Why does mitochondrial read enrichment matter in ATAC-seq QC?

Scientific Value: Identifies accessible chromatin regions that serve as regulatory DNA elements where transcription factors bind, enabling interrogation of therapeutic hypotheses in T cell-mediated pathways.
Operational Value: Provides a sensitive, low-input alternative to DNase-seq or FAIRE-seq for profiling chromatin accessibility in primary human lymphocytes.
Predictive Value: Supports functional target validation by revealing active regulatory landscapes that correlate with gene expression in immune contexts.

High mitochondrial DNA reads indicate poor nuclei isolation or cell damage, which can confound chromatin accessibility signals; the protocol considers libraries acceptable only if 6–20% of reads map to the mitochondrial genome.

How does primer pair enrichment validate ATAC-seq library quality?

Enrichment of positive control primer pairs (at least 25-fold for pair three, 75-fold for pair four) relative to negative controls confirms successful transposition and library amplification before sequencing.

What peak count threshold indicates a successful ATAC-seq library?

Obtaining 1,000 to 2,000 peaks after initial sequencing (10 million reads) and passing FastQC parameters suggests sufficient signal-to-noise for deeper sequencing (30 million reads).

Why is nuclei isolation critical for accurate ATAC-seq results in primary T lymphocytes?

Intact nuclei are required for efficient transposition; disruption during lysis can lead to mitochondrial DNA contamination or loss of true chromatin accessibility signals.

What statistical threshold supports proceeding to deep sequencing after initial ATAC-seq run?

Libraries must pass FastQC quality checks, show 1,000–2,000 peaks from peak calling, and exhibit adequate primer enrichment to justify sequencing beyond 30 million reads for enhanced resolution.