Regulates Wnt proteins sorting and secretion in a feedback regulatory mechanism. This reciprocal interaction plays a key role in the regulation of expression, subcellular location, binding and organelle-specific association of Wnt proteins. Also plays an important role in establishment of the anterior-posterior body axis formation during development. Interacts with WNT3A (By similarity). Interacts with WNT1, WNT3 and WNT5. Expressed in the brain, skeletal muscle, heart muscle, lung, gut, liver, and kidney (at protein level) (PubMed:20652957). In the brain, expressed in the cortex, striatum, hippocampus and to a lesser extent in the cerebellum (at protein level) (PubMed:20652957). Expressed in kidney, lung, skin, intestine, brain, spinal cord, skeleton, eyes, excretion glands, tooth and palatal shelves (PubMed:19841259). In the cerebellum, expressed in Purkinje cells (PubMed:19841259). Detected at 6.25 dpc in the proximal epiblast at the junction between the embryonic and extraembryonic tissue. Later expression is more restricted to the primitive streak and mesoderm extending to the distal tip of the embryo. Strong expression is found in both posterior visceral endoderm and epiblast at the prestreak, but switched to the mesoderm at late-streak. Up-regulated by WNT1. Transcriptionally activated by beta-catenin and by LEF/TCF-dependent transcription. N-glycosylated. Mice display embryonic lethality before 10.5 dpc. Embryos show defects in the establishment of the body axis and in the primitive streak and mesoderm formation. Belongs to the wntless family.