and harness the specific capacities of individual microbes to clean up the array of potentially deleterious chemicals produced during some types of modern food manufacturing.

This work was supported by the National Institutes of Health (NIH), grant numbers DK70977, DK078669, and DK30292; the American Diabetes Association, grant number 1-16-PDF-125; the Damon Runyon Cancer Research Foundation, grant number DRG-2303-17; and by the Russian Science Foundation, grant number 19-14-00305.

Gordon is a co-founder of Matatu Inc., a company characterizing the role of diet-by-microbiota interactions in animal health.

The atlas, published today (9 October 2019) in Nature, was created by researchers from the Wellcome Sanger Institute, Wellcome — MRC Cambridge Stem Cell Institute, Newcastle University, University of Cambridge and their collaborators. It is a comprehensive, high-resolution resource that improves our understanding of normal development and assists medical efforts to tackle diseases, such as leukemia and immune disorders, which can form during development.

Until now, it was unknown precisely how the blood and immune systems develop in humans — a process known as haematopoiesis. As adults, it is bone marrow that creates our blood and immune cells. But in early embryonic life, the yolk sac and liver play a major role in making blood and immune cells. These cells subsequently seed peripheral tissues such as skin, kidney and finally bone marrow.

Scientists used single cell technology to analyse 140,000 liver cells and 74,000 skin, kidney and yolk sac cells. By isolating cells from the developing liver, they could identify them by what genes they were expressing and see what the cells looked like. Haematopoietic cells in sections of developmental liver were ‘tagged’ using heavy metal markers so researchers could map each cell to its location.

Professor Muzlifah Haniffa, a senior author of the study from Newcastle University and Senior Clinical Fellow at the Wellcome Sanger Institute, said: “Until now research in this area has been a little bit like blindfolded people studying an elephant, with each describing just a small part of it. This is the first time that anyone has described the whole picture, how the blood and immune systems develop in such detail. It’s been an extraordinary, multidisciplinary effort that is now available as a tool for the whole scientific community.”

A developing fetus requires huge amounts of oxygen to fuel growth. The research discovered that during development, ‘mother’ haematopoietic stem cells stay in the liver. But as the liver alone cannot supply sufficient red blood cells, the next generation ‘daughter’ cells — known as progenitor cells — travel to other tissues. They mature in places such as the skin, where they develop into red blood cells to help meet the high demand for oxygen.

Dr Elisa Laurenti, a senior author from the Wellcome — MRC Cambridge Stem Cell Institute and the Department of Haematology at the University of Cambridge, said: “We knew that as adults age our immune system changes. This study shows how the liver’s ability to make blood and immune cells changes in a very short space of time, even between seven and 17 weeks post-conception. If we can understand what makes the stem cells in the liver so good at making red blood cells, it will have important implications for regenerative medicine.”

Researchers also mapped genes known to be involved in immune deficiencies to see which cells were expressing them. Gene mutations can lead to immune disorders such as leukemia, and it is hoped that by understanding how the healthy developing liver functions, it will be possible to understand how immune disorders arise and even how to treat them.

Dr Sarah Teichmann, a senior author from the Wellcome Sanger Institute, University of Cambridge and co-chair of the Human Cell Atlas Organising Committee, said: “The first comprehensive cellular map of the developmental liver is another milestone for the Human Cell Atlas initiative. The data is now freely available for anyone to use and will be a great resource to better understand healthy cellular development and disease-causing genetic mutations.”

Dr Katrina Gold, Genetics and Molecular Sciences Portfolio Manager at Wellcome, said: “Our immune system is vital in helping to protect us from disease, yet we know very little about how immune cells develop and behave in the early embryo. This study is hugely important, laying a critical foundation for future research that could help improve our understanding of disorders linked to the early immune system, such as childhood leukemias. The Human Cell Atlas has the potential to transform our understanding of health and disease and we’re excited to see these first discoveries from our Wellcome-funded multidisciplinary team of scientists.”

The study was published in the Journal of the American Heart Association on Oct. 9.

After a successful one-year intensive lifestyle weight-loss intervention, maintaining the weight loss (as opposed to regaining it) was better for all cardiometabolic risk factors assessed three years later, including HDL cholesterol, triglyceride, fasting glucose and glycated hemoglobin concentrations, blood pressure, and waist circumference.

