Protein and mRNA expression of serum and glucocorticoid-dependent kinase 1in metanephrogenesis

Expression of serum and glucocorticoid-dependent kinase 1 (SGK1) during dev elopment in mouse kidney (embryonic day [E] 14 to postnatal day [P] 1) was studied by in situ hybridization and immunofluorescence. In whole embryos, SGK1 mRNA was highly abundant in the developing metanephros, where SGK1 mRN A was expressed in the ureteric buds of the branching collecting duct syste m and in the mesenchymal blastema-derived comma- and s-shaped bodies. In E1 4 kidneys, SGK1 protein was below detection level, whereas at day E16, uret eric buds, s-shaped bodies and outgrowing loops of Henle expressed detectab le amounts of SGK1 protein. SGK1 protein was also expressed in E16 primary tubules of the collecting duct system. In PI kidneys, no or only faint SGK1 protein expression was apparent in comma- and s-shaped bodies, whereas SGK 1 was continuously expressed by medullary collecting ducts. In conclusion, SGK1 is developmentally expressed in metanephrogenesis. High expression in developing collecting duct and in blastema-derived comma- and s-shaped bodi es suggests a dual function of SGK1 in maturation of the reabsorbing collec ting duct epithelium and in epithelial transition of the blastema cells. (C ) 2001 Wiley-Liss, Inc.