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Genetic Risk for Blindness might potentially be Lower than Previously Thought, New Study Finds
A groundbreaking new study challenges long-held assumptions about inherited retinal degenerations (IRDs), suggesting that carrying a genetic variant linked to blindness doesn’t guarantee the disease will develop. Published Monday in The American Journal of Human Genetics, the research indicates the actual risk may be considerably lower than previously estimated.
For over a century, the prevailing understanding in genetics has been that Mendelian disorders – rare inherited diseases caused by a mutation in a single gene – predictably manifest when that gene is altered. In the case of IRDs, a leading cause of legal blindness in working-age adults, it was widely believed a single gene modification invariably led to vision loss. However,this new research casts doubt on that deterministic view.
The study’s findings stem from an analysis of large-scale population data, addressing a critical flaw in previous genetic research. “Many genetic studies are done in the clinic,with people and families already affected,which may overestimate how often the genetic variant leads to the appearance of the disease,” one researcher explained. This phenomenon, known as selection bias, occurs when studies disproportionately include individuals already exhibiting symptoms, skewing the perceived link between genetic variants and disease.
To overcome this bias, a team led by Eric Pierce, director of the Ocular Genomics Institute at Mass Eye and Ear and a professor at Harvard Medical School, examined data from two extensive biobanks: the All of Us Research Program (AoU) of the National Institutes of Health (NIH) and the UK Biobank (UKB). Researchers compiled a list of 167 known pathogenic variants in 33 genes associated with IRDs. They then screened these variants in 317,964 AoU participants, identifying 481 individuals with genotypes potentially linked to the conditions.
The results were striking. Using stringent diagnostic criteria based on ICD (International Classification of Diseases) codes from electronic health records, researchers found that only 9.4% of individuals with these genetic variants had a confirmed diagnosis of IRD.Expanding the diagnostic criteria to include broader categories of retinal disease and vision loss increased the proportion to 28.1%, still well below the expected rate based on previous assumptions.
For further validation, the team analyzed data from the UK Biobank, which included retinal imaging for approximately 100,000 participants. This analysis revealed that between 16.1% and 27.9% of individuals with IRD-associated variants showed signs of retinal damage – figures consistent with those observed in the AoU data. Importantly, factors such as age, demographics, lifestyle choices, and other health conditions did not significantly improve the prediction of disease manifestation among those carrying the genetic variants.
These findings suggest that the presence of a known genetic variant is not enough to guarantee the progress of IRD. “For the disease to manifest, other modifying factors, genetic or environmental, are necessary, beyond the identified pathogenic variant,” the researchers concluded. This implies a more complex interplay between genes and surroundings than previously understood.
The implications of this research are far-reaching. The study’s authors believe these results will reshape how genetic testing is interpreted and could pave the way for novel therapies targeting not just the primary genetic defect, but also the modifying factors that influence disease expression. A similar approach has already proven valuable in managing conditions like familial hypercholesterolemia.This research offers a renewed hope for individuals at risk o
