367: Ancestral Splice Variation Fuels Cichlid Jaw Diversification

Singh P et al., PNAS - This paper compares alternative splicing (AS) and gene expression (GE) across 200 transcriptomes from oral and pharyngeal jaws of 18 haplochromine cichlid species across Lakes Victoria, Malawi, and Tanganyika. The authors show that rapid changes in AS, often from low-frequency ancestral isoforms and some novel isoforms, contributed more to early trophic diversification than shifts in GE. Key terms: alternative splicing, adaptive radiation, cichlids, gene regulation, craniofacial development. Study Highlights:Using 200 jaw transcriptomes spanning three East African cichlid radiations, the authors found that alternative splicing (AS) diverged faster than gene expression (GE) and was enriched for craniofacial and jaw morphogenesis genes. Most adaptive isoforms were present at low levels in nonradiating ancestral lineages and increased in frequency in radiating lineages, consistent with standing splice variation fueling rapid adaptation. A subset of novel isoforms evolved rapidly, some within a few thousand years, and mapped to candidate craniofacial genes such as col21a1. Younger radiations (Victoria, Malawi) showed stronger AS divergence while the older Tanganyika radiation displayed more GE differences. Conclusion:Ancestral alternative splice variation, supplemented by rapidly evolved novel isoforms, provided a labile reservoir of protein-coding diversity that likely enabled the extremely rapid trophic diversification of African cichlid radiations; integrating splicing into regulatory perspectives is essential to understand rapid adaptive evolution. Music:Enjoy the music based on this article at the end of the episode. Article title:Ancestral splice variation is a key substrate for rapid diversification in African cichlids First author:Singh P Journal:PNAS DOI:10.1073/pnas.2516477123 Reference:Singh P., Ahi E.P., Duenser A., Durdevic M., Gessl W., Schaeffer S., Gall J., Seehausen O., Sturmbauer C. Ancestral splice variation is a key substrate for rapid diversification in African cichlids. PNAS. 2026;123(20):e2516477123. doi:10.1073/pnas.2516477123 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/ancestral-splice-variation-african-cichlids QC:This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-05-15. QC Scope:- article metadata and core scientific claims from the narration- excludes analogies, intro/outro, and music- transcript coverage: Audited the transcript sections describing AS vs GE dynamics, ancestral standing variation, novel isoforms (col21a1), lake-by-lake evolutionary patterns, and convergent/trophic evolution; cross-checked against the original article.- transcript topics: Adaptive radiation and jaw anatomy in African cichlids; Gene expression vs alternative splicing (GE vs AS); Ancestral standing variation and novel isoforms; Temporal patterns: young vs old radiations (Victoria/Malawi vs Tanganyika); Key genes: col21a1 and craniofacial pathways; Convergent vs divergent regulation across radiations 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...