In this study researchers identified two new genes that cause MLC, named AQP4 and GPRC5B. Along with MLC1 and GLIALCAM, this now makes a total of 4 genes associated with MLC, although mutations in AQP4 and GPRC5B appear to be more rare. AQP4 encodes Aquaporin-4, an important brain water channel expressed in astrocytes. GPRC5B is what we call a G protein-coupled receptor, which is a broad family of membrane proteins of various functions. The family of receptors to which GPRC5B belongs is targeted by many human drugs, making GPRC5B an interesting target for future therapy development.