Stories about: neuroscience

How do we sense moonlight? Daylight? There’s a cell for that

environmental light sensing must span a wide spectrum of light intensities

To run our circadian clocks, regulate sleep and control hormone levels, we rely on light-sensing neurons known as M1 ganglion cell photoreceptors. Separate from the retina’s rods and cones, M1 cells specialize in “non-image” vision and function even in people who are blind.

Reporting in today’s Cell, neuroscientists at Boston Children’s Hospital describe an unexpected system that M1 cells use to sense changing amounts of environmental illumination. They found that the cells divvy up the job, with particular neurons tuned to different ranges of light intensity.

“As the earth turns, the level of illumination ranges across many orders of magnitude, from starlight to full daylight,” says Michael Do, PhD, of the F.M. Kirby Neurobiology Center at Boston Children’s Hospital, senior author on the paper. “How do you build a sensory system that covers such a broad range? It seems like a straightforward problem, but the solution we found was a lot more complex than expected.”

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Novel therapeutic cocktail could restore fine motor skills after spinal cord injury and stroke

CST axons sprout from intact to injured side
Therapeutic mixture induces sprouting of axons from healthy (L) into the injured (R) side of the spinal cord.

Neuron cells have long finger-like structures, called axons, that extend outward to conduct impulses and transmit information to other neurons and muscle fibers. After spinal cord injury or stroke, axons originating in the brain’s cortex and along the spinal cord become damaged, disrupting motor skills. Now, reported today in Neuron, a team of scientists at Boston Children’s Hospital has developed a method to promote axon regrowth after injury.

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From mice to humans: Genetic syndromes may be key to finding autism treatment

Boy and a mouse eye-to-eye
(Aliaksei Lasevich/stock.adobe.com)

A beautiful, happy little girl, Emma is the apple of her parents’ eyes and adored by her older sister. The only aspect of her day that is different from any other 6-month-old’s is the medicine she receives twice a day as part of a clinical trial for tuberous sclerosis complex (TSC).

Emma’s mother was just 20 weeks pregnant when she first heard the words “tuberous sclerosis,” a rare genetic condition that causes tumors to grow in various organs of the body. Prenatal imaging showed multiple benign tumors in Emma’s heart.

Emma displays no symptoms of her disease, except for random “spikes” on her electroencephalogram (EEG) picked up by her doctors at Boston Children’s Hospital. The medication she is receiving is part of the Preventing Epilepsy Using Vigabatrin in Infants with TSC (PREVeNT) trial. Her mother desperately hopes it is the active antiepileptic drug, vigabatrin, rather than placebo.

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Late-breaking mutations may play an important role in autism

somatic mutations in autism may occur at different times in the embryo
Post-zygotic mutations, which arise spontaneously in an embryonic cell after sperm meets egg, are important players in autism spectrum disorder, a large study suggests.

Over the past decade, mutations to more than 60 different genes have been linked with autism spectrum disorder (ASD), including de novo mutations, which occur spontaneously and aren’t inherited. But much of autism still remains unexplained.

A new study of nearly 6,000 families implicates a hard-to-find category of de novo mutations: those that occur after conception, and therefore affect only a subset of cells. Findings were published today in Nature Neuroscience.

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What genetic changes gave us the human brain? A $10 million center aims to find out

genes and human brain evolution

How did our distinctive brains evolve? What genetic changes, coupled with natural selection, gave us language? What allowed modern humans to form complex societies, pursue science, create art?

While we have some understanding of the genes that differentiate us from other primates, that knowledge cannot fully explain human brain evolution. But with a $10 million grant to some of Boston’s most highly evolved minds in genetics, genomics, neuroscience and human evolution, some answers may emerge in the coming years.

The Seattle-based Paul G. Allen Frontiers Group today announced the creation of an Allen Discovery Center for Human Brain Evolution at Boston Children’s Hospital and Harvard Medical School. It will be led by Christopher A. Walsh, MD, PhD, chief of the Division of Genetics and Genomics at Boston Children’s and a Howard Hughes Medical Institute investigator.

“To understand when and how our modern brains evolved, we need to take a multi-pronged approach that will reflect how evolution works in nature, and identifies how experience and environment affect the genes that gave rise to modern human behavior,” Walsh says.

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A new inlet to treating neurological disease

Image of brains showing red tracer dye, indicating passage of molecules through the blood-brain barrier
These brain images tell a story about the blood-brain barrier: At left, the brain before injection of red tracer dye. At center, an injection of tracer dye shows only a small amount of molecules can infiltrate the blood brain barrier. At right, a new approach for crossing the blood-brain barrier increases the tracer’s penetration into brain tissue.

The blood-brain barrier was designed by nature to protect the brain and central nervous system (CNS) from toxins and other would-be invaders in the body’s circulating blood. Made up of tightly-packed cells, the barrier allows nutrients to pass into the CNS and waste products from the brain to be flushed out, while blocking entry of harmful substances.

