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Andrea García Llorca, Franziska Becker, Margrét Helga Ogmundsdottir, Helder Andre, Eiríkur Steingrímsson, Thor Eysteinsson; Microphthalmia-associated transcription factor (Mitf) modulates autophagy in mouse primary RPE cells. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4020.
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Microphthalmia-associated transcription factor (Mitf) is a basic helix-loop-helix leucine zipper transcription factor that regulates the differentiation and development of the retinal pigment epithelium (RPE). Recent evidence from the laboratory shows that MITF regulates starvation-induced autophagy genes in melanoma. Accumulation of damaged organelles and toxic proteins including lipofuscin is related to autophagy deregulation. The purpose of this work was to determine whether Mitf regulates autophagy in RPE cells using normal and Mitf mutant mice.
C57BL/6J (wild type) and Mitfmi-vga9/+ mutant mice 3 months old, were used in this study. Fundus images were taken from wild type and mutant mice using the Micron IV rodent imaging system (Phoenix Research Labs). Primary RPE cells were isolated from wild type and Mitfmi-vga9/+ by enzymatic dissociation. Expression of MITF and LC3 was analyzed using western blotting and confocal microscopy, untreated or incubated in starvation medium with or without bafilomycin A1, a known inhibitor of the late phase of autophagy. Hanks Balanced Salt Solution (HBSS) was used as a starvation medium.
Yellow spots with non-pigmented areas were observed in Mitfmi-vga9/+ mutant mice suggesting the presence of lipofuscin deposits, whereas no such accumulation was noted in the wild type mice. Confocal analysis and immunoblotting of lysates from wild type and mutant RPE cells showed that starvation resulted in increased levels of LC3-II in mutant RPE cells compared to wild type cells.
This study suggests that Mitf may play a role in lipofuscin accumulation in RPE cells. Furthermore, analysis of RPE cells from Mitfmi-vga9/+ mutant mice showed that the autophagy process is altered, indicating a role of Mitf in autophagy in RPE cells.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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