The goal of this project is to use biochemical, molecular and cellular means to elucidate the mechanisms that lead to brain aging and cognitive decline. The specific aims of Project 2 are to: 1) Determine age-related changes in gene expression in prefrontal cortical white and gray matter, and in electrophysiologically characterized pyramidal neurons. Using gene microarray analyses, we will assess whether changes in gene expression in prefrontal subcortical white matter precede cognitive impairment and whether the expression of genes specifically implicated in aging and cognitive function, such as Klotho, are altered in cognitively impaired, aged animals, 2) Determine the function of Klotho in brain and neuronal cultures. The anti aging gene Klotho is of particular interest because a deletion of the gene has been shown to cause premature aging in mice with manifestations resembling aging in humans. We found a decrease in its expression in the white matter of aged monkeys in our microarray analysis. We plan to test the hypothesis that the age-related decreased expression of Klotho causes oligodendrocyte injury and demyelination, and neuronal dysfunction, and 3) Decipher the mechanism of CNP accumulation, and determine the role of the proteasome and calpain-1 in CNP degradation. Our earlier studies in brain white matter showed an increased expression and fragmentation of CNP, an oligodendrocyte microtubule-associated protein that participates in the regulation of myelin proteins and membrane formation. It is hypothesized that these CNP changes are related to an age associated decrease in proteasomal degradation and posttranslational modifications of CNP in the lipid rafts of the oligodendrocytes that leads to oligodendrocyte and myelin dysfunction. The proposed studies will use an array of molecular and biochemical studies designed to test the specific hypothesis that normal age- related cognitive decline begins in middle age with white matter degeneration and inflammation leading to neuronal dysfunction, and may suggest points for therapeutic intervention in the aging process.