Base by Base

About Base by Base

Base by Base explores advances in genetics and genomics, with a focus on gene-disease associations, variant interpretation, protein structure, and insights from exome and genome sequencing. Each episode breaks down key studies and their clinical relevance—one base at a time. Powered by AI, Base by Base offers a new way to learn on the go. Special thanks to authors who publish under CC BY 4.0, making open-access science faster to share and easier to explore.

Publisher

Gustavo Barra

Category

health & fitness · science

Language

en

Explicit

No

First episode

15 Apr 2025

Latest episode

18 Oct 2026

Latest episodes

468 episodes in the feed.

1. 

   18 Oct 2026

   467: Finding mutations carried by fewer than 1 in 100 cells

   Jang Y et al., The American Journal of Human Genetics - Every cell in the body picks up its own small set of DNA changes over a lifetime, and many of these somatic mutations are carried by only a tiny fraction of cells. This study, part of the SMaHT Network, asks how reliably standard bulk whole-genome sequencing can find mutations present at a variant allele fraction below 1%. The team built a ground truth from one donor's skin: clonal stem cell lines grown from single fibroblasts defined real mutations, and lines from other skin biopsies of the same donor defined mutations that should be absent. With about 1,360× Illumina coverage confirmed by PacBio and AVITI, point mutations below 1% were detected accurately in the easily mapped parts of the genome. Key terms: somatic mosaicism, whole-genome sequencing, variant allele fraction, benchmarking, SMaHT. Study Highlights:Primary fibroblasts from a 29-year-old donor contained five subclones, captured as clonal iPSC lines, giving benchmark mutations from 0.1% to 25% variant allele fraction, while iPSC lines from other biopsies of the same donor supplied negative controls; both sets held about 11,000 SNVs and 2,800 indels. Using the negative controls, PacBio and AVITI had the lowest substitution error rates in easy regions, 0.003% and 0.005%, and mismatch rates rose by 1 to 2 orders of magnitude in harder regions. In fibroblasts, more than 99.5% of bulk-only calls above 1% were confirmed by PacBio or AVITI, the estimated false-positive rate was near zero above 0.8% and about 11% below 0.5%, and homopolymer indels could be detected reliably only above 3%. In postmortem lung and colon, combining about 200× from two tissues found 13 additional shared mutations, a 145% gain in sensitivity below 3%, all confirmed by PacBio or single-cell data. Conclusion:Ultra-deep bulk whole-genome sequencing can detect point mutations below 1% allele fraction with high accuracy, provided calling is restricted to easily mapped regions and sample quality is checked, and pooling coverage across tissues from one donor recovers shared developmental mutations. The benchmark comes from a single donor's fibroblasts, confirmation below 0.5% was limited by long-read and AVITI coverage, most indels sit in homopolymers or hard regions where detection remains unreliable, and postmortem samples needed extra filtering. Article title:Accurate detection of sub-1% frequency somatic mutations by whole-genome sequencing First author:Jang Y Journal:The American Journal of Human Genetics DOI:10.1016/j.ajhg.2026.09.010 Reference:Jang Y., Gardiner S., Wang Y., Natu A., Dehankar M.K., Tomasini L., et al. Accurate detection of sub-1% frequency somatic mutations by whole-genome sequencing. The American Journal of Human Genetics. (2026). https://doi.org/10.1016/j.ajhg.2026.09.010 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 is independent and ad-free — no sponsors, no paywall. If an episode was worth your time, chip in and keep the papers audited and the original songs coming:❤️ Support monthly: https://buy.stripe.com/cNifZhclVebvagk2JDgEg01☕ One-time donation: https://donate.stripe.com/7sY4gz71B2sN3RWac5gEg00▶️ Watch with chapters on YouTube: https://www.youtube.com/@basebybase More at 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/detecting-sub-1-percent-somatic-mutations-wgs QC:This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-10-18. QC Scope:- article metadata...

2. 

