Researchers at Gladstone Institutes have traced a specific molecular chain linking APOE4, the strongest known genetic risk factor for Alzheimer's disease, to changes in brain cells that begin well before memory falters. Writing in Nature Aging, the team reports that in mouse models, APOE4 ramps up production of a protein called Nell2, which causes neurons to shrink and fire excessively.
The timing is the striking part. These circuit changes showed up in young mice that were still learning and remembering normally, and the degree of early neuronal hyperactivity predicted how severe their memory problems became later in life. As the researchers put it, this is, to their knowledge, the first study to directly examine what APOE4 does to neuronal function at different ages.
When the team dialed down Nell2 production, neurons returned to their normal size and firing patterns - and this worked even in adult mice already carrying the APOE4 gene, not just in young animals. That suggests the damage is not locked in from the outset, and it points to Nell2 as a possible drug target for people who carry APOE4 and face elevated Alzheimer's risk.
The work was done in mice, so whether blocking Nell2 would produce the same recovery in human carriers remains an open question. Still, identifying a measurable early change that forecasts later cognitive decline gives researchers something concrete to aim at, potentially years before symptoms would otherwise bring someone to a clinic.