In Europe roughly one child in 4,000 is born with a hereditary retina disorder. The most common disorder is retinitis pigmentosa, of which there are a number of different variants. Although ophthalmologists can diagnose the destruction of nerve cells in the retina, in most cases they can’t offer patients any treatment. In addition, the way the disorder develops varies from patient to patient. Some patients go completely blind, in others their vision is “only” seriously impaired. “This uncertainty is there in the back of the minds of those affected, ” says Franz Badura, a member of the board of the Pro Retina Foundation and head of the Department of Research and Therapy of the self-help organization Pro Retina Deutschland e.V.
So far researchers have succeeded in characterizing almost 140 genes and in finding the genes that cause the hereditary eye disorder. “There are about 40 different genes involved in the various forms of retinitis pigmentosa alone,“ says Professor Bernhard Weber, director of the Institute for Human Genetics at the University of Regensburg. This enormous genetic variety is one reason why until now human geneticists have only been able to find the responsible gene in 10-20 percent of patients. In this situation it is, for example, difficult or even impossible to predict how great a child’s risk is of developing the disease.
This will now be changed by the Ret Chip. The chip contains 300,000 base pairs – the building blocks of the genetic substance DNA – and 72 different genes, which can be analyzed in parallel in a single process. As well as the genes that cause the different forms of retinitis pigmentosa and the hereditary forms of macula degeneration, the chip also includes a group of genes which not only cause the retina to degenerate but are also responsible for problems in other organs, such as Usher syndrome and Bardet-Biedl syndrome.“The new technology will now allow us to test a very large number of genes simultaneously, thus increasing the likelihood of detecting a mutation and thus the cause of the disease. That is of course a huge step forward,” Weber says.
More precise diagnosis may make it easier in the future for doctors to make a prognosis, i. e., to predict how the disease will develop in individual cases and thus allay the fears and uncertainty of many patients. “In Morbus Stargardt, for example, the mutation allows us to see whether the corresponding protein is actually being produced or to what extent it is still active. We can thus say approximately how the disease will develop,” Weber explains.
Initially the Regensburg researchers will be subjecting the chip to critical tests in collaboration with several centres in Germany. At the centres in Berlin, Bonn-Siegburg, Tübingen and Regensburg patients will undergo clinical examinations and will receive a genetic consultation. There a blood sample will be taken that will then be genetically analyzed back in Regensburg. “In view of the new approaches in the field of gene therapy the status of molecular diagnostics is growing,” Franz Badura stresses. “It will become increasingly important for patients to know the genetic causes of their disorders.”
The Pro Retina Foundation for the Prevention of Blindness, supported by the self-help organization for people with degeneration of the retina, Pro Retina e.V., provided 250,000 euros in funding for the development of the Ret Chip. “Our organization has been involved in research funding for many years and has so far raised one million euros,” says Dr. Claus Gehrig, chairman of the patients’ organization. “The Ret-Chip will clearly have a direct link to patients,” Gehrig continued. “That is more than just basic research. We hope very much that the new technology will make the diagnosis and prognosis of hereditary retina disorders easier.”
It is not yet clear exactly how expensive a Ret-Chip examination will be, since not all the genes on the chip need to be used fully in every case, but Weber thinks it will cost between 3,000 and 4,000 euros. It is expected that the cost will be borne by the health insurance funds.
Barbara Ritzert | alfa
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