Patterns of expression for the mRNA corresponding to the four isoforms of phospholipase Cβ in mouse brain

Ligand binding to neurotransmitter and hormone receptors which couple to the Go subclass of GTP-binding protein leads to the activation of phospholipase C beta (PLC beta) which hydrolyses phosphatidyl-inositol 4,5-bisphosphate, yielding a pair of second messengers, diacylglycerol and inositol 1,4,5-trisphosphate (IP3), The expression of PLC beta 1-4 mRNAs was comparatively examined by in situ hybridization in the mouse brain. in adults, PLC beta 1 mRNA was expressed predominantly in the telencephalon, including the cerebral cortex, hippocampus, amygdala, lateral septum and olfactory bulb, with little expression in most thalamic nuclei, PLC beta 2 mRNA was distributed in the white matter, suggesting its expression in non-neuronal cells, most likely oligodendrocytes. PLC beta 3 mRNA was specifically expressed in cerebellar Purkinje cells, The highest levels of PLC beta 4 mRNA were detected in Purkinje cells. High levels of PLC beta 4 mRNA were also found in the thalamus and medial septum, whereas weak signals were detected in most telencephalic regions, thus showing an expression pattern almost reciprocal to that of PLC beta 1 mRNA. During development, such characteristic regional expression of PLC beta 1 and PLC beta 4 were observed starting in late foetal stages, while specific expression of PLC beta 2 and PLC beta 3 appeared in early postnatal stages. We conclude that despite the existence of four PLC beta isoforms, only one or two of them is expressed in individual neurons and glial cells, The distinct expression of PLC beta s provides a molecular basis for analysing the nature of the specific signal transduction pathway leading to the production of diacylglycerol and IP3 in distinct cell types and in different regions of the brain.