AUTHOR=Hirano Keizo , Kaneko Ryosuke , Izawa Takeshi , Kawaguchi Masahumi , Kitsukawa Takashi , Yagi Takeshi 

TITLE=Single-neuron diversity generated by Protocadherin-β cluster in mouse central and peripheral nervous systems

JOURNAL=Frontiers in Molecular Neuroscience

VOLUME=5

YEAR=2012

URL=https://www.frontiersin.org/journals/molecular-neuroscience/articles/10.3389/fnmol.2012.00090

DOI=10.3389/fnmol.2012.00090

ISSN=1662-5099

ABSTRACT=<p>The generation of complex neural circuits depends on the correct wiring of neurons with diverse individual characteristics. To understand the complexity of the nervous system, the molecular mechanisms for specifying the identity and diversity of individual neurons must be elucidated. The clustered <italic>protocadherins</italic> (<italic>Pcdh</italic>) in mammals consist of approximately 50 <italic>Pcdh</italic> genes (<italic>Pcdh-α</italic>, <italic>Pcdh-β</italic>, and <italic>Pcdh-γ</italic>) that encode cadherin-family cell surface adhesion proteins. Individual neurons express a random combination of <italic>Pcdh-α</italic> and <italic>Pcdh-γ</italic>, whereas the expression patterns for the <italic>Pcdh-β</italic> genes, 22 one-exon genes in mouse, are not fully understood. Here we show that the <italic>Pcdh-β</italic> genes are expressed in a 3′-polyadenylated form in mouse brain. <italic>In situ</italic> hybridization using a pan-<italic>Pcdh-β</italic> probe against a conserved <italic>Pcdh-β</italic> sequence showed widespread labeling in the brain, with prominent signals in the olfactory bulb, hippocampus, and cerebellum. <italic>In situ</italic> hybridization with specific probes for individual <italic>Pcdh-β</italic> genes showed their expression to be scattered in Purkinje cells from P10 to P150. The scattered expression patterns were confirmed by performing a newly developed single-cell 3′-RACE analysis of Purkinje cells, which clearly demonstrated that the <italic>Pcdh-β</italic> genes are expressed monoallelically and combinatorially in individual Purkinje cells. Scattered expression patterns of individual <italic>Pcdh-β</italic> genes were also observed in pyramidal neurons in the hippocampus and cerebral cortex, neurons in the trigeminal and dorsal root ganglion, GABAergic interneurons, and cholinergic neurons. Our results extend previous observations of diversity at the single-neuron level generated by <italic>Pcdh</italic> expression and suggest that the <italic>Pcdh-β</italic> cluster genes contribute to specifying the identity and diversity of individual neurons.</p>