The identification of α-SMA in capillary pericytes may contribute to clarify the current paradox between functional and histological studies, and expand our understanding of the mechanisms regulating blood flow at the single-capillary level in neurodegenerative conditions including stroke, retinal ischemia, diabetic retinopathy and Alzheimer’s disease. Here, ACTA1 is linked to early-onset autosomal dominant Alzheimer disease.