About Retinitis Pigmentosa (RP) and RNU4-2/RNU6 Disease
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Overview
RP is an inherited eye disease that causes gradual loss of vision over time. People with RP often first notice difficulty seeing at night or in dim light, followed by a loss in peripheral and then central vision. The disease progresses over years and usually leads to severe visual impairment or blindness.
Recent scientific discoveries have identified a new cause of RP involving 5 closely related genes called RNU4-2, RNU6-1, RNU6-2, RNU6-8, and RNU6-9. This discovery was published in January 2026 and ended a long diagnostic odyssey for many families. But many families still are searching for a diagnosis.
The discovery of RNU4 and RNU6 related retinal disease has opened an important new chapter in inherited blindness research. Scientists are now working to better understand how these mutations damage the retina and develop treatments to slow, stop, or someday reverse vision loss. CURE4/6 was created to help accelerate that effort and bring together families, researchers, physicians, and advocates focused on finding answers and cures.
Gene-specific pages: RNU4-2 retinitis pigmentosa and RNU6 retinitis pigmentosa.
How RNU4-2 and RNU6 mutations cause RP
Every part of the eye can be affected by different genetic diseases. RP affects the retina, the part of the eye that converts images from the outside world into electrical signals that are sent to the brain. RP begins with loss of night vision and usually leads to severe visual impairment. Mutations in hundreds of different genes can cause RP. CURE4/6 is dedicated to finding treatments for one specific type of genetic mutation that causes RP: those that affect the RNU genes.
To better understand how these specific mutations cause RP, imagine a book describing how to build a house. This book has 23 chapters — like the 23 pairs of human chromosomes. But each chapter contains thousands of pages of details that explain what is needed to build a house. Each chapter has the main building plans, every engineering detail, every alternate design, every correction note, every footnote, and every tiny technical specification imaginable. The book doesn't simply say, "Install the roof." Instead, it includes every nail size, every measurement, every possible roofing material, every engineering calculation, and every special circumstance that might apply in rare situations. Any error in one of those details will cause the house to have defects. If there are no errors in the text, the house will be perfectly built.
The author of this enormous book wants to publish a much shorter version that contains the minimum amount of information needed to start building the house. He expects that the reader will consult all the thousands of pages that have been edited out and stored for reference, if needed.
To accomplish this goal, the author hires a team of editors to go over every single word and remove every detail an average person wouldn't need. The author instructs the team of editors to remove 98% of the information and store it away. Each team member has a specific job to do in the editing process: proofread the text, review the content and decide what is necessary and what to cut, compile what is left and send it to the printer. When all the team members are working efficiently, the desired product is produced. But if any member of the editing team is slow or sloppy, the final product will have mistakes. Some parts that should have been included are not, some parts that should have been deleted are not, and mistakes creep into the final text. The reader who buys this book gets confused and doesn't know exactly what to do.
In our metaphor, the huge unedited book is the human genome. The abridged version is the proteins that build and operate the cell. The editor in each cell of our body is a molecular machine called the spliceosome. The spliceosome consists of many proteins and 5 different strands of RNA, a chemical similar to DNA.
Most types of RP are caused by mutations in one of the hundreds of proteins needed for the retina to work properly. But some patients with RP have mutations in the DNA that codes for the spliceosome machinery. There are twelve such genes. Seven genes code for the RNA that cells use to manufacture the core operating proteins of the spliceosome. Five genes code for the RNA strands, RNU4-2 and four types of RNU6. These small RNA strands do not instruct the cell to make proteins but guide how the cell processes other RNA. The spliceosome is responsible for producing a final set of instructions on how the retina should work and mutations in any of these twelve genes cause the spliceosome to make mistakes — slowly but ultimately leading to degeneration of the retina and progressive vision loss.