Tag Archives: #brain

Bourneville’s Tuberous Sclerosis: Everything Unfolds in the Brain Shortly After Birth (Neuroscience)

A Canadian research team has uncovered a new mechanism involved in Bourneville tuberous sclerosis (BTS), a genetic disease of childhood. The team hypothesizes that a mutation in the TSC1 gene causes neurodevelopmental disorders that develop in conjunction with the disease.

Seen in one in 6,000 children, tuberous sclerosis causes benign tumours or lesions that can affect various organs such as the brain, kidneys, eyes, heart and skin. While some patients lead healthy lives, others have significant comorbidities, such as epilepsy, autism and learning disabilities.

Although the role that the TSC1 gene plays in the disease is already known, Montreal scientists have only now identified a critical period in the postnatal development of GABAergic interneurons that are so important to the development of the brain.

The results of their study are reported today in Nature Communications.

An essential ‘pathway’

All mammalian cells, and the proteins that form them, need a ‘pathway’ to regulate their individual growth, which scientists call a ‘signaling pathway,’ explained Clara A. Amegandjin, a doctorate’s student in neurosciences at Université de Montréal and first author of the new study.

“The signaling pathway of mTOR (mechanistic target of rapamycin) controls several aspects of the development of brain cells – the neurons – by regulating different metabolic processes: the proliferation, growth and mobility of neurons, as well as the biosynthesis and transcription of their proteins,” she said.

“The pathway is therefore pivotal in ensuring the development of neurons in an ideal environment.”

When the mTOR signaling pathway is disrupted, certain diseases such as type-2 diabetes, obesity, neurodegeneration and cancer can occur.

“A mutation in the negative regulator of the TSC1 gene of the mTOR pathway is known to produce hyperactivation of the signaling pathway, resulting in abnormal cell proliferation,” said UdeM neurosciences professor Graziella Di Cristo, a researcher at CHU Sainte-Justine children’s hospital.

“This disruption is responsible for neurodevelopmental disorders associated with autism, intellectual disability and epilepsy in tuberous sclerosis, but the underlying mechanisms were not well understood,” said Di Cristo, who oversaw the study.

A conductor that can’t keep time

Di Cristo’s laboratory specializes in the study of GABAergic interneurons. This type of neuron acts as a conductor in the cortex by controlling the dynamics of neural networks and circuits that regulate brain function. They are of critical importance for brain development.

“Our original hypothesis was to see if this mutation in the mTOR pathway affected the development of GABAergic cells,” said Amegandjin. “In many cases of autism, these cells are deregulated. However, in tuberous sclerosis, few studies have examined their involvement in the expression of neurological comorbidities.”

Using an organotypic culture that mimics brain development (growth, maturation, and stabilization) ex vivo, the research team introduced the TSC1 gene mutation into GABAergic cells of mice at specific periods during their brain development.

Using biomarkers, the researchers found early and very rapid proliferation occuring in the growth phase of the mutated cells. Synaptic connections that form too quickly become ‘defective’ once they mature.

“We therefore have evidence that neurodevelopmental disorders are mediated by hyperactivity of the mTOR pathway caused by the absence of the TSC1 gene,” said Amegandjin.

Application in humans

Rapamycin is a drug whose mechanism of action is related to the inhibition of the mTOR protein.

“By administering this protein in preclinical models – in this case, mice – we are able to ‘rescue’ synaptic connections and prevent neurodevelopmental disorders,” said Di Cristo. “Based on our results, this therapeutic approach would be most appropriate to prevent premature maturation of neurons.”

However, she cautioned “since mTOR plays a very broad role in neuronal development, it is important to determine the exact timing of administration to avoid undesirable and possibly fatal results. We need to continue our research to confirm that these observations apply to humans.”

The study was funded by the Canadian Institutes of Health Research (CIHR), the Canada Foundation for Innovation (CFI), the Canada Research Chairs Program and the Natural Sciences and Engineering Research Council of Canada (NSERC).

Reference: Amegandjin, C.A., Choudhury, M., Jadhav, V. et al. Sensitive period for rescuing parvalbumin interneurons connectivity and social behavior deficits caused by TSC1 loss. Nat Commun 12, 3653 (2021). https://doi.org/10.1038/s41467-021-23939-7

Provided by University of Montreal

Researchers Controls Neuronal Activity In The Brain Using Light For The First Time (Neuroscience)

A study led by researchers from IBEC and IDIBAPS achieves, for the first time, the control of brain state transitions using a molecule responsive to light, named PAI.  The results not only pave the way to act on the brain patterns activity, but they also could lead to the development of photomodulated drugs for the treatment of brain lesions or diseases such as depression, bipolar disorders or Parkinson’s or Alzheimer’s diseases. 

The brain presents different states depending on the communication between billions of neurons, and this network is the basis of all our perceptions, memories, and behaviours. It is often considered a “black box”, with difficult access for clinicians and researchers, as few limited tools are available to perform accurate and spaciotemporal studies on brain neuronal behaviour. Now, researchers from the Institute for Bioengineering of Catalonia (IBEC) in collaboration with August Pi i Sunyer Biomedical Research Institute (IDIBAPS) and have added some light to the subject: they succeeded for the first time in controlling neuronal activity in the brain using a molecule responsive to light.  

The study included participants from the Autonomous University of Barcelona (UAB) and was carried out in the frame of the Human Brain Project of the EU. It describes the first way to directly photomodulate brain state transitions in vivo

The work, led by ICREA Research Professors Pau Gorostiza (IBEC-CERCA, BIST, CIBER-BBN) and Mavi Sanchez-Vives (IDIBAPS) and has been recently published in the journal Advanced Science. Results show that this new molecule, named PAI (for Phthalimide-Azo-Iper) can specifically and locally control the muscarinic cholinergic receptors, that is, the acetylcholine receptors, a brain neurotransmitter very important in several processes as learning attention or memory.   

