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High expression of Pitx-2 in the ICAT-deficient metanephros leads to developmental arrest.

Hasegawa Y, Iizuka-Kogo A, Akiyama T, Senda T - Acta Histochem Cytochem (2010)

Bottom Line: In order to examine the process of this developmental defect, molecular changes were analyzed in fetal ICAT-/- kidneys with a focus on Wnt-signaling associated factors.There was no genotypic difference in the expression level of another Wnt target gene, c-Ret.In the ICAT-/- kidneys which developed to E18.5 without any apparent defect, renal glomeruli, convoluted tubules and collecting ducts were decreased in density and showed abnormal structure.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy I, Fujita Health University School of Medicine, Toyoake, Aichi 470-1192, Japan.

ABSTRACT
ICAT (Inhibitor of β-catenin and T cell factor) inhibits the interaction between β-catenin and TCF/LEF transcription factor and serves as a negative regulator of Wnt signaling. In a subset of ICAT knockout mice, significant delay in the ureteric bud branching and renal agenesis are observed. In order to examine the process of this developmental defect, molecular changes were analyzed in fetal ICAT-/- kidneys with a focus on Wnt-signaling associated factors. The protein level of active β-catenin was elevated in ICAT-/- kidneys. DNA microarray and immunohistochemical analyses revealed that the expression of a Wnt target gene Pitx-2 was enhanced in ICAT-/- kidneys. There was no genotypic difference in the expression level of another Wnt target gene, c-Ret. These results suggest that the enhancement of Pitx-2 expression induced by activated Wnt signaling leads to delays in ureteric bud branching and subsequent renal agenesis. In the ICAT-/- kidneys which developed to E18.5 without any apparent defect, renal glomeruli, convoluted tubules and collecting ducts were decreased in density and showed abnormal structure. ICAT may be required for various developmental stages during renal development.

No MeSH data available.


Related in: MedlinePlus

Double immunofluorescence staining for active β-catenin and Pitx-2 in kidneys at E12.5. (A, C, E, G) ICAT+/+ kidney. Dotted circles indicate a renal vesicle. (B, D, F, H) ICAT−/− kidney. (C, D) Active β-catenin. Note the elevated expression of active β-catenin in accumulated mesenchymal cells around the ureteric bud epithelium in the ICAT−/− kidney. (E, F) Pitx-2. Pitx-2 expression is very low in the ICAT+/+ kidney but is substantial in the ICAT−/− kidney. (G, H) Nuclear staining with DAPI. Bar=20 µm.
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Figure 2: Double immunofluorescence staining for active β-catenin and Pitx-2 in kidneys at E12.5. (A, C, E, G) ICAT+/+ kidney. Dotted circles indicate a renal vesicle. (B, D, F, H) ICAT−/− kidney. (C, D) Active β-catenin. Note the elevated expression of active β-catenin in accumulated mesenchymal cells around the ureteric bud epithelium in the ICAT−/− kidney. (E, F) Pitx-2. Pitx-2 expression is very low in the ICAT+/+ kidney but is substantial in the ICAT−/− kidney. (G, H) Nuclear staining with DAPI. Bar=20 µm.

Mentions: Before the identification of the Wnt target genes, we checked for any additional effect of ICAT gene disruption on the Wnt signaling pathway by examining the expression of dephosphorylated “active” β-catenin in ICAT knockout mice using immunofluorescence. In kidneys of ICAT+/+ mice, the active β-catenin was localized in the apical part of the cytoplasm and at the cell-cell adhesion site of the epithelial cells in the ureteric bud, while the expression in mesenchymal cells was faint (Fig. 2C). In the kidneys of ICAT−/− mice, strong expression of active β-catenin was found in the cytoplasm of aggregated mesenchymal cells surrounding the ureteric bud (Fig. 2D), as well as in the apical part of the cytoplasm and the cell-cell adhesion sites of epithelial cells in ureteric bud. The signal intensities of active β-catenin in the ureteric epithelium and the aggregated mesenchyme of ICAT−/− kidneys were 1.17-fold (P=0.016) and 1.23-fold (P=0.018) higher than those of ICAT+/+ kidneys, respectively. On the other hand, the immunoreactivity by another antibody which recognizes total β-catenin regardless of phosphorylation status was statistically unchanged in ICAT−/− kidneys (data not shown). These results show that the cytoplasmic amount of active β-catenin was increased in ICAT−/− kidneys.


