C3 and age-related macular degeneration: Intriguingly, several ECM-associated genes implicated in deposit-forming phenotypes akin to AMD are substrates of HTRA1 (i.e., C1QTNF5, EFEMP1, C3) and/or are directly associated with AMD (i.e., FBLN5) (20, 21, 23, 47–49).