   16 Oct 2026

   466: A quieter MECP2 switch and the male bias in autism

   Meyer-Schuman R et al., The American Journal of Human Genetics - Autism is diagnosed about four times more often in male individuals than in female individuals, and one explanation is mild variants in dosage-sensitive genes on the X chromosome, which a female carrier can buffer with her second copy but a male cannot. This study tests that idea in MECP2, the Rett syndrome gene, by looking at the switches that control how much of it is made rather than the gene itself. Using a massively parallel reporter assay in human stem-cell-derived neurons, the team mapped the active transcription factor binding sites in five MECP2 regulatory elements and tested 22 ultra-rare variants passed from unaffected mothers to autistic sons. Two variants changed regulatory activity, and one in the promoter lowered MECP2 RNA and protein by about 30% when edited into the native gene. Key terms: MECP2, autism, massively parallel reporter assay, noncoding variants, X chromosome. Study Highlights:Whole-genome data from 30,916 individuals in 8,245 autism families yielded 22 ultra-rare noncoding variants in MECP2 regulatory elements, each private to one family, found only in male probands and inherited from an unaffected mother, tested alongside 19 gnomAD control variants. Shuffling predicted transcription factor motifs mapped activator or repressor hotspots in four of the five elements, and knocking down two predicted activators, TCF3 and ZNF281, lowered MECP2 RNA by about 55% and 47% after three weeks. A variant in the primate-specific repressor element CRE A, carried by two affected brothers, increased activity in both the reporter and luciferase assays. The promoter variant g.154097837A>G, found in a boy with autism and ADHD and a full-scale IQ of 97, weakened NFY-B binding at the MECP2 promoter from the 51st to the 9th percentile of bound promoters and reduced MECP2 RNA and protein by about 30% in edited neurons. Conclusion:The findings suggest that noncoding MECP2 variants that modestly lower or raise expression can contribute to idiopathic, male-biased autism, and they provide a framework for finding regulatory variants in other X chromosome neurodevelopmental genes. The evidence rests on two families and on reporter assays and edited neurons in a dish, which take short sequences out of their native chromatin context, so the link between these variants and autism still needs additional variant discoveries and molecular validation. Article title:A massively parallel reporter assay of MECP2 cis-regulatory elements reveals genetic candidates for male-biased autism First author:Meyer-Schuman R Journal:The American Journal of Human Genetics DOI:10.1016/j.ajhg.2026.09.011 Reference:Meyer-Schuman R., Cherry F., Sui Y., Papastathopoulos-Katsaros A., Zhong Y., Li Y., et al. A massively parallel reporter assay of MECP2 cis-regulatory elements reveals genetic candidates for male-biased autism. The American Journal of Human Genetics. (2026). https://doi.org/10.1016/j.ajhg.2026.09.011 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 is independent and ad-free — no sponsors, no paywall. If an episode was worth your time, chip in and keep the papers audited and the original songs coming:❤️ Support monthly: https://buy.stripe.com/cNifZhclVebvagk2JDgEg01☕ One-time donation: https://donate.stripe.com/7sY4gz71B2sN3RWac5gEg00▶️ Watch with chapters on YouTube: https://www.youtube.com/@basebybase More at 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/mecp2-regulatory-variants-male-biased-autism QC:<...

3. 

   11 Oct 2026

   465: When a lysosomal storage gene shows up only in the retina

   Lin et al., The American Journal of Human Genetics - Bi-allelic variants in IDUA classically cause mucopolysaccharidosis type I, a lysosomal storage disorder that affects many organs from childhood. This study describes 14 adults and young adults from 12 families who first came to eye clinics with retinitis pigmentosa and were later found to carry bi-allelic IDUA variants. Seven of them showed no systemic features of the disease even after detailed assessment, and enzyme activity in white blood cells was reduced but never absent. Cell-based enzyme assays and long-read RNA sequencing explain how mild, hypomorphic alleles can leave just enough enzyme to spare the body but not the retina. Key terms: IDUA, mucopolysaccharidosis type I, retinitis pigmentosa, hypomorphic variants, splicing. Study Highlights:Individuals aged 19 to 73 were recruited from inherited retinal disease cohorts in the UK, Ireland, Italy, the Netherlands and the United States, and none carried two null alleles; most had a loss-of-function allele paired with a missense variant. Leukocyte alpha-L-iduronidase activity was reduced but detectable in all nine individuals tested, and urine glycosaminoglycans were above normal in only half of those tested, with modest elevations. In an IDUA-knockout cell line, several missense variants, including p.His91Tyr and p.Arg383His, showed relative specific activity around 0.5% to 1.5% of wild type, with poor processing or stability. The recurrent c.298A>G variant left enzyme activity intact as a protein change, but nanopore long-read sequencing showed that it mostly causes exon 2 skipping, with only about 1.3% of reads from that allele spliced normally. Conclusion:Hypomorphic IDUA genotypes that leave low residual enzyme activity can cause late-onset retinitis pigmentosa with mild or apparently no systemic disease, extending the known spectrum of MPS I and arguing for including IDUA in inherited retinal disease gene panels. The cohort is small and mostly of European ancestry, systemic assessment varied in depth, and without longitudinal follow-up some individuals classed as having isolated retinal disease may still develop systemic features. Article title:Hypomorphic IDUA genotypes are associated with retinitis pigmentosa in individuals without syndromic mucopolysaccharidosis type I First author:Lin Journal:The American Journal of Human Genetics DOI:10.1016/j.ajhg.2026.09.008 Reference:Lin, S., Yu, S.-H., Browning, A. C., et al., Roosing, S., Steet, R., and Arno, G. (2026). Hypomorphic IDUA genotypes are associated with retinitis pigmentosa in individuals without syndromic mucopolysaccharidosis type I. The American Journal of Human Genetics 113, 1-12. https://doi.org/10.1016/j.ajhg.2026.09.008 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 is independent and ad-free — no sponsors, no paywall. If an episode was worth your time, chip in and keep the papers audited and the original songs coming:❤️ Support monthly: https://buy.stripe.com/cNifZhclVebvagk2JDgEg01☕ One-time donation: https://donate.stripe.com/7sY4gz71B2sN3RWac5gEg00▶️ Watch with chapters on YouTube: https://www.youtube.com/@basebybase More at 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/idua-hypomorphic-retinitis-pigmentosa-mps-i QC:This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-10-11. QC Scope:- article metadata and core scientific claims from the narration- excludes analogies, intro/out...

Who has been a guest on Base by Base

Names identified in recent episode analyses. Showing up to five guests.

• Vatsa A
• Templeton CW
• Laimins L

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Apple Podcasts (US)

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2 ratings

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5.0 / 5

8 ratings

Podcast Authority Score: 52 / 100

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Quality

91

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0

Engagement

32

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