Analysis of the brain transcriptome in lines of laying hens divergently selected for feather pecking

Background: Feather pecking (FP) in laying hens reduces animal welfare and leads to economic losses for the layer industry. FP is considered a heritable condition that is influenced by dysregulation of neurotransmitter homeostasis, the gut microbiome, and the immune system. To identify genes and biological pathways responsible for FP behavior we compared the brain transcriptomes of 48 hens divergently selected for FP. In addition, we tested if high feather peckers (HFP) and low feather peckers (LFP) respond differently to light since light has been shown to trigger FP behavior.Results: Of approximately 48 million reads/sample an average of 98.4 % were mapped to the chicken genome (GRCg6a). We found 13,070 expressed genes in the analyzed brains of which 423 showed differential expression between HFP and LFP. Genes of uncertain function and non-coding RNAs were overrepresented among those transcripts. Functional analyses revealed the involvement of cholinergic signaling, postsynaptic activity, membrane channels, and the immune system. After the light stimulus, 28 genes were found to be differentially expressed. These included an interaction cluster of core components of the circadian clock. However, differences in the response to light between HFP and LFP were not detectable.Conclusions: Genes involved in cholinergic signaling, channel activity, synaptic transmission, and immune response were found to be involved in FP behavior. We propose a model in which the gut microbiota modulates the immune system, which in turn affects cholinergic signaling. This might have an influence on monoamine signaling with possible involvement of GABA or glutamate signaling.

背景：蛋鸡啄羽行为（Feather pecking, FP）会损害动物福利，并给蛋鸡养殖业造成经济损失。该行为被视为一种可遗传性状，其发生受神经递质稳态失调、肠道微生物组（gut microbiome）与免疫系统的共同调控。为鉴定与啄羽行为相关的基因及生物学通路，本研究对48只经啄羽性状定向选育的差异品系母鸡开展大脑转录组对比分析。此外，鉴于已有研究表明光照可诱发啄羽行为，本研究同时测试了高啄羽鸡（HFP）与低啄羽鸡（LFP）对光照的响应是否存在差异。
结果：每个样本的原始测序reads约为4800万条，平均98.4%的reads可比对至鸡参考基因组（GRCg6a）。本次分析共在脑组织中鉴定到13070个表达基因，其中423个在高、低啄羽鸡群体间呈现差异表达。在这些差异转录本中，功能未知基因与非编码RNA（non-coding RNAs）占比偏高。功能富集分析显示，胆碱能信号通路、突触后活动、膜通道及免疫系统均参与该过程。经光照刺激后，共鉴定到28个差异表达基因，其中包含生物钟核心组分的相互作用簇。但未检测到高、低啄羽鸡在光照响应上存在显著差异。
结论：本研究发现，胆碱能信号通路、通道活动、突触传递以及免疫应答相关基因均与啄羽行为密切相关。我们提出如下模型：肠道菌群可通过调控免疫系统，进而影响胆碱能信号通路，该过程或通过γ-氨基丁酸（GABA）或谷氨酸信号通路参与单胺类信号的调控。