BAI3 is an Orphan-B GPCR with an unknown ligand. Two isoforms of BAI3 are produced by alternative splicing. Along with BAI3, there are two other brain-specific angiogenesis inhibitor genes, designated BAI1 and BAI2, which have similar tissue specificities and structures. BAI3 has been reported primarily in the brain, but is also localized to lung, testis, and pancreas. ESTs have been isolated from adrenal, B-cell/lung/testis, brain, liver/spleen, pituitary, and testis libraries.