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Transcriptomics & Workflow Architecture Proof Series

Translational Transcriptomics: Reproducible RNA-Seq & Snakemake Pipelines

An in-depth research publication documenting end-to-end bulk expression profiling, quality control, differential expression matrices, and automated workflow orchestrations.

Topic 01

Raw Sequencing Quality Control & MultiQC Metrics

High-throughput RNA sequencing begins with thorough inspection of raw FASTQ reads. Assessing base quality scores, adapter contamination, and GC content distributions ensures that downstream alignment steps operate on high-fidelity nucleotide sequences.

FastQC Per Base Sequence Quality Distribution
Fig 1.1: Per-base sequence quality score trends across raw reads.
MultiQC Aggregated Sample Quality Dashboard
Fig 1.2: MultiQC report aggregating sample-level metrics.

Automated aggregation via custom wrapper tools catches outlier sequencing runs early in the lifecycle, preventing skewed expression profiles from propagating into final statistical matrices.

Topic 02

Snakemake Orchestration & Modular Workflow Design

To achieve complete reproducibility across diverse computational environments, our pipelines are structured using the transcriptomics-snakemake repository. Snakemake enables scalable parallel execution from raw FASTQs to count matrices.

Snakemake Directed Acyclic Graph (DAG) Pipeline Architecture
Fig 2.1: Directed Acyclic Graph (DAG) visualizing rule dependencies within the Snakemake pipeline.

By decoupling rule configurations from execution scripts, containerized software environments (Conda/Docker) ensure that every dependency version remains locked and verifiable across independent high-performance computing clusters.

Topic 03

Alignment & Quantification with STAR & featureCounts

Accurate transcript mapping requires splice-aware aligners capable of handling complex exon-exon junctions. Our pipeline integrates STAR alignment modules mapped against reference genomes followed by precise gene-level summarization.

STAR Alignment Rate Metrics
Fig 3.1: Unique versus multi-mapping alignment rates.
featureCounts Gene Assignment Bar Plot
Fig 3.2: Assignment distribution ratios computed via featureCounts.

The resulting gene count matrix acts as the foundational quantitative dataset required for rigorous comparative modeling and disease biomarker characterization.

Topic 04

Differential Gene Expression Analysis via DESeq2

Identifying statistically significant transcriptional changes between experimental conditions requires generalized linear models based on negative binomial distributions, effectively accounting for biological overdispersion.

DESeq2 Volcano Plot Highlighting Differentially Expressed Genes
Fig 4.1: Volcano plot highlighting upregulated and downregulated target transcripts.

Shrinkage estimators for fold changes (such as apeglm) provide stable ranking metrics, filtering out noise driven by low counts and highlighting robust biological drivers.

Topic 05

Functional Enrichment, GSEA & Downstream Networks

Moving past individual gene lists, functional enrichment analysis and Gene Set Enrichment Analysis (GSEA) contextualize expression findings within canonical pathways and molecular interaction frameworks.

GSEA Enrichment Pathway Plot
Fig 5.1: Normalized enrichment score (NES) distribution curves.
Protein-Protein Interaction Network Mapping
Fig 5.2: Hub gene identification within core regulatory networks.

This systems-biology synthesis completes the transcriptomic discovery loop, turning raw sequencing runs into prioritized targets ready for downstream experimental validation.