Region- and cell-type-specific pattern of tau phosphorylation in dog brain.

A study of brains of 16 dogs from one to 19 years of age showed a structure- and cell-type- specific pattern of tau protein phosphorylation at mAb Tau-1 site and the absence of phosphorylation at the mAb AT8 site. Strong immunolabeling with mAb Tau-1 of the mossy fibers and perikarya of neurons in sectors CA3 and CA4 of the cornu Ammonis, less intensive staining in the cytoplasm in neocortical and subcortical neurons, and selective staining of some pyramidal cells in sectors CA1 and CA2 show differences in the amount of phosphorylated tau, not only in different types of neurons, but also in different parts of the cell. The immunoreactivity of oligodendrocytes and the absence of the reaction in astrocytes reflect differences in tau phosphorylation in glial cells. Marked immunoreactivity in 13 dogs but minimal reaction in brains of three other dogs appears to reflect interindividual differences, which are associated presumably with genetic background. Shrinkage of neurons, tortuosity of mossy fibers, accumulation of phosphorylated tau in the nucleoplasm, and deformation of the nuclei of neurons and oligodendrocytes suggest that excessive phosphorylation at the mAb Tau-1 site is associated with neuronal and oligodendrocyte degeneration and, possibly, cell death.