(A) Organization of the murine Pcdh gene clusters. White: Pcdhα alternate genes; Aqua: Pcdhβ genes; Grey: Pcdhγ alternate genes; Purple: c-type genes from the Pcdh α and γ clusters. Arrows indicate all the promoters of the Pcdh genes. (B) Example of a stochastic and combinatorial expression of Pcdh genes from all three clusters in olfactory sensory neurons (OSNs). (C) Example of a stochastic and combinatorial expression of Pcdh alternate genes from all three clusters in Purkinje neurons. In these neurons, the c-type are biallelically and constitutively expressed in every cell. (D) Example of a determinative expression of the sole cluster Pcdhαc2 in serotonergic neurons.
The expression of Pcdh genes shown in (B-C) is meant to summarize expression from both chromosomes, as the two chromosomes behave independently with regards to Pcdh promoter choice.