Allelic gene regulation of Pcdh-α and Pcdh-γ clusters involving both monoallelic and biallelic expression in single Purkinje cells

Abstract

The molecular basis for providing the identity and diversity of single neurons is a key for realizing the brain system. Diverse protocadherin isoforms encoded by the Pcdh-α and Pcdh-γ gene clusters are expressed in all of the vertebrates studied. For the Pcdh-α isoforms, differential expression patterns have been found in single Purkinje cells by unusual monoallelic and combinatorial types of gene regulation. Here we investigated total allelic gene regulation in the Pcdh-α and -γ clusters, including the C-type variable exons (C1 to C5) and the Pcdh-γA and -γB variable exons in single Purkinje cells. Using split single-cell reverse transcription-PCR analysis, almost all of the Purkinje cells at postnatal day 21 biallelically expressed all the C-type isoforms, whereas the Pcdh-α isoforms showed both monoallelic and combinatorial expression. The Pcdh-γA and -γB isoforms also showed differential regulation in each cell with both monoallelic and combinatorial gene regulation. These data indicated that different types of allelic gene regulation (monoallelic versus biallelic) occurred in the Pcdh-α and -γ clusters, although they were spliced into the same constant exons. It has been reported that each C-type Pcdh-α or -γ transcript has a different expression pattern during brain development, suggesting that the different C-type variable exons may code temporal diversity, although the Pcdh-α, -γA, and -γB isoforms were differential and combinatorial gene regulation within a single cell. Thus, the multiple gene regulations in the Pcdh-α and -γ clusters had a potential mechanism for increasing the diversity of individual neurons in the brain. © 2006 by The American Society for Biochemistry and Molecular Biology, Inc.