“Regaining weight was associated with a reversal of the benefits seen from losing weight,” said senior and corresponding author Alice H. Lichtenstein, a nutrition scientist and director of the Cardiovascular Nutrition Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging. “If you lose weight and maintain the weight loss for a long period of time, do the benefits continue? The answer is yes and sometimes the benefits get even stronger. If you lose weight and don’t maintain it, the benefits are diminished or disappear. These findings emphasize the dual importance of not only achieving a heathy body weight but maintaining a healthy body weight.”

“What we need to focus on now is how we can support not only healthy approaches to losing weight but healthy approaches to helping those who are successful in losing weight maintain the weight loss. The latter may be the most challenging,” Lichtenstein continued.

The team also sought to identify the point distinguishing “maintaining” from “regaining” and at what percentage the cardiometabolic risk benefits of weight loss were diminished, but found no clear point of demarcation. Few studies have directly compared successful weight loss maintenance with weight regain, in part because no standardized definition for successful weight-loss maintenance exists.

The study used data from the Look AHEAD trial, a multicenter controlled clinical trial assessing the association between weight loss and cardiovascular disease risk in individuals with obesity and type 2 diabetes.

Story Source:

Materials provided by Tufts University, Health Sciences Campus. Note: Content may be edited for style and length.

A new study from The Ohio State University provides a potential blueprint for finding the immunological sweet spot — a vaccine weak enough that it doesn’t make people sick but strong enough that it prompts an ample immune response, ensuring that the body will recognize RSV as an intruder in the future, and quickly mount a protective defense.

In a study published today (Oct. 9, 2019) in the journal Nature Communications, researchers report success in knocking out an epigenetic modification known as N6-methyladenosine in RSV RNA — a technique that proved to tamp down the virus and prompt a robust immune response in cotton rats.

“We now have a novel target to go after, and are working with industry toward a vaccine,” said the study’s senior author, Jianrong Li, an Ohio State professor of virology in the Department of Veterinary Biosciences.

Using a technique called reverse genetics, Ohio State researchers generated RSV that is defective in N6-methyladenosine methylation — one of the most common modifications that our cells make to RNA.

“What makes this especially exciting is that using this modified virus in a vaccine is likely to enhance a person’s innate immune response, a challenge that has stood in the way of vaccine development in the past,” said Miaoge Xue, the study’s lead author and a graduate student in Li’s laboratory.

“This approach may also work for similar viruses, such human metapneumovirus and human parainfluenza virus 3,” said Xue, who recently presented these findings at the annual meeting of the American Society for Virology.

This discovery could also make vaccine production more economically feasible because it does not slow RSV growth in the lab — a critical step in vaccine production, said Li, who is also a member of Ohio State’s Infectious Disease Institute.

RSV is common, easily spread and usually causes mild, cold-like symptoms. But in severe cases — particularly in babies younger than a year and the elderly — it can be life-threatening. RSV kills about 14,000 older Americans every year, and it’s the top reason for pediatric hospitalizations most years.

“Worldwide, more than 80,000 kids die from these infections each year,” said study co-author Mark Peeples, a pediatrics professor at Ohio State and researcher at Nationwide Children’s Hospital in Columbus. “An effective and affordable vaccine could save tens of thousands of lives annually.”

The Bill & Melinda Gates Foundation is supporting work to develop a vaccine that could be given to pregnant mothers who, in turn, produce antibodies and pass them to their fetus before birth to prevent RSV in infancy. But by 6 months of age, that protection would fade, leaving the young child vulnerable again, Peeples said.

“A vaccine based on this new study would be given to a baby at around that time, to stimulate the baby’s immune system so that the baby’s body can produce its own antibodies and T cells the next winter so they won’t get sick if they’re infected with RSV,” Peeples said.

“What Dr. Li’s lab has found is that when they make this modification in the genome of the virus, the cells that the virus infects produce a strong and early immune response. In particular, they produce more interferon, an early emergency signal that is your first line of defense.”

Li said his technique also leaves the virus genetically stable, meaning that a live, attenuated (weakened) RSV with these mutations could not revert back to a stronger virus and wreak havoc in the human body.

It’s an important concern, considering the long and rocky quest for an RSV vaccine. In the 1960s, an experimental “killed virus” vaccine was tested in children and unexpectedly increased the chances of hospitalization when they were later infected with RSV. Since then, research has focused on a live, attenuated vaccine. But creating a vaccine that is genetically stable and has the right balance of safety and protection has been challenging.

“RSV was isolated within a year of when measles virus was isolated, back in the 1950s. Within nine years, we had a vaccine for measles and 60 years later, we still don’t have one for RSV, but this study puts us closer,” Peeples said.