Control of brain states transitions with light 

Transitions between brain states, such as going from being asleep to awake, or waking up from a coma, are based on the transmission of chemical and electrical signals among groups of neurons involved in different functions. Current techniques to modulate neuronal activity as transcranial-magnetic or ultrasound stimulation have limitations in spatiotemporal and spectral performance. Another technique with high precision that also uses light to control the neurons in the optogenetics, but it depends on genetic manipulation, making difficult its translation to humans due to safety reasons.  

Here, researchers applied photopharmacology to tackle these problems. To do so they used a molecule previously developed at IBEC, PAI, that is light responsive and allows a spatiotemporally controlled modulation of brain neurons, binding and controlling the activity of muscarinic cholinergic receptors, key receptors on neuronal interaction and communication. By using this approach, the cholinergic-innervation dependent brain state transitions can be controlled by light using drugs chemically designed to be photosensitive.  

“The control of neuronal activity in the brain is key to perform both basic and applied research, and to develop safe and accurate techniques to perform therapeutic brain interventions in clinical neurology” 

Fabio Riefolo (IBEC), co-first author of the study.

Changes in brain states 

Different brain states and transitions among them are associated with brain function. They are closely linked to changes in brain activation patterns, which in turn reflect the activity and parameters of specific neuronal networks. Thus, manipulation of neurons with a spatiotemporal control is fundamental to determine the relation among brain states and behaviour and to study the influence of neuronal circuits on specific behaviours. In addition, PAI is pharmacologically specific for a muscarinic receptor subtype, M2, which offers exciting prospects to study the pharmacology of brain waves. 

 When applying PAI to the intact brain, and subsequently white light, researchers could modulate the spontaneous emerging slow oscillations in neuronal circuits and reversibly manipulate the brain oscillatory frequency. This new chemically-engineered tool allowed to induce and investigate in detail, in a controlled and non-invasive way, the transitions of brain from sleep- to awake-like states using direct illumination. 

 In our brain, neuronal activity is driven by molecules known as neuromodulators, for example acetylcholine (ACh), through their binding to cholinergic receptors. However, it is not completely understood the contribution of the different cells expressing ACh receptors in the global brain behaviour. The use of selective and photoswitchable cholinergic drugs as PAI to achieve a spatiotemporal precise modulation of brain activity opens the way to perform accurate basic neuroscience research and to develop future brain therapies and stimulation. 

“The photocontrol of endogenous receptors and their functions in the central nervous system, such as the transition between different brain states, is an achievement for neuromodulation technologies”. 

Dr. Almudena Barbero-Castillo (IDIBAPS), co-first author of the study.

Reference article:  

Almudena Barbero-Castillo, Fabio Riefolo, Carlo Matera, Sara Caldas-Martínez, Pedro Mateos-Aparicio, Julia F. Weinert, Aida Garrido-Charles, Enrique Claro, Maria V. Sanchez-Vives, Pau Gorostiza. Control of Brain State Transitions with a Photoswitchable Muscarinic Agonist. (2021). Advanced Science. May 21; e2005027 

 Dr. F. Riefolo, Dr. C. Matera, Dr. A. Garrido-Charles, Prof. P. Gorostiza are members of the Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER- BBN).

Provided by IBEC

Omega-3s May Hold Key to Unlocking Blood-Brain Barrier (Neuroscience)

Spectacular images of a molecule that shuttles omega-3 fatty acids into the brain may open a doorway for delivering neurological therapeutics to the brain.

“We’ve managed to obtain a three-dimensional structure of the transporter protein that provides a gateway for omega-3s to enter the brain. In this structure, we can see how omega-3s bind to the transporter. This information may allow for the design of drugs that mimic omega-3s to hijack this system and get into the brain,” says first author Rosemary J. Cater, PhD(link is external and opens in a new window), a Simons Society Fellow in the Mancia Lab(link is external and opens in a new window) at Columbia University Vagelos College of Physicians and Surgeons.

The study(link is external and opens in a new window) was published online on June 16 in the journal Nature.

A major challenge in treating neurological diseases is getting drugs across the blood-brain barrier—a layer of tightly packed cells that lines the brain’s blood vessels and zealously blocks toxins, pathogens, and some nutrients from entering the brain. Unfortunately, the layer also blocks many drugs that are otherwise promising candidates to treat neurological disorders.

Essential nutrients like omega-3s require the assistance of dedicated transporter proteins that specifically recognize them and get them across this barrier. “The transporters are like bouncers at a club, only letting molecules with invites or backstage passes in,” Cater says.

“The Transporters are like bouncers at a club, only letting molecules with invites or backstage passes in.”

The transporter—or bouncer—that lets omega-3s in is called MFSD2A and is the focus of Cater’s research. “Understanding what MFSD2A looks like and how it pulls omega-3s across the blood-brain barrier may provide us with the information we need to design drugs that can trick this bouncer and gain entry passes.”

To visualize MFSD2A, Cater used a technique called single-particle cryo-electron microscopy.

“The beauty of this technique is that we’re able to see the shape of the transporter with details down to a fraction of a billionth of a meter,” says study co-leader Filippo Mancia, PhD(link is external and opens in a new window),  associate professor of physiology & cellular biophysics at Columbia University Vagelos College of Physicians and Surgeons and an expert in the structure and function of membrane proteins. “This information is critical for understanding how the transporter works at a molecular level.”

