Children with Usher syndrome type 2 are born with a hearing loss and develop the first symptoms of deteriorating vision around puberty. In addition to an increasingly narrow field of vision, some may also have a (significant) increase in hearing loss.
52% of all people with Usher syndrome have mutations in the USH2a gene. USH2c is the third most common form of Usher syndrome.
Although more than half of all people suffering from Usher Syndrome has mutations in the USH2A gene, this gene is not globally targeted in the current studies into the development of gene replacement therapy. This is because of the size of the protein coding sequence of the USH2A gene (> 15,000 bases!). A DNA fragment of such a length does simply not fit into the currently used gene therapeutic vectors (harmless viruses used for packaging genetic material and delivering this at its destination).
In the ‘minigenes’ project, which was co-financed by Stichting Ushersyndroom, the USH2A gene is artificially made smaller by taking specific parts of the gene and sticking these together (= minigene). These minigenes were inserted in the current vectors for application of genetic therapy. Subsequently, the therapeutic effect of shortened USH2A protein was tested in the zebrafish models. These results will be published shortly.
The next step will be a pre-clinical treatment method for USH2A-related retina degeneration. For this additional studies are to be conducted in order to demonstrate the safety and effectiveness of the treatment method. These additional studies cost money. Will you help?