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!
A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
On the way to developing a new active ingredient against chronic infections
18.08.2017 | Deutsches Zentrum für Infektionsforschung
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
18.08.2017 | Life Sciences
18.08.2017 | Physics and Astronomy
18.08.2017 | Materials Sciences