Receptor for R-spondins that potentiates the canonical Wnt signaling pathway and acts as a stem cell marker of the intestinal epithelium and the hair follicle. Upon binding to R-spondins (RSPO1, RSPO2, RSPO3 or RSPO4), associates with phosphorylated LRP6 and frizzled receptors that are activated by extracellular Wnt receptors, triggering the canonical Wnt signaling pathway to increase expression of target genes. In contrast to classical G-protein coupled receptors, does not activate heterotrimeric G-proteins to transduce the signal. Involved in the development and/or maintenance of the adult intestinal stem cells during postembryonic development. Identified in a complex composed of RNF43, LGR5 and RSPO1 (By similarity). Also interacts with other R-spondin ligands, including RSPO2, RSPO3 and RSPO4 (By similarity). Rapidly and constitutively internalized to the trans-Golgi network at steady state. Expressed in the gonads, the adrenal gland, and in the brain. In the central nervous system expression is restricted to the olfactory bulb. In the adrenal gland detected only in the neural-crest derived chromaffin cells of the medulla, but not in the cells of the adrenal cortex. In the gonads, the expression is high in Graafian follicle, but absent from primary and secondary follicles. In the intestine, exclusively expressed in cycling crypt base columnar cells. Expressed in the lower bulge and secondary germ area of telogen hair follicles and in the lower outer root sheath of anagen hair follicle. First expressed at 8.5 dpc in a few cells of the ectoplacental cone and, at 9.5 dpc, in a greater number of cells in the labyrinthine region of the forming placenta. In the embryo per se, expression starts at 9.5 dpc. At 10.5 dpc, detected in the facial area in the tissue overlaying the mandibular cleft and in the optic cup. In the central nervous system, expressed in the neuroepithelium at the roof of the mesencephalon and in the spinal cord. At 11.5 dpc, in the central nervous system, expressed in the neuroepithelium at the border between mes- and metencephalon and that lining the fourth ventricle and the retina, as well as in the spinal cord. Outside the nervous system, at 11.5 dpc, expressed in the mesenchyme over-laying the mandibular cleft, in the distal limb buds, especially the hind limb buds, as well as in the perichordal mesenchyme in the rostral region of the embryo. At 12.5 dpc, in the central nervous system, highly expressed in the rhombencephalic isthmus. In the facial area, expressed in the mesenchyme surrounding the olfactory epithelium and the forming vibrissae. Expression in the hind and front limb buds increases and spreads to more proximal directions, but is restricted to the area were the digits develop. At 13.5 dpc, the expression in the brain becomes restricted to the border between mes- and diencephalon. Also detected in the pituitary. Strongly expressed in the mesenchyme adjacent to the mandibular cleft, as well as in the most lateral aspects of the tongue and the teeth anlagen. Weak expression in the body wall and mesenchyme surrounding internal organs. At 14.5 dpc, becomes hardly detectable in the nervous system. In the body, expressed in the perichondrium, but levels decrease with ongoing age (PubMed:9920770). In the limbs, at 14.5 dpc, expressed in the mesenchyme, but not in the overlying ectoderm of the limb bud. In developing lungs, at 14.5 dpc, expressed at low levels in both the epithelium and mesenchyme lineages (PubMed:29769720). Mice exhibit malformation of the tongue and of lower jam causing newborns to swallow air leading to 100% neonatal lethality. Conditional knockout of both Lgr4 and Lgr5 in the gut results in Wnt signaling inhibition and results in the rapid demise of intestinal crypts (PubMed:21727895). Simultaneous knockdown of LGR4, LGR5 and LGR6 results in developmental phenotypes, such as cleft palate and ankyloglossia, but not in tetra-amelia with lung agenesis (PubMed:29769720). LGR5 is used as a marker of adult tissue stem cells in the intestine, stomach, hair follicle, and mammary epithelium. Belongs to the G-protein coupled receptor 1 family.