ChIPmentation-based mapping of histone modifications in aging: Experimental design and analytical considerations

Aging is accompanied by progressive alterations in chromatin organization that contribute to transcriptional dysregulation, genomic instability, and loss of cellular identity. Among the epigenetic mechanisms implicated, histone modifications play a central role in regulating chromatin accessibility and gene expression during aging. Changes in key histone marks, including H3K9me3, H3K27me3, H4K20me3, and histone acetylation signatures, are associated with heterochromatin loss, increased transcriptional noise, and altered cellular function across diverse tissues and organisms. These modifications are dynamically regulated by histone-modifying enzymes and are responsive to metabolic and stress signaling pathways, linking environmental cues to chromatin state and longevity. Genome-wide profiling of histone modifications is essential to understand these age-associated chromatin changes. ChIPmentation, a streamlined approach that integrates chromatin immunoprecipitation with transposase-mediated tagmentation, enables rapid and sensitive mapping of histone marks with reduced input requirements and simplified library preparation. This method is particularly advantageous for aging studies, where sample availability is often limiting. In this chapter, we outline the principles and experimental workflow of ChIPmentation, including crosslinking, chromatin fragmentation, immunoprecipitation, tagmentation, library preparation, sequencing, and data analysis. Additionally, we discuss computational strategies for processing and analyzing ChIPmentation data, including alignment, normalization, peak calling, and reproducibility assessment. Together, this chapter provides a comprehensive methodological framework for studying histone modification landscapes in aging systems, enabling robust investigation of epigenetic mechanisms underlying age-associated phenotypes.