Base by Base

Kapoor RR et al., PNAS - A systematic screen of 319 arthropod genomes reveals genes formed by in‑frame fusion of horizontally transferred nonmetazoan sequences with endogenous metazoan regions. Many of these HGT-chimeras are transcribed, conserved, and show coherent domain architectures, implicating them in diverse biological processes. Key terms: horizontal gene transfer, gene fusion, arthropods, novel genes, molecular evolution.

Study Highlights:
The authors developed an intragenic phylogenetic pipeline and screened 319 high-quality arthropod genomes to identify HGT-chimeras. They report 274 chimeric genes corresponding to 104 independent origination events derived from bacteria, viruses, fungi, and plants. RT-PCR and Sanger sequencing validated contiguous chimeric mRNA expression for 36 of 41 tested chimeras, and molecular evolution analyses show widespread purifying selection and functional domain assembly. Evidence indicates gene duplication and postfusion divergence often accompany chimera formation, suggesting a recurrent route to novel gene functions.

Conclusion:
Fusion of horizontally acquired sequences with endogenous metazoan sequences has been a recurrent source of novel genes in arthropods, producing expressed, conserved chimeric proteins that likely contribute to organismal biology and evolution.

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

Article title:
Evolutionary innovation through fusion of sequences from across the tree of life

First author:
Kapoor RR

Journal:
PNAS

DOI:
10.1073/pnas.2602557123

Reference:
Kapoor RR, Rona I, Extavour CG, et al. Evolutionary innovation through fusion of sequences from across the tree of life. Proc Natl Acad Sci U S A. 2026;123(29):e2602557123. doi:10.1073/pnas.2602557123

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:
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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/hgt-chimeras-fusion-across-tree-of-life

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-07-18.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited the transcript's core scientific narrative: definition and existence of HGT-chimeras in arthropods; the 319-genome screen; 274 chimeras in 104 origination events; RT-PCR validation (36/41 across 18 species); evidence of purifying selection (dN/dS < 1) and selected exemplars (shrimp, copepod, damselfly, mosquito
- transcript topics: HGT-chimera concept and definition; Scope of arthropod genome survey (319 genomes); Quantitative results (274 chimeras, 104 origination events, 109 HGT intervals); RT-PCR validation and transcriptional evidence (36/41 across 18 species); Purifying selection and dN/dS interpretation; Exemplar cases: shrimp cluster 12, copepod cluster 14, damselfly cluster 41, mosquito cluster 9

QC Summary:
- factual score: 10/10
- metadata score: 10/10
- supported core claims: 4
- 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:
- 319 high-quality arthropod genomes analyzed
- 274 HGT-chimera genes identified across arthropods
- 104 independent origination events inferred
- RT-PCR and Sanger sequencing validated contiguous chimera transcripts for 36 of 41 chimeras across 18 species
- Most HGT-chimeras show gene-wide dN/dS < 1 (purifying selection); neutrality rejected in many cases
- A shrimp chimera (cluster 12) aged ~83.1 million years with dN/dS of 0.29 for the chimera interval

QC result: Pass.

PNAS - This episode breaks down a PNAS study that identifies a druggable pocket in the ERG transcription factor PNT domain and describes PBITE-1, a small-molecule probe that binds this pocket to inhibit ERG-driven prostate cancer models. Key terms: ERG, PNT domain, PBITE-1, prostate cancer, small-molecule inhibitor.

Study Highlights:
The authors show that TMPRSS2:ERG-positive prostate cancer cells remain dependent on ERG for survival and tumor maintenance. A domain-focused DSF screen identified F0341 as a PNT-domain binder and SAR optimization yielded PBITE-1, which engages a solvent-exposed pocket spanning two helices and a flexible loop. PBITE-1 selectively stabilizes ERG in cells, suppresses ERG target genes, reduces proliferation and invasion, induces apoptosis in ERG-positive cell lines and organoids, and triggers tumor cell apoptosis in VCaP xenografts.

Conclusion:
The ERG N-terminal PNT domain contains a structurally coherent, ligandable pocket; PBITE-1 provides proof-of-concept that ERG can be directly targeted by small molecules, laying groundwork for future ERG-directed inhibitors and degrader strategies for TMPRSS2:ERG-driven cancers.

