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Epigenetic marks: regulators of livestock phenotypes and conceivable sources of missing variation in livestock improvement programs.

Ibeagha-Awemu EM, Zhao X - Front Genet (2015)

Bottom Line: Accumulating evidence shows that epigenetic marks influence gene expression and phenotypic outcome in livestock species.However, epigenetic research activities on farm animal species are currently limited partly due to lack of recognition, funding and a global network of researchers.Therefore, considerable less attention has been given to epigenetic research in livestock species in comparison to extensive work in humans and model organisms.

View Article: PubMed Central - PubMed

Affiliation: Dairy and Swine Research and Development Centre, Agriculture and Agri-Food Canada Sherbrooke, QC, Canada.

ABSTRACT
Improvement in animal productivity has been achieved over the years through careful breeding and selection programs. Today, variations in the genome are gaining increasing importance in livestock improvement strategies. Genomic information alone, however, explains only a part of the phenotypic variance in traits. It is likely that a portion of the unaccounted variance is embedded in the epigenome. The epigenome encompasses epigenetic marks such as DNA methylation, histone tail modifications, chromatin remodeling, and other molecules that can transmit epigenetic information such as non-coding RNA species. Epigenetic factors respond to external or internal environmental cues such as nutrition, pathogens, and climate, and have the ability to change gene expression leading to emergence of specific phenotypes. Accumulating evidence shows that epigenetic marks influence gene expression and phenotypic outcome in livestock species. This review examines available evidence of the influence of epigenetic marks on livestock (cattle, sheep, goat, and pig) traits and discusses the potential for consideration of epigenetic markers in livestock improvement programs. However, epigenetic research activities on farm animal species are currently limited partly due to lack of recognition, funding and a global network of researchers. Therefore, considerable less attention has been given to epigenetic research in livestock species in comparison to extensive work in humans and model organisms. Elucidating therefore the epigenetic determinants of animal diseases and complex traits may represent one of the principal challenges to use epigenetic markers for further improvement of animal productivity.

No MeSH data available.


Related in: MedlinePlus

Epigenetic marks respond to internal and environmental cues (A) resulting in various effects on chromatic conformation and gene expression. (B) Compact chromatin: tends to contain silent genes, modified DNA and histones. A number of nuclear factors such as DNA methyltransferases (DNMTs), methyl-CpG binding domain proteins (MBDs), histone methyltransferases (HMT, K9, H3), histonedeactylases (HDACs), and DNA methylation are involved in silencing gene expression. In the compact state, genes are inaccessible to transcription factors and non-coding RNAs (ncRNAs). (C) Relaxed chromatin: has dispersed appearance and is gene rich. Transcriptionally active genes are rich in unmethylated DNA. Histones are generally hyperacetylated. Histone methyltransferases (HMT, K4, H3) and acetyltransferaces (HATs) are associated with unmethylated promoters and transcriptional activity. Genes are accessible to transcription factors and ncRNAs. (D) Diverse phenotypes may result.
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Figure 1: Epigenetic marks respond to internal and environmental cues (A) resulting in various effects on chromatic conformation and gene expression. (B) Compact chromatin: tends to contain silent genes, modified DNA and histones. A number of nuclear factors such as DNA methyltransferases (DNMTs), methyl-CpG binding domain proteins (MBDs), histone methyltransferases (HMT, K9, H3), histonedeactylases (HDACs), and DNA methylation are involved in silencing gene expression. In the compact state, genes are inaccessible to transcription factors and non-coding RNAs (ncRNAs). (C) Relaxed chromatin: has dispersed appearance and is gene rich. Transcriptionally active genes are rich in unmethylated DNA. Histones are generally hyperacetylated. Histone methyltransferases (HMT, K4, H3) and acetyltransferaces (HATs) are associated with unmethylated promoters and transcriptional activity. Genes are accessible to transcription factors and ncRNAs. (D) Diverse phenotypes may result.

Mentions: DNA methylation is a form of epigenetic modification that involves covalent addition of a methyl group to the 5’ position of cytosine base in DNA sequence in a reaction catalyzed by a class of enzymes known as DNA methyltransferases (DNMT1, DNMT3a, and DNMT3b) with S-adenosyl-methionine as the methyl donor (Miranda and Jones, 2007). The enzymatic activity of DNMT1 maintains DNA methylation during DNA replication while DNMT3a and DNMT3b are responsible for de novo methylation of unmodified DNA. DNA methylation is crucial for genomic stability and is used by mammalian cells to maintain development. DNA methylation occurs mostly at cytosine-phosphate-guanosine (CpG) dinucleotides and to a lesser extent at CpA, CpT, or CpC dinucleotides (Ziller et al., 2011). DNA methylation in the promoter region of genes has been generally associated with transcriptional repression, while their hypomethylation is linked with transcriptional activation leading to increased expression of genes (Figure 1). On the other hand, methylation in the body of genes can actually lead to increased transcriptional activation (Langevin and Kelsey, 2013). Therefore, even though all the cells of an organism contain the same genetic information, different tissue/cell types have a unique DNA methylation profile that arises during development and is consequently maintained after DNA replication and cellular differentiation for tissue/cell-specific gene expression.


