5-Hydroxymethylcytosine: Far Beyond the Intermediate of DNA Demethylation

Epigenetics plays a pivotal role in regulating gene expression and cellular differentiation. DNA methylation, involving the addition of methyl groups to specific cytosine bases, is a well-known epigenetic modification. The recent discovery of 5-hydroxymethylcytosine (5hmC) has provided new insights into cytosine modifications. 5hmC, derived from the oxidation of 5-methylcytosine (5mC), serves as both an intermediate in demethylation and a stable chemical modification in the genome. In this comprehensive review, we summarize the recent research advancements regarding the functions of 5hmC in development and disease. We discuss its implications in gene expression regulation, cellular differentiation, and its potential role as a diagnostic and prognostic marker in various diseases. Additionally, we highlight the challenges associated with accurately detecting and quantifying 5hmC and present the latest methodologies employed for its detection. Understanding the functional role of 5hmC in epigenetic regulation and further advancing our understanding of gene expression dynamics and cellular processes hold immense promise for the development of novel therapeutic strategies and precision medicine approaches.