CCAAT ENHANCER-BINDING PROTEIN-ALPHA AND PROTEIN-BETA IN BROWN ADIPOSE-TISSUE - EVIDENCE FOR A TISSUE-SPECIFIC PATTERN OF EXPRESSION DURINGDEVELOPMENT/

CCAAT/enhancer-binding protein (C/EBP) alpha mRNA and its protein prod ucts C/EBP alpha and 30 kDa C/EBP alpha are expressed in rat brown-adi pose tissue. Results also demonstrate the expression of C/EBP beta mRN A and its protein products C/EBP beta and liver inhibitory protein (LI P) in the tissue. The abundance of C/EBP alpha and C/EBP beta proteins in adult brown fat is similar to that found in adult liver. However, the expression of C/EBP alpha and C/EBP beta is specifically regulated in brown fat during development. C/EBP alpha, 30 kDa C/EBP alpha, C/E BP beta and LIP content is severalfold higher in fetal brown fat than in the adult tissue, or liver at any stage of development. Peak values are attained in late fetal life, in concurrence with the onset of tra nscription of the uncoupling protein (UCP) gene, the molecular marker of terminal brown-adipocyte differentiation. When adult rats are expos ed to a cold environment, which is a physiological stimulus of brown-a dipose tissue hyperplasia and UCP gene expression, a specific rise in C/EBP beta expression with respect to C/EBP alpha, 30 kDa C/EBP alpha and LIP is observed. Present data suggest that the C/EBP family of tra nscription factors has an important role in the development and termin al differentiation of brown-adipose tissue.