Spatio-temporal expression of membrane transporters, Megalin and Cubilin, in renal development of C57BL/6 mice

Abstract

Objective To observe the distribution of membrane transporters, Megalin and Cubilin, in the renal development of mice, and to reveal the temporal and spatial rules of their functional differentiation during renal development. Methods C57BL/6 mice were housed in a female/male ratio of 1∶1, and the kidneys were isolated at embryonic (Ed) ages of E10, E12, E14, E16 and E18 d, and postnatal ages of P1, P3, P7, P14, P28 and P42 d. A modified block staining technique was applied to fix and stain the whole kidney tissues at different developmental stages, and conventional paraffin and resin 812 embedding were performed to make continuous paraffin sections (5 μm). The target sections in the continuous sections were selected, and immunohistochemical and immunofluorescence assays were used to localize the mouse kidney membrane transporters Megalin and Cubilin at different developmental stages, and to observe their expression levels. Results Megalin and Cubilin were expressed in the epithelial cells of the mesonephric tubules at E10d, and in the proximal luminal surface on the epithelial cells in the ureteric buds of the kidneys at E12d, with co-expression in the proximal luminal surface on the epithelial cells in the ureteric buds of the kidneys, and were expressed weakly in the free margin of the epithelial cells of comma cells and S-shaped cells in the kidneys of the mice at the onset of the developmental process from E14d, and were expressed in the free margins of epithelial cells of proximal tubules of the kidneys. Megalin and Cubilin were not expressed in the fine segments, the distal tubules, the collecting duct system, or the mesangial portion of the kidney. Conclusion The sequential expression pattern of the membrane transporters Megalin and Cubilin in the mesonephric tubules, ureteric buds, comma vesicles, S-shaped vesicles, and proximal tubules suggests that the mouse kidney begins to have a protein or polypeptide transport function during the period of mesonephric formation. In addition, both proteins appear stably in the more mature proximal tubules and more weakly in the immature proximal tubules, suggesting that their protein reabsorption function is related to the maturity of the proximal tubular structure.

Keywords

• kidney
• organogenesis and development
• megalin
• cubilin
• membrane transporter