Genetic Mutation Linked with Typical Form of Migraine

A research team led by a Howard Hughes Medical Institute investigator at the University of California, San Francisco has identified a genetic mutation that is strongly associated with a typical form of migraine.

In a paper published on May 1 in Science Translational Medicine, the team linked the mutation with evidence of migraine in humans, in a mouse model of migraine and in cell culture in the laboratory.

The mutation is in the gene known as casein kinase I delta (CKIdelta).

“This is the first gene in which mutations have been shown to cause a very typical form of migraine,” said senior investigator Louis J. Ptáček, an investigator at HHMI and a professor of neurology at UCSF. “It’s our initial glimpse into a black box that we don’t yet understand.”

Migraine, the causes of which are still unknown, affects 10 to 20 percent of all people, and causes “huge losses in productivity, not to mention immense suffering,” said Ptáček. Typical symptoms include a pounding headache; lowered pain threshold; hypersensitivity to mild stimuli including sound and touch; and aura, which Ptáček describes as “a visual sensation that presages the headache to come.”

The paper presents both clinical and basic scientific evidence that the mutation causes migraine.

In the study, the scientists first analyzed the genetics of two families in which migraine was common, and found that a significant proportion of migraine sufferers in the families either had the mutation or were the offspring of a mutation carrier.

In the laboratory, the team demonstrated that the mutation affects the production of the casein kinase I delta enzyme, which carries out a number of vital functions in the brain and body. “This tells us that the mutation has real biochemical consequences,” said Ptáček.

The scientists then investigated the effects of the mutation in a line of mice that carry it. “Obviously, we can’t measure headache in a mouse,” Ptáček noted, “but there are other things that go along with migraine that we can measure.”

Pain threshold, explained Ptáček, can be lowered in mice by the administration of nitroglycerin. The mutant mice had a significantly lower threshold for nitroglycerin-induced peripheral pain than did normal mice.

Another piece of evidence was cortical spreading depression (CSD), a wave of electrical “silence” in the brain that follows electrical stimulation, spreading out from the point of stimulation in a predictable pattern. The researchers found that the mutant mice had a significantly lower electrical threshold for the induction of CSD.

The CSD experiments are “especially intriguing,” said Ptáček, because it is known that CSD spreads through the brain at 3 millimeters per minute. “Functional brain imaging has shown that in the occipital lobes of people with migraine aura, changes in blood flow spread at the same rate.”

Finally, Ptáček and his team found that astrocytes – brain cells that are essential to neuronal functioning and health – from the brains of mutant mice showed increased calcium signaling compared with astrocytes from the brains of normal mice.

“This is significant because we think astrocyte functioning is very, very relevant to migraine,” said Ptáček. “This is an enzyme, and so it modifies proteins. The question is, which protein or proteins does it modify that is relevant to migraine? How does it change astrocyte activity?”

The research “puts us one step closer to understanding the molecular pathway to pain in migraine,” he said. “And, as we come to a clearer understanding, we can start thinking about better therapies. Certain molecules might be targets for new drugs.” There are good drugs now, said Ptáček, “but they only help some patients, some of the time. The need for better treatments is huge.”

The CKIdelta mutation is “far from the only mutation likely to be associated with migraine,” Ptáček cautioned. “There are likely several, in different combinations in different people. This is simply the first one we’ve found.”

New methods to explore astrocyte effects on brain function

A study in The Journal of General Physiology [1, 2] presents new methods to evaluate how astrocytes contribute to brain function, paving the way for future exploration of these important brain cells at unprecedented levels of detail.

Astrocytes—the most abundant cell type in the human brain—play crucial roles in brain physiology, which may include modulating synaptic activity and regulating local blood flow. Existing research tools can be used to monitor calcium signals associated with interactions between astrocytes and neurons or blood vessels. Until now, however, astrocytic calcium signals have been investigated mainly in their somata (cell bodies) and large processes, rather than in distal fine processes close to neuronal synapses or the endfeet that surround blood vessels. Previous studies have also mainly investigated immature specimens rather than mature brain cells.

Now, a team of California researchers provides detailed methods to visualize calcium signals throughout entire astrocytes in hippocampal slices from adult mice. The team observed numerous spontaneous localized calcium signals throughout the entire astrocyte, including the branchlets and endfeet. Their results indicated that calcium signals in endfeet were independent of those in somata and occurred more frequently. In addition to the specific findings, their methods can be used in future studies to advance our understanding of the physiology of astrocytes and their interactions with neurons and the microvasculature of the brain.

