Mice hemizygous for the Thy1-COL25A1 allele are viable, fertile, normal in size and do not display any gross physical or behavioral abnormalities. Collagen XXV alpha 1 (COL25A1), also known as collagen-like Alzheimer's amyloid plaque component precursor, is a type II transmembrane protein expressed in neurons that colocalizes with Amyloid β (Aβ) in senile plaques in the brains of Alzheimer's patients. In the Thy1-COL25A1 mouse, overexpression of human COL25A1 is regulated by a murine Thy1.2 promoter (Thy1), which leads to expression in the cortex and the hippocampus. This overexpression results in accumulation of Aβ and increased levels of p35/p25 and β-site APP-cleaving enzyme 1 (BACE1), which may induce synaptic dysfunction leading to the behavioral changes associated with Alzheimer's Disease. COL25A1 precursor is expressed in cell membranes of cortical neurons, in 2 month old mice. At 6 months, COL25A1 precursor was expressed in the cortex, CA1 pyramidal neurons, dentate gyrus (DG), granule neurons, and thalamic cells, while secreted forms of were detected in extracellular matrix (ECM) of cortex and DG and formed fibrillar ECM deposits. In 1-year-old mice, both forms of COL25A1 were detected in the entire brain. These mice may be useful for studying the accumulation of protease-resistant plaques in the pathogenesis of Alzheimer's Disease.
