XB-ART-23585Mech Dev July 1, 1992; 38 (1): 69-81.
Characterization and developmental expression of Xenopus C/EBP gene.
The Xenopus homolog of the transcription factor C/EBP (CCAAT/enhancer core binding protein), cloned from an adult Xenopus liver cDNA library, encodes a protein whose sequence is 67% homologous to that of rat C/EBP at the amino acid level, with virtually identical sequence of the basic-zipper region at the carboxyl terminus. As determined by gel electrophoretic mobility shift assays, the protein synthesized from xC/EBP cDNA bound specifically to the consensus binding site for C/EBP-like proteins. Northern blotting and RNase protection revealed a single species of xC/EBP mRNA of 2.7 kb which was most abundant in adult Xenopus liver, with smaller amounts in spleen, kidney, oviduct and brain and undetectable in heart and skeletal muscle. Although a small amount of this transcript could be detected in unfertilized eggs and early embryos, its accumulation rose sharply at the onset of metamorphosis (stage 55/56), and continued to increase through metamorphic climax to reach its highest level in stage 66 froglet liver, but thereafter declining in adult liver. In situ hybridization revealed a uniform pattern of distribution of xC/EBP mRNA in the liver and fat body throughout metamorphosis. Towards the end of metamorphosis, high levels of xC/EBP mRNA were detected in epithelial cells of the digestive tract. However, the spatial pattern of cells expressing the transcript changed markedly in the developing kidney. Our results suggest that xC/EBP may be involved as a transcription factor in the establishment of the adult phenotype during post-embryonic development of Xenopus.
PubMed ID: 1525039
Article link: Mech Dev
Species referenced: Xenopus
Genes referenced: cebpa
Article Images: [+] show captions
|Fig. 7. Localization of xC/EBP mRNA by in situ hybridization during early metamorphosis. Bright-field (a, c, e and g) and dark-field (b, d, f and h) images of localization of xC/EBP mRNA in different tissues of stages 55/56 and 57/58 Xenopus tadpoles. Sagittal sections were hybridized with antisense or sense 35S-labelled xC/EBP cRNA probe (1 x 105 cpm/tzl) and subsequently treated with RNase A as described by Wilkinson and Green (1990). Sense probe gave virtually no hybridization in the kidney and fat body but low background was observed in the liver. (a, b) Liver of stage 55/56 tadpole. (c, d) Liver of stage 57/58 tadpole. (e, f) Kidney and fat body (Fb) of stage 55/56 tadpole. (g, h) Kidney of stage 57/58 tadpole. Note that pigmented layers (Pi) appear as bright zones in dark-field images, also seen with sense probe controls. Autoradiographs exposed for two weeks. The bars represent 100/xm|
|Fig. 8. Localization of xC/EBP mRNA by in situ hybridization at the beginning (Stage 59/60) and end (Stage 65/66) of metamorphic climax. Bright-field (a, c, e, and g) and dark-field (b, d, f, and h) visualization. (a, b) Small intestine of Stage 59/60 tadpole. (c, d) Small intestine of Stage 65/66 tadpole. (e, f) Stomach of stage 65/66 tadpole. (g, h) Fat body of stage 65/66 tadpole. The bars represent 100/xm.|
|Cebpa expression in stomach of stage 65/66 tadpole|