Chromatin immunoprecipitation followed by massively parallel sequencing (ChIP-seq) is a powerful technology to profile genome-wide chromatin modification patterns and is increasingly being used to study the molecular mechanisms of brain diseases such as drug addiction. This protocol discusses the typical procedures involved in ChIP-seq data generation, bioinformatic analysis, and interpretation of results, using a chronic cocaine treatment study as a template. We describe an experimental design that induces significant chromatin modifications in mouse brain, and the use of ChIP-seq to derive novel information about the chromatin regulatory mechanisms involved. We describe the bioinformatic methods used to preprocess the sequencing data, generate global enrichment profiles for specific histone modifications, identify enriched genomic loci, find differential modification sites, and perform functional analyses. These ChIP-seq analyses provide many details into the chromatin changes that are induced in brain by chronic exposure to cocaine, and generates an invaluable source of information to understand the molecular mechanisms underlying drug addiction. Our protocol provides a standardized procedure for data analysis and can serve as a starting point for any other ChIP-seq projects.
Keywords: Bioinformatics; ChIP-seq; Chromatin immunoprecipitation (ChIP); Cocaine; Epigenetics; Histone modifications; Next generation sequencing (NGS).