CIG30, A MOUSE MEMBER OF A NOVEL MEMBRANE-PROTEIN GENE FAMILY, IS INVOLVED IN THE RECRUITMENT OF BROWN ADIPOSE-TISSUE

We have identified a previously uncharacterized gene that is implicate d in the thermogenic function of brown adipose tissue of mice. This ge ne, termed Cig30, is the first mammalian member of a novel gene family comprising several nematode and yeast genes, such as SUR4 and FEN1, m utation of which is associated with highly pleiotropic phenotypes. It codes for a 30-kDa plasma membrane glycoprotein with five putative tra nsmembrane domains. The Cig30 mRNA was readily detected only in brown fat and liver. When animals were exposed to a 3-day cold stress, the C ig30 expression was selectively elevated in brown fat more than 200-fo ld, Similar increases were brought about in two other conditions of br own fat recruitment, namely during perinatal development and after caf eteria diet, The magnitude of Cig30 mRNA induction in the cold could b e mimicked by chronic norepinephrine treatment in vivo. However, in pr imary cultures of brown adipocytes, a synergistic action of norepineph rine and dexamethasone was required for full expression of the gene, i ndicating that both catecholamines and glucocorticoids are required fo r the induction of Cig30. We propose that the CIG30 protein is involve d in a pathway connected with brown fat hyperplasia.