HTRA1 and cerebral amyloid angiopathy: Other examples are several point mutations in the amyloid precursor protein (APP) gene that lead to cerebral amyloid angiopathy (CAA)9 as well as mutations in HtrA Serine Peptidase 1 (HTRA1) and Collagen Type IV Alpha 1 Chain (COL4A1) or COL4A2 genes.10