Changes in subcellular distribution of protocadherin gamma proteins accompany maturation of spinal neurons

Protocadherins gamma (Pcdhgamma) are a family of transmembrane proteins in which variable extracellular domains are associated with an invariant cytoplasmic domain, potentially allowing these proteins to trigger common cellular responses through diverse extracellular signals. We studied the expression of the family by in situ hybridisation and immunohistochemistry for the conserved portion of the mRNA or protein. During mouse development, Pcdhgamma expression is highest in neural tissues, but is also present in some nonneural tissues. In the adult, Pcdhgamma expression is maintained at high levels in brain, in particular in hippocampus and in the Purkinje cells of the cerebellum, whereas it is downregulated in spinal cord. Using antibodies against the conserved cytoplasmic domain, we show that in cultured embryonic spinal cord neurons, Pcdhgamma protein is present initially in both axonal and dendritic growth cones. At later stages of differentiation in vitro, Pcdhgamma distribution becomes polarised to the somatodendritic compartment. We propose that members of the Pcdhgamma family may play roles in neuronal growth and maturation.