After Brain Injury, New Astrocytes Play Unexpected Role in Healing

The production of a certain kind of brain cell that had been considered an impediment to healing may actually be needed to staunch bleeding and promote repair after a stroke or head trauma, researchers at Duke Medicine report.

These cells, known as astrocytes, can be produced from stem cells in the brain after injury. They migrate to the site of damage where they are much more effective in promoting recovery than previously thought. This insight from studies in mice, reported online April 24, 2013, in the journal Nature, may help researchers develop treatments that foster brain repair.

“The injury recovery process is complex,” said senior author Chay T. Kuo, M.D., PhD, George W. Brumley Assistant Professor of Cell Biology, Pediatrics and Neurobiology at Duke University. “There is a lot of interest in how new neurons can stimulate functional recovery, but if you make neurons without stopping the bleeding, the neurons don’t even get a chance. The brain somehow knows this, so we believe that’s why it produces these unique astrocytes in response to injury.”

Each year, more than 1.7 million people in the United States suffer a traumatic brain injury, according to the Centers for Disease Control and Prevention. Another 795,000 people a year suffer a stroke. Few therapies are available to treat the damage that often results from such injuries.

Kuo and colleagues at Duke are interested in replacing lost neurons after a brain injury as a way to restore function. Once damaged, mature neurons cannot multiply, so most research efforts have focused on inducing brain stem cells to produce more immature neurons to replace them.

This strategy has proved difficult, because in addition to making neurons, neural stem cells also produce astrocytes and oligodendrocytes, known as glial cells. Although glial cells are important for maintaining the normal function of neurons in the brain, the increased production of astrocytes from neural stem cell has been considered an unwanted byproduct, causing more harm than good. Proliferating astrocytes secrete proteins that can induce tissue inflammation and undergo gene mutations that can lead to aggressive brain tumors.

In their study of mice, the Duke team found an unexpected insight about the astrocytes produced from stem cells after injury. Stem cells live in a special area or “niche” in the postnatal/adult brain called the subventricular zone, and churn out neurons and glia in the right proportions based on cues from the surrounding tissue.

After an injury, however, the subventricular niche pumps out more astrocytes. Significantly, the Duke team found they are different from astrocytes produced in most other regions of the brain. These cells make their way to the injured area to help make an organized scar, which stops the bleeding and allows tissue recovery.

When the generation of these astrocytes in the subventricular niche was experimentally blocked after a brain injury, hemorrhaging occurred around the injured areas and the region did not heal.  Kuo said the finding was made possible by insights about astrocytes from Cagla Eroglu, PhD, whose laboratory next door to Kuo’s conducts research on astrocyte interactions with neurons.

“Cagla and I started at Duke together and have known each other since our postdoctoral days,” Kuo said. “To have these stem cell-made astrocytes express a unique protein that Cagla understands more than anyone else, it’s just a wonderful example of scientific serendipity and collaboration.”

Additionally, Kuo said first author Eric J. Benner, M.D., PhD, a former postdoctoral fellow who now has his own laboratory at Duke, provided key clinical correlations on brain injury as a physician-scientist and practicing neonatologist in the Jean and George Brumley Jr. Neonatal-Perinatal Research Institute.

“We are very excited about this innate flexibility in neural stem cell behavior to know just what to do to help the brain after injury,” Kuo said. “Since bleeding in the brain after injury is a common and serious problem for patients, further research into this area may lead to effective therapies for accelerated brain recovery after injury.”

Researchers find that alcohol consumption damages brain’s support cells

Alcohol consumption affects the brain in multiple ways, ranging from acute changes in behavior to permanent molecular and functional alterations. The general consensus is that in the brain, alcohol targets mainly neurons. However, recent research suggests that other cells of the brain known as astrocytic glial cells or astrocytes are necessary for the rewarding effects of alcohol and the development of alcohol tolerance. The study, first-authored by Dr. Leonardo Pignataro, was published in the February 6th issue of the scientific journal Brain and Behavior.

"This is a fascinating result that we could have never anticipated. We know that astrocytes are the most abundant cell type in the central nervous system and that they are crucial for neuronal growth and survival, but so far, these cells had been thought to be involved only in brain’s support functions. Our results, however, show that astrocytes have an active role in alcohol tolerance and dependence," explains Dr. Pignataro.