For cryo-EM analysis, protein molecules are suspended in a thin layer of ice under an electron microscope. Powerful cameras take millions of pictures of the proteins from countless angles which can then be pieced together to construct a 3D map.

Multiple 2D images of the omega-3 transporter were obtained with cryo-electron microscopy and used to construct a 3D map of the protein. Image from Cater et al. (2021).

Into this map researchers can build a 3D model of the protein, putting each atom in its place. “It reminds me of solving a jigsaw puzzle,” Mancia explains. This technique has become remarkably powerful in visualizing biological molecules in recent years, thanks in part to Joachim Frank, PhD, professor of biochemistry & molecular biophysics at Columbia University Vagelos College of Physicians and Surgeons, who won the Nobel Prize in 2017 for his role in developing cryo-electron microscopy data analysis algorithms.

“Our structure shows that MFSD2A has a bowl-like shape and that omega-3s bind to a specific side of this bowl,” Cater explains. “The bowl is upside down and faces the inside of the cell, but this is just a single 3D snapshot of the protein, which in real life has to move to transport the omega-3s. To understand exactly how it works, we need either multiple different snapshots or, better yet, a movie of the transporter in motion.”

To understand what these movements might look like, a second co-leader of the study, George Khelashvili, PhD(link is external and opens in a new window), assistant professor of physiology and biophysics at Weill Cornell Medicine, used the 3D model of the protein as a starting point to run computational simulations that revealed how the transporter moves and adapts its shape to release omega-3s into the brain. A third co-leader of the study, David Silver, PhD(link is external and opens in a new window), professor at the Duke-NUS Medical School in Singapore and pioneer in MFSD2A biology, together with his team tested and confirmed hypotheses derived from the structure and the computational simulations on how MFSD2A works to pinpoint specific parts of the protein that are important.

The team also included researchers from the New York Structural Biology Center, the University of Chicago, and the University of Arizona, all using their specific skills to make this project possible.

The team is now investigating how the transporter first recognizes omega-3s from the bloodstream. “But our study has already given us tremendous insight into how MFSD2A delivers omega-3s to the brain, and we are really excited to see where our results lead to,” Cater says.

More information

Read more about the discovery on the Duke-NUS Medical School(link is external and opens in a new window) and Weill Cornell Medicine(link is external and opens in a new window) websites.

The study is titled “Structural basis of omega-3 fatty acid transport across the blood–brain barrier.” 

Other authors: Geok Lin Chua (Duke-NUS Medical School), Satchal K. Erramilli (University of Chicago), James E. Keener (University of Arizona), Brendon C. Choy (Columbia), Piotr Tokarz (University of Chicago), Cheen Fei Chin (Duke-NUS Medical School), Debra Q.Y. Quek (Duke-NUS Medical School), Brian Kloss (New York Structural Biology Center), Joseph G. Pepe (Columbia), Giacomo Parisi (Columbia), Bernice H. Wong (Duke-NUS Medical School), Oliver B. Clarke (Columbia), Michael T. Marty (University of Arizona), and Anthony A. Kossiakoff (University of Chicago).

The study was supported by funds from the National Institutes of Health (grants R35 GM132120, R21 MH125649, R35 GM128624, and R01 GM117372); the National Research Foundation and Ministry of Health, Singapore; the Simons Society of Fellows; the HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute of Computational Biomedicine at Weill Cornell Medical College through the 1923 Fund; and the Khoo Postdoctoral Research Fellowship.

David Silver is a scientific founder and advisor of Travecta Therapeutics, which has developed a drug delivery platform that uses MFSD2A transport. All other authors declare no competing interests.

Featured image: Models of MFSD2A show how the molecule transports omega-3s and other lipids into the brain. Here, two snapshots of MFSD2A show two lipids—LPC 18:3 (left) and omega-3 (right)— inside the transporter’s intracellular cavity. Image from Cater, et al. (2021)

Provided by Columbia University Irving Medical Center

P-glycoprotein Removes Alzheimer’s-associated Toxin From The Brain (Neuroscience)

Discovery could lead to new Alzheimer’s treatment

A team of SMU biological scientists has confirmed that P-glycoprotein (P-gp) has the ability to remove a toxin from the brain that is associated with Alzheimer’s disease.    

The finding could lead to new treatments for the disease that affects nearly 6 million Americans. It was that hope that motivated lead researchers James W. McCormick and Lauren Ammerman to pursue the research as SMU graduate students after they both lost a grandmother to the disease while at SMU. 

In the Alzheimer’s brain, abnormal levels of amyloid-β proteins clump together to form plaques that collect between neurons and can disrupt cell function. This is believed to be one of the key factors that triggers memory loss, confusion and other common symptoms from Alzheimer’s disease. 

“We were able to demonstrate both computationally and experimentally that P-gp, a critical toxin pump in the body, is able to transport this amyloid-β protein,” said John Wise, associate professor in the SMU Department of Biological Sciences and co-author of the study published in PLOS ONE.

“If you could find a way to induce more P-glycoprotein in the protective blood-brain barrier for people who are susceptible to Alzheimer’s disease, perhaps they could take such a treatment and it would help postpone or prevent the onset of the disease,” he said. Wise stressed that the theory needs more research. 

The SMU (Southern Methodist University) study also provides strong evidence for the first time that P-gp may be able to pump out much larger toxins than previously believed.  

(A) The first frame of SMU’s simulation shows amyloid-β bound to the drug binding domains of P-gp. (B) The final frame of the same simulation shows P-gp pushing an amyloid protein through the cell membrane to outside the cell.  © SMU

P-gp is nature’s way of removing toxins from cells. Similar to how a sump pump in your house removes water from the basement, P-gp swallows harmful drugs or toxins within the cell and then spits them back outside the cell.

