Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584CG Utrecht, The Netherlands.
Biol Open. 2014 Jan 15;3(1):50-8. doi: 10.1242/bio.20136890.
The giant fiber system of the squid Loligo pealei mediates the escape response and is an important neurobiological model. Here, we identified an abundant transcript in the stellate ganglion (SG) that encodes a FMRFamide precursor, and characterized FMRFamide and FI/LRF-amide peptides. To determine whether FMRFamide plays a role in the adult and hatchling giant fiber system, we studied the expression of the Fmrf gene and FMRFamide peptides. In stage 29 embryos and stage 30 hatchlings, Ffmr transcripts and FMRFamide peptide were low to undetectable in the SG, in contrast to groups of neurons intensely expressing the Fmrf gene in several brain lobes, including those that innervate the SG. In the adult SG the Fmrf gene was highly expressed, but the FMRFamide peptide was in low abundance. Intense staining for FMRFamide in the adult SG was confined to microneurons and fibers in the neuropil and to small fibers surrounding giant axons in stellar nerves. This shows that the Fmrf gene in the SG is strongly regulated post-hatching, and suggests that the FMRFamide precursor is incompletely processed in the adult SG. The data suggest that the SG only employs the Fmrf gene post-hatching and restricts the biosynthesis of FMRFamide, demonstrating that this peptide is not a major transmitter of the giant fiber system. This contrasts with brain lobes that engage FMRFamide embryonically as a regulatory peptide in multiple neuronal systems, including the afferent fibers that innervate the SG. The biological significance of these mechanisms may be to generate diversity within Fmrf-expressing systems in cephalopods.
鱿鱼 Loligo pealei 的巨大纤维系统介导逃避反应，是重要的神经生物学模型。在这里，我们鉴定了星状神经节 (SG) 中大量转录本，该转录本编码 FMRFamide 前体，并对 FMRFamide 和 FI/LRF-amide 肽进行了特征描述。为了确定 FMRFamide 是否在成年和孵化的巨型纤维系统中发挥作用，我们研究了 Fmrf 基因和 FMRFamide 肽的表达。在 29 期胚胎和 30 期孵化幼体中，SG 中的 Ffmr 转录本和 FMRFamide 肽低至无法检测到，而在包括支配 SG 的神经节的几个脑叶中，存在大量表达 Fmrf 基因的神经元群。在成年 SG 中，Fmrf 基因高度表达，但 FMRFamide 肽含量低。在成年 SG 中，FMRFamide 的强烈染色仅限于神经胶质中的微神经元和纤维以及星状神经纤维中围绕巨大轴突的小纤维。这表明 SG 中的 Fmrf 基因在孵化后受到强烈调节，并表明 FMRFamide 前体在成年 SG 中未完全加工。这些数据表明，SG 仅在孵化后使用 Fmrf 基因，并限制 FMRFamide 的生物合成，表明该肽不是巨型纤维系统的主要递质。这与脑叶形成对比，脑叶在胚胎期将 FMRFamide 作为调节肽用于包括支配 SG 的传入纤维在内的多个神经元系统。这些机制的生物学意义可能是在头足类动物中产生 Fmrf 表达系统的多样性。