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

Article title:
A ligandable PNT domain establishes ERG as a directly targetable oncogenic driver in prostate cancer

Journal:
PNAS

DOI:
10.1073/pnas.2537437123

Reference:
https://doi.org/10.1073/pnas.2537437123

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
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/erg-pnt-pbite-1

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-07-18.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited the transcript sections describing ERG dependency in TMPRSS2:ERG-positive prostate cancer, DSF screening and hit identification (F0341), SAR optimization to PBITE-1, binding and target engagement assays (NMR, BLI, CETSA), cellular effects (viability, apoptosis, ERG target gene suppression), organoid and in vivo
- transcript topics: ERG dependency in TMPRSS2:ERG-positive prostate cancer; Domain-focused differential scanning fluorimetry (DSF) screen; PBITE-1 discovery and SAR optimization; PBITE-1 binding interface mapping to ERG PNT domain (NMR, docking, H2/H6); Target engagement and cellular effects (CETSA, cell viability, apoptosis, ERG target genes); Organoid and in vivo VCaP xenograft data

QC Summary:
- factual score: 10/10
- metadata score: 10/10
- supported core claims: 7
- 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:
- TMPRSS2:ERG fusion occurs in approximately 50% of prostate cancers in patients of European ancestry.
- PBITE-1 engages a discrete solvent-exposed surface within the ERG PNT domain, defining a ligand-binding pocket.
- PBITE-1 directly binds the ERG PNT domain and stabilizes full-length ERG in cells.
- PBITE-1 binds the PNT domain with a KD around 264 µM and shows selectivity for the PNT domain over the ETS domain.
- PBITE-1 selectively inhibits proliferation and induces apoptosis in ERG-positive cell lines, sparing ERG-negative models.
- PBITE-1 significantly suppresses ERG target genes (e.g., TDRD1, PLAT/PLA1A) in ERG-positive contexts.

QC result: Pass.

Carballar-Lejarazúa R et al., PNAS (2026) - This episode summarizes a 2-year, 35-generation multireplicate cage trial evaluating three autonomous Cas9/gRNA gene-drive strains (AcTP13, AcTP43 in Anopheles coluzzii; AgTP13 in Anopheles gambiae). The study tracked drive inheritance, cassette integrity, resistance allele emergence, off-target activity, and sustained antiparasite efficacy against Plasmodium falciparum. Key terms: gene drive, Anopheles, Cas9/gRNA, parasite suppression, long-term stability.

Study Highlights:
Over 2 years (35 generations) triplicate cage trials of three Cas9/gRNA gene-drive strains monitored drive dynamics, cassette integrity, resistance, off-target effects, and parasite suppression. All A. coluzzii replicates achieved rapid fixation and remained stable; two AgTP13 replicates fixed while one accumulated a functional cleavage-resistant allele that reduced drive frequency. Effector transgene sequences and mRNA expression were largely preserved, though one AcTP43 replicate lost a TP10 monomer copy. Parasite challenge assays at low and medium-low gametocytemias showed significant reductions in oocyst and sporozoite prevalence and intensity.

Conclusion:
Multimetric longitudinal data show that Cas9/gRNA-based population-modifying drives can remain genetically stable and retain antiparasite activity over a 2-year period in laboratory Anopheles populations, with replicate-level resistance emergence underscoring the need for replicated risk assessment and monitoring.

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

Article title:
Long-term stability and performance of Cas9/guide RNA-based gene drives in anopheline mosquitoes

First author:
Carballar-Lejarazúa R

Journal:
PNAS (2026)

DOI:
10.1073/pnas.2605739123

Reference:
Carballar-Lejarazúa R, Winokura L, Pham TB, Tushar T, Tao M, Dimopoulos G, James AA, et al. Long-term stability and performance of Cas9/guide RNA-based gene drives in anopheline mosquitoes. PNAS. 2026;123(28):e2605739123. doi:10.1073/pnas.2605739123

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
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/414-gene-drive-stability-anopheles