Epigenetic marks: regulators of livestock phenotypes and conceivable sources of missing variation in livestock improvement programs.

Ibeagha-Awemu EM, Zhao X - Front Genet (2015)

Epigenetic marks respond to internal and environmental cues (A) resulting in various effects on chromatic conformation and gene expression. (B) Compact chromatin: tends to contain silent genes, modified DNA and histones. A number of nuclear factors such as DNA methyltransferases (DNMTs), methyl-CpG binding domain proteins (MBDs), histone methyltransferases (HMT, K9, H3), histonedeactylases (HDACs), and DNA methylation are involved in silencing gene expression. In the compact state, genes are inaccessible to transcription factors and non-coding RNAs (ncRNAs). (C) Relaxed chromatin: has dispersed appearance and is gene rich. Transcriptionally active genes are rich in unmethylated DNA. Histones are generally hyperacetylated. Histone methyltransferases (HMT, K4, H3) and acetyltransferaces (HATs) are associated with unmethylated promoters and transcriptional activity. Genes are accessible to transcription factors and ncRNAs. (D) Diverse phenotypes may result.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4585011&req=5

Figure 1: Epigenetic marks respond to internal and environmental cues (A) resulting in various effects on chromatic conformation and gene expression. (B) Compact chromatin: tends to contain silent genes, modified DNA and histones. A number of nuclear factors such as DNA methyltransferases (DNMTs), methyl-CpG binding domain proteins (MBDs), histone methyltransferases (HMT, K9, H3), histonedeactylases (HDACs), and DNA methylation are involved in silencing gene expression. In the compact state, genes are inaccessible to transcription factors and non-coding RNAs (ncRNAs). (C) Relaxed chromatin: has dispersed appearance and is gene rich. Transcriptionally active genes are rich in unmethylated DNA. Histones are generally hyperacetylated. Histone methyltransferases (HMT, K4, H3) and acetyltransferaces (HATs) are associated with unmethylated promoters and transcriptional activity. Genes are accessible to transcription factors and ncRNAs. (D) Diverse phenotypes may result.
Mentions: DNA methylation is a form of epigenetic modification that involves covalent addition of a methyl group to the 5’ position of cytosine base in DNA sequence in a reaction catalyzed by a class of enzymes known as DNA methyltransferases (DNMT1, DNMT3a, and DNMT3b) with S-adenosyl-methionine as the methyl donor (Miranda and Jones, 2007). The enzymatic activity of DNMT1 maintains DNA methylation during DNA replication while DNMT3a and DNMT3b are responsible for de novo methylation of unmodified DNA. DNA methylation is crucial for genomic stability and is used by mammalian cells to maintain development. DNA methylation occurs mostly at cytosine-phosphate-guanosine (CpG) dinucleotides and to a lesser extent at CpA, CpT, or CpC dinucleotides (Ziller et al., 2011). DNA methylation in the promoter region of genes has been generally associated with transcriptional repression, while their hypomethylation is linked with transcriptional activation leading to increased expression of genes (Figure 1). On the other hand, methylation in the body of genes can actually lead to increased transcriptional activation (Langevin and Kelsey, 2013). Therefore, even though all the cells of an organism contain the same genetic information, different tissue/cell types have a unique DNA methylation profile that arises during development and is consequently maintained after DNA replication and cellular differentiation for tissue/cell-specific gene expression.

Bottom Line: Accumulating evidence shows that epigenetic marks influence gene expression and phenotypic outcome in livestock species.However, epigenetic research activities on farm animal species are currently limited partly due to lack of recognition, funding and a global network of researchers.Therefore, considerable less attention has been given to epigenetic research in livestock species in comparison to extensive work in humans and model organisms.

View Article: PubMed Central - PubMed

Affiliation: Dairy and Swine Research and Development Centre, Agriculture and Agri-Food Canada Sherbrooke, QC, Canada.

ABSTRACT
Improvement in animal productivity has been achieved over the years through careful breeding and selection programs. Today, variations in the genome are gaining increasing importance in livestock improvement strategies. Genomic information alone, however, explains only a part of the phenotypic variance in traits. It is likely that a portion of the unaccounted variance is embedded in the epigenome. The epigenome encompasses epigenetic marks such as DNA methylation, histone tail modifications, chromatin remodeling, and other molecules that can transmit epigenetic information such as non-coding RNA species. Epigenetic factors respond to external or internal environmental cues such as nutrition, pathogens, and climate, and have the ability to change gene expression leading to emergence of specific phenotypes. Accumulating evidence shows that epigenetic marks influence gene expression and phenotypic outcome in livestock species. This review examines available evidence of the influence of epigenetic marks on livestock (cattle, sheep, goat, and pig) traits and discusses the potential for consideration of epigenetic markers in livestock improvement programs. However, epigenetic research activities on farm animal species are currently limited partly due to lack of recognition, funding and a global network of researchers. Therefore, considerable less attention has been given to epigenetic research in livestock species in comparison to extensive work in humans and model organisms. Elucidating therefore the epigenetic determinants of animal diseases and complex traits may represent one of the principal challenges to use epigenetic markers for further improvement of animal productivity.

No MeSH data available.


Related in: MedlinePlus