A test of the calcium hypothesis of Alzheimers disease

The calcium hypothesis of Alzheimer’s disease (AD) posits that dysregulation of calcium homeostasis is the point of convergence of the many factors risk factors and molecular mechanisms that lead to development of AD and its associated neurodegeneration. A corollary of the calcium hypothesis of AD is that restoration of calcium homeostasis will ameliorate AD pathophysiology and reverse neuronal dysfunction. Surprisingly, despite being nearly 3 decades old, this hypothesis has not been definitively tested in vivo. We propose to directly test the calcium hypothesis by normalizing resting free intracellular calcium levels through exogenous expression of the simple calcium buffer proteins calbindin-9Dk and parvalbumin-α in the brains of 5XFAD mice, a model of amyloid pathology in AD. In Aim 1, we will determine if increasing calcium buffering in the brains of amyloid plaque-containing 5XFAD mice can restore electrophysiological and cognitive impairments. In Aim 2, we will determine if reduced resting free calcium cures the dystrophic axons and neurites that develop around plaques and likely contribute to neuronal dysfunction and increased amyloid generation. Two adeno-associated viruses will be co-injected into the ventricles of postnatal P0 mouse pups, resulting in viral transduction throughout the brain and lifelong transgene expression. One virus expresses the calcium sensor GCaMP6 from the calmodulin kinase II (CaMKII) promoter, which drives expression in the excitatory neurons of the forebrain. The second virus co-expresses mCherry and a calcium buffer protein (either calbindin-9Dk or parvalbumin-α) under the control of a tetracycline-off (TetO) promoter. In mice that express the tetracycline transactivator protein (tTA) under the control of a CaMKII promoter, the calcium buffer protein and mCherry will be expressed in the same population of cells as the calcium sensor GCaMP6 in the absence of the tetracycline analog doxycycline (dox). The pregnant mothers a