The notorious genetic marker of Alzheimer's disease and other forms of dementia, ApoE4, may not be a lone wolf. Researchers from the University of Southern California (USC) and the University of Manchester have found that another gene, TOMM40 (image depicts TOMM40 protein), complicates the picture. Although ApoE4 plays a greater role in some types of aging-related memory ability, TOMM40 may pose an even greater risk for other types. TOMM40 and APOE genes are neighbors, adjacent to each other on chromosome 19, and they are sometimes used as proxies for one another in genetic studies. At times, scientific research has focused chiefly on one APOE variant, ApoE4, as the No. 1 suspect behind Alzheimer's and dementia-related memory decline. The literature also considers the more common variant of APOE, ApoE3, neutral in risk for Alzheimer's disease. USC researchers believe their new findings raise a significant research question: Has TOMM40 been misunderstood as a sidekick to ApoE4 when it is really a mastermind, particularly when ApoE3 is present? "Typically, ApoE4 has been considered the strongest known genetic risk factor for cognitive decline, memory decline, Alzheimer's disease, or dementia-related onset," said Dr. T. Em Arpawong, the study's lead author and a post-doctoral fellow in the USC Dornsife College of Letters, Arts and Sciences Department of Psychology. "Although prior studies have found some variants of this other gene TOMM40 may heighten the risk for Alzheimer's disease, our study found that a TOMM40 variant was actually more influential than ApoE4 on the decline in immediate memory - the ability to hold onto new information."
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