Expression of the dominant-negative regulator Id4 is induced during adipocyte differentiation

Expression of the Id4 gene was investigated during differentiation of 3T3-L 1 preadipocytes into mature adipocytes. Id4 isa member of a family encoding non-DNA binding helix-loop-helix proteins proposed to inhibit the activity of basic HLH (bHLH) proteins important in many developmental processes. We show here that Id4 expression is low in confluent preadipocytes and rapidl y induced by treatment with the combination of hormones which causes differ entiation into mature adipocytes. Id4 expression is also induced by treatme nt with individual hormones, especially dexamathasone. Id4 mRNA can be dete cted in mouse and human adipose tissue, Genes:encoding E-proteins (bHLH pro teins known to interact with and be regulated by Id proteins) are expressed and regulated during differentiation in 3T3-L1 cells. These data suggest t hat the Id4 transcriptional regulator is playing a role in adipose cell dif ferentiation and suggest that DNA-binding HLH proteins may also be importan t in regulation of differentiation of these cells, (C) 1999 Academic Press.