Enhanced Expression of Serotonin Receptor 5-Hydroxytryptamine 2C is Associated with Increased Feather Damage in Dongxiang Blue-Shelled Layers

Molecular biology of serotonergic systems in avian brains

Serotonin (5-hydroxytryptamine, 5-HT) is a phylogenetically conserved neurotransmitter and modulator. Neurons utilizing serotonin have been identified in the central nervous systems of all vertebrates. In the central serotonergic system of vertebrate species examined so far, serotonergic neurons have been confirmed to exist in clusters in the brainstem. Although many serotonin-regulated cognitive, behavioral, and emotional functions have been elucidated in mammals, equivalents remain poorly understood in non-mammalian vertebrates. The purpose of this review is to summarize current knowledge of the anatomical organization and molecular features of the avian central serotonergic system. In addition, selected key functions of serotonin are briefly reviewed. Gene association studies between serotonergic system related genes and behaviors in birds have elucidated that the serotonergic system is involved in the regulation of behavior in birds similar to that observed in mammals. The widespread distribution of serotonergic modulation in the central nervous system and the evolutionary conservation of the serotonergic system provide a strong foundation for understanding and comparing the evolutionary continuity of neural circuits controlling corresponding brain functions within vertebrates. The main focus of this review is the chicken brain, with this type of poultry used as a model bird. The chicken is widely used not only as a model for answering questions in developmental biology and as a model for agriculturally useful breeding, but also in research relating to cognitive, behavioral, and emotional processes. In addition to a wealth of prior research on the projection relationships of avian brain regions, detailed subdivision similarities between avian and mammalian brains have recently been identified. Therefore, identifying the neural circuits modulated by the serotonergic system in avian brains may provide an interesting opportunity for detailed comparative studies of the function of serotonergic systems in mammals.

Effects of poor plumage conditions on egg production, antioxidant status and gene expression in laying hens

The objective of this study was to investigate the effects of poor plumage conditions on production performance, antioxidant status and gene expression in laying hens. Two hundred ten 54-week-old laying hens with similar body weights were assigned into two groups based on plumage conditions (the poor plumage conditions (PPC) group and the control group). All the birds had free access to water and crumbled feed, and received the same management in step cages. Compared with hens in the control group, the hens in the PPC group consumed more feed and produced lighter eggs (P < 0.05). Hens in the PPC group showed lower serum concentrations of glutathione peroxidase and total antioxidant capacity and higher malondialdehyde content than those in the control group. The eggshell breaking strength was lower in the PPC group than in the control group (P < 0.05). The eggshell shape index and yolk colour in the PPC group were significantly higher than those in the control group. The mRNA expression level of HTR2C in the neck skin and that of IL-2 in the liver and breast muscle were higher in the PPC group than in the control group (P < 0.05). The results indicated that PPC may increase feed consumption and influence egg quality, antioxidant status and gene expression in laying hens.

Whole-genome resequencing reveals aberrant autosomal SNPs affect chicken feathering rate

Previous studies have shown that the feather growth rate of chicks is determined by two alleles located on the sex chromosome Z; however, in chicken production, feathering is usually not consistently controlled by the sex chromosome. To identify whether the feathering rate is related to autosomal inheritance, whole-genome resequencing was performed in eight chickens with slow- and fast-feathering rate. A total of 54,984 autosomal single nucleotide polymorphisms (SNPs) were identified, including 393 and 376 exonic SNPs in slow-feathering and fast-feathering chickens, respectively. Mutated genes were mainly involved in response to stimuli and growth and reproduction processes. Mutated genes related to slow-feathering rate were mainly involved in wingless-type MMTV integration site signaling pathway and mitogen-activated protein kinase signaling pathway, whereas mutated genes associated with fast-feathering rate were primarily enriched in autophagy, calcium signaling pathway, extracellular matrix-receptor interaction, and Focal adhesion processes. Importantly, two SNPs, involved in feather development, were found in the exonic regions of Wnt signaling genes. These results shed new light on the relationship between genetic mutation and feather growth rate from the perspective of autosomal inheritance and may have economic significance in chicken breeding.