Differential day-night expression of tight junction components in murine retinal pigment epithelium. (April 2020)

• Record Type: Journal Article
• Authors: Louer, Elja M.M.; Günzel, Dorothee; Rosenthal, Rita; Carmone, Claudia; Yi, Guoqiang; Stunnenberg, Henk G.; den Hollander, Anneke I.; Deen, Peter M.T.
• Is Part Of: Experimental eye research. Volume 193(2020)
• Publication Date: 2020-04
• Subjects: Retinal pigment epithelium -- Epithelial transport -- Tight junctions -- Actin cytoskeleton; Ophthalmology -- Periodicals; Eye -- Periodicals; Œil -- Périodiques; Ophthalmology; Periodicals; Electronic journals; 612.8405
• DOI: 10.1016/j.exer.2020.107985
• Languages: English
• ISSNs: 0014-4835

Abstract

Abstract: Strong communication and interaction between the retinal pigment epithelium (RPE) and the photoreceptor (PR) cells is essential for vision. RPE cells are essential for supporting and maintaining PR cells by transporting nutrients, waste products and ions, and phagocytosing photoreceptor outer segments (POS). POS phagocytosis follows a circadian pattern, taking place in the morning in human, mice and other organisms. However, it remains unknown whether other RPE processes follow a daily rhythm. To study the daily rhythm of RPE cells, we isolated murine RPE cells at six different time points during a 24 h period, after which RNA was isolated and sequenced. Murine RPE flatmounts were isolated at four different time points to study daily rhythm in protein abundance and localisation. EnrichR pathway analysis resulted in 13 significantly-enriched KEGG pathways (p < 0.01) of which seven showed a large number of overlapping genes. Several genes were involved in intracellular trafficking, possibly playing a role in nutrient transport, POS phagocytosis or membrane protein trafficking, with different expression patterns during the day-night cycle. Other genes were involved in actin cytoskeleton building, remodelling and crosslinking and showed a high expression in the morning, suggesting actin cytoskeleton remodelling at this time point. Finally, tight junction proteins Cldn2 and Cldn4 showed a difference in RNA and protein expression and tight junction localisation over time. Our study suggests that several important processes in the RPE follow a day-night rhythm, including intracellular trafficking, and processes involving the actin cytoskeleton and tight junctions. The differential protein localisation of Cldn2 in the RPE during the day-night cycle suggest that Cldn2 may facilitate paracellular water and sodium transport during the day. Highlights: Cldn2 RNA and protein expression show clear differences over time in RPE cells. Paracellular water and sodium transport in RPE might be facilitated by Cldn2 during the day. Genes involved in intracellular trafficking show differential day-night expression. Genes involved in cytoskeleton remodelling show high expression in the morning.