Repeat Coding in Gene Region Linked to Risk of Late-onset Alzheimer’s, Study Suggests

Repeat Coding in Gene Region Linked to Risk of Late-onset Alzheimer’s, Study Suggests
Longer sequence repeats in or near two genes may be linked to a higher risk of late-onset Alzheimer's disease, a study reports. The study "Alzheimer Disease Pathology-Associated Polymorphism in a Complex Variable Number of Tandem Repeat Region Within the MUC6 Gene, Near the AP2A2 Gene" was published in the Journal of Neuropathy and Experimental Neurology. Late-onset Alzheimer's, or symptoms first evident after age 60, is highly heritable. However, previous research has failed to identify genetic variations (mutations) accounting for a significant proportion of the risk for this disorder. In a study in elderly twins in Sweden, inheritance explained 79% of the risk, but common mutations accounted for only up to 50% of the variable clinical presentations. One possible reason for this is that certain regions of the genome are harder to analyze than others. In particular, regions with a high number of sequence repetitions have historically been difficult to analyze. (Sequence repetitions are repeated units of coding in genes, the nucleotides A,T,G, and C that are the building blocks of DNA.) Researchers at the Sanders-Brown Center on Aging at University of Kentucky used whole-exome sequencing to find new genetic variants associated with late-onset Alzheimer's. This technique focuses on the small DNA bits (exons) that contain information to make proteins. The team used two large databases, the Alzheimer’s Disease Genetic Consortium (ADGC) and the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium. Overall, this included genetic data on 5,142 people with Alzheimer's and 4,889 people without the disease serving as controls. All were of European ancestry. This leads to greater genetic similarity within the sample to lim
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