Matthiessen, P. A. | bioRxiv Science

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↗

bioRxiv2024

Loss of Bbs8 leads to cystic kidney disease in mice and affects tubulin acetylation through HDAC2

Primary cilia dysfunction underlies a group of severe disorders known as ciliopathies. These include Bardet-Biedl syndrome (BBS), which is caused by mutations in BBS genes encoding for components of ciliary protein complexes essential for the assembly and maintenance of primary cilia. As in most ciliopathies, a hallmark feature of BBS is the development of cystic kidney disease. However, the molecular mechanisms linking ciliary dysfunction to cystogenesis remain incompletely understood. Here, we show that Bbs8-/- mice develop late-onset cystic kidney disease accompanied by increased regulated cell death and fibrosis. While the number and length of cilia are not affected, loss of BBS8 reduces K40 acetylation of -tubulin within primary cilia, compromising ciliary stability. Notably, proteomic analysis revealed a significant upregulation of histone deacetylase HDAC2 in Bbs8-/- kidneys, which we confirmed in Bbs8-/- mouse embryonic fibroblasts (MEFs) and in urine-derived renal epithelial cells (URECs) from a BBS8 patient. We further demonstrate the protein interaction between BBS8 and HDAC2, implicating a disrupted BBS8-HDAC2 regulatory axis in disease pathogenesis. Consistent with a role of excessive HDAC2 activity in the BBS8 deficient cells, pharmacological inhibition of HDAC2 restored tubulin acetylation in BBS8 urine-derived cells. Thus, modulation of HDAC2 activity may represent a strategy to alter ciliary stability in vivo which could explain positive effects of class I specific HDAC inhibitors in models of cystic kidney disease.

genetics↗