epigenetic programming of gene expression

Definition

Target type: biologicalprocess

A epigenetic process that happens during embryonic development that modulates gene expression potential at later stages of development of the organism, including the adult. Epigenetic regulation takes place via chromatin remodeling either by modifying higher order chromatin fiber structure, nucleosomal histones, or cytosine DNA methylation. [GOC:go_curators, PMID:12138111, PMID:22868271]

Epigenetic programming of gene expression is a dynamic and intricate process that orchestrates the accessibility and activity of genes without altering the underlying DNA sequence. It involves modifications to chromatin, the complex of DNA and proteins that packages the genome within the nucleus of a cell. These modifications can be inherited through cell division and influence diverse cellular functions, including development, differentiation, and disease susceptibility.

Key players in this process include:

1. **DNA methylation:** The addition of a methyl group to cytosine bases in DNA, often at CpG dinucleotides. Methylation patterns can be established during development and maintained throughout life. Generally, methylation silences gene expression by hindering the binding of transcription factors and recruiting proteins that compact chromatin.

2. **Histone modifications:** Histone proteins act as spools around which DNA is wrapped. Modifications to histone tails, such as acetylation, methylation, phosphorylation, and ubiquitination, can alter the accessibility of DNA to transcription factors. For instance, histone acetylation typically promotes gene expression by loosening chromatin structure, while histone methylation can either activate or repress gene expression depending on the specific amino acid residue and the degree of methylation.

3. **Non-coding RNAs:** A diverse class of RNA molecules that do not encode proteins but play critical roles in gene regulation. Some non-coding RNAs, such as microRNAs (miRNAs), can silence gene expression by targeting messenger RNA (mRNA) for degradation or translational repression. Others, like long non-coding RNAs (lncRNAs), can act as scaffolds for protein complexes that modulate chromatin structure and gene expression.

4. **Chromatin remodeling complexes:** These protein complexes can reposition nucleosomes, the basic units of chromatin, to expose or conceal specific DNA sequences. Their activities are often regulated by signals from the cellular environment or by other epigenetic modifications.

These modifications, acting in concert, establish a complex and dynamic epigenetic landscape that influences gene expression profiles. During development, epigenetic programming helps establish cell fate by specifying which genes are active or inactive in different cell types. This process is essential for the proper development and function of tissues and organs.

Epigenetic programming is also involved in the adaptation of organisms to environmental challenges and in disease pathogenesis. For example, exposure to environmental toxins can lead to epigenetic modifications that contribute to cancer development. Conversely, lifestyle interventions, such as exercise and diet, can influence epigenetic patterns and potentially promote health and longevity.

The field of epigenetics is rapidly evolving, and new discoveries are constantly shedding light on the intricate mechanisms and far-reaching implications of epigenetic programming. Understanding this process is crucial for developing strategies to treat diseases, prevent adverse health outcomes, and optimize human health.'
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