Junjie Guo, Ph.D., Assistant Professor of Neuroscience, Yale University School of Medicine, New Haven, CT
Mechanism and functions of repeat expansion self-exonization in C9orf72 ALS/FTD
As intricate as the DNA replication process is, sometimes errors happen. Some neurological diseases are linked to a particular type of error called nucleotide repeat expansion (NRE), in which a short DNA segment is repeated over and over in hundreds or more copies. Where these repeats occur in the genome matters: during a critical step in gene expression called RNA splicing, only certain pieces (exons) of the RNA transcribed from DNA are joined together to become the final messenger RNA, whereas the remaining RNA sequences (introns) between exons will be broken down.
However, in some cases, introns with NREs are not broken down, but manage to instruct the making of a variety of repeat proteins that are harmful to nerve cells. A well-known example is an intron NRE within a gene called C9orf72, which is the most common genetic cause of amyotrophic lateral sclerosis (ALS, or Lou Gehrig’s disease) and frontotemporal dementia (FTD). In his research, Dr. Guo hopes to uncover how this intron NRE disrupts RNA splicing and causes the production of toxic repeat proteins.
Guo and his team will first test a variety of NRE mutations to see which are able to change the splicing pattern so the intron can escape degradation. Their second aim will test the hypothesis that these changes in the splicing pattern are critical for the C9orf72 NRE RNA to increase its export out from the cell nucleus into the cytoplasm and instruct the making of toxic repeat proteins. Finally, their research will explore the possibility that differences between the ways in which each cell splices its RNAs may explain why certain types of nerve cells such as motor neurons are more vulnerable in ALS.
Juliet K. Knowles, MD, PhD, Assistant Professor of Neurology, Stanford University School of Medicine, Palo Alto, CA
Neuron-to-OPC synapses in adaptive and maladaptive myelination
In her role as a pediatric clinician specializing in epilepsy, Dr. Knowles sees firsthand how this neurological disorder (actually a collection of several related but distinct diseases) is experienced and how it progresses. As a neuroscientist, she has the opportunity to help uncover how and why. Knowles and her team are focusing their research on the role of neuronal activity in myelination in patients with generalized epilepsy, a common form of the disease that is characterized by the presence of seizures and absence seizures.
Myelination is the process by which the axons (projections) of neurons are encased in myelin, which enhances the speed of axon signal transmission, and makes neural networks more efficient. The process involves oligodendrocyte progenitor cells (OPCs) which can develop into oligodendrocytes, cells that produce myelin. In earlier research, Knowles uncovered that the neural activity of absence seizures promotes myelination of the seizure circuit, making it more efficient. This appears to lead to an increase in absence seizure frequency and severity; when Knowles and her team blocked the OPCs’ response to neural activity, seizure-induced myelination did not occur, and the seizures didn’t progress.
Knowles’ new research will now explore how this happens and identify possible approaches for future therapies. One aim will document the neuron to OPC synapses in both epileptic and healthy mouse models. A second aim will compare neuron-to-OPC synaptic activity and synaptic gene expression in healthy or epileptic mice – specifically focusing on how myelination promoted by a seizure differs from that promoted by learning. A third aim will explore how disrupting the post-synaptic receptors on oligodendrocytes affects the progression of epilepsy, not just in terms of seizures, but related symptoms such as disrupted sleep and cognitive impairment, both of which are common in individuals affected by epilepsy.
Akhila Rajan, Ph.D., Associate Professor, Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA
Adipocyte-brain mitochondrial signaling and its impacts on brain function
Communication between organs and the brain is critical to an animal’s survival and health. Signals tell the brain when the body needs more energy, is hungry, or needs to sleep, move or perform countless other tasks. But recent research has revealed that communication can include more than hormones – packets of material can also be passed to brain cells. Dr. Rajan’s research focuses on the phenomena of fat cells (adipocytes) sending bits of mitochondria – the organelles within cells that generate energy, among other roles – to the brain, and how that affects brain function.
Previous research has found that when these mitochondrial bits reach the brain, it makes the fly model Rajan’s team works with more hungry, specifically for high sugar foods, promoting a cycle of obesity and further sending of material. There is a known correlation between obesity and a range of neurological disorders, including sleep disorders and cognitive decline, and this new research hopes to shed light on these links and potentially identify targets for future therapies.
Working with the fly model, Rajan and her team aim to identify how exactly these bits of mitochondria are gaining access to neurons in the brain without being degraded; what happens when these bits of fat cell mitochondria integrate with neuronal mitochondria, specifically how it alters an animal’s behavior in terms of sleep and feeding; and what effect this process has on neuronal health overall. The research will take advantage of very precise genetic manipulations at which Rajan’s lab excels, involve cross-disciplinary insights provided by lab team members, and use advanced insect physiology chambers that let the team document feeding and changes in behavior at a level unavailable to previous generations of researchers.
