FZD4 and persistent hyperplastic primary vitreous: In animal models, various signaling pathways have been implicated in the pathogenesis of PHPV including protooncogene ski, p53, tumor suppressor gene Arf, ephrin-B2, βA3/A1-crystallin, LRP5, ang-2, Bax and Bak, FZD4, and ephrin-A5.