Researchers at Washington University School of Medicine in St. Louis have identified DNA elements that control when and where genes linked to blindness are “switched on,” a finding that may help treat some of the almost 200 inherited forms of blindness. Using a computational analysis of DNA to search for elements that can turn on genes in the photoreceptor cells of the eye, the investigators have identified hundreds of potential cis-regulatory elements (DNA segments involved in activating and deactivating genes). They confirmed 19 of these elements, more than doubling the number known to scientists. The newly discovered elements can be used as switches to activate blindness therapies; with further studies of the new and previously established sites, the researchers expect to determine the basic rules that appear to govern how the sites work. The results of this study are also being used to design gene therapy vectors for a form of Leber’s congenital amaurosis.