G protein-coupled receptors (GPRs) are a protein family of transmembrane receptors that transmit an extracellular signal (ligand binding) into an intracellular signal (G protein activation). GPR signaling is an evolutionarily ancient mechanism used by all eukaryotes to sense environmental stimuli and mediate cell-cell communication. All of the receptors have seven membrane-spanning domains and the extracellular parts of the receptor can be glycosylated. These extracellular loops also contain two highly conserved cysteine residues which create disulfide bonds to stabilize the receptor structure. GPR12 is a 334 amino acid peptide that is expressed primarily in brain, particularly in regions where neuronal differentiation takes place. GPR12 is coupled to an inhibitory G protein. It positively influences differentiation and maturation of post-mitotic neurons, and it may promote the growth of neuronal precursor cells.