High expression of Pitx-2 in the ICAT-deficient metanephros leads to developmental arrest.

Hasegawa Y, Iizuka-Kogo A, Akiyama T, Senda T - Acta Histochem Cytochem (2010)

Double immunofluorescence staining for active β-catenin and Pitx-2 in kidneys at E12.5. (A, C, E, G) ICAT+/+ kidney. Dotted circles indicate a renal vesicle. (B, D, F, H) ICAT−/− kidney. (C, D) Active β-catenin. Note the elevated expression of active β-catenin in accumulated mesenchymal cells around the ureteric bud epithelium in the ICAT−/− kidney. (E, F) Pitx-2. Pitx-2 expression is very low in the ICAT+/+ kidney but is substantial in the ICAT−/− kidney. (G, H) Nuclear staining with DAPI. Bar=20 µm.
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Related In: Results  -  Collection

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Figure 2: Double immunofluorescence staining for active β-catenin and Pitx-2 in kidneys at E12.5. (A, C, E, G) ICAT+/+ kidney. Dotted circles indicate a renal vesicle. (B, D, F, H) ICAT−/− kidney. (C, D) Active β-catenin. Note the elevated expression of active β-catenin in accumulated mesenchymal cells around the ureteric bud epithelium in the ICAT−/− kidney. (E, F) Pitx-2. Pitx-2 expression is very low in the ICAT+/+ kidney but is substantial in the ICAT−/− kidney. (G, H) Nuclear staining with DAPI. Bar=20 µm.
Mentions: Before the identification of the Wnt target genes, we checked for any additional effect of ICAT gene disruption on the Wnt signaling pathway by examining the expression of dephosphorylated “active” β-catenin in ICAT knockout mice using immunofluorescence. In kidneys of ICAT+/+ mice, the active β-catenin was localized in the apical part of the cytoplasm and at the cell-cell adhesion site of the epithelial cells in the ureteric bud, while the expression in mesenchymal cells was faint (Fig. 2C). In the kidneys of ICAT−/− mice, strong expression of active β-catenin was found in the cytoplasm of aggregated mesenchymal cells surrounding the ureteric bud (Fig. 2D), as well as in the apical part of the cytoplasm and the cell-cell adhesion sites of epithelial cells in ureteric bud. The signal intensities of active β-catenin in the ureteric epithelium and the aggregated mesenchyme of ICAT−/− kidneys were 1.17-fold (P=0.016) and 1.23-fold (P=0.018) higher than those of ICAT+/+ kidneys, respectively. On the other hand, the immunoreactivity by another antibody which recognizes total β-catenin regardless of phosphorylation status was statistically unchanged in ICAT−/− kidneys (data not shown). These results show that the cytoplasmic amount of active β-catenin was increased in ICAT−/− kidneys.

Bottom Line: In order to examine the process of this developmental defect, molecular changes were analyzed in fetal ICAT-/- kidneys with a focus on Wnt-signaling associated factors.There was no genotypic difference in the expression level of another Wnt target gene, c-Ret.In the ICAT-/- kidneys which developed to E18.5 without any apparent defect, renal glomeruli, convoluted tubules and collecting ducts were decreased in density and showed abnormal structure.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy I, Fujita Health University School of Medicine, Toyoake, Aichi 470-1192, Japan.

ABSTRACT
ICAT (Inhibitor of β-catenin and T cell factor) inhibits the interaction between β-catenin and TCF/LEF transcription factor and serves as a negative regulator of Wnt signaling. In a subset of ICAT knockout mice, significant delay in the ureteric bud branching and renal agenesis are observed. In order to examine the process of this developmental defect, molecular changes were analyzed in fetal ICAT-/- kidneys with a focus on Wnt-signaling associated factors. The protein level of active β-catenin was elevated in ICAT-/- kidneys. DNA microarray and immunohistochemical analyses revealed that the expression of a Wnt target gene Pitx-2 was enhanced in ICAT-/- kidneys. There was no genotypic difference in the expression level of another Wnt target gene, c-Ret. These results suggest that the enhancement of Pitx-2 expression induced by activated Wnt signaling leads to delays in ureteric bud branching and subsequent renal agenesis. In the ICAT-/- kidneys which developed to E18.5 without any apparent defect, renal glomeruli, convoluted tubules and collecting ducts were decreased in density and showed abnormal structure. ICAT may be required for various developmental stages during renal development.

No MeSH data available.


Related in: MedlinePlus