GPR56, an orphan G protein-coupled receptor (GPCR), was identified one decade ago by two independent groups through a degenerate PCR-based approach for secretin-like GPCRs and by differential display of melanoma cell lines with different metastatic potentials. The finding that GPR56 was significantly downregulated in high metastatic melanoma cell lines suggests its possible role in cancer metastasis. However, the function of GPR56 remained unclear until 2004 when mutations in the human GPR56 gene were found to cause a specific brain malformation called bilateral frontoparietal polymicrogyria. Although GPR56 is expressed in a wide range of tissues, the consequences of loss-of-function mutations in the GPR56 gene have only been observed in the central nervous system. Studies from knockout mouse model indicate that GPR56 regulates brain development by affecting the integrity of the pial basement membrane in the developing brain.