247: Genome graphs reveal structural variation in M. tuberculosis

Canalda-Baltrons A et al., Nature Communications - Long-read assemblies and a pangenome reference graph uncover widespread structural variants that shape Mycobacterium tuberculosis evolution and contribute to drug resistance. Key terms: structural variation, pangenome graph, Mycobacterium tuberculosis, drug resistance, long-read sequencing.

Study Highlights:
The authors built an M. tuberculosis pangenome reference graph from 859 high-quality long-read assemblies and identified 3,077 unique structural variants genome-wide. They developed miniwalk to genotype SVs from graph-mapped assemblies and showed higher precision for short-read SV genotyping (0.7 vs 0.46 for manta) at modest cost to recall. SVs cluster in GC-rich PE/PPE regions and include recurrent events such as a ppe25-ppe27 deletion fixed in L4.4 and diverse deletions of the copper exporter ctpV specific to sub-lineage L1.2.1 that alter copper-associated transcription. Genotyping 41,134 isolates revealed non-canonical SVs and SV-gene burdens associated with resistance to multiple first- and second-line drugs

Conclusion:
Structural variants are an important and previously underappreciated driver of M. tuberculosis evolution and drug resistance, and pangenome graph approaches improve their detection

Music:
Enjoy the music based on this article at the end of the episode.

Article title:
Genome graphs reveal the importance of structural variation in Mycobacterium tuberculosis evolution and drug resistance

First author:
Canalda-Baltrons A

Journal:
Nature Communications

DOI:
10.1038/s41467-025-65779-9

Reference:
Canalda-Baltrons A., Theys D., Chang X., Viberg L. T., Sherry N. L., Coin L., Dunstan S. J., Silcocks M., Hall M. B. Genome graphs reveal the importance of structural variation in Mycobacterium tuberculosis evolution and drug resistance. Nature Communications. 2025;16:10746. https://doi.org/10.1038/s41467-025-65779-9

License:
CC BY 4.0 International License (CC-BY-4.0)

Support:
Base by Base – Stripe donations: https://donate.stripe.com/7sY4gz71B2sN3RWac5gEg00

Official website https://basebybase.com

On PaperCast Base by Base you’ll discover the latest in genomics, functional genomics, structural genomics, and proteomics.

Episode link: https://basebybase.com/episodes/structural-variation-mtb-pangenome

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-01-02.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Substantive auditing of transcript segments describing: PRG construction and miniwalk SV genotyping; genome-wide SV landscape across lineages; ESX loci and ppe25-ppe27 deletion; copper exporter ctpV deletions in L1.2.1 with copper accumulation signals; DR associations across 41,134 isolates; and clinical implications.
- transcript topics: PRG construction and miniwalk SV genotyping; Genome-wide SV landscape across M. tuberculosis lineages; ESX secretion systems SVs and ppe25-ppe27 deletion; Copper homeostasis and ctpV deletions in L1.2.1; SV-based drug resistance associations across 41,134 isolates; Clinical implications and integration into sequencing pipelines

QC Summary:
- factual score: 10/10
- metadata score: 10/10
- supported core claims: 6
- 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:
- PRG built from 859 long-read Mtb assemblies; 821 assemblies used for SV genotyping
- Miniwalk SV genotyping on Illumina data yields precision 0.7 vs manta 0.46
- 3077 unique SVs identified across...