[Summary]

 A research group led by Associate Professor Hiroshi Tomita and Assistant Professor Eriko Sugano at Tohoku University Institute for International Advanced Interdisciplinary Research has succeeded in explaining visual property acquired by introducing channelrhodopsin 2 (ChR2). The research group has made genetically-modified (transgenic) rats that have naturally ChR2, and showed that sight acquired by ChR2 has the same function as normal vision. Gene therapy using ChR2 is expected to be a medical cure to recover visual function.

  The research group has already reported the recovery of visual function by transferring ChR2 gene. However, it has not been clarified that how much visual acuity will be recovered when ChR2 is introduced into whole cells including various types of neurons play many roles. The group has made genetically-modified rats that have naturally ChR2, and conducted behavioral studies of sight acquired by ChR2. The experiment found out that genetically-modified blind rats can recognize revolving stripe pattern that has shading of blue-black in various widths. The result showed that genetically-modified rats have the same visual function as those with normal sight. It may be possible to provide vision that recognizes shapes or movement of objects by introducing ChR2 into retina.

 The research has been conducted in collaboration with Graduate School of Life Sciences, Graduate School of Medicine, Tohoku University, and National Institute for Physiological Sciences (NIPS). The research results are produced by the aide of the following:

Ministry of Health, Labor and Welfare
Ministry of Education, Culture, Sports, Science and Technology
Suzuken Memorial Foundation
Japan Science and Technology Agency (JST)
Japanese　Retinitis　Pigmentosa　Society (JRPS)

 The research results have been published in Public Library of Science (PLoS) ONE, a highly praised American journal in science and medicine, on November 4, 2009.

[Detail]
 After photoreceptor cells in retina that first acquires external information are damaged, retina can not receive optical information and visual function will be lost even if other neuronal cells in retina perform normally. Age-related macular degeneration (AMD) and retinitis pigmentosa rank among the highest causes of vision loss. An effective therapy has not been established, and there is no method to recover visual function. These diseases progress in various ways, and not necessarily lead to vision loss. It is known that ganglion cells in retina remain the function to transmit visual information to the brain even after photoreceptor cells lose its function thoroughly.

  The research group has conducted studies on the recovery of visual function by introducing ChR2 into ganglion cells to be able to acquire optical information. The group has already showed that genetically-blind rats recovered sight by the new therapy in electrophysiological studies, and that these rats can recognize stripe pattern.

 The targeted ganglion cells for the transfer of ChR2 has various types, and each type plays an important role in processing visual information such as contrast enhancement at retina.　In previous studies, what visual information is processed has not been clarified because all ganglion cells have produced ChR2-protein.

 The research group has made genetically-modified rats that specifically produce ChR2-protein in ganglion cells. The study explains visual property in genetically modified rats produced ChR2 protein into the ganglion cells. Genetically modified rats, which has photo-sensensitive ganglion cells, show a high contrast sensitivity at a spatial frequency around 0.1cycle/degree (wide stripe pattern), compared to those with normal sight that show the highest contrast sensitivity at a spatial frequency of 0.2cycle/degree. The former contrast sensitivity is higher than the latter. When discriminating blue-black stripe pattern, blind genetically-modified rats recovered almost the same visual function as normal vision, and can discriminate wide stripe pattern at the lower contrast. The research results shows that there is a high possibility to recover vision that recognizes shapes or movement of objects when all types of ganglion cells change into photoreceptor cells by introducing ChR2.

[Contact]
Associate Professor Hiroshi Tomita
Tohoku University Institute for International Advanced Interdisciplinary Research
Tel: +81-22-717-8207

Akira Nakamura, Administrative Staff
Comprehensive Strategy Research and Education Planning Office
Tel: +81-22-795-5746