New Usher Syndrome Gene Discovered
June 15, 2012 – Researchers conducting a genetic study of Old Order Amish and Mennonite populations have identified five new genes in which defects cause congenital diseases, including a previously unidentified type of Usher syndrome, type 3B. Caused by mutations in the gene HARS, Usher syndrome type 3B leads to progressive hearing loss and vision loss from retinitis pigmentosa. The condition can also cause balance problems.
Dr. Eric Puffenberger, lead investigator of the study from The Clinic for Special Children in Lancaster County, Pennsylvania, says that while HARS mutations were found among the Amish, he predicts that they will be found in other populations. “We expect that the condition is present around the world, but different HARS mutations will be found in different populations,” he says.
Dr. Stephen Rose, chief research officer of the Foundation, says that this discovery is important because finding the genetic defect for a retinal disease is a critical step in identifying targets for treatments. “Once we know the gene, we can begin to better understand why vision loss occurs,” he says. “With the genetic information, we can develop animal models for studying disease pathways and testing potential therapies.”
HARS is the 10th gene to be linked to Usher syndrome. Researchers believe that defects in HARS cause problems with the building of proteins that are necessary for the health and function of cells in the retina and the inner ear. But more work is needed to determine how the defects lead to hearing and vision loss.
The most common cause of combined vision and hearing loss, Usher syndrome affects approximately 45,000 people in the United States. The condition is divided into three groups — type 1 generally being the most severe, type 3 the least. Each group is subdivided by a letter representing a specific disease-causing gene.
In addition to finding a new gene linked to Usher syndrome, Dr. Puffenberger and his colleagues found new genes linked to: Lethal nenonatal rigidity and seizure syndrome; a non-syndromic form of mental retardation; microcephaly with chorioretinopathy; and symptomatic epilepsy and skull dysplasia.
Results of the study were published in the journal Public Library of Science.
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