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-07-17.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited the transcript sections describing gene-drive mechanism, target-product profile criteria, long-term cage trials, molecular/cassette integrity, resistance emergence, off-target analysis, and parasite-suppression outcomes, with attention to quantitative results and limitations.
- transcript topics: Gene-drive mechanism and inheritance (Cas9/gRNA, HDR); Target Product Profile (TPP) criteria for gene-drive systems; Long-term cage trial design (AcTP13, AcTP43 in Anopheles coluzzii; AgTP13 in Anopheles gambiae); Cargo design and tracking markers (CFP, mCherry) and antiparasite effectors (M1C3, M2A10, MultiEff, TP10, EPIP); Resistance emergence at the target site (AgTP13) and 3 bp insertion; Payload stability and tandem repeats (TP10)

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:
- 2-year duration with 35 generations of nonoverlapping cage trials
- Three drive lines tested: AcTP13 and AcTP43 in A. coluzzii; AgTP13 in A. gambiae
- Total mosquitoes scored across all cages: 1,873,420
- AcTP13 and AcTP43 achieved drive fixation by generation 3 and remained stable for 35 generations
- AgTP13 replicate A3 developed a functional resistance allele via a 3 bp insertion; A1 and A2 reached fixation, with A3 showing resistance dynamics
- M1C3 and M2A10 antibodies showed no structural mutations across samples; expression remained post-blood meal

QC result: Pass.

Wu J-S et al., PNAS - A PNAS study using smFRET and nano-positioning triangulation maps dynamic positioning of the Rpc34 WH2 domain in yeast Pol III elongation complexes and presents a thiol-capping SPAAC labeling strategy to enable selective site-specific fluorophore attachment. Key terms: RNA polymerase III, Rpc34, winged helix, smFRET, bio-orthogonal labeling.

Study Highlights:
Using smFRET with ALEX and nano-positioning triangulation, the authors show Rpc34 WH2 occupies three discrete positions across the Pol III DNA-binding cleft and dynamically interconverts among them. A bio-orthogonal labeling workflow—azido-UAA incorporation plus SPAAC with thiol-capping—enabled selective labeling in the cysteine-rich complex. Maf1 binding locks WH2 into the upstream/distal state, validating positional assignments, and HMM dwell-time analysis revealed ordered transitions that proceed through the middle state with characteristic lifetimes. These results indicate Rpc34 WH2 engages the elongation complex via transient, weak DNA and protein contacts, with potential roles in bubble stabilization and rapid reinitiation.

Conclusion:
Rpc34 WH2 is a mobile, multifunctional cleft-associated module that occupies three ordered positions to transiently engage the Pol III elongation complex, and the thiol-capping SPAAC labeling approach provides a robust route for smFRET studies of large native assemblies.

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

Article title:
Dynamic positioning of Rpc34 winged helix in RNA polymerase III elongation complex for its stability with implications for reinitiation

First author:
Wu J-S

Journal:
PNAS

DOI:
10.1073/pnas.2601775123

Reference:
Wu J-S, Chang W-H, et al. Dynamic positioning of Rpc34 winged helix in RNA polymerase III elongation complex for its stability with implications for reinitiation. Proc Natl Acad Sci U S A. 2026;123(27):e2601775123. doi:10.1073/pnas.2601775123

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
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/base-by-base-413-rpc34-wh2-pol3-dynamics

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-07-12.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited the transcript portions describing Rpc34 WH2 dynamics, labeling strategy, three-state model, Maf1 effects, NPS localization, and rapid reinitiation implications, comparing to the original article.
- transcript topics: Rpc34 WH2 dynamics in Pol III elongation complex; smFRET labeling strategy (azido-UAA, SPAAC, MMTS); Maf1 regulation of WH2 mobility; Nano-positioning system (NPS) localization; Three-state model: distal, middle, proximal; Implications for rapid reinitiation and Pol III processivity

QC Summary:
- factual score: 9/10
- 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:
- Rpc34 WH2 dynamically transitions among three discrete states across the Pol III DNA-binding cleft during elongation
- States are designated distal, middle, and proximal
- Maf1 stabilizes WH2 in the distal/upstream state, constraining mobility
- A bio-orthogonal labeling strategy (azido-UAA + SPAAC) with MMTS thiol-capping enables selective labeling of Rpc34 WH2
- NPS triangulation locates three spatial positions (distal, middle, proximal) across the DNA-binding cleft
- Mobility of Rpc34 WH2 is proposed to support rapid reinitiation and EC stability

QC Flagged Items (audited and not fully supported):
- Numeric claim uncertain: Dwell-time lifetimes: high-FRET ≈ 9.37 s, middle-FRET ≈ 3.12 s, low-FRET ≈ 1.41 s
Internal QC note: manual editorial review is recommended before publication.

