Probably in association with the cell surface receptor unc-40, positively modulates the BMP-like Sma/Mab signaling pathway through interaction with both the ligand dbl-1 and its type I receptor sma-6 (PubMed:24004951). Regulates body size and this may be through modulation of the Sma/Mab signaling pathway (PubMed:20534671, PubMed:24004951). Interacts with unc-40 (via FN6 domain), dbl-1 and sma-6. Expressed in pharyngeal, hypodermal and intestinal cells. Expressed from the 1-M to 4-M stage of mesodermal M lineage development during the larval development. Smaller body size compared to wild-type. Belongs to the repulsive guidance molecule (RGM) family.