Adaptation to challenging environmental conditions is crucial for the survival/fitness of all organisms. Alongside genetic mutations that provide adaptive potential during environmental challenges, epigenetic modifications offer dynamic, reversible, and rapid mechanisms for regulating gene expression in response to environmental changes in both evolution and daily life, without altering DNA sequences or relying on accidental favorable mutations. The widespread conservation of diverse epigenetic mechanisms - like DNA methylation, histone modifications, and RNA interference across diverse species, including plants - underscores their significance in evolutionary biology. Remarkably, environmentally induced epigenetic alterations are passed to daughter cells and inherited transgenerationally through germline cells, shaping offspring phenotypes while preserving adaptive epigenetic memory. Throughout anthropoid evolution, epigenetic modifications have played crucial roles in: i) suppressing transposable elements and viral genomes intruding into the host genome; ii) inactivating one of the X chromosomes in female cells to balance gene dosage; iii) genetic imprinting to ensure expression from one parental allele; iv) regulating functional alleles to compensate for dysfunctional ones; and v) modulating the epigenome and transcriptome in response to influence from the gut microbiome among other functions. Understanding the interplay between environmental factors and epigenetic processes may provide valuable insights into developmental plasticity, evolutionary dynamics, and disease susceptibility.
Keywords: Epigenetics; Rett syndrome; adaptation; fragile X; gut microbiome; imprinting.
Living things need to adapt to survive in tough environmental conditions. While changes in DNA could help with this in long term, there’s another way called epigenetics that can quickly turn genes on or off without altering the DNA sequence in response to the environment changes. Epigenetics works in many different living things, from microbes to plants and animals. It can even pass changes from one generation to the next generations. Hence, what happens to parents can affect their kids without changing their DNA. In human-like animals, epigenetics has been important for: i) stopping the activity of harmful viral DNA entered into our DNA to prevent potential troubles, ii) turning off one X chromosome in females to inhibit twofold gene expression, iii) making sure only one parent’s gene is used for some traits, iv) helping to regulate the activity of some genes that their similar equivalents don’t work right, v) responding to the impacts of tiny organisms (microbes) living in our guts. Understanding how the environment affects epigenetics and how our body responds to environmental effects could help us learn more about how living things grow, change over time, and get sick. This can also help prevent or treat diseases.