Reddy's laboratory observed increased expression of Drp1 and Fis1 in the frontal cortices of patients at Braak stages I and II (early AD), III and IV (definite AD), and V and VI (severe AD) compared to controls, whereas the expression of Mfn1, Mfn2, OPA1, and TOM40 decreased. Here, OPA1 is linked to Alzheimer disease.