MFG-E8 in the retina and retinal pigment epithelium of rat andmouse

[摘要] Purpose: To study the distribution of milk fat globule epidermalgrowth factor E8 (MFG-E8) in the rodent eye and to investigate apotential role for this molecule in the phagocytosis of photoreceptorouter segments (POS) by the retinal pigment epithelium (RPE).Methods: We have used immunohistochemistry, in situ hybridization,Northern and Western blotting to demonstrate the presence anddistribution of MFG-E8 in the rat and mouse retina. siRNA technology wasused to knock down MFG-E8 mRNA and to study the effect of such knockdownon the phagocytosis of POS by the RPE.Results: We identified a novel long form of this protein (MFG-E8L)in rat tissues, which contains a 56 amino acid insert that is rich inproline and threonine. This is the first demonstration that MFG-E8L ispresent in a species other than the mouse. Immunohistochemistry and insitu hybridization demonstrate that MFG-E8 is present in the retina andRPE. Northern blotting and PCR show that the short form of MFG-E8(MFG-E8S) is present in both the retina and RPE, but MFG-E8L is foundonly in the RPE. Our results do not demonstrate a role for MFG-E8 in POSphagocytosis by cultured RPE cells.Conclusions: In all tissues in which MFG-E8 has been localized, ithas been shown to perform an important role in cell-cell binding, or inpromoting phagocytosis. The localization of this glycoprotein in theretina and RPE, and particularly the specific localization of MFG-E8L inthe RPE, suggests that this molecule may play an important, but as yetunknown role in retinal function.

[学科分类] 生物化学/生物物理