KOKORO-Biology Group, Laboratories for Integrated Biology, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita Osaka 565-0871, Japan.
Front Mol Neurosci. 2012 Aug 31;5:90. doi: 10.3389/fnmol.2012.00090. eCollection 2012.
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 protocadherins (Pcdh) in mammals consist of approximately 50 Pcdh genes (Pcdh-α, Pcdh-β, and Pcdh-γ) that encode cadherin-family cell surface adhesion proteins. Individual neurons express a random combination of Pcdh-α and Pcdh-γ, whereas the expression patterns for the Pcdh-β genes, 22 one-exon genes in mouse, are not fully understood. Here we show that the Pcdh-β genes are expressed in a 3'-polyadenylated form in mouse brain. In situ hybridization using a pan-Pcdh-β probe against a conserved Pcdh-β sequence showed widespread labeling in the brain, with prominent signals in the olfactory bulb, hippocampus, and cerebellum. In situ hybridization with specific probes for individual Pcdh-β 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 Pcdh-β genes are expressed monoallelically and combinatorially in individual Purkinje cells. Scattered expression patterns of individual Pcdh-β 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 Pcdh expression and suggest that the Pcdh-β cluster genes contribute to specifying the identity and diversity of individual neurons.
复杂神经回路的产生依赖于具有不同个体特征的神经元的正确连接。为了理解神经系统的复杂性，必须阐明指定单个神经元的身份和多样性的分子机制。哺乳动物中的聚类原钙黏蛋白 (Pcdh) 由大约 50 个 Pcdh 基因 (Pcdh-α、Pcdh-β 和 Pcdh-γ) 组成，这些基因编码钙黏蛋白家族细胞表面粘附蛋白。单个神经元表达 Pcdh-α 和 Pcdh-γ 的随机组合，而 22 个单外显子基因的 Pcdh-β 基因的表达模式尚未完全了解。在这里，我们展示了 Pcdh-β 基因在小鼠大脑中以 3'-多聚腺苷酸化形式表达。使用针对保守 Pcdh-β 序列的泛 Pcdh-β 探针进行原位杂交显示大脑中广泛标记，在嗅球、海马体和小脑中有明显信号。使用针对单个 Pcdh-β 基因的特异性探针进行原位杂交显示它们的表达在 P10 至 P150 的浦肯野细胞中分散。通过对浦肯野细胞进行新开发的单细胞 3'-RACE 分析，确认了分散的表达模式，该分析清楚地表明 Pcdh-β 基因在单个浦肯野细胞中以单等位基因和组合方式表达。在海马体和大脑皮层的锥体神经元、三叉神经和背根神经节神经元、GABA 能中间神经元和胆碱能神经元中也观察到单个 Pcdh-β 基因的分散表达模式。我们的结果扩展了先前关于 Pcdh 表达产生的单个神经元水平多样性的观察结果，并表明 Pcdh-β 簇基因有助于指定单个神经元的身份和多样性。
