NRGN and early-onset autosomal dominant Alzheimer disease: In Alzheimer’s disease (AD), the concentration of the postsynaptic protein neurogranin, which is involved in synaptic plasticity and enhances the strength of connections, is elevated [2, 5–9], and in amyloid-positive people with mild cognitive impairment, raised neurogranin levels are associated with cognitive decline and conversion to dementia [10].