Utoh R et al. (2003), Platelet-derived growth factor signaling as a c...

XB-ART-5263

Dev Dyn 2003 Jun 01;2272:157-69. doi: 10.1002/dvdy.10302.

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Platelet-derived growth factor signaling as a cue of the epithelial-mesenchymal interaction required for anuran skin metamorphosis.

Utoh R , Shigenaga S , Watanabe Y , Yoshizato K .

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The anuran remodels the larval skin into the adult counterpart during metamorphosis. The construction of the precursor of adult epidermis (preadult epidermis) in Xenopus laevis larvae was coordinated with the development of the secondary connective tissue (s-ct) underneath the basement membrane, suggesting that the epithelial-mesenchymal interaction plays a critical role in the metamorphic conversion of the larval skin. mRNAs of platelet-derived growth factor A (PDGF-A) and PDGF receptor (PDGFR) -alpha were markedly up-regulated in the skin during spontaneous and thyroid hormone (TH) -induced metamorphosis. In situ hybridization experiments identified preadult epidermal basal cells and fibroblasts in developing subepidermal connective tissues at the late prometamorphic stage as PDGF-A and PDGFR-alpha mRNA-expressing cells, respectively. We developed an in vitro model of larval skin that was remodeled to the adult skin under the influence of TH. The presence of either of AG1296, a specific inhibitor of PDGFR tyrosine kinase autophosphorylation, or an excess of recombinant proteins of the soluble extracellular domain of PDGFR-alpha inhibited the following TH-induced processes, the proliferation of adult basal cells, the terminal differentiation of adult basal cells, and the activation of subepidermal fibroblasts. However, the inhibitors did not inhibit the TH-induced proliferation of preadult basal cells. We concluded that PDGF/PDGFR signaling is one of the prime cues in the epithelial-mesenchymal interaction required for the metamorphic skin remodeling.

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Species referenced: Xenopus laevis
Genes referenced: krt12.6 krt55 krt61 krt62 krt7 pdgfa pdgfra rpl8
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	Fig. 1. Changes in mRNAs levels of platelet-derived growth factor A (PDGF-A) and PDGF receptor (PDGFR) - during spontaneous and 3,3 ,5-triiodothyronine (T3) -induced metamorphosis. Total RNA was extracted from the back skin of tadpoles, 1 g of which was used as a template for reverse transcriptase-polymerase chain reaction (RT-PCR). The amplified products were electrophoresed on gels and visualized with ethidium bromide. RT-PCR was done with 27 cycles, which produced a 510- and 444-bp product for PDGF-A and PDGFR- , respectively. Amplification of the rpL8 gene was performed with 28 cycles as an internal control. A: RT-PCR for tadpoles at the stages indicated above the gel. B: RT-PCR for tadpoles at stage 54/55 treated with T3 for the days indicated above the gel. RT-PCR was performed two times for RNAs extracted from different samples for each determination, and similar results were obtained reproducibly.

	Fig. 4. Effects of 3,3 ,5-triiodothyronine (T3) on the mRNA expression of Xenopus larval keratin (XLK), Xenopus adult keratin (XAK) -B, XAK-C, platelet-derived growth factor A (PDGF-A), and PDGF receptor (PDGFR) - in cultures of larval skin. Larval back skins at stage 54/55 were cultured with ( T3) or without (-T3) 100 nM T3. Total RNA was extracted from them at 0, 3, 6, and 9 days of culture and used as templates of reverse transcriptase-polymerase chain reaction (RT-PCR) for quantifying mRNAs of XLK, XAK-B, XAK-C, PDGF-A, PDGFR- , and rpL8 as in Figure 1. RT-PCR was performed four times for RNAs extracted from different samples, and similar results were obtained reproducibly.

	krt5.5 (keratin 5, gene 5 ) gene expression in Xenopus laevis embryos, NF stage 54, as assayed by immunohistochemistry. Coronal section of skin, superficial up.
	krt5.5 (keratin 5, gene 5 ) gene expression in Xenopus laevis embryos, NF stage 54, as assayed by immunohistochemistry. Coronal section of skin, superficial up.