The team of researchers from Columbia and Yale Universities analyzed how alcohol exposure changes gene expression in astrocyte cells and identified gene sets associated with stress, immune response, cell death, and lipid metabolism, which may have profound implications for normal neuronal activity in the brain. “Our findings may explain many of the long-term inflammatory and degenerative effects observed in the brain of alcoholics,” says Dr. Pignataro. “The change in gene expression observed in alcohol-exposed astrocytes supports the idea that some of the alcohol consumed reaches the brain and that ethanol (the active component of alcoholic beverages) is locally metabolized, increasing the production free radicals that react with cell components to affect the normal function of cells. This activates a cellular stress response in the cells in an attempt to defend from this chemical damage. On the other hand, the body recognizes these oxidized molecules as “foreign objects” generating an immune response against them that leads to the death of damage cells. This mechanism can explain the inflammatory degenerative process observed in the brain of chronic alcoholics, allowing for the development of different and novel therapeutically approaches to treat this disease” added Dr. Pignataro.

The consequences of alcohol on astrocytes revealed in this study go far beyond what happens to this particular cell type. Astrocytes play a crucial role in the CNS, supporting normal neuronal activity by maintaining homeostasis. Therefore, alcohol changes in gene expression in astrocytes may have profound implications for neuronal activity in the brain.

These findings will help scientists better understand alcohol-associated disorders, such as the brain neurodegenerative damage associated with chronic alcoholism and alcohol tolerance and dependence. “We hope that this newly discovered role of astrocytes will give scientists new targets other than neurons to develop novel therapies to treat alcoholism,” Leonardo Pignataro concluded.

To Make Mice Smarter, Add A Few Human Brain Cells

For more than a century, neurons have been the superstars of the brain. Their less glamorous partners, glial cells, can’t send electric signals, and so they’ve been mostly ignored.

Now scientists have injected some human glial cells into the brains of newborn mice. When the mice grew up, they were faster learners. The study, published Thursday in Cell Stem Cell, not only introduces a new tool to study the mechanisms of the human brain, it supports the hypothesis that glial cells — and not just neurons — play an important role in learning.

The scientific obsession with neurons really began at the end of the 19th century. Spanish anatomy professor Santiago Ramon y Cajal used a special dye to stain brain tissue. Under the microscope, neurons were revealed in exquisite detail. “A dense forest,” Ramón y Cajal called it — a field of little branching cells that would soon be named neurons.

With beautiful ink drawings, Ramón y Cajal painstakingly mapped neural networks and slowly developed the theory that neurons are the telegraph lines of thought (an idea later embraced by Schoolhouse Rock). Every idea and memory — every aspect of learning — could be traced back to the electric signals sent between neurons. Ramón y Cajal won the Nobel Prize for his work, and scientists focused on neurons for the next century.

But neurons aren’t the only cells in the brain.

"We’ve overlooked half the brain," says Douglas Fields, a neuroscientist at the National Institutes of Health. "We’ve only been studying one kind of cell in the brain." The other kind of cell — glial cells — are at least as abundant as neurons. But early scientists thought they were so boring they didn’t even merit a singular noun. "Glia is plural — there is no singular," Fields says. "We have ‘neuron’ but we don’t have ‘glion.’ "

Glial cells lacked the ability to send electric signals, and most scientists thought they were housekeeping cells, helping provide nutrients and insulation.

It was only in the last decade or so that scientists realized glial cells were more than that. Special types of glial cells, called astrocytes, which are named for the star-like patterns of their cellular structure, have their own form of chemical signaling. They have the potential to coordinate whole groups of neurons. “Glia are in a position to regulate the flow of information through the brain,” Fields says. “This is all missing from our models.”

And there’s something else. This type of glial cell, these astrocytes, have changed a lot as humans have evolved, while neurons have pretty much stayed the same. A mouse neuron and a human neuron look so much alike, even experienced neuroscientists can’t tell them apart.

"I can’t tell the differences between a neuron from a bird or a mouse or a primate or a human," says Steve Goldman, a neuroscientist at the University of Rochester who has studied brain cells for decades. But Goldman says glial cells are easy to tell apart.

"Human glial cells — human astrocytes — are much larger than those of lower species," he says. "They have more fibers and they send those fibers out over greater distances."

The thought is maybe these glial cells have played a role in making humans smarter. So Goldman teamed up with this wife, Maiken Nedergaard, to test this idea.

They injected some human glial cells into the brains of newborn mice. The mice grew up, and so did the human glial cells. The cells spread through the mouse brain, integrating perfectly with mouse neurons and, in some areas, outnumbering their mouse counterparts. All the while Goldman says the glial cells maintained their human characteristics.

"They very much thought that they were in the human brain, in terms of how they developed and integrated," he says.

So what are these mice like, the ones with brains full of functioning human cells? Their neural circuitry is still just the same, so they act completely normal. They still socialize with other mice and still seem interested in mousey things.

