HTRA2 and Alzheimer disease: The immunostaining of OMI/HTRA2 exhibited two distinct staining patterns in the neurons of the frontal cortex of the AD compared to control brains: some neurons showed punctuate staining and others a diffuse cytosolic staining, which may reflect the release of OMI/HTRA2 into the cytosol of the neurons (Fig. 1a, b).