May accelerate cholesterol efflux from endothelial cells to high-density lipoprotein (HDL) and thereby regulates angiogenesis. May orchestrate hematopoietic stem and progenitor cell emergence from the hemogenic endothelium, a type of specialized endothelium manifesting hematopoietic potential. YJEFN3-mediated cholesterol efflux activates endothelial SREBF2, the master transcription factor for cholesterol biosynthesis, which in turn transactivates NOTCH and promotes hematopoietic stem and progenitor cell emergence (By similarity). May play a role in spermiogenesis and oogenesis (PubMed:17533573). Interacts with APOA1 (PubMed:23719382). Binds to HDL (PubMed:17533573). Expressed in theca cells in ovary and in Leydig cells in testis (at protein level). Also expressed in brain and mammary gland.