is not expressed as the rod and cone photoreceptor cells are
destroyed. The scientists found that medium wavelength cone
. Opsin is usually expressed only in
cone photoreceptor cells and makes it sensitive to green-yellow light.
Prof. Isacoff (molecular
and cell biology and director of the Helen Willis Neuroscience Institute) who
specializes in G-protein coupled receptors in the nervous system thought that
opsin would reconnect to the signaling system in the retinal ganglial cells.
Prior to trying opsin, the team tried rhodopsin found in rods. The introduction
of rhodopsin in mice activated the light sensitivity of the degenerated rods
and cones and the mice were able to faintly detect light. However, the team
found rhodopsin to be too slow and also failed to enable image and object
The research team
then used an adeno-associated virus to target retinal ganglion cells and loaded
it with the gene for green opsin. After being injected into the eye, the virus
carried the gene into the ganglion cells insensitive to light
and made them sensitive to light thereby restoring sight.
Opsin responded 10 times
faster than rhodopsin
and the researchers found that 90% of ganglion
cells became light sensitive. A blind mouse affected by retinitis pigmentosa
regained enough sight to
distinguish between parallel and horizontal lines on an iPad.
Isacoff and Flannery
(molecular and cell biology and school of optometry) went one step further and
tested if the mice were able to recognize three-dimensional objects. The team
is further enthusiastic about refining the therapy to enable color vision and
increase visual acuity.
Isacoff and Flannery said that this simple solution could have been worked out 20 years ago. The
team reported the study in an article in Nature Communications
Currently, Isacoff and
Flannery are raising funds to take this successful gene therapy into human
trials which they hope can be worked out in the next three years. Isacoff
believes that this therapy can be successfully used in humans to restore
enough vision to move around.
- Berry, Michael H., Amy Holt, Autoosa Salari, Julia Veit, Meike Visel, Joshua Levitz, Krisha Aghi et al. "Restoration of high-sensitivity and adapting vision with a cone opsin." Nature Communications 10, no. 1 (2019): 1221. Retrieved on 20 March 2019 from