“You find P-gp wherever the body is looking to protect an organ from toxins, and the brain is no exception,” explained co-author Pia Vogel, SMU professor and director of SMU’s Center for Drug Discovery, Design and Delivery

Amyloid-β’s large size created questions about whether P-glycoprotein could actually inhale it and pump it back out.   

“Amyloid-β is maybe five times bigger than the small, drug-like molecules that P-glycoproteins are well-known to move. It would be like taking New York pizza and trying to stuff that whole slice in your mouth and swallow it,” Wise said.

The fact that P-gp appears to be able to do just that “greatly expands the possible range of things that P-gp can transport, which opens the possibility that it may interact with other factors that were previously thought impossible,” said McCormick, a former SMU graduate student in biological sciences. 

The research was personal

SMU researchers might never have investigated the link between P-gp and amyloid-β proteins if not for McCormick’s dogged pursuit of the connection. The Ph.D. student, who graduated in 2017, had seen preliminary work suggesting that P-gp might play a role in pulling amyloid protein out of the brain and asked his faculty advisors, Vogel and Wise, if he could take some time to check it out. 

The professors concede they first tried to discourage him because they were more focused on P-gp’s role in creating resistance to chemotherapy in cancer patients. However, McCormick was “passionate,” about figuring out if P-gp might be able to shield someone from getting Alzheimer’s, Vogel said.   

He devoted hours of his own time to use a computer-generated model of P-glycoprotein that he and Wise created. The model allows researchers to dock nearly any drug to the P-gp protein and observe how it would behave in P-gp’s “pump.” Vogel, Wise and other SMU scientists have been studying the protein for years to identify compounds that might reverse chemotherapy failure in aggressive cancers. 

McCormick completed the computational work with the help of his fiancé, Ammerman, who got her Ph.D in biology from SMU in May.

Together, they ran multiple simulations of the P-gp protein using SMU’s high performance computer, ManeFrame II, and found that each time, P-gp was able to “swallow” amyloid-β proteins and push them out of cells.  

“For the scientist in me, it was just absolutely amazing that this pump could consume something that big,” Vogel said. “John [Wise] and I did not predict that would be possible.”

Two in vitro experiments confirmed the computational work

The researchers conducted two experiments in the lab to confirm the computational results.  

In one experiment, Ammerman used lab-purchased amyloid-β proteins that had been dyed fluorescent green, allowing them to be easily spotted easily in a microscope. In multiple trials, Ammerman exposed human cells to these amyloid-β proteins. She used two types of human cells — one where P-gp was strongly expressed and one where P-gp was not. This allowed Ammerman to test the difference between the two and see if P-gp was pumping amyloid-β out.       

The amyloid proteins were clearly shown to be pushed out of the human cells that had overexpressed P-gp in them, supporting the theory that P-gp removes amyloid proteins on contact. 

Another in vitro experiment reached the same conclusion from a different direction. Former graduate student Gang (Mike) Chen worked in SMU’s Center for Drug Discovery, Design and Delivery to show that an Alzheimer’s-linked amyloid-β caused changes in the P-gp’s usage of adenosine triphosphate (ATP), indicating that there was a physical interaction between the two. 

ATP hydrolysis produces the energy that P-gp uses to transport toxins or drugs out of the cell. When no toxins are present, P-gp’s rate of ATP stays pretty low. When challenged with transporting cargo, P-gp’s ATP hydrolysis activity usually increases quite dramatically.

“Even though our work can’t help our grandparents, I hope that it might help others in the future,” Ammerman said. “The more we know, the more power we have – and researchers after us – to address and target these devastating diseases.”

Featured image: Lauren Ammerman and James McCormick, who are getting married in November, sought to do research on Alzheimer’s disease after both SMU graduate students lost a grandmother to the disease. © SMU

Reference: McCormick JW, Ammerman L, Chen G, Vogel PD, Wise JG (2021) Transport of Alzheimer’s associated amyloid-β catalyzed by P-glycoprotein. PLoS ONE 16(4): e0250371. doi:10.1371/journal.pone.0250371

Provided by SMU

Researchers Find New Infant Sleep Stage (Neuroscience)

Human babies do even more than we thought while sleeping.

A new study from University of Iowa researchers provides further insights into the coordination that takes place between infants’ brains and bodies as they sleep.

The Iowa researchers have for years studied infants’ twitching movements during REM sleep and how those twitches contribute to babies’ ability to coordinate their bodily movements. In this study, the scientists report that beginning around three months of age, infants see a pronounced increase in twitching during a second major stage of sleep, called quiet sleep.

“This was completely surprising and, for all we know, unique to humans and human infants,” says Mark Blumberg, F. Wendell Miller Professor and chair in the Department of Psychological and Brain Sciences and one of the study’s authors. “We were seeing things that we could not explain, based on our years of observation in baby rats and what’s available in the scientific literature.”

The researchers recorded 22 sleeping infants, ranging from one week of age to seven months, and their twitches. At first, the scientists paid attention solely to the twitches occurring alongside REM sleep, in keeping with their previous research of REM sleep-associated twitching in other mammals.

But then the surprise happened: The researchers noticed the infants were twitching their limbs outside of REM sleep as well.

“The twitches looked exactly the same,” says Greta Sokoloff, research scientist in the Department of Psychological and Brain Sciences at Iowa and the study’s lead author. “We did not expect to see twitches during quiet sleep—after all, quiet sleep got that name because humans and other animals typically don’t move during that state.”

