A flagship molecule that prevents vision and behavioral disorders in mice

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Nestled deep in the middle of the vertebrate brain is a center of multisensory integration and movement control called the superior colliculus. In rodents, this region of the brain integrates multisensory inputs (visual cues, sounds, tactile information, and smells) and provides output signals to a variety of motor control centers in the brain, coordinating the animal’s movements in response. to its environment.

Although the superior colliculus makes up a relatively small portion of brain volume in mice, it is a processing powerhouse, in part because it is made up of precise cell layers that organize and refine signaling patterns.

Now, a team of researchers led by Michael Fox, a professor at VTC’s Fralin Biomedical Research Institute, has discovered a key link in how the layers of this treatment center develop to decode the eye’s visual cues. and regulate key survival instincts in mice. The study was published in the Proceedings of the National Academy of Sciences.

“This region of the brain is interesting because it integrates data from multiple sensory inputs, helps form a binocular picture of the world, and then dictates the animal’s innate behaviors, such as running away from a predator or hunting for prey, depending on these data, ”said Fox, who is also director of the School of Neuroscience at Virginia Tech College of Science.

Early in brain development, weeks before a mouse first opens its eyes, neurons extend long axonal processes from the back of the eye, forming the optic nerve. These growing cells eventually branch out to form thousands of complex connections in specific regions of the brain, including the superior colliculus.

How these cells know where to migrate remains largely a mystery, Fox says. But understanding this key phase of development could potentially provide new information that could help researchers in future studies identify ways to regenerate injured optic nerve fibers.

“If our goal is to ever regenerate damaged brain circuitry to restore vision, we first need to know how to get the cell’s axons to develop at a specific destination in the brain,” Fox said.

Fox and his team investigated how a specific subtype of optic nerve cells, ipsilateral retinal ganglion cells, reaches the superior colliculus during brain development.

The researchers used a virus to identify the types of neurons with which the retinal ganglion cells made connections once inside the superior colliculus. This led them to identify two proteins that chaperone this circuit formation.

A protein, released by a type of excitatory neuron in the superior colliculus, draws the optic nerve cell closer like a molecular beacon. Once the migrating cell is in the right place, this protein attaches to a perfectly matched receptor protein located on the membrane of the nerve cell. This chemical reaction tells the cell that it has reached its destination.

When the flagship molecule, called nephronectin, is absent, a visual layer of the upper colliculus does not form properly and mice find it difficult to hunt their prey.

The superior mouse colliculus has been studied extensively for over 60 years. Although it is present in all species of mammals, in humans, this region of the brain occupies less relative volume and is thought to play a role in stabilizing our image of a moving world by controlling the movements of the head. , neck and eyes.

Fox says this study represents a first research collaboration between the National Children’s Hospital and researchers at the Fralin Biomedical Research Institute. He remembers when Michael Friedlander, vice president of health science and technology at Virginia Tech, hooked up Fox and Jason Triplett, a senior researcher at Children’s National Hospital in Washington, DC, seven years ago.

“We talked about studying how these neurons project onto the colliculus in 2013 and have since worked together on many grant-funded projects,” Fox said. “This document was born from those early discussions.”

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More information:
Jianmin Su et al, A cell-ECM mechanism for connecting the ipsilateral eye to the brain, Proceedings of the National Academy of Sciences (2021). DOI: 10.1073 / pnas.2104343118

Provided by Virginia Tech

Quote: A flagship molecule that prevents vision, behavioral problems in mice (2021, October 18) retrieved October 18, 2021 from https://phys.org/news/2021-10-beacon-molecule-vision-behavioral- problems.html

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