Biology subjects

Nandrot, E. F.

Publications and source records attributed to Nandrot, E. F..

4 recordsLinked to original sources

bioRxiv2026

CD14 and and TLR4 contribute to the circadian regulation of retinal phagocytosis as co-receptors

Retinal pigment epithelium (RPE) cells perform crucial functions for vision, among which the daily clearance of photoreceptor outer segment (POS) oxidized extremities. POS phagocytosis is under circadian regulation, peaking only once a day despite the constant contact between both cell types. Alphavbeta5 integrin receptors and MFG-E8 ligands synchronize POS phagocytosis and activate the MerTK internalization receptor via an intracellular signaling cascade. Recently, we identified scavenger receptors CD36 and SR-B2/LIMP2 as POS internalization regulators. We now highlight that innate immunity receptors CD14 and TLR4 interact with POS as stimulatory coreceptors in a tissue-specific fashion. CD14 and TLR4 associate partially with lipid rafts, and their activation triggers MyD88-dependent JNK and ERK1/2 (p44/42) kinases. In vivo, CD14 and TLR4 protein levels are replenished in the hours leading to the phagocytic peak. In addition, the phagocytic peak is lost in Tlr4-/- RPE cells, thus confirming that TLR4 regulates this function. Finally, CD14 and TLR4 associate with SR-B2, partner with CD36 and MerTK, highlighting that several receptors contribute together to the fine regulation of POS phagocytosis as a macromolecular machinery.

cell biology↗

bioRxiv2025

Patient induced pluripotent stem cells identify specificities of a reticular pseudodrusen phenotype in age-related macular degeneration

BackgroundAge-related macular degeneration (AMD) is a leading cause of vision loss. Reticular pseudodrusen (RPD), deposits on the apical side of the retinal pigment epithelium (RPE), signify a distinctive and critical AMD phenotype. Yet, their molecular basis and relationship to the conventional drusen seen in AMD remain unclear. ResultsWe generated induced pluripotent stem cell-derived RPE cells from a clinically phenotyped cohort comprising only individuals with conventional drusen (AMD/RPD-) or drusen coexisting with RPD (AMD/RPD+). From these cells, we generated single-cell transcriptomics, proteomics, and functional data to identify differences between the two cohorts. We show that AMD/RPD+ RPE cells exhibit enrichment in extracellular matrix (ECM) remodelling, cytoskeletal, and hypoxia-responsive programs, whereas AMD/RPD- RPE cells display a relatively greater representation of mitochondrial and protein homeostasis pathways. Both subtypes engaged pathways classically linked to ageing, including ECM remodelling and mitochondrial function, but differed in the direction and extent of these changes. Expression and protein quantitative trait loci (QTLs) highlight shared genetic influences on mitochondrial and iron-handling pathways, while disease-interacting eQTLs and transcriptome-wide association study identify regulatory signals that are distinctive of the RPD subtype within AMD, including through regulation of ECM. Functionally, all iPSC-derived RPE formed drusen-like deposits in vitro: AMD/RPD-lines generated more basal deposits, whereas AMD/RPD+ cells exhibited greater structural instability under bisretinoid-induced stress. ConclusionsThese findings indicate that AMD with and without RPD represent mechanistically distinct entities and provide novel insight into the molecular mechanisms underlying disease heterogeneity in AMD.

genetics↗

bioRxiv2025

Loss of ciliary proteins IFT20 and IFT88 results in defective phagocytosis and metabolism in the RPE

A major proportion of retinal disease-causing genes are related to the primary cilium, a microtubule-based signalling organelle essential for multiple developmental pathways. Previous work has shown that the primary cilium plays a crucial role in the development of the retinal pigment epithelium (RPE) affecting homeostasis and function, in particular phagocytosis. We used a cell biology approach to analyse the influence of ciliary genes on RPE phagocytosis and dissect the underlying molecular mechanisms. We found that loss of ciliary trafficking via depletion of Ift20 and Ift88 in RPE-J cells resulted in impaired phagocytosis, specifically by reducing photoreceptor outer segments binding, changes in apical membrane morphology and altered mitochondrial metabolism, whereas loss of Bbs6 showed no functionality phenotype. In addition, proteomics revealed mis-regulated pathways and targets, through which new phagocytosis-related proteins were identified. Our data highlight the role of primary cilia proteins in RPE function and metabolism, essential for visual health.

cell biology↗

bioRxiv2025

Energetic failure and oxidative stress underlie the Prpf31 splicing factor-related mouse phenotype

Mutations of ubiquitous PRPF splicing factors represent the second cause of retina-specific autosomic dominant retinitis pigmentosa. Prpf31 downregulation decreases phagocytosis of mouse and human retinal pigment epithelial (RPE) cells, thus suggesting similar pathogenesis between species. With time, the mouse RPE ultrastructure shows signs of cellular stress such as cytoplasmic vacuoles. To decipher the primary cellular origin of Prpf31-related deleterious processes we first confirmed the gradual accumulation of protein and lipid oxidations. We then showed deregulation in the expression levels of oxidative and endoplasmic reticulum stress markers as well as of mitochondrial respiratory chain constituants, first and foremost in the RPE from 3 months onward. For the first time we analyzed the energetic metabolism of freshly dissected RPE/choroid, retina and peritoneal macrophages, and showed that mitochondrial respiration and global energy production were decreased solely in Prpf31+/- RPE cells. Therefore, our results indicate that metabolic impairments and associated stress might contribute to pathogenesis first in Prpf31+/- RPE cells before affecting the retina.

pathology↗