Because the researchers were recording brain waves in the sleeping babies, they were able to study brain activity associated with the twitches. As expected, they noticed that during quiet sleep, the infants produced large brain oscillations—called sleep spindles—about once every 10 seconds.

Sleep spindles offer a window into the brain’s coordination with its motor system. The researchers found the rate of sleep spindles in the infant subjects increased beginning around three months to seven months of age and were concentrated along the sensorimotor strip, where the cortex processes sensory and motor information. These facts about sleep spindles were particularly important once the researchers discovered that the sleep spindles and twitches were synchronized.

“Sleep spindles have been widely linked with learning and memory,” Sokoloff says. “So our findings suggested to us that what the infants are doing is learning about their bodies through twitching during a period of sleep that we previously thought was defined by behavioral silence.”

The finding opens a whole new avenue of research into the brain-body communication that takes place while infants are asleep.

“Our finding could reflect something important about the cortical contributions to motor control,” Blumberg says. “Infants have to integrate the brain with the body, to get the system set up and working properly. It’s not all connected at birth. There’s a lot of development that has to happen after birth. What we think we’re seeing is a new mode of integration among different parts of the brain and the body.”

The researchers note the study has a small sample size, especially at the younger ages, and the infants were recorded during short periods of daytime sleep. They plan to recruit more infants and study their sleep during the day and night to confirm the findings.

The study, “Twitches emerge postnatally during quiet sleep in human infants and are synchronized with sleep spindles,” was published online June 16 in the journal Current Biology.

Contributing authors from Iowa include James Dooley, Ryan Glanz, Rebecca Wen, Meredith Hickerson, Laura Evans, Haley Laughlin, and Keith Apfelbaum.

The National Institute of Child Health and Human Development, a branch of the National Institutes of Health, funded the research.

Featured image: A University of Iowa team has found that babies twitch during a sleep stage called quiet sleep, not just during REM sleep. The results may show there’s more communication between snoozing infants’ brains and motor systems than previously known. Photo by Kevin Keith/Unsplash.

Provided by University of Iowa

A ‘Pump’ Gene’s Surprising Role in Early Brain Formation (Neuroscience)

A mutation in four children with polymicrogyria illuminates the role of bioelectricity in early brain development

In polymicrogyria, the cortex of the brain has many irregular, small folds (gyria) and disorganization of its layers. Many affected children have severe developmental delay, intellectual disabilities, and epilepsy, and many need to use a wheelchair. Mutations in several different genes can cause this “overfolding of the brain” condition.

Studying four patients with polymicrogyria, Richard Smith, PhD, identified mutations in a gene that caused him to do a double-take. His curiosity drove him to investigate the role of this gene, called ATP1A3, in the developing brain.

“ATP1A3 is critical to many cell biological processes,” says Smith, an investigator the Division of Genetics and Genomics at Boston Children’s Hospital. “It’s one of the most important genes we have in our brains.”

Bio-electricity and brain development

ATP1A3 encodes a protein that makes up part of a cellular pump. It moves sodium and potassium ions across the cell membrane, allowing our cells to maintain differing concentrations of charged ions on either side, similar to a battery. This difference enables electrical currents to flow into or out of cells, driving action potentials in neurons and other essential cell functions.

“For me it was very compelling to understand how these pump proteins, and the flow of ions, contribute to core mechanisms in brain development,” says Smith, an electrophysiologist by training. “We got a lot of great biological insights by studying these four patients.”

A spatial and temporal ‘atlas’ of ATP1A3

When and where in the typical developing brain is ATP1A3 turned on? To answer this question, Smith, with senior investigator Christopher Walsh, MD, PhD and colleagues at multiple other sites, obtained donated human tissues from several hospital tissue banks and the NIH NeuroBiobank. The investigators analyzed samples from two times in early brain development: at around 20 weeks’ gestation, when the fetal cortex, initially smooth, starts to fold, and in infants soon after birth.

Using single-cell RNA sequencing (DropSeq) in collaboration with Marta Florio, PhD, at Harvard Medical School, they looked for expression (turning on) of ATP1A3 in about 125,000 individual neurons from 11 areas of the prenatal cortex. They also profiled about 52,000 neurons from the infants, sampling four areas of the cortex.

Overall, ATP1A3 expression levels were highest in the prefrontal cortex at both time points, and highest in the most active, frequently-firing neurons in the cortex. In the fetal cortex, ATP1A3 expression was particularly high in the subplate, a layer that disappears later in development. Electrical activity in the subplate is thought to be a hub of signaling driving synapse formation, neuron migration, and other brain developmental processes.

“In the infants, we found increased expression of the gene in interneurons, which are inhibitory,” says Smith. “We think that ATP1A3 mutations may disrupt the balance of excitation and inhibition in the brain, which could contribute to epilepsy in other ATP1A3-related conditions.”

Lessons for other ATP1A3-related diseases?

The work, published in PNAS, underscores how research in rare diseases can yield fundamental insights in biology — in this case, how the brain develops its contours and organizational pattern. It provides a map for future studies of how mutations in ATP1A3 cause the brain to form abnormally.

“When we first published this as a preprint, we had a lot of people reach out to us with patients with overlapping phenotypes, so it is very exciting to better understand this disease,” says Smith.

The findings may also inform scientists’ understanding of other known ATP1A3-related disorders. While the patients with polymicrogyria had severe mutations causing loss of function of the gene, milder mutations cause a spectrum of later-onset neurologic diseases including alternating hemiplegia of childhood, which causes bouts of temporary paralysis; a movement disorder known as rapid onset dystonia parkinsonism; and childhood-onset schizophrenia. These later-onset disorders may be more amenable to therapeutic intervention.

