Expression of Robo2 gene during the renal development in mice
Objective　To observe the expression of Robo2 gene, and explore its role during the renal development of mice. Methods　Real-time quantitative RT-PCR was used to semi-quantitatively measure the expression level of Robo2 mRNA in the developing murine kidney at fetal age of 12.5, 13.5, 14.5, 15.5, 16.5 and 17.5 days, and also 1 day, 1 week, 5 weeks after birth. Immunofluorescence staining was used to examine the expression location of Robo2 protein at different stages of embryonic and postnatal kidney. Results　Real-time quantitative RT-PCR analysis revealed that Robo2 was highly expressed in embryonic kidney at fetal age of 12.5, 13.5 and 14.5 days, while the expression level declined quickly thereafter and maintained at very low level after birth. Immunofluorescence staining showed that the expression of Robo2 protein could be primarily detected in metanephric mesenchyme of the developing kidney, but not in the ureteric bud. With the development of embryonic kidney, Robo2 protein was expressed in cell membrane of metanephric mesenchyme, condensed cap mesenchyme surrounding the tip of the ureteric bud, comma-shaped body, S-shaped body and renal capsule, finally expressed in the podocytes. Besides, Robo2 protein was also weakly expressed in part of the proximal tubular epithelial cells. Absence of Robo2 gene resulted in abnormal development of nephron, and broadening of some renal tubules and collecting ducts. Conclusion　Robo2 plays an important role in the nephron development in mice by regulating the interaction of metanephric mesenchyme and ureteric bud.