Resistin, a recently discovered hormone that may play a crucial role in obesity-associated diabetes, is the founding member of a novel family of cysteine-rich proteins that are secreted by specific cell types. Three other members of this family have been described to date and were termed resistin-like molecules (RELMs). Here we describe the cloning and functional characterization of RELMgamma. The mouse RELMgamma-cDNA encodes a protein of 117 amino acids that contains a signal peptide leading to secretion of the protein. By Northern blotting the RELMgamma-mRNA is detectable in bone marrow, spleen, and lung as well as in peripheral blood granulocytes. Promyelocytic HL60 cells transfected with a RELM-gamma expression plasmid have an increased proliferation rate compared to mock-transfected cells and display an altered response to retinoic acid-induced granulocytic differentiation. Taken together, these data provide the first experimental evidence that RELMgamma is a secreted molecule with a restricted expression pattern that may play a role in promyelocytic differentiation. (C) 2003 Elsevier Inc. All rights reserved.