“Polymicrogyria is at the extreme end of severity, but we think that ATP1A3-related disorders in the “middle” of this spectrum could have early pathogenic roots that could possibly be treated before they become more severe,” says Smith.

He adds that if newborn DNA sequencing becomes common, it could offer a window of opportunity for treating ATP1A3 related disorders before they manifest clinically.

As for polymicrogyria, “a structural malformation is trickier to reverse, but infant brains are amazingly plastic and capable of reorganizing,” says Smith. “So if you could lessen the epilepsy-related damage from the earliest point, you might be able to improve quality of life.”

Smith is supported by the NIH National Institute of Neurological Disorders and Stroke and the Tommy Fuss Foundation. Walsh is a HHMI Investigator, and receives funding from the Paul Allen Discovery Foundation and the NIH.

Featured image: In polymicrogyria, the cortex of the brain has many irregular, small folds (gyria) and disorganization of its layers, caused by mutations in one of several genes. Many affected children have severe developmental delay, intellectual disabilities, and epilepsy, © Richard Smith/Sebastian Stankiewicz, Boston Children’s Hospital

Provided by Boston Children’s Hospital

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Gender Differentiates How Facial Expressions are Processed in the Brains of Alcoholics (Neuroscience)

Should treatment of alcoholics be different based on gender? Yes, according to a new study that shows that alcoholic men and women respond differently to their disease resulting in different levels of brain activity and brain abnormalities. Research indicates that they  distinguish facial expressions differently and that this is an important clue as to how treatment strategies might be tailored.

Chronic long-term Alcohol Use Disorder (AUD) or “alcoholism,” is a harmful condition that has been associated with deficits in emotion and memory, including memory for the emotional expressions of faces. In addition to its effects on memory for facial emotions, AUD also has been associated with impairments in the processing of facial emotional expressions which can endure after months or years of sobriety.

While prior studies have shown that ones’ gender influences alcohol’s impacts on the brain, this new research has found that the brain responds to emotional facial expressions differently in men and women. “Surprisingly, there were brain abnormalities for abstinent men with AUD that turned out to be unlike the abnormalities of abstinent women with AUD,” said corresponding author and research scientist Kayle S. Sawyer, PhD, from the Psychology Research Service of the VA Boston Healthcare System, the department of anatomy and neurobiology at BUSM, and radiology at Massachusetts General Hospital (MGH).

This project, led by BUSM’s Marlene Oscar Berman, PhD, and MGH’s Gordon Harris, PhD, used functional magnetic resonance imaging (fMRI) to measure the brain activity of a group of men and women with and without a history of AUD while they completed an emotional face memory task. The researchers then looked at activation differences between when they were looking at a fixation stimulus (plus signs) and when they were looking at photographs of faces with different facial expressions.

They found the faces elicited a similar overall pattern of activation for all four groups. “But when we compared the groups, we noticed important differences in their levels of activation. For example, the alcoholic men showed abnormally high activity in the frontal area of the brain that was not obvious in the alcoholic women,” explained Sawyer. “These findings indicate that the experiences and mechanisms of alcohol addiction differ for the two genders,” he added.

The researchers believe this study has implications for clinical research and more generally suggests that clinicians should consider gender carefully when treating alcohol use disorders.

“Researchers should examine gender differences in many medical conditions, so that prevention and treatment strategies can be better tailored to individuals instead of applied generically using group averages. One important way that they can be tailored is by treating men and women differently when that is appropriate and beneficial and when justified by the research.”

Prior research by this same group found abstinent alcoholic men have more diminished brain activity in areas responsible for emotional processing (limbic regions including the amygdala and hippocampus), as well as memory and social processing (cortical regions including the superior frontal and supramarginal regions) among other functions compared to alcoholic women.

These findings appear online in the journal PLOS One.

Reference: Oscar-Berman M, Ruiz SM, Marinkovic K, Valmas MM, Harris GJ, Sawyer KS (2021) Brain responsivity to emotional faces differs in men and women with and without a history of alcohol use disorder. PLoS ONE 16(6): e0248831. doi:10.1371/journal.pone.0248831

Provided by BUSM

How HIV Infection Shrinks The Brain’s White Matter? (Neuroscience)

Researchers from Penn and CHOP detail the mechanism by which HIV infection blocks the maturation process of brain cells that produce myelin, a fatty substance that insulates neurons.

It’s long been known that people living with HIV experience a loss of white matter in their brains. As opposed to gray matter, which is composed of the cell bodies of neurons, white matter is made up of a fatty substance called myelin that coats neurons, offering protection and helping them transmit signals quickly and efficiently. A reduction in white matter is associated with motor and cognitive impairment.

Earlier work by a team from the University of Pennsylvania and Children’s Hospital of Philadelphia (CHOP) found that antiretroviral therapy (ART)—the lifesaving suite of drugs that many people with HIV use daily—can reduce white matter, but it wasn’t clear how the virus itself contributed to this loss. 

In a new study using both human and rodent cells, the team has hammered out a detailed mechanism, revealing how HIV prevents the myelin-making brain cells called oligodendrocytes from maturing, thus putting a wrench in white matter production. When the researchers applied a compound blocking this process, the cells were once again able to mature. 

The work is published in the journal Glia.

“Even when people with HIV have their disease well-controlled by antiretrovirals, they still have the virus present in their bodies, so this study came out of our interest in understanding how HIV infection itself affects white matter,” says Kelly Jordan-Sciutto, a professor in Penn’s School of Dental Medicine and co-senior author on the study. “By understanding those mechanisms, we can take the next step to protect people with HIV infection from these impacts.”

