Frizzled-4 expression during chick kidney development.

Wnts have been implicated in metanephric kidney development. To determine whether Frizzleds, the genes that encode Wnt receptors, are present at early stages of nephrogenesis, we examined the expression of several recently identified Frizzled genes in the chick by in situ hybridization. Here we report the cloning and characterization of chick Frizzled-4 (cFz-4), which we found to be expressed in the developing chick kidney. cFz-4 was first expressed in the pronephros caudal to the third somite at Hamburger and Hamilton stage 10. Its expression increased with maturation, becoming restricted to the newly induced glomeruli and tubules in the mesonephros and metanephros. Within the metanephros, cFz-4 and Wnt-4 expression patterns were similar, whereas Wnt-11 was expressed solely in the tips of the branching ureteric bud. cFz-4 expression was compared with that of known kidney markers. It preceded that of Lmx-1, but was similarly restricted to developing glomeruli and tubules. In contrast, Pax-2 expression and Lim 1/2 antibody labeling occurred in intermediate mesoderm caudal to the fifth somite in the early pronephros, and each persisted in both the tubules and nephric ducts throughout further development.