MERTK and retinal degeneration: Absence of retinal degeneration in Tyro3 knockout mice led one group to conclude that the gene does not contribute to retinal homeostasis [25], while the presence of TYRO3 protein in the murine RPE led others to posit that it functions there in an unspecified manner [26], but that MERTK has a predominant role in RPE phagocytosis [27].