“When people think about the brain, they think of neurons, but they often don’t think about white matter, as important as it is,” says Judith Grinspan, a research scientist at CHOP and the study’s other co-senior author. “But it’s clear that myelination is playing key roles in various stages of life: in infancy, in adolescence, and likely during learning in adulthood too. The more we find out about this biology, the more we can do to prevent white matter loss and the harms that can cause.”

Jordan-Sciutto and Grinspan have been collaborating for several years to elucidate how ART and HIV affect the brain, and specifically oligodendrocytes, a focus of Grinspan’s research. Their previous work on antiretrovirals had shown that commonly used drugs disrupted the function of oligodendrocytes, reducing myelin formation.

In the current study, they aimed to isolate the effect of HIV on this process. Led by Lindsay Roth, who recently earned her doctoral degree within the Biomedical Graduate Studies group at Penn and completed a postdoctoral fellowship working with Jordan-Sciutto and Grinspan, the investigation began by looking at human macrophages, one of the major cell types that HIV infects.

Scientists had hypothesized that HIV’s impact on the brain arose indirectly through the activity of these immune cells since the virus doesn’t infect neurons or oligodendrocytes. To learn more about how this might affect white matter specifically, the researchers took the fluid in which macrophages infected with HIV were growing and applied it to rat oligodendrocyte precursor cells, which mature into oligodendrocytes. While this treatment didn’t kill the precursor cells, it did block them from maturing into oligodendrocytes. Myelin production was subsequently also reduced.

“Immune cells that are infected with the virus secrete harmful substances, which normally target invading organisms, but can can also kill nearby cells, such as neurons, or stop them from differentiating,” Grinspan says. “So the next step was to figure out what was being secreted to cause this effect on the oligodendrocytes.” 

The researchers had a clue to go on: Glutamate, a neurotransmitter, is known to have neurotoxic effects when it reaches high levels. “If you have too much glutamate, you’re in big trouble,” says Grinspan. Sure enough, when the researchers applied a compound that blunts glutamate levels to HIV-infected macrophages before the transfer of the growth medium to oligodendrocyte precursors, the cells were able to mature into oligodendrocytes. The result suggests that glutamate secreted by the infected macrophages was the culprit behind the precursor cells getting “stuck” in their immature form.

There was another mechanism, however, that the researchers suspected might be involved: the integrated stress response. This response integrates signals from four different signaling pathways, resulting in changes in gene expression that serve to protect the cell from stress or to prompt the cell to die, if the stress is overwhelming. Earlier findings from Jordan-Sciutto’s lab had found the integrated stress response was activated in other types of brain cells in patients who had cognitive impairment associated with HIV infection, so the team looked for its involvement in oligodendrocytes as well. 

Indeed, they found evidence that the integrated stress response was activated in cultures of oligodendrocyte precursor cells. 

Taking this information with what they had found out about glutamate, “Lindsay was able to tie these two things together,” Jordan-Sciutto says. She demonstrated that HIV-infected macrophages secreted glutamate, which activated the integrated stress response by turning on a pathway governed by an enzyme called PERK. “If you blocked glutamate, you prevented the activation of the integrated stress response,” Jordan-Sciutto says.

To take these findings further, and potentially test out new drug targets to address HIV-related cognitive impairments, the team hopes to use a well-characterized rat model of HIV infection.  

“HIV is a human disease, so it’s a hard one to model,” says Grinspan. “We want to find out if this model recapitulates human disease more accurately than others we’ve used in the past.”

By tracking white matter in this animal model and comparing it to imaging studies done on patients with HIV, they hope to get at a better understanding of what factors shape white matter loss. They’re particularly interested in looking at a cohort of adolescents being treated at CHOP, as teens are a group in whom HIV infection rates are climbing.

Ultimately, the researchers want to discern the effects of the virus from the drugs used to treat it in order to better evaluate the risks of each. 

“When we put people on ART, especially kids or adolescents, it’s important to understand the implications of doing that,” says Jordan-Sciutto. “Antiretrovirals may prevent the establishment of a viral reservoir in the central nervous system, which would be wonderful, but we also know that the drugs can cause harm, particularly to white matter.

“And then of course we can’t forget the 37 million HIV-infected individuals who live outside the United States and may not have access to antiretrovrials like the patients here,” she says. “We want to know how we can help them too.”

Kelly Jordan-Sciutto is vice chair and professor in the University of Pennsylvania School of Dental Medicine’s Department of Basic & Translational Sciences and is director of Biomedical Graduate Studies.

Judith Grinspan is research scientist at the Children’s Hospital of Philadelphia and research professor of neurology at the the Perelman School of Medicine at the University of Pennsylvania.

Lindsay Roth, who recently earned her doctoral degree from the Biomedical Graduate Group at the University of Pennsylvania, was first author on the paper. 

Roth, Grinspan, and Jordan-Sciutto’s coauthor was Çagla Akay-Espinoza, from Penn’s School of Dental Medicine.

The study was supported by the National Institutes of Health (grants MH098742, MH118121, and MH109382) and the Cellular Neuroscience Core of the Institutional Intellectual and Developmental Disabilities Research Core of the Children’s Hospital of Philadelphia (grants HD26979 and GM008076).

