Abstract
Purpose: :
MerTK receptor tyrosine kinase regulates RPE phagocytosis, and its deficiency causes photoreceptor degeneration and visual loss. This study has been performed to investigate MerTK regulation of microRNAs in retinal pigmental epithelial (RPE) cells, which regulate expression of their target genes that potentially affect phagocytosis.
Methods: :
Both WT and MerTK mutant mice were housed in a 12-hour light-dark cycle with lights turned on at 0700 hr (7 AM) and off at 1900 hr (7 PM). For analysis of miRNA expression profile, we prepared total RNA samples from RPE by mechanically dissociation of the RPE sheets from the enucleated eyecups isolated from WT and MerTK mutant mice at 0900 hr and 1900 hr. After confirmation of the RNA integrity, miRNAs were fluorescent labeled and hybridized to miRCURYTM Array (Exiqon). The array images were collected with the Axon GenePix 4000B microarray scanner and digitized by GenePix pro V6.0 (Axon Instruments). Real-time qPCR analysis of miRNA expression was performed using Mir-X miRNA first-strand synthesis and quantification kit (Clontech).
Results: :
Compared with WT RPE cells in the morning, 7 miRNAs in the mutants were significantly up-regulated, whereas 10 were significantly down-regulated. With similar comparison, 15 miRNAs were significantly up-regulated and 11 were down regulated in the evening. To search for those that may participate in regulating cytoskeletal protein expression during phagocytosis, we examined the potential target genes that might participate in phagosome formation. There were 11 among those altered miRNAs, which potentially regulated cytoskeletal protein expression. Downregulation of those proteins have been confirmed by qPCR.
Conclusions: :
MerTK regulates RPE phagocytosis, and its deficiency causes photoreceptor degeneration and visual loss. Loss of MerTK alters microRNA expression, which in turn affects downstream target gene expression.
Keywords: phagocytosis and killing • gene microarray • retina