Harvard Medical School researchers have discovered nearly all the genes responsible for vision, which could help in diagnosing and treating blinding diseases.Macular degeneration affects 20 per cent of people over age 75. Discovery of the full set of photoreceptor genes expressed int he retinal cells, which was made in mice, could also lead to new methods for preserving and restoring the vision of those affected.
Photoreceptors - cones, which are activated by light, and rods, which operate only at night - are susceptible to a wide variety of inherited diseases, suchas retinitis pigmentosa and cone-rod dystrophy. The newly identified gene set, which is reported in the journal Cell, could lead to the identification of genes which, when mutated, cause these degenerative diseases.
According to Connie Cepko, HMS professor of genetics and senior author of the study the search for disease genes was cut by 100-fold. People at risk for inherited retinal disease - estimated to be one person in 2000 - could be screened for these mutants. The newly identified genetic database could lead to new methods for slowing or staying the course of disease once it occurs. "The more we know about how the genes work, the better we will be able to find ways to treat, and possibly, prevent disease," said Cepko. Information about how the genes work inside photoreceptors - which genes are turned on and when -could even lead to ways to replace dead or damaged cells. "Can we manipulate these genes in such a way to coax stem cells to becoem photoreceptors?" she said.
A little more than half of the mutant genes for degenerative diseases of the retina had been identified when Cepko began his study. Using a computer program that compares snippets of genetic material taken from mouse retinal tissue with a huge genetic database from the mouse and human genome project, the researchers identified approximately 300 photoreceptor genes - five times the number that were previously known. Two hundred and sixty four of these were newly identified genes. Of these, 241 had homologs in humans.
"This makes photoreceptors the most well characterised cell type in the body," said Cepko. The database provides a genetic lantern by which to see the goings on inside photoreceptors. Fro ex, by removing a gene, and hence its protein, we can understand how that protein usually functions in cells.
Thus the research says that this is a "boon for human beings"..