Featured image: A confocal microscope image shows an oligodendrocyte in cell culture, labeled to show the cell nucleus in blue and myelin proteins in red, green, and yellow. Researchers from Penn and CHOP have shown that HIV infection prevents oligodendrocytes from maturing, leading to a reduction in white matter in the brain. (Image: Raj Putatunda)

Provided by Penn Today

Sight through Touch: The Secret Is in the Hand Movements (Neuroscience)

Recreating the “feel” of an object as participants move their fingers enables them to use their ingrained sensing strategies

Vision and touch employ a common strategy: To make use of both these senses, we must actively scan the environment. When we look at an object or scene, our eyes continuously survey the world by means of tiny movements; when exploring an object by touch, we move the tips of our fingers across its surface. Keeping this shared feature in mind, Weizmann Institute of Science researchers have designed a system that converts visual information into tactile signals, making it possible to “see” distant objects by touch.  

Converting information obtained with one sense into signals perceived by another – an approach known as sensory substitution – is a powerful means of studying human perception, and it holds promise for improving the lives of people with sensory disabilities, particularly the blind. But even though sensory substitution methods have been around for more than fifty years, none have been adopted by the blind community for everyday use.

(l-r) Prof. Ehud Ahissar, Dr. Amos Arieli, and Dr. Yael Zilbershtain-Kra. At the tips of their fingers © Weizmann Institute of Science and Technology

The Weizmann researchers assumed that the main obstacle has been the fact that most methods are incompatible with our natural perception strategies. In particular, these methods leave out the component referred to as active sensing. Thus, most vision-to-touch systems make finger movement unnecessary by converting the visual stimuli to vibratory skin stimulations.

Dr. Amos Arieli and Prof. Ehud Ahissar of the Neurobiology Department, together with intern Dr. Yael Zilbershtain-Kra, set themselves the goal to develop a vision-to-touch system that would more closely mimic the natural sense of touch. The idea was to enable the user to perceive information by actively exploring the environment, without the confusing intervention of artificial stimulation aids.

“Our system not just enables but, in fact, forces people to perform active sensing – that is, to move a hand in order to ‘see’ distant objects, much as they would to palpate a nearby object,” Arieli says. “The sensation occurs in their moving hand, as in regular touch.”

In the Weizmann system – called ASenSub – a small lightweight camera is attached to the user’s hand, and the image it captures is converted into tactile signals via an array of 96 pins placed under the tips of three fingers of the same hand. After the camera’s frame is mapped onto the pins, the height of each pin is determined by the brightness of the corresponding pixel in the frame. For example, if the camera scans a black triangle on a white surface, the pins corresponding to white pixels stay flat, while those mapped to black pixels are raised the moment the camera meets the triangle, producing a virtual feeling of palpating an embossed triangle.

In the ASenSub system, a special converter (1) creates tactile signals on the basis of visual information captured by a small camera (2) © Weizmann Institute of Science and Technology

Zilbershtain-Kra, with the help of ophthalmologist Dr. Shmuel Graffi, tested ASenSub in a series of experiments with sighted, blindfolded, participants and with people blind from birth. Both groups were at first asked to identify two-dimensional geometrical shapes, then three-dimensional objects, such as an apple, a toy rhinoceros and a pair of scissors. 

Following training of less than two and a half hours, both groups learned to identify objects correctly within less than 20 seconds – an unprecedented level of performance compared with existing vision-to-touch methods, which generally require lengthy training and enable perception that remains frustratingly slow. No less significant was the fact that the high performance was preserved over a long period: Participants invited for another series of experiments nearly two years later were quick to identify new shapes and objects using ASenSub.

“Our approach has demonstrated the brain’s amazing plasticity, which, in a way, enabled people to acquire a new ‘sense'”

In the triple array of pins sensed by the tips of three fingers (right), the raised pins (black) represent a black triangle captured by the camera © Weizmann Institute of Science and Technology

Yet another striking quality of ASenSub: It gave blind-from-birth participants a true “feel” for what it’s like to see objects at a distance. Says Graffi: “As a clinician, it was fascinating for me that they could actually experience optical properties they’d previously only heard about, such as shadows or the reduced size of distant objects.”

Sighted and blind participants performed equally well in the experiments, but analysis of results showed that their scanning strategies were different. Sighted people tended to focus to a great extent on the object’s unique feature, for example, the tip of the triangle, the rhino’s tale or scissor blades. In contrast, blind people encompassed each object along its entire contour, much as they commonly do to identify objects by unaided touch.

In other words, people relied on a strategy that’s most familiar to them through experience, which suggests that it’s learning and experience that mainly guide us in the use of our senses, rather than some inborn, genetically preprogrammed property of the brain. And this conclusion, in turn, suggests that in the future, it may be possible to teach people with sensory disabilities to make more optimal use of their senses.

“In broader terms, our study provides further support for the idea that natural sensing is primarily active,” Ahissar says. “We let people be active and to do so in an intuitive way, using their automatic perceptual systems that work with closed loop interactions between the brain and the world. This is what likely led to dramatic improvement compared to other vision-to-touch methods.” Zilbershtain-Kra adds: “Our approach has demonstrated the brain’s amazing plasticity, which, in a way, enabled people to acquire a new ‘sense.’ After seeing how fast they acquired a new perception method via active sensing, I’ve started applying similar principles when teaching students – making sure that they stay active throughout the learning process.”

The ASenSub system may be used for further fundamental studies of human perception, and it can be applied for daily use by the blind. For the latter purpose, it needs to be scaled down to a miniature device that can be worn as a glove or incorporated into a walking cane.

Science Numbers

Compared to other existing methods, the perceptional accuracy and speed of identifying both 2- and 3-D objects in the system that converts visual information into tactile signals, based on “active sensing”, have improved on average by 300% and 600% respectively.

Featured image: Yellow and red, showing the most frequently scanned areas, reveal the differences in scanning strategies employed by the sighted people (left) and the blind (right) while using ASenSub © Weizmann Institute of Science and Technology

Provided by Weizmann Institute of Science