Stories about: neuroscience

Sensing light without sight: The visual system’s ‘third eye’

ipRGCs provide non-image vision, responding to light independently of rods and cones
Intrinsically photosensitive retinal ganglion cells, rich in melanopsin, respond to light independently of rods and cones. (Courtesy Elliott Milner, PhD)

Michael Tri H. Do, PhD, is an investigator in the F.M. Kirby Neurobiology Center at Boston Children’s Hospital and an assistant professor of neurology at Harvard Medical School.

Light affects us even without impinging on our awareness. In 1995, Charles Czeisler and colleagues at Harvard Medical School described people who lacked visual perception due to retinal degeneration, but nevertheless responded to light subconsciously — despite being blind, their melatonin level was suppressed, and they appeared to synchronize their circadian clock with the solar day. Across the pond at Oxford, Russell Foster and colleagues were finding the same in mice, and learned that these responses began in the eye.

These discoveries spurred an intense research effort that continues to this day. What system confers subconscious sight, and how does it differ from the system that generates visual experience?

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Mutations accumulate in our brain cells as we age. Do they explain cognitive loss?

the aging brain - do DNA mutations in neurons account for cognitive loss?

Scientists have long wondered whether somatic, or non-inherited, mutations play a role in aging and brain degeneration. But until recently, there was no good technology to test this idea.

Enter whole-genome sequencing of individual neurons. This fairly new technique has shown that our brain cells have a great deal of DNA diversity, making neurons somewhat like snowflakes. In a study published online today in Science, the same single-neuron technique provides strong evidence that our brains acquire genetic mutations over time.

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What’s trending in neurological drug development?

Advanced MRI scans of the brain showing neural network connections
Credit: Boston Children’s Hospital

Momentum has been growing in the field of neuroscience in our ability to understand and treat various disorders affecting the brain, central nervous system, neuromuscular network and more. So what are the key ways that researchers and drug industry collaborators are discovering new therapies for preventing or reversing neurological disease?

Experts weighed in recently to offer their insights.

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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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