QC result: Warning. Items above were flagged during automated QC; the editorial team reviewed them before release.

Scurich N et al., PNAS - A concise breakdown of a PNAS perspective that analyzes forensic proficiency testing practices using the 2023 CTS firearms test as a case study. The authors identify test design and administration flaws—easy items, consensus scoring, handling of inconclusives, nonblind verification, shot‑to‑shot variability, and contextual bias—that undermine claims about examiner accuracy and the utility of reported error rates for courts and laboratories. Key terms: forensic proficiency testing, firearm identification, false positive rate, test design, cognitive bias.

Study Highlights:
The authors analyze CTS Test 23‑5262 and report a false‑positive rate of about 20% for bullet comparisons, highlighting broader concerns. They identify structural issues in proficiency testing including ceiling effects from easy items, inconsistent scoring of inconclusives, reliance on consensus rather than ground truth, and nonblind verification. The paper argues these features confound examiner performance with test properties, limiting the tests’ ability to estimate operational error rates and inform court decisions. The authors recommend better test design, blind verification, confidence ratings, and use of objective metrics to improve validation and lab practice.

Conclusion:
Current forensic proficiency testing practices can conceal fundamental weaknesses in examiner performance and test design; systemic, evidence‑based reform is needed to provide courts and laboratories with meaningful estimates of reliability and to reduce risks of wrongful outcomes.

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

Article title:
Assessing the foundations of forensic identification evidence: A critical examination of proficiency test design and results

First author:
Scurich N

Journal:
PNAS

DOI:
10.1073/pnas.2528192123

Reference:
Scurich N, Albright TD. Assessing the foundations of forensic identification evidence: A critical examination of proficiency test design and results. PNAS. 2026; Vol.123:e2528192123. doi:10.1073/pnas.2528192123

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
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/fault-lines-forensic-proficiency-testing

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-07-12.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited the transcript sections describing CTS proficiency testing (Test 23-5262), the reported false-positive rates, consensus scoring and inconclusives, out-of-class eliminations, shot-to-shot variability and reproducibility, contextual bias and NIBIN leads, nonblind verification, signal detection theory as reform, a
- transcript topics: CTS proficiency testing overview and purpose; CTS Test 23-5262 design and ground truth; False-positive rate findings (around 20%; 19.2% excluding item 4; 22% at least one false positive); Consensus scoring and handling of inconclusives; Out-of-class eliminations (Item 4) and associated errors; Class characteristics and reproducibility concerns across test sets

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:
- CTS Test 23-5262 false-positive rate ~20%
- Excluding item 4 yields ~19.2% false positives
- Approximately 22% of examiners made at least one false positive
- Item 4 was an out-of-class elimination; 1.5% failed; one called it an Identification; four called inconclusive
- Bullets from the same gun show shot-to-shot variability; test sets differed in marking/clarity
- NIBIN leads can prompt confirmation and influence examiner judgment

QC result: Pass.

Nihata A et al., PNAS - This PNAS study describes the development of EKV, a humanized dividing cell line that propagates bona fide sporadic CJD (sCJD) prions, and the Human Prion Assay (HPA), a cell-based method that quantifies infectivity with sensitivity comparable to transgenic mouse bioassay while enabling rapid therapeutic screening. Key terms: sCJD, EKV cells, Human Prion Assay, prion infectivity, anti-PrP antibody.

