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Review
. 2023 May 5;24(9):8287.
doi: 10.3390/ijms24098287.

Chicken Erythrocyte: Epigenomic Regulation of Gene Activity

Tasnim H Beacon  1 , James R Davie  1
Affiliations
Review

Chicken Erythrocyte: Epigenomic Regulation of Gene Activity

Tasnim H Beacon et al. Int J Mol Sci. .

Abstract

The chicken genome is one-third the size of the human genome and has a similarity of sixty percent when it comes to gene content. Harboring similar genome sequences, chickens' gene arrangement is closer to the human genomic organization than it is to rodents. Chickens have been used as model organisms to study evolution, epigenome, and diseases. The chicken nucleated erythrocyte's physiological function is to carry oxygen to the tissues and remove carbon dioxide. The erythrocyte also supports the innate immune response in protecting the chicken from pathogens. Among the highly studied aspects in the field of epigenetics are modifications of DNA, histones, and their variants. In understanding the organization of transcriptionally active chromatin, studies on the chicken nucleated erythrocyte have been important. Through the application of a variety of epigenomic approaches, we and others have determined the chromatin structure of expressed/poised genes involved in the physiological functions of the erythrocyte. As the chicken erythrocyte has a nucleus and is readily isolated from the animal, the chicken erythrocyte epigenome has been studied as a biomarker of an animal's long-term exposure to stress. In this review, epigenomic features that allow erythroid gene expression in a highly repressive chromatin background are presented.

Keywords: chicken erythrocyte; epigenetics; histone (H4R3me2a) and DNA modifications.

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Conflict of interest statement

The authors declare that they have no known competing financial interest or personal relationship that could have appeared to influence the work reported in this paper.

Figures

Figure 1
Figure 1
Repressed and transcriptionally active chromatin. In chicken polychromatic erythrocytes, repressed chromatin on the left has a condensed 30 nm chromatin structure and is insoluble at physiological ionic strength. Transcriptionally active chromatin shown on the right has a decondensed chromatin structure that is soluble at physiological ionic strength. Histone acetylation plays a key role in keeping the chromatin fibers separated. Histone PTMs and variants associated with each chromatin state are listed.
Figure 2
Figure 2
Representation of the typical chromatin structure in vertebrates. The illustration shows chromosome territories, compartments, and topologically associating domains, which chicken erythrocytes do not have. Compartment B has repressed chromatin and repressive histones marks, while compartment A has transcribed chromatin and active marks. Created with BioRender.com (accessed on 24 March 2023).
Figure 3
Figure 3
Chromatin fractionation schema. For further details of the chromatin fractionation protocol, see [12]. Transcriptionally active/poised chromatin is enriched in fractions F1, F2, and F3 which contain highly acetylated core histones. The P150 chromatin fraction has transcriptionally repressed chromatin. The PE fraction has the residual nuclear material including the nuclear matrix, and transcriptionally active/poised and repressed chromatin. Ac, acetylated histone.
Figure 4
Figure 4
The β-globin domain in chicken erythrocytes is shown. LCR, locus control region, HS, hypersensitive site (nucleosome-free region). The arrows indicate the direction of transcription. The curved arrows show the interactions between the LCR and the HBBA enhancer and insulator element.
Figure 5
Figure 5
The β-globin domain in chicken polychromatic erythrocytes. Shown are the tracks for F1 Seq, FAIRE Seq, and ChIP Seq for H3K4me3, H3K27ac, H3R2me2s, and H4R3me2a.
Figure 6
Figure 6
Innate immune response in chicken erythrocytes. Activation of the TLR3 and TLR4 receptors by dsRNA and LPS, respectively, initiates a series of modification and protein binding events resulting in the expression of pro-inflammatory cytokines and interferon (IFN).
See this image and copyright information in PMC

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