Metamorphosis-dependent transcriptional regulation of xak-c, a novel Xenopus type I keratin gene

Yusuke Watanabe, Rumi Tanaka, Hisao Kobayashi, Rie Utoh, Ken Ichi Suzuki, Masanobu Obara, Katsutoshi Yoshizato

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23 Citations (Scopus)


Anuran larvae transform their epidermis to the adult counterpart during metamorphosis. The major event of this process is the proliferation of larval pidermal basal cells and their differentiation into adult ones. The present study isolated novel type I keratin cDNA dubbed xak-c (Xenopus adult keratin-c) that was exclusively expressed in adult epidermal basal cells. The gene started its expression in the larval epidermis at the onset of metamorphosis. Thyroid hormone (TH) induced the precocious expression of the gene in the epidermis of premetamorphic tadpoles. To study the transcriptional regulation of this gene in relation to epidermal metamorphosis, a 2.8 kb 5′-flanking region of xak-c was cloned and its promoter activity was investigated. Gene constructs were made so as to contain the xak-c promoter region and gene of EGFP or luciferase as a reporter gene and were transfected into various types of cells, which revealed that the 5′-flanking region had an epidermal cell-specific transcriptional activity in both anurans and mammals. Larval skin tissues of Xenopus were transfected with the constructs and cultured in the presence and absence of TH, which showed that the promoter region is responsive to TH, although the region did not contain the consensus TH response element-like sequence. In sharp contrast, the promoter region did not respond to TH in the adult skin, clearly indicating that the cloned region contains specific. sequences that respond to metamorphosis-dependent transcription factor(s).

Original languageEnglish
Pages (from-to)561-570
Number of pages10
JournalDevelopmental Dynamics
Issue number4
Publication statusPublished - 2002 Dec 1


  • Amphibian metamorphosis
  • EGFP
  • Epidermis
  • Gene gun
  • Luciferase gene
  • Promoter
  • Thyroid hormone

ASJC Scopus subject areas

  • Developmental Biology


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