Expression of CCAAT/enhancer binding protein δ is closely associated with degeneration of surface mucous cells of larval stomach during the metamorphosis of Xenopus laevis

CCAAT/enhancer binding protein δ (C/EBP δ) is one of the transcription factors that have a basic-leucine zipper domain. In mammals, it has been suggested that this transcription factor plays a role in differentiation of adipocytes or in apoptosis of mammary gland epithelial cells. The factor also plays a role in acute-phase response in injury, infection and inflammation. We cloned Xenopus homologues of the C/EBP δ gene from metamorphosing stomach by subtractive hybridization and analyzed spatio-temporal expression pattern of the homologues. Two isoforms of C/EBP δ were isolated and named C/EBP δ-1 and −2. Their deduced amino acid sequences were highly similar to each other (identity, 91.2%). Expression of the C/EBP δ mRNAs in the stomach transiently increased during its metamorphosis-associated remodeling, and the transient up-regulation was also found in thyroid hormone-induced metamorphosis. The C/EBP δ mRNAs were exclusively localized in degenerating larval surface mucous cells, not in newly proliferating and differentiating adult-type epithelial cells. The result suggests a possibility that Xenopus C/EBP δ plays a role in apoptotic cell death of larval-type epithelium during the stomach remodeling.