GREM1 belongs to the DAN family. It contains 1 CTCK (C-terminal cystine knot-like) domain. GREM1 is a cysteine knot-secreted protein and acts as an inhibitor in the TGF beta signaling pathway. It inhibits BMP-2, -4, and -7. Inhibition by Grem 1 of BMPs in mice allows the expression of fibroblast growth factors (FGFs) 4 and 8 and Sonic hedgehog (Shh) which are necessary for proper limb development. It interacts with SLIT1 and SLIT2 in a glycosylation-dependent manner. As a cytokine, GREM1 may play an important role during carcinogenesis and metanephric kidney organogenesis, as a BMP antagonist required for early limb outgrowth and patterning in maintaining the FGF4-SHH feedback loop. It down-regulates the BMP4 signaling in a dose-dependent manner. It also acts as an inhibitor of monocyte chemotaxis. GREM1 is highly expressed in the small intestine, fetal brain, and colon.