But the researchers say these mice are measurably smarter. In classic maze tests, they learn faster. “They make many fewer errors, and it takes them less time to come to the appropriate answer,” Goldman says.

It might take a normal mouse four or five attempts to learn the correct route, for example. But a mouse with human brain cells could get it on the second try. Glial cells — those boring glial cells — somehow enhance learning.

In fact, they could be changing what it means to be a mouse, and that raises ethical questions for this kind of research.

"Maybe bioethicists have been a little bit too cavalier assuming that a mouse with some human brain cells in it is just your normal old mouse," says Robert Streiffer, a bioethicist from the University of Wisconsin-Madison. "Well, it’s not going to be human, but that doesn’t mean it’s a normal old mouse either."

Streiffer says it’s not just that these mice can get through a maze more quickly — they’re better at recognizing things that scare them. And perception of fear is one of the things bioethicists must weigh when they decide the types of experiments you can do on an animal.

"So you have to sort of step back and do some hardcore philosophy," he says. Like, will these types of human-animal hybrids eventually get close enough to humanity that we would feel uncomfortable performing experiments on them?

The researchers in this study say we’re really, really far from that point. And if you want to investigate the role of glial cells, these hybrid mice are the best tools available.

Star-Shaped Glial Cells Act as the Brain’s “Motherboard”

The transistors and wires that power our electronic devices need to be mounted on a base material known as a “motherboard.” Our human brain is not so different — neurons, the cells that transmit electrical and chemical signals, are connected to one another through synapses, similar to transistors and wires, and they need a base material too.

But the cells serving that function in the brain may have other functions as well. PhD student Maurizio De Pittà of Tel Aviv University’s Schools of Physics and Astronomy and Electrical Engineering says that astrocytes, the star-shaped glial cells that are predominant in the brain, not only control the flow of information between neurons but also connect different neuronal circuits in various regions of the brain.

Using models designed to mimic brain signalling, De Pittà’s research, led by his TAU supervisor Prof. Eshel Ben-Jacob, determined that astrocytes are actually “smart” in addition to practical. They integrate all the different messages being transferred through the neurons and multiplexing them to the brain’s circuitry. Published in the journal Frontiers in Computational Neuroscience and sponsored by the Italy-Israel Joint Neuroscience Lab, this research introduces a new framework for making sense of brain communications — aiding our understanding of the diseases and disorders that impact the brain.

Transcending boundaries

"Many pathologies are related to malfunctions in brain connectivity," explains Prof. Ben-Jacob, citing epilepsy as one example. "Diagnosis and the development of therapies rely on understanding the network of the brain and the source of undesirable activity."

Connectivity in the brain has traditionally been defined as point-to-point connections between neurons, facilitated by synapses. Astrocytes serve a protective function by encasing neurons and forming borders between different areas of the brain. These cells also transfer information more slowly, says Prof. Ben-Jacob — one-tenth of a second compared to one-thousandth of a second in neurons — producing signals that carry larger amounts of information over longer distances. Aastrocytes can transfer information regionally or spread it to different areas throughout the brain — connecting neurons in a different manner than conventional synapses.

De Pittà and his fellow researchers developed computational models to look at the different aspects of brain signalling, such as neural network electrical activity and signal transfer by synapses. In the course of their research, they discovered that astrocytes actually take an active role in the way these signals are distributed, confirming theories put forth by leading experimental scientists.

Astrocytes form additional networks to those of the neurons and synapses, operating simultaneously to co-ordinate information from different regions of the brain — much like an electrical motherboard functions in a computer, or a conductor ensuring that the entire orchestra is working in harmony, explains De Pittà.

These findings should encourage neuroscientists to think beyond neuron-based networks and adopt a more holistic view of the brain, he suggests, noting that the two communication systems are actually interconnected, and the breakdown of one can certainly impact the other. And what may seem like damage in one small area could actually be carried to larger regions.

A break in communication

According to Prof. Ben-Jacob, a full understanding of the way the brain sends messages is significant beyond satisfying pure scientific curiosity. Many diseases and disorders are caused by an irregularity in the brain’s communication system or by damage to the glial cells, so more precise information on how the network functions can help scientists identify the cause or location of a breakdown and develop treatments to overcome the damage.

In the case of epilepsy, for example, the networks frequently become overexcited. Alzheimer’s disease and other memory disorders are characterized by a loss of cell-to-cell connection. Further understanding brain connectivity can greatly aid research into these and other brain-based pathologies.

