BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: zebrafish

Zebrafish: The Cure to Vision Loss?

Sight is one way in which we, along with many animals, interact with the world. Unfortunately, some people are unable to interact with the world in that same manner. Whether it is hereditary blindness or vision loss due to a neurodegenerative disease, vision loss and eye damage is difficult to fix, especially at a neurological level.

Neurons are present throughout the body and are connected via the nervous system. Their function is to transmit information to the brain and the rest of the body. They do this by signaling other cells by what is called neuronal firing. Individual nerve cells send electrical impulses to others allowing the message to reach other parts of the body. Simply put in the case of eyes and sight, the lens collect and bend the light and that information is sent through the optic nerve to the brain which then processes the information to produce an image. Therefore, if the neurons in the eye are damaged, that information cannot be collected and sent to the brain.

One such eye problem is Macular Degeneration which targets the macula. The macula is the central part of the retina that collects details images from the center of one’s field of vision. Damage to the macula results in a loss of central vision. Those who have it still retain their peripheral vision, but if the case is severe enough, they are deemed legally blind. As of now, there is no known cure.

However, Johns Hopkins Medicine researchers have been studying some animals’ ability to regrow neurons. Fish, along with other cold-blooded animals have the ability to repair eye neurons after injury, and for a long time it was thought that these genes were not present in mammals. According to Seth Blackshaw, professor of neuroscience at John Hopkins University, “[there is] the potential for regeneration is there in mammals, including humans, but some evolutionary pressure has turned it off” (ScienceDaily.com).

Blackshaw’s team has been studying the supportive cells in the back of the eye in zebrafish. These cells, known as the Müller glia, are able to repair the retina by growing neurons. Blackshaw’s team examined the retinal damage and repair of zebrafish, chickens, and mice. They found that while chicken and mice both have the capacity and gene pathways to generate neurons, the transcription factors were blocked so that the neurons don’t regenerate. Blackshaw suspects that the inability to regenerate neurons is due to the fact that animals that are more prone to disease in the brain, or other neurological tissue, may have lost this regenerative ability in order to protect other brain cells.

All of this is very exciting news and I think it is fascinating that studying cells from a fish could potentially help people who suffer from vision loss. I never would have thought that an animal that seems so different from us could help solve a problem that people have been dealing with for centuries. However, I think it is the fact that perhaps we aren’t so different from animals, at least on a biological level, that we are able to study them in order to better understand ourselves. For example, as Blackshaw and his team has discovered, we have those same gene pathways that allow zebrafish to regenerate neurons. And while ours don’t work the same way as of now, they are still present despite years and years of evolution. In the end, I think that the similarities we share with other animals is something to think about.

Just Keep Swimming…and Fixing Paralysis!

 

Zebrafish (Danio rerio)

Zebrafish (Danio rerio)- from Flickr

The zebrafish may just look like a cute aquatic animal, but they actually have a unique power that humans don’t: they can heal a severed spinal cord. While this uncanny ability sounds almost magical, it can be explained by the work of a certain protein, CTGF (connective tissue growth factor), that humans have as well. Because of this commonality, recent research conducted by Duke University suggests that by learning from the mechanism that allows the Zebrafish to do this, humans may eventually be able to regenerate their lost spinal tissue!

Essentially, the zebrafish is able to regenerate their spinal cord by forming a cellular bridge across the damaged or missing area. They can be fully healed in as little as 8 weeks! But how is this “bridge” possible on a molecular level? When the fish get injured, dozens of genes get activated. Seven of these genes code for proteins that are secreted from cells. The researchers at Duke found that CTGF, one of these proteins, is crucial to the bridge-making process. They found this by looking at the glia, which are the supporting cells that help initially form the bridge before the arrival of nerve cells. After forming the bridge, CTGF levels rose marginally in these glia. When the researchers genetically deleted CTGF from the glia, the whole regeneration process failed. This research proved exciting because humans also have a very similar form of CTGF, and when they added this human-version of the gene to the glia, regeneration was even faster, only taking 2 weeks! The researchers even discovered which of the four parts of CTGF was the important one in this regeneration phenomenon, which in the future would make it easier to create therapies modeled after this part for humans.

However, using this knowledge to help human tissue regeneration is not as straightforward as it may seem. Mammals such as ourselves form scar tissue around damaged areas, complicating the matter further. The group plans on experimenting with other mammals, namely mice to compare and contrast their CTGF levels with those of zebrafish. Do you think that CTGF research is the best way to achieve human tissue regeneration? Is there any way to prevent scar tissue from forming around our wounds? Let me know in the comments!

 

Original Article: https://www.sciencedaily.com/releases/2016/11/161103142321.htm

Photo Credit to Tohru Murakami: https://flic.kr/p/nb2gGH

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