128: L1 elements, chromatin and CRISPRi

Adami A et al., Cell Genomics - This episode covers analyses of L1 retrotransposon subfamilies (L1PA2/3/4, L1HS), their chromatin signatures (including H3K4me3), and perturbation experiments using CRISPRi. The source text includes comparative plots across primates and gene-level readouts such as PPP1R1C. Key terms: L1 retrotransposon, L1PA2, L1HS, H3K4me3, CRISPRi. Study Highlights:The paper maps H3K4me3 and related chromatin signals at L1 subfamilies including L1HS and L1PA2/3/4 and presents comparative timelines across primates. Targeted CRISPRi against L1 elements was used and compared with controls, with gene-level examples shown (PPP1R1C). Figures include genomic tracks, heatmaps, and quantification of signal changes tied to specific L1 subfamilies. Conclusion:L1 subfamilies carry distinct H3K4me3-associated chromatin signatures and can be transcriptionally modulated by CRISPRi, with measurable effects on nearby gene expression. The data and comparative analyses across primates highlight subfamily-specific regulatory potential of L1 elements. Music:Enjoy the music based on this article at the end of the episode. Article title:LINE-1 retrotransposons mediate cis-acting transcriptional control in human pluripotent stem cells and regulate early brain development First author:Adami A Journal:Cell Genomics DOI:10.1016/j.xgen.2025.100979 Reference:Adami A., Garza R., Gerdes P., Johansson P.A., Dorazehi F., Koutounidou S., et al.. LINE-1 retrotransposons mediate cis-acting transcriptional control in human pluripotent stem cells and regulate early brain development. Cell Genomics, 5, 100979. (2025). https://doi.org/10.1016/j.xgen.2025.100979 License:This episode is based on an open-access article published under the Creative Commons Attribution 4.0 International License (CC BY 4.0) – https://creativecommons.org/licenses/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/line1-promoters-orchestrate-early-human-brain-development QC:This episode was checked against the original article PDF and publication metadata for the episode release published on 2025-09-05. QC Scope:- article metadata and core scientific claims from the narration- excludes analogies, intro/outro, and music- transcript coverage: Audited the transcript's presentation of L1 biology, promoter activity, CRISPRi silencing of young L1 promoters (L1HS/L1PA2), downstream gene/lncRNA effects (PPP1R1C, Len NC_00648), organoid differentiation outcomes, evolutionary context, and methodological limitations, cross-checking these with the canonical article.- transcript topics: L1 biology and chromatin signatures; Long-read sequencing and transcript mapping to resolve L1 copies; CRISPR interference (CRISPRi) silencing of L1 promoters; L1 antisense promoters driving PPP1R1C and Len NC_00648 transcripts; Organoid models and neural progenitor differentiation; Evolutionary context of L1 subfamilies (L1HS, L1PA2/3/4) 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:- L1HS and L1PA subfamilies show H3K4me3-associated chromatin signals in human cells- CRISPRi targeting of evolutionarily young L1 promoters (L1HS/L1PA2) silences transcription locally- L1 elements function as alternative promoters for a set of genes includ...