Humsa Venkatesh, Ph.D., Assistant Professor of Neurology, Brigham and Women’s Hospital & Harvard Medical School, Boston, MA
The neurobiology of glioma: Understanding malignant neural circuits instructing tumor growth
Cancers, including brain tumors, have traditionally been studied at a cellular or molecular level. Researchers are addressing questions such as what subpopulation of cells are involved, how do they mutate, and what can we do to those malignant cells to get them to stop replicating? Dr. Venkatesh is interested in looking at how the nervous system is also involved in cancer progression and has already discovered that neurons form synaptic connections to cancer cells.
Venkatesh and her lab are studying both primary and secondary brain tumors but have evidence that these findings apply to cancers in other parts of the body. The insight that tumors are interacting with neurons, and not just killing off nerves as had once been thought, has opened many possibilities. These malignant growths are taking signals from the nervous system intended to pass information to other cells and instead reinterpreting them to instruct the cancer to grow. Now researchers can explore how to harness the nervous system to help treat or manage this malignant disease. In an exciting development, Venkatesh’s previous work in this space has already led to clinical trials that repurpose existing drugs targeting the nervous system and apply them to cancer treatment.
This new research goes even further into understanding the mechanisms governing neural circuit activity-driven glioma progression. Using advanced neuroscience technologies and patient-derived cell lines, Venkatesh will be able to modulate and study the malignant neural networks, encompassing both neurons and tumor cells, that influence cancer growth. Understanding this activity-dependent mechanism and how it can be targeted without disrupting healthy neuronal function could open new fields of cancer research and novel therapeutic opportunities.
Lisa Beutler, M.D., Ph.D., Assistant Professor of Medicine in Endocrinology, Feinberg School of Medicine, Northwestern University, Chicago, IL
Dissecting the gut-brain dynamics underlying anorexia
Feeding is at the very core of an animal’s survival, so it’s no surprise that the gut and brain are in constant communication to coordinate appropriate food intake and stable bodyweight. However, in the presence of inflammation, this system may break down. One of the hallmarks of inflammation-associated anorexia (not to be confused with anorexia nervosa) is decreased appetite, which can be severe enough to cause malnutrition. Current therapies – including IV-delivered nutrition and intestinal feeding tubes – can reduce quality of life and have significant collateral consequences.
Dr. Beutler aims to use advanced neural observation and manipulation techniques to dissect the underlying mechanisms involved in inflammation-associated anorexia. Beutler’s team will use calcium imaging to reveal the effects individual cytokines (signals released during inflammation) have on specific groups of feeding-related neurons. Her group will also use cutting-edge genetic tools to try to override the inappropriate ‘don’t eat’ signals that result from severe inflammation. Finally, she will study how specific models of inflammatory disease change the neural response to nutrient intake.
Beutler’s research will be the first to study these specific processes at this level of detail in a living organism. By identifying precise neurological targets of cytokine release, and deciphering how this modulates appetite, Beutler hopes to identify therapeutic targets for malnutrition associated with inflammatory diseases. Moreover, her lab aims to create a road map of gut-brain-immune signaling that may have major implications not only for treating inflammation-mediated anorexia, but broadly for future feeding and metabolism research.
Jeremy Day, Ph.D., Associate Professor, Department of Neurobiology, Heersink School of Medicine, University of Alabama – Birmingham; and Ian Maze, Ph.D., Professor – Departments of Neuroscience and Pharmacological Sciences, Director – Center for Neural Epigenome Engineering, Icahn School of Medicine at Mount Sinai, New York City
Leveraging single-cell epigenomics for targeted manipulation of drug-activated ensembles
Drug addiction is a serious problem both for individuals and society as a whole. While there has been significant research into understanding and treating addiction, 60% of those treated will suffer a relapse. In fact, the craving for drugs may actually increase over time, incubating in those who have been addicted even without further drug exposures. Dr. Day and Dr. Maze aim to research addiction at a new level – drilling down to the epigenetic effects of drug use on specific cells at a single-cell level, and how these may predispose a subject to a relapse.
Preliminary research has shown that exposure to drugs over time alters how genes are expressed. In essence, drugs can hijack genetic regulatory elements known as “enhancers,” which when activated cause certain genes to be expressed in brain cells that motivate the subject to seek out these drugs. Day and Maze have designed a project to identify these enhancers in a cell-type specific fashion that are activated (or unsilenced) by cocaine – a well understood and researched stimulant – and then create and insert viral vectors into cells that will only become active in the presence of that unsilenced enhancer. Using this strategy, the viral vector will express its cargo only in cell ensembles that are affected by cocaine and allow researchers to optogenetically or chemogenetically activate or deactivate the affected cells.
