Khaberni - Researchers from Radboud University Medical Center and University of Basel have discovered new genetic causes for hereditary blindness.
A new study has shown that changes in certain parts of the DNA (DNA) play a role in processing genetic information, and may lead to retinitis pigmentosa.
About one in 5000 people worldwide suffer from retinitis pigmentosa, which often leads to narrowing of the visual field and vision loss.
Understanding the disease and its mechanism
Retinitis pigmentosa is a disorder in which the rod and cone cells in the retina gradually deteriorate. The disease typically begins with night blindness, followed by narrowing of the visual field, and some sufferers may completely lose their vision as the condition progresses.
Despite knowing more than a hundred genes that cause the disease, the genetic cause remains unknown for 30 to 50% of patients even after extensive DNA testing. Researchers have managed to solve part of this puzzle through precise genetic study.
Starting with one family
The discovery began with an American family consisting of a father and eight children suffering from blindness and other hereditary diseases.
Susan Rosing, a molecular geneticist at Radboud Center, says, "They came to us wondering about the cause of their conditions, whether there is one gene responsible or several."
The initial analyses did not show any defect in the known genes causing the disease, so the team performed a complete DNA analysis of the parents and children. This analysis explained some other conditions, but it did not explain retinitis pigmentosa, prompting the team to search for a new cause.
Eventually, they discovered a mutation in the RNU4-2 gene.
This gene produces ribonucleic acid (RNA) that is not converted into protein, but it plays a vital role in modifying genetic information before producing proteins. The researchers found that the mutation in the American family disrupts a critical regulatory mechanism in the retina, causing blindness.
Comprehensive analysis of 5000 patients
The team expanded their research in collaboration with researchers from the University of Basel and international colleagues, analyzing the DNA of 5000 patients whose cause of retinitis pigmentosa was unknown. This led to the discovery of four additional similar genes, allowing for molecular diagnosis of 153 individuals from 67 families.
These variants now explain about 1.4% of the undiagnosed cases globally.
Kim Rodenburg, a genetics researcher, says, "We not only discovered a new cause of blindness but also demonstrated that parts of the DNA that do not encode for proteins are of great importance."
This discovery shows that looking beyond protein-coding genes may be necessary to understand hereditary diseases.
