DNA Methylation

Definition

DNA methylation is a biochemical process involving the addition of a methyl group to the DNA molecule, typically at the cytosine base in the context of CpG dinucleotides. This modification plays a critical role in regulating gene expression and is crucial during cellular differentiation and reprogramming, as it can silence genes or activate them based on the cellular context. Through these mechanisms, DNA methylation influences how cells differentiate into various cell types and how they can be reprogrammed back to a pluripotent state.

5 Must Know Facts For Your Next Test

1. DNA methylation is often associated with gene silencing, meaning that when methyl groups are added to certain gene regions, those genes are less likely to be expressed.
2. During development, specific patterns of DNA methylation are established that help determine cell identity and function by controlling which genes are active in different cell types.
3. Reprogramming somatic cells back to pluripotency involves extensive changes in DNA methylation patterns, allowing for the reactivation of genes necessary for stem cell properties.
4. Abnormal DNA methylation patterns have been implicated in various diseases, including cancer, where tumor suppressor genes may become silenced.
5. Techniques such as bisulfite sequencing allow researchers to study DNA methylation patterns and understand their role in development and disease.

Review Questions

• How does DNA methylation contribute to the process of cellular differentiation?
  • DNA methylation contributes to cellular differentiation by regulating gene expression patterns essential for specific cell functions. As cells differentiate, specific genes are silenced through increased DNA methylation at their promoter regions. This selective silencing ensures that only the necessary genes for a particular cell type are active while repressing those that are not required, thus establishing distinct cellular identities.
• Discuss the role of DNA methylation in maintaining pluripotency in stem cells versus its role in differentiation.
  • In stem cells, low levels of DNA methylation at key regulatory regions help maintain pluripotency, allowing these cells to express a broad array of genes necessary for self-renewal. As differentiation begins, specific genes become hypermethylated, leading to their silencing and promoting the expression of lineage-specific genes. This dynamic regulation enables a balance between maintaining stem cell characteristics and transitioning into specialized cell types.
• Evaluate how abnormal DNA methylation patterns can impact human health, particularly in the context of cancer.
  • Abnormal DNA methylation patterns can significantly impact human health by leading to the silencing of tumor suppressor genes or the activation of oncogenes in cancer. In many cancers, hypermethylation occurs at promoter regions of critical genes that control cell growth and apoptosis, effectively disabling their protective roles against tumor formation. Additionally, global hypomethylation can lead to genomic instability, further contributing to cancer progression. Understanding these methylation changes offers insights into potential therapeutic targets for cancer treatment and prevention.

Related terms

Epigenetics: The study of changes in gene expression that do not involve alterations to the underlying DNA sequence, including processes like DNA methylation and histone modification.

Pluripotency:

The ability of a stem cell to develop into any cell type in the body, which is influenced by the methylation patterns that regulate gene expression.

Histone Modification: The chemical alteration of histone proteins around which DNA is wrapped, which works alongside DNA methylation to regulate gene activity.