Study Highlights:
The authors engineered EKV cells by reconstituting CAD5 PrP-knockdown cells with human PrP (V129) and iterative single-cell cloning to enrich prion susceptibility. EKV cells propagate de novo infectious sCJD prions that reproduce strain-specific pathology when transmitted to humanized Tg152c mice. The Human Prion Assay (HPA) using EKV cells quantifies sCJD infectivity across a wide dynamic range with sensitivity comparable to mouse bioassay but in weeks rather than years. Persistently infected iEKV clones can be cured by the anti-PrP monoclonal antibody ICSM18, validating the platform for high-throughput therapeutic screens.

Conclusion:
EKV cells and the HPA provide a renewable, scalable, and faster alternative to animal bioassays for measuring authentic human sCJD infectivity and for screening and validating anti-prion therapeutics, while retaining strain-specific biological properties.

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

Article title:
A scalable, dividing cell model for the robust propagation and quantification of human sporadic Creutzfeldt–Jakob disease prions

First author:
Nihata A

Journal:
PNAS

DOI:
10.1073/pnas.2600341123

Reference:
Nihata A, Collinge J, Linehan J, Brandner S, Mead S, Schmidt C, Rayner MLD, Jat PS, Arora P, et al. A scalable, dividing cell model for the robust propagation and quantification of human sporadic Creutzfeldt–Jakob disease prions. PNAS. 2026;123(27):e2600341123. doi:10.1073/pnas.2600341123.

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
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/ekv-human-prion-assay

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-07-09.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Substantive audit focused on EKV cell development and validation, in vitro propagation of human sCJD prions, HPA implementation and benchmarking against mouse bioassay, drug-screening demonstration, and documented limitations (codon 129 mismatch, occult infectivity).
- transcript topics: Prion biology and strain concepts (PRNP codon 129 polymorphism); Historical barriers to human prion culture and need for cell-based infectivity assays; Engineering EKV cells: CAD5-KDB3, human PrP V129, mouse signal peptide; Iterative single-cell cloning and enrichment to EKV; Infectivity validation via transmission to Tg152c mice; Development and validation of the Human Prion Assay (HPA)

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:
- EKV cells propagate de novo infectious human sCJD prions in culture
- Infectivity validated by transmission to Tg152c mice; 100% (18/18) succumbed to prion disease with incubation ~251 days
- Human Prion Assay (HPA) detects sCJD infectivity with titer ~5.66 logTCIU50/g, comparable to mouse bioassay ~5.88 logLD50/g
- HPA achieves detection across type 2 and 3 prion strains, with MM prions less efficiently propagated due to codon 129 mismatch
- Persistently infected iEKV lines (e.g., 1G2, 1E10) maintained infection over ≥15 passages; ICSM18 cures infection in iEKV
- Occult infectivity observed: KDB3 control exposed to brain homogenate still produced a single prion disease case after six passages

QC result: Pass.

Abson KL et al., PNAS - A cross-species synthesis and theory paper showing that simple molecular diversity metrics poorly predict short-term adaptive potential. The authors compiled >2,100 quantitative genetics estimates (evolvability and heritability) across ~193 eukaryotic species and compared them to nucleotide diversity (π) and microsatellite heterozygosity (He). They find nucleotide diversity explains only ~1.1% of interspecific variation in evolvability and that doubling π corresponds to a modest ~11.7% increase in evolvability. Theoretical models indicate this weak relationship is expected when trait variance is shaped by stabilizing selection, mutation rates, and effective population size dynamics. Key terms: nucleotide diversity, evolvability, adaptive potential, conservation genetics, microsatellites.

Study Highlights:
The authors compiled 2,113 evolvability estimates across 193 eukaryotic species and matched these to measures of nucleotide diversity (π) and microsatellite heterozygosity (He). They found no meaningful association between ln(IA) (evolvability) and ln(π): π explained ~1.1% of interspecific variation and doubling π predicts only an ~11.7% increase in evolvability. Microsatellite and nucleotide diversity were uncorrelated across species, and both molecular measures were weak predictors of quantitative genetic variation. Theoretical mutation–selection–drift models show weak associations are expected under stabilizing selection and when VA depends more on mutation rate and selection than on neutral diversity.

Conclusion:
Simple, genome-wide molecular diversity metrics (π, He) are poor predictors of short-term adaptive potential (evