Körber Christoph, Dondzillo Anna, Eisenhardt Gisela, Herrmannsdörfer Frank, Wafzig Oliver, Kuner Thomas
Department of Functional Neuroanatomy, Institute of Anatomy and Cell Biology, Heidelberg University, Heidelberg, Germany.
Eur J Neurosci. 2014 Sep;40(6):2867-77. doi: 10.1111/ejn.12661. Epub 2014 Jul 3.
Calyx of Held giant presynaptic terminals in the auditory brainstem form glutamatergic axosomatic synapses that have advanced to one of the best-studied synaptic connections of the mammalian brain. As the auditory system matures and adjusts to high-fidelity synaptic transmission, the calyx undergoes extensive structural and functional changes - in mice, it is formed at about postnatal day 3 (P3), achieves immature function until hearing onset at about P10 and can be considered mature from P21 onwards. This setting provides a unique opportunity to examine the repertoire of genes driving synaptic structure and function during postnatal maturation. Here, we determined the gene expression profile of globular bushy cells (GBCs), neurons giving rise to the calyx of Held, at different maturational stages (P3, P8, P21). GBCs were retrogradely labelled by stereotaxic injection of fluorescent cholera toxin-B, and their mRNA content was collected by laser microdissection. Microarray profiling, successfully validated with real time quantitative polymerase chain reaction and nCounter approaches, revealed genes regulated during maturation. We found that mostly genes implicated in the general cell biology of the neuron were regulated, while most genes related to synaptic function were regulated around the onset of hearing. Among these, voltage-gated ion channels and calcium-binding proteins were strongly regulated, whereas most genes involved in the synaptic vesicle cycle were only moderately regulated. These results suggest that changes in the expression patterns of ion channels and calcium-binding proteins are a dominant factor in defining key synaptic properties during maturation of the calyx of Held.
听觉脑干中的 Held 壶腹巨大突触前终末形成了谷氨酸能轴体突触，这是哺乳动物脑中研究得最为深入的突触连接之一。随着听觉系统的成熟并适应高保真突触传递，Held 壶腹会经历广泛的结构和功能变化——在小鼠中，它大约在出生后第 3 天（P3）形成，在大约 P10 听力开始前实现不成熟功能，从 P21 起可被认为是成熟的。这种情况为研究出生后成熟过程中驱动突触结构和功能的基因库提供了独特的机会。在这里，我们确定了球状毛细胞（GBCs）在不同成熟阶段（P3、P8、P21）的基因表达谱，球状毛细胞是产生 Held 壶腹的神经元。通过立体定位注射荧光霍乱毒素 B 对 GBCs 进行逆行标记，并通过激光显微切割收集它们的 mRNA 含量。通过实时定量聚合酶链反应和 nCounter 方法成功验证的微阵列分析揭示了成熟过程中受调控的基因。我们发现，大多数与神经元一般细胞生物学相关的基因受到调控，而大多数与突触功能相关的基因在听力开始时左右受到调控。其中，电压门控离子通道和钙结合蛋白受到强烈调控，而大多数参与突触小泡循环的基因仅受到适度调控。这些结果表明，离子通道和钙结合蛋白表达模式的变化是在 Held 壶腹成熟过程中定义关键突触特性的主导因素。