With this, Day and Maze will perturb the ensembles to investigate their effects on drug seeking behavior in a rodent model of volitional cocaine self-administration. Their work builds on recent advances in the ability to target individual cells and small groups of cells, rather than entire populations of cells or cell types as has been the focus of earlier research. Now that it is possible to focus on the role specific cells play, the hope is that better treatments may be developed that address the genetic roots of addiction and relapse, and without the negative side effects of manipulating larger, less targeted populations of brain cells.
Stephan Lammel, Ph.D., Associate Professor of Neurobiology, University of California – Berkeley
Neurotensin mediated regulation of hedonic feeding behavior and obesity
The brain is obsessed with finding and consuming food. When calorie-dense food is found – rare in the wild – animals will instinctively consume it rapidly. For humans with ready access to calorie-dense food, the instinct sometimes leads to overeating, obesity, and related health issues. But research has also shown that in some cases, the drive to feed on high-calorie food may diminish when such food is always available. Dr. Lammel seeks to identify the neural processes and brain regions involved in such feeding behavior and its regulation.
Studies over the years have linked feeding to the hypothalamus, an ancient and deep part of the brain. However, evidence also points to a role for the reward and pleasure centers of the brain. Lammel’s preliminary research found that links from the lateral nucleus accumbens (NAcLat) to the ventral tegmental area (VTA) are central to hedonistic feeding – activating that link optogenetically led to increased feeding of calorie-rich foods, but not regular food. Other research identified the amino acid neurotensin (NTS) as a player in the regulation of feeding, in addition to other roles.
Lammel’s research seeks to map out the circuitry and roles of the various parts of the brain that lead animals to eat hedonistically as well as the role of NTS, which is expressed in the NAcLat. Subjects are presented with a normal diet or a calorie-rich jelly diet, and activity on the NAcLat-to-VTA pathway is recorded and mapped to feeding behaviors. He will also track changes over time with prolonged exposure to hedonistic food. Further research will look at changes in NTS presence in cells, and how its presence in different amounts affects cell function. By understanding the pathways and molecular mechanics involved in feeding and obesity, this work may contribute to future efforts help manage obesity.
Lindsay Schwarz, Ph.D., Assistant Professor in Developmental Neurobiology, St. Jude Children’s Research Hospital, Memphis, TN
Identifying brain circuits that connect respiration and cognitive state
Breathing is automatic in animals, but unlike other comparably essential functions – heartbeat, digestion, etc. – animals can consciously control breathing. Breathing is also tied to emotional and mental state in a two-way manner: emotional triggers can cause changes in breathing, but consciously changing breathing has also been shown to influence state of mind. In her research, Dr. Schwarz aims to identify which breathing-related neurons are selectively activated by physiological and cognitive cues and map the brain regions they connect with. This research may prove helpful in studying a variety of neurological disorders where breathing is impacted, such as sudden infant death syndrome (SIDS), central sleep apnea, and anxiety disorders.
Schwarz aims to take advantage of advances in neural tagging to study these neurons which, located deep in the brain stem, have traditionally been difficult to isolate and record in vivo. But with activity tagging, Schwarz can identify the neurons activated during innate vs. active respiration. For the latter, subjects are conditioned to a stressful stimulus that causes them to freeze and alter their breathing. Researchers then can examine the tagged neurons to identify which were active in the conditioned subjects, and address whether these overlap with neurons active during innate respiration.
A second aim is to identify the molecular identity of the breathing-related neurons that were activated during conditioning to more precisely understand which cells are part of the breathing circuit. Finally, having identified those neurons, Schwarz will use viral vector approaches developed by other researchers to determine what parts of the brain those activated cells connect to. Identifying the links between brain states and breathing, the overlap of conscious and unconscious breathing circuits, and the connection between breathing and certain diseases may lay the groundwork for better therapies as well as a fuller understanding of how our most fundamental functions are wired.
Rui Chang, Ph.D., Assistant Professor, Departments of Neuroscience and of Cellular and Molecular Physiology, Yale University School of Medicine
Sreeganga Chandra, Ph.D. Associate Professor, Departments of Neurology and Neuroscience, Yale University School of Medicine
From gut to brain: Understanding the propagation of Parkinson’s Disease
Parkinson’s Disease is a widely known but still mysterious neurological degenerative disease that dramatically affects quality of life. Exactly how the disease initiates is unknown, but recent research indicates that at least some Parkinson’s cases originate in the gut and propagate to the brain via the vagus nerve, a long, complex, multifaceted nerve connecting many organs to the brain.