Modeling Alzheimer’s disease using iPSCs reveals stress phenotypes associated with intracellular Aβ and differential drug responsiveness

Working with a group from Nagasaki University, a research group at the Center for iPS Cell Research and Application (CiRA) has successfully modeled Alzheimer’s disease (AD) using both familial and sporadic patient-derived induced pluripotent stem cells (iPSCs), and revealed stress phenotypes and differential drug responsiveness associated with intracellular amyloid β oligomers in AD neurons and astrocytes.

In a study published online in Cell Stem Cell, Associate Professor Haruhisa Inoue and his team at CiRA and a research group led by Professor Nobuhisa Iwata of Nagasaki University generated cortical neurons and astrocytes from iPSCs derived from two familial AD patients with mutations in amyloid precursor protein (APP), and two sporadic AD patients. The neural cells from one of the familial and one of the sporadic patients showed endoplasmic reticulum (ER)-stress and oxidative-stress phenotypes associated with intracellular Aβ oligomers. The team also found that these stress phenotypes were attenuated with docosahexaenoic acid (DHA) treatment. These findings may help explain the variable clinical results obtained using DHA treatment, and suggest that DHA may in fact be effective only for a subset of patients.
Using both familial and sporadic AD iPSCs, the researchers discovered that pathogenesis differed between individual AD patients. For example, secreted Aβ42 levels were depressed in familial AD with APP E693Δ mutation, elevated in familial AD with APP V717L mutation, but normal in sporadic AD.

"This shows that patient classification by iPSC technology may contribute to a preemptive therapeutic approach toward AD," said Inoue, a principal investigator at CiRA who is also a research director for the CREST research program funded by the Japan Science and Technology Agency. "Further advances in iPSC technology will be required before large-scale analysis of AD patient-specific iPSCs is possible."

Astrocytes Identified as Target for New Depression Therapy

Neuroscience researchers from Tufts University have found that our star-shaped brain cells, called astrocytes, may be responsible for the rapid improvement in mood in depressed patients after acute sleep deprivation. This in vivo study, published in the current issue of Translational Psychiatry, identified how astrocytes regulate a neurotransmitter involved in sleep. The researchers report that the findings may help lead to the development of effective and fast-acting drugs to treat depression, particularly in psychiatric emergencies.

Drugs are widely used to treat depression, but often take weeks to work effectively. Sleep deprivation, however, has been shown to be effective immediately in approximately 60% of patients with major depressive disorders. Although widely-recognized as helpful, it is not always ideal because it can be uncomfortable for patients, and the effects are not long-lasting.

During the 1970s, research verified the effectiveness of acute sleep deprivation for treating depression, particularly deprivation of rapid eye movement sleep, but the underlying brain mechanisms were not known.

Most of what we understand of the brain has come from research on neurons, but another type of largely-ignored cell, called glia, are their partners. Although historically thought of as a support cell for neurons, the Phil Haydon group at Tufts University School of Medicine has shown in animal models that a type of glia, called astrocytes, affect behavior.  

Haydon’s team had established previously that astrocytes regulate responses to sleep deprivation by releasing neurotransmitters that regulate neurons. This regulation of neuronal activity affects the sleep-wake cycle. Specifically, astrocytes act on adenosine receptors on neurons. Adenosine is a chemical known to have sleep-inducing effects.

During our waking hours, adenosine accumulates and increases the urge to sleep, known as sleep pressure. Chemicals, such as caffeine, are adenosine receptor antagonists and promote wakefulness. In contrast, an adenosine receptor agonist creates sleepiness.

“In this study, we administered three doses of an adenosine receptor agonist to mice over the course of a night that caused the equivalent of sleep deprivation. The mice slept as normal, but the sleep did not reduce adenosine levels sufficiently, mimicking the effects of sleep deprivation. After only 12 hours, we observed that mice had decreased depressive-like symptoms and increased levels of adenosine in the brain, and these results were sustained for 48 hours,” said first author Dustin Hines, Ph.D., a post-doctoral fellow in the department of neuroscience at Tufts University School of Medicine (TUSM).

“By manipulating astrocytes we were able to mimic the effects of sleep deprivation on depressive-like symptoms, causing a rapid and sustained improvement in behavior,” continued Hines.

“Further understanding of astrocytic signaling and the role of adenosine is important for research and development of anti-depressant drugs. Potentially, new drugs that target this mechanism may provide rapid relief for psychiatric emergencies, as well as long-term alleviation of chronic depressive symptoms,” said Naomi Rosenberg, Ph.D., dean of the Sackler School of Graduate Biomedical Sciences and vice dean for research at Tufts University School of Medicine. “The team’s next step is to further understand the other receptors in this system and see if they, too, can be affected.”

(Image: Paul De Koninck)