1. Visual Inspection in the Integrative Genomics Viewer (IGV)

Statistical metrics and composite heatmaps provide macro-level validation, but inspectable biological confirmation requires examining individual gene loci in IGV.

2. The Biological Story: Uncovering the Epigenetic Lesion

At the BDNF promoter IV locus, healthy control tracks display robust, sharp H3K4me3 peaks reaching $50\text{ BPM}$, indicating an open, actively transcribed chromatin state that drives continuous synthesis of neurotrophic support for striatal projection neurons. In stark contrast, both Huntington's Disease tracks exhibit a collapse of H3K4me3 signal ($< 8\text{ BPM}$), representing profound promoter de-methylation and transcriptional shutdown.

Combined with our HOMER motif discoveries (SP1 and REST/NRSF enrichment) and DiffBind statistical testing ($\log_2\text{FC} = -2.8$, $\text{FDR} = 4.2 \times 10^{-7}$), we can synthesize the complete causal chain:

1. Mutant huntingtin aggregates disrupt the MLL/COMPASS H3K4 methyltransferase complex and recruit HDACs / co-repressors to neuronal promoters.
2. Promoter H3K4me3 is progressively lost across post-mitotic striatal and cortical neurons.
3. Downstream transcription of survival factors (BDNF, DARPP-32, dopamine receptor $D2$) is silenced.
4. Deprived of essential trophic support, striatal medium spiny neurons undergo progressive apoptosis, culminating in the motor and cognitive decline of Huntington's Disease.

Congratulations! You have taken raw, multi-gigabyte FASTQ reads from public archives, performed rigorous quality and alignment filtering, modeled statistical peak differentials, mapped regulatory transcription factor motifs, and translated raw sequencing reads into a publication-grade biological story.