CXCR4 immunoreactivity in CXCR7 deficient kidneys.

<p>(<b>A,B</b>) In situ hybridizations with a radiolabeled CXCR4 probe show similar CXCR4 expression patterns and labeling intensities in the E14.5 kidney of a wildtype and a CXCR7 deficient mutant. (<b>C,D</b>) Immunostaining of the CXCR4 protein in E16.5 kidney sections of a wildtype and a CXCR7 mutant littermate show severely reduced immunoreactivity in the nephrogenic zone (nz), in glomerular tufts (arrowheads) but not in tubular structures (arrows) of the mutant. (<b>E–H</b>) Higher magnification pictures showing CXCR4 protein signals in wildtype and CXCR7 deficient nephrogenic zone (E,F) and tubular structures (G,H). In the cap mesenchyme (cm) of the CXCR7^−/− embryo (F), CXCR4 immunoreactivity is heavily reduced to single protein signals allocated to the cytoplasm of the mesenchymal cells (arrows). CXCR4 protein signals at the apical site of tubular epithelial cells (ep) are similar in a CXCR7 wildtype (G) and a mutant littermate (H). (<b>I</b>) Measurement of CXCR4 mRNA-radiosignal positive area in the nephrogenic zone (see A,B: nz). (<b>J</b>) Measurement of CXCR4 immunoreactivity positive area in the nephrogenic zone (see C,D: nz) reveals severe downregulation of the CXCR4 protein in CXCR7^−/− kidney sections (Mann-Whitney U test, p&lt;0.001). Data represent mean values ±SEM as percentage of the wildtype group (I,J). (<b>K</b>) Western Blot showing CXCR4 protein expression from 22 pooled E14.5 kidneys of control and CXCR7 knockout embryos. Endogenous transferring receptor (TFR) was used as loading control. lum, lumen; rp, renal pelvis: ub, ureteric bud. Scale bars equal 100 µm (B), 200 µm (D) and 10 µm (F,H).