Alzheimer's researchers and drug companies have for years concentrated on one hallmark of Alzheimer’s disease: the production of toxic shards of a protein that accumulate in plaques on the brain.
But now, in a surprising coincidence, two groups of researchers working from entirely different starting points have converged on a mutated gene involved in another aspect of Alzheimer’s disease: the immune system’s role in protecting against the disease. The mutation is suspected of interfering with the brain’s ability to prevent the buildup of plaque.
The discovery, researchers say, provides clues to how and why the disease progresses. The gene, known as TREM2, is only the second found to increase Alzheimer’s risk substantially in older people.
“It points very specifically to a potential metabolic pathway that you could intervene in to change the course of Alzheimer’s disease,” said William Thies, chief medical and scientific officer of the Alzheimer's Association.
Much work remains to be done before scientists understand precisely how the newly discovered gene mutation leads to Alzheimer’s, but already there are some indications from studies in mice. When the gene is not mutated, white blood cells in the brain spring into action, gobbling up and eliminating the plaque-forming toxic protein, beta amyloid. As a result, Alzheimer’s can be staved off or averted.
But when the gene is mutated, the brain’s white blood cells are hobbled, making them less effective in their attack on beta amyloid.
People with the mutated gene have a threefold to fivefold increase in the likelihood of developing Alzheimer’s disease in old age.