In the phosphoinositide (PI) cycle, phospholipase C (PLC) catalyzes hydrolysis of a plasma membrane phospholipid, phosphatidylinositol 4,5-bisphosphate, generating 2 second messengers, the water soluble 1,4,5-inositol trisphosphate and the membrane-associated 1,2-diacylglycerol. In mammalian tissues, several groups of PLCs have been characterized, including PLC-beta, and each group contains at least 3 isoforms. PLCb4 catalyzes the formation of inositol 1,4,5-trisphosphate and diacylglycerol from phosphatidylinositol 4,5-bisphosphate. This reaction uses calcium as a cofactor and plays an important role in the intracellular transduction of many extracellular signals in the retina. Two transcript variants encoding different isoforms have been found for this gene.