International Journal of Molecular Zoology 2024, Vol.14, No.5, 290-296 http://animalscipublisher.com/index.php/ijmz 291 2 Current Insights in Epigenetics 2.1 Mechanisms of epigenetic regulation Epigenetic regulation involves modifications that alter gene expression without changing the DNA sequence itself (Figure 1). Two primary mechanisms are DNA methylation and histone modifications (Gagnidze and Pfaff, 2022). DNA methylation typically suppresses gene expression by adding methyl groups to DNA, often at cytosine bases in CpG islands. Histone modifications, such as acetylation and methylation, alter the chromatin structure, making DNA more or less accessible for transcription (Feil and Fraga, 2012). These mechanisms are crucial for cellular differentiation and development, allowing genetically identical cells to perform diverse functions (Lu, 2024). Figure 1 Sketch illustrating the multi-layered control of gene expression by various epigenetic processes. DNA is subject to direct chemical modification by addition or removal of methyl groups at cytosine bases. Epigenetic processes regulating gene expression at a higher level of DNA compaction include histone tail modifications and control of chromatin accessibility by ATP dependent chromatin remodeling complexes. Once transcribed, mRNA can be further regulated by the microRNA network which provides an additional layer of epigenetic control of gene expression. Together, these epigenetic mechanisms function in concert to help fine-tune gene expression within the cell (Adopted from Gopinathan and Diekwisch, 2022) 2.2 Epigenetic changes in response to environmental factors Environmental factors such as diet, pollutants, temperature, and stress can induce epigenetic changes that affect gene expression and phenotype (McCaw et al., 2020). These changes can be stable and sometimes heritable, influencing not only the individual exposed but also subsequent generations (Wang et al., 2017). For instance, exposure to certain chemicals or nutritional components can lead to DNA methylation changes that persist through cell divisions and potentially across generations, affecting development and health (Vaiserman, 2011). This adaptability highlights the dynamic interplay between an organism's genome and its environment, suggesting that epigenetic mechanisms are a means by which organisms can rapidly respond to environmental changes (Jaenisch and Bird, 2003).
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