Retinal dystrophies result from inherited defects in nearly every step of the so-called "visual cycle," a series of biochemical reactions known to occur in vertebrates, which recycles the molecule that enables light detection in eye cells. "Therapeutic approaches to tackle such retinal dystrophies are very limited," says Craig Montell, Ph.D., a professor of biological chemistry and of neuroscience at the Johns Hopkins University School of Medicine. "So it's useful to take advantage of simpler experimental model organisms, like fruit flies, to tease apart complex systems like vision, then translate that to use in vertebrates."
This visual cycle previously was not thought to exist in invertebrate eyes. In fact, according to Montell, those who study fly vision long thought that as the molecules in the fly eye responsible for capturing photons of light can be regenerated by absorbing more light, they don't need a visual cycle for the cells to reuse the molecule.
Curious about whether one particular enzyme in the fly eye — pigment-cell-enriched dehydrogenase (PDH) — plays a role in the fly's ability to make the molecules that sense light, Montell and his research team generated flies carrying a mutation in the gene encoding PDH. They found the newly hatched flies lacking PDH to be totally normal in their ability to respond to light.
"It was a surprise. Initially the PDH looked dispensable as the visual responses were normal, but over time the pigment degraded," says Montell. "This led us to ask the question: If PDH doesn't make new light-sensing molecules, and flies can recycle them using light anyway, why are these flies losing their light-detecting molecules and consequently their sight?"
As it turns out, Montell and his team found PDH is required to help recycle the used light-capturing molecules in a previously unrecognized visual cycle in flies. Flies can recycle the molecules by absorbing light, but eventually the protein that holds the molecules in the cells needs to be replaced with new protein. When this happens the biochemical visual cycle is needed to regenerate the light sensing molecules. Over time, in pdh mutant flies, without a functional visual cycle, the used light-sensitive molecules were not regenerated causing cells in the retina to die, leading to vision loss.
To get an idea of how comparable the visual cycle is in flies and mammals, the team replaced the fly gene for PDH with a gene for a similar mammalian enzyme. These flies had normal electrical activity in cells of the retina in response to light, were able to maintain proper levels of light sensitive molecules, and had healthy retinas. This experiment showed the researchers that there are similarities in the visual cycles in mammals and flies.
"Flies are a good model in which to study and test new therapies for retinal degeneration," says Montell. "This research opens the door to using flies as a way to look for drugs to reduce human retinal degeneration due to defects in the visual cycle."
This study was funded by the National Eye Institute.
Authors of the text were Xiaoyue Wang, Tao Wang, Yuchen Jiao and Craig Montell from Johns Hopkins University and Johannes von Lintig from the Case Western Reserve University School of Medicine, Cleveland.On the Web:
Current Biology: http://www.cell.com/current-biology/
Audrey Huang | EurekAlert!
Make way for the mini flying machines
21.03.2018 | American Chemical Society
New 4-D printer could reshape the world we live in
21.03.2018 | American Chemical Society
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.
In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...
Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...
19.03.2018 | Event News
16.03.2018 | Event News
13.03.2018 | Event News
21.03.2018 | Physics and Astronomy
21.03.2018 | Materials Sciences
21.03.2018 | Life Sciences