26: Reannotation reveals functional non-coding mutations in melanoma

Pepe D et al., The American Journal of Human Genetics (112:1–21, June 5, 2025) - Pepe et al. show that annotating cancer mutations to the transcripts actually expressed in tumors uncovers previously overlooked non-coding promoter mutations in melanoma. Using TCGA mutation calls, RNA-seq, and an automated Salmon+VEP pipeline, they reclassify multiple hotspots and validate functional effects for IRF3/BCL2L12 and KNSTRN promoter mutations with CRISPR-Cas9 and reporter assays. Key terms: melanoma, non-coding mutations, synonymous mutations, transcript annotation, CRISPR-Cas9.

Study Highlights:
The authors reannotated TCGA melanoma mutation clusters to expressed transcripts and found that 22% (11/50) of identified clusters previously labeled as coding are non-coding promoter mutations. They validated IRF3/BCL2L12 promoter mutations in isogenic CRISPR-Cas9 Mel-ST models and reporter assays, showing reduced IRF3, BCL2L12, and downstream TP53 expression. KNSTRN and SLC27A5 clusters were also reclassified as promoter mutations, and transcription-factor binding analyses implicate disruption of ETS/SP/E2F sites. The study presents a simple Salmon+VEP workflow to improve mutation annotation and notes an association between IRF3/BCL2L12 promoter mutations and poorer immunotherapy response.

Conclusion:
Integrating RNA-seq expression data into mutation annotation reveals functional non-coding promoter mutations missed by reference-transcript annotation; a Salmon+VEP reannotation workflow improves accuracy and highlights clinically relevant non-coding events in melanoma.

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2025-05-20.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music

QC Summary:
- factual score: 10/10
- metadata score: 10/10
- supported core claims: 8
- claims flagged for review: 0
- metadata checks passed: 4
- metadata issues found: 0

Metadata Audited:
- article_doi
- article_title
- article_journal
- license

Factual Items Audited:
- 22% (11/50) mutation clusters in melanoma are misannotated as coding mutations when using expressed transcripts, and are actually non-coding promoter mutations.
- IRF3/BCL2L12 promoter mutations downregulate IRF3, BCL2L12, and TP53 expression in melanoma contexts.
- KNSTRN and SLC27A5 promoter mutations were identified as functional non-coding promoter mutations in melanoma.
- CRISPR-Cas9 knockin in Mel-ST cells demonstrates that IRF3/BCL2L12 promoter mutations reduce IRF3 and BCL2L12 mRNA and protein levels, and influence TP53 pathway components.
- Promoter non-coding mutations in IRF3/BCL2L12 region are associated with a worse response to immunotherapy in melanoma patients.
- Salmon+VEP automated annotation achieves about 90% accuracy in annotating expressed transcripts for mutations in melanoma.

QC result: Pass.