Bone morphogenetic proteins (BMPs) belong to the transforming growth factor-beta (TGF-β) superfamily of signaling molecules. Secreted BMP ligands bind cell surface receptors to initiate activation of a intracellular phosphorylation cascade, including both the type I and type II receptors, receptor-associated Smads (R-Smads), and common-mediator Smads (Co- Smads). The BMP pathway is highly conserved and functions across metazoans to regulate embryonic development and adult homeostasis. Perturbations of cell communication can wreak havoc on downstream processes, causing developmental disorders or diseases. As such, the BMP pathway must be tightly regulated in space, time, level, and duration. The Liu Lab uses C. elegans as a model system to identify and investigate modulators of a BMP-like pathway. Leveraging a highly specific forward genetic screen, our lab has identified new BMP pathway modulators including the secreted modular calcium binding (SMOC-1) protein.Here, I demonstrate that C. elegans SMOC-1 promotes BMP signaling in a cell non-autonomous fashion by acting through the BMP ligand in a positive feedback loop. SMOC proteins are secreted proteins containing a thyroglobulin type-1 (TY) domain followed by an extracellular calcium binding (EC) domain. To understand the roles of each SMOC-1 domain, I have implemented techniques to express fully functional tagged SMOC-1 from overexpressed transgenes or the endogenous smoc-1 locus. I have found that overexpression of SMOC-1(EC) can robustly promote the BMP pathway, yet endogenous levels of the EC domain are only partially functional. Both overexpression and endogenous expression of SMOC-1(TY) has limited abilities to effect BMP signaling. I further showed that when tethered to the membrane, overexpression of full length SMOC-1 can partially function in BMP signaling, but SMOC-1(EC) alone is not sufficient to function, suggesting that SMOC-1’s TY domain is required for SMOC-1 function at the membrane. These findings indicate that SMOC-1 can function as both a long range and local modulator of BMP signaling. Finally, we have identified LON- 2/glypican as a SMOC-1-interacting protein in C. elegans, with evidence that the EC domains is primarily responsible for the interaction. Taken together, my work supports a model where SMOC-1 outcompetes the DBL-1/ligand from binding to the negative regulator LON-2/glypican, thus promoting BMP signaling.