A dysfunctional blood-brain barrier can contribute to CNS diseases including Alzheimer’s and multiple sclerosis (MS). But, ironically, the same blood-brain barrier can keep out drugs intended to treat CNS disease. Scientists have long been seeking ways to overcome this obstacle.

Now, Timothy Hla, PhD, and members of his laboratory in the Boston Children’s Hospital Vascular Biology Program have found a way to selectively control openings in the blood brain barrier to allow passage of small drug molecules.

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Optic nerve regeneration: One approach doesn’t fit all

alpha retinal ganglion cells optic nerve regeneration
Alpha-type retinal ganglion cells (RGCs) in part of an intact mouse retina. The cell axons lead to the optic nerve head (top right) and then exit into the optic nerve. The alpha RGCs are killed by the transcription factor SOX11 despite its pro-regenerative effect on other types of RGCs. (Fengfeng Bei)

Getting a damaged optic nerve to regenerate is vital to restoring vision in people blinded through nerve trauma or disease. A variety of growth-promoting factors have been shown to help the optic nerve’s retinal ganglion cells regenerate their axons, but we are still far from restoring vision. A new study published yesterday in Neuron underscores the complexity of the problem.

A research team led by Fengfeng Bei, PhD, of Brigham and Women’s Hospital, Zhigang He, PhD, and Michael Norsworthy, PhD, of Boston Children’s Hospital, and Giovanni Coppola, MD, of UCLA conducted a screen for transcription factors that regulate the early differentiation of RGCs, when axon growth is initiated. While one factor, SOX11, appeared to be critical in helping certain kinds of RGCs regenerate their axons, it simultaneously killed another type — alpha-RGCS (above)— when tested in a mouse model.

At least 30 types of retinal ganglion cell message the brain via the optic nerve. “The goal will be to regenerate as many subtypes of neurons as possible,” says Bei. “Our results here suggest that different subtypes of neurons may respond differently to the same factors.”

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Science Seen: Disrupted developmental genes cause ‘split brain’

split brain syndrome
The two halves of the brain on the right, from a patient with the DCC mutation, are almost completely disconnected. The mutation — first recognized in worms — prevents axons (nerve fibers) from crossing the midline of the brain by interfering with guidance cues. Image courtesy Ellen Grant, MD, director, Fetal-Neonatal Neuroimaging and Developmental Science Center.

Tim Yu, MD, PhD, a neurologist and genomics researcher at Boston Children’s Hospital, was studying autism genes when he saw something on a list that rang a bell. It was a mutation that completely knocked out the so-called Deleted in Colorectal Carcinoma gene (DCC), originally identified in cancer patients. The mutation wasn’t in a patient with autism, but in a control group of patients with brain malformations he’d been studying in the lab of Chris Walsh, MD, PhD.

Yu’s mind went back more than 20 years. As a graduate student at University of California, San Francisco, he’d conducted research in roundworms, studying genetic mutations that made the worms, which normally move in smooth S-shaped undulations, move awkwardly and erratically.

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Science Seen: Brain myelination in tuberous sclerosis complex

tuberous sclerosis brain myelination improved with CTGF deletion

Tuberous sclerosis complex (TSC) strikes about 1 in 6,000 people and is marked by numerous benign tumors in the brain, kidneys, heart, lungs and other tissues. Children with TSC often have epilepsy, intellectual disability and/or autism, showing disorganized white matter in their brains. Work in the lab of Mustafa Sahin, MD, PhD, has shown that the TSC1 mutation disrupts the brain’s ability to adequately wrap its nerve fibers in myelin, the insulating coating that enhances nerves’ ability to conduct signals. A new study from the lab shows why: neurons lacking functional TSC1 secrete increased amounts of connective tissue growth factor (CTGF). This impairs the development of oligodendrocytes, the cells that do the myelinating. Here, electron microscopy in a TSC mouse model shows a decreased number of nerve fibers wrapped in myelin (dark ovals) on the left. On the right, genetic deletion of CTGF increases myelination. Sahin plans to delve further to develop potential pharmaceutical approaches to restore myelination in TSC. Read more in the Journal of Experimental Medicine. (Image: Ebru Ercan et al.)

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Zinc chelation: A better way to regenerate the optic nerve?

optic nerve zinc chelation

For more than two decades, researchers have tried to regenerate the injured optic nerve using different growth factors and/or agents that overcome natural growth inhibition. They’ve had partial success, sometimes even restoring rudimentary elements of vision in mouse models.

But at best, these methods get only about 1 percent of the injured nerve fibers to regenerate and reconnect the retina to the brain. That’s because most of the damaged cells, known as retinal ganglion cells (RGCs), eventually die, says Larry Benowitz, PhD, of the F.M. Kirby Neurobiology Center at Boston Children’s Hospital.

Benowitz and colleagues now show a surprising new approach that gets RGCs to live longer and regenerate robustly: using chelating agents to bind up zinc that’s released as a result of the injury.

These studies, too, were done in mice. If the findings hold up in human studies, they could spell hope for people with optic nerve injury due to trauma, glaucoma or other causes, and possibly even spinal cord injury.

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