Characterisation and developmental regulation of the xenopus laevis CCAAT-enhancer binding protein b gene

Abstract

We report here the cloning, characterisation and developmental expression profile of the Xenopus laevis CCAAT-enhancer binding protein b (xC/EBPb) gene. The protein synthesised from the xC/EBPb gene interacts specifically with a C/EBP-recognition sequence and acts as a transcriptional activator. Several conserved regions are present in the xC/EBPb sequence, including the basic region, leucine zipper, activation domains, three in-frame AUG codons, and a consensus site for mitogen activated protein kinase. The corresponding mRNA is present at high levels in the kidney, liver, lung, muscle and adipose tissue, and at low levels in the ovary, brain and heart. Although the xC/EBPb mRNA and protein are present throughout embryogenesis, there is a biphasic increase in their expression levels during development. Whole-mount in situ hybridisation shows a restricted spatial expression profile of the xC/EBPb gene during early embryogenesis, with transcripts present around the blastopore lip and in the endodermal cells at the mid-gastrula stage, and, the whole dorsal side at the neurula and early tailbud stage. The expression domain becomes almost ubiquitous during later embryonic development, and includes the brain, spinal cord, somites and regions that give rise to the liver and the heart.  1998 Elsevier Science Ireland Ltd. All rights reserved