260: TSS hypermutability in human germline linked to RNAP II stalling, R-loops and early embryonic mosaics

Nature Communications - Transcription start sites experience a high influx of heritable variants fueled by early development Music:Enjoy the music based on this article at the end of the episode. Article title:Transcription start sites experience a high influx of heritable variants fueled by early development Journal:Nature Communications DOI:10.1038/s41467-025-66201-0 License:CC BY 4.0 International License 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. QC:This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-01-15. QC Scope:- article metadata and core scientific claims from the narration- excludes analogies, intro/outro, and music- transcript coverage: Audited the transcript for core germline mutagenesis mechanisms around transcription start sites (TSS), mosaic vs de novo variation, mechanistic links (RNAP II stalling, R-loops, divergent transcription), mutational signatures, purifying selection, disease links, and clinical implications as described in the article.- transcript topics: Germline TSS mutational hotspot; Extremely rare variants and mosaicism; De novo mutations vs mosaic filtering; Transcription-associated mutagenesis mechanisms (RNAP II stalling, R-loops, divergent transcription); Mutational signatures (SBS3, SBS40b, SBS40c; SBS39 maternal clusters; SBS12/SBS16); Divergent transcription at promoters 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:- Germline transcription start sites harbor a mutational hotspot spanning several hundred base pairs upstream and downstream of the TSS- Non(CpG > TpG) variations show a mutational excess at the TSS, up to ~35% in 100-bp windows around the TSS- De novo mutations (DNMs) do not show a significant TSS excess due to misclassification/ filtering; the hotspot is revealed by mosaic variants- Early mosaic mutations are enriched near the TSS, with a 52% excess immediately downstream of the TSS- Divergent transcription, RNAP II stalling, and R-loop formation are associated with the TSS hotspot- Mutational signatures SBS3, SBS40b, SBS40c indicate non-canonical DSB repair; SBS39 linked to maternal mutation clusters QC result: Pass.