Dr. Chang and Dr. Chandra are taking this gut-to-brain propagation insight to the next level with their research. Their first two aims seek to identify exactly which vagal neuron populations transmit Parkinson’s and the process by which the gut and these neurons interact. The experiment uses a mouse model, injections of proteins that can induce Parkinson’s, and a novel process to tag and selectively ablate (shut down) specific types of neurons. Through experiments in which certain neurons are ablated, the protein introduced, and the mice examined for Parkinson’s, the team will narrow in on specific candidates. In the third aim, the team hopes to uncover the mechanism by which the disease is transported at the molecular level within neurons.
The research is a collaborative, interdisciplinary effort drawing upon Dr. Chang’s experience researching the vagal nerve and enteric system and Dr. Chandra’s expertise in Parkinson’s Disease and its pathology. It is hoped that with a better, more precise understanding of how the disease reaches the brain, new targets farther from the brain can be identified for treatment that are more precise, allowing treatment to delay or diminish the onset of Parkinson’s without harming the brain or affecting the many other important functions of the extraordinarily complex vagal nerve or the enteric system.
Rainbo Hultman, Ph.D., Assistant Professor, Department of Molecular Physiology and Biophysics, Iowa Neuroscience Institute – Carver College of Medicine, University of Iowa
Brain-wide electrical connectivity in migraine: Toward the development of network-based therapeutics
Migraine is a widespread, often debilitating disorder. It is complex and notoriously difficult to treat; sufferers have differing symptoms, often triggered by sensory hypersensitivity, that may include pain, nausea, visual impairment, and other effects. Migraine affects multiple interconnected parts of the brain, but not always in the same way, and treatments often won’t have the same effect from person to person. Dr. Hultman’s research proposes to examine migraines using new tools with the aim of illuminating new paths for treatment.
The research builds upon her team’s discovery of electome factors, measurements of electrical activity patterns in the brain tied to specific brain states. Using implants to measure brain activity in mouse models representing both acute and chronic migraine, her team will observe which parts of a mouse brain are activated and in what sequence on a millisecond scale for the first time. Machine learning will help organize the collected data, and the electome maps created can be used to help identify the parts of the brain affected, and how the electome changes over time, particularly through the onset of chronicity. The experiment also examines electrical activity patterns tied to behavioral response; for example, the electrical signals observed in the brain of a subject who seeks to avoid bright lights may offer a way to predict more severe responses to migraine.
A second part of Dr. Hultman’s research will then use the same tools to look at how available therapeutics and prophylactics work. Electome factors of subjects treated with these therapeutics will be collected and compared with controls to identify what parts of the brain are affected and in what way, helping reveal the effect of each therapeutic/prophylactic, as well as the effects of medication overuse headache, a common side effect experienced by migraine sufferers who seek to manage their condition.
Gregory Scherrer, Ph.D., Associate Professor, Department of Cell Biology and Physiology, UNC Neuroscience Center, University of North Carolina
Elucidating the neural basis of pain unpleasantness: Circuits and new therapeutics to end the dual epidemic of chronic pain and opioid addiction
Pain is how our brain perceives potentially harmful stimuli, but it’s not a single experience. It’s multidimensional, involving transmissions from nerves to the spinal cord and brain, processing of the signal, triggering of reflexive action, and then follow-up neural activity involved in actions to soothe the pain in the near term and complex learning processes to avoid it in the future.
Pain is also at the core of what Dr. Scherrer sees as two interrelated epidemics: the epidemic of chronic pain, affecting some 116 million Americans, and the opioid epidemic that results from the misuse of powerful and often addictive drugs to treat it. In his research, Dr. Scherrer is looking to find out exactly how the brain encodes the unpleasantness of pain. Many drugs seek to affect that sense of unpleasantness but are often overbroad and also trigger the reward and breathing circuits, leading to addiction (and by extension overuse) and the respiratory shutdown responsible for opioid-related deaths.
Dr. Scherrer’s team will generate a brain-wide map of pain emotional circuits using genetic trapping and labelling of neurons activated by pain with fluorescent markers. Second, activated brain cells will be separated out and their genetic code will be sequenced, looking for common receptors on those cells that may be targets for therapeutics. Finally, the research will investigate compounds in chemical libraries designed to interact with any of those identified target receptors; the effects those compounds have on the unpleasantness of pain; and whether these compounds also carry risk of overuse or affect the respiratory system. Ultimately, the intention is to help find better ways to relieve all types of pain and to improve the well-being and quality of life of patients who experience it.