While PAD2, PAD3, and PAD4 protein expression was confirmed in the rat brains, including in the cortex, hippocampus, and white matter, there was no significant difference in PAD isozyme protein levels, although some elevated levels were noted for PAD4 and to a lesser level for PAD3 protein in the pre-motor PD brains. This evidence concerns the gene PADI4 and Parkinson disease.