CCDC85C expression in rat glomeruli and its role in kidney development

Coiled-coil domain containing 85c (CCDC85C), a protein located at cell junctions, has attracted attention for its role in regulating cellular differentiation and polarization. To clarify CCDC85C function, we previously established Ccdc85c knockout (KO) rats. Our previous studies reported that CCDC85C is expressed during the kidney development and that its expression gradually decreases as maturation. The finding implies that CCDC85C is involved in kidney development. However, CCDC85C localization and the detailed kidney histology of Ccdc85c KO animals remain unclear. In the present study, we examined the expression patterns of CCDC85C and the histological consequences of Ccdc85c KO rat kidneys. Immunofluorescence revealed that CCDC85C was expressed in glomeruli at 4, 25 and 50 weeks of age, and distal renal tubules at 4 weeks of age. CCDC85C consistently co-localized with a tight junction marker, zonula occludens-1 (ZO-1) in the podocytes at 4, 25, and 50 weeks of age. At 4 weeks of age, Ccdc85c KO rats showed a thin renal cortex, small and variable size of glomeruli, flattened podocytes and indistinct slit diaphragms. These immature histological features suggest developmental retardation (hypoplasia). In conclusion, CCDC85C is expressed in glomeruli with its presence persisting into late adulthood in rats. The specific localization of CCDC85C suggests its involvement in the tight junction compartment of podocyte foot processes, where it likely maintains the filtration barrier. We propose that CCDC85C is important for the proper development and structural maintenance of the rat kidney.