Soluble frizzled-related proteins (sFRPS) function as modulators of Wnt signaling through direct interaction with Wnts. They have a role in regulating cell growth and differentiation in specific cell types. Cell membrane or extracellular matrix-associated. Released by heparin-binding (By similarity). Expression first detected at the pre-streak stage, uniformly distributed throughout the blastula. During primitive streak formation, expression localized to the anterior blastoderm including the anterior tip of primitive streak. At the beginning of Hensen node regression, strongly expressed, anterior to the node, in the ectoderm, in the presumptive neuroectoderm as well as in prechordal and lateral mesoderm. Later expression in the blastoderm anterior to Hensen node. During neurulation, high levels detected in the anterior neural plate. Expression also found in the neural folds including the pre-migratory cephalic neural crest cells, in the anterior ectoderm, in the lateral mesoderm, in the precordal plate and weaker expression in the notochord. From stage 10-14, strong expression in the anterior neural tube, including the optic vessels, where expression is limited to the presumptive neural retina and the overlying ectoderm. Later expression in the lens placode and the outer layer of the optic cup. Expression also in the prechordal plate, the Rathke pouch and later in the infundibular region. Expression in head mesenchyme, including migrating cephalic neural crest cells. Restricted expression within the metencephalic vesicle and ventral neural tube. Also expressed in the notochord, the otic vesicles, dorsal mesocardium and the area vasulosa. From stages 18-26, expression found in the telencephalic vesicles, in the epiphysis, in the optic cup, the trigeminal ganglia, and in a band which occupies the basal plate of prosomere one. During neural tube differentiation, expression follows a rosto-caudal gradient. Expression appears in the floor plate and in cells that occupy the medial neural tube. Expression also localized to the mesenchyme of the developing branchial arches, the most distal and ventral portion of the developing limb buds, including the ectodermal apical ridge and to the mesoderm of the developing kidney. The FZ domain is involved in binding with Wnt ligands. Belongs to the secreted frizzled-related protein (sFRP) family.