ATAC-Seq Analysis of Accessible Chromatin: From Experimental Steps to Data Analysis

Accessible chromatin often represents gene regulatory elements, including promoters and enhancers, essential for gene expression. Assay for Transposase Accessible Chromatin sequencing (ATAC-seq) is one of the most popular techniques to investigate chromatin accessibility across the genome. Here we describe, step by step, a series of optimized experimental methods and bioinformatics pipelines for ATAC-seq analysis. As an example, we present an analysis of murine spermatogenic cells: a method to isolate germ cells, a reaction step using Tn5 transposase to insert sequencing adapters into accessible DNA, a library preparation method for high-throughput sequencing, and bioinformatics analysis of sequencing data. Overall, we introduce a framework of ATAC-seq analysis that can be applied to any cell population to identify cell-type-specific gene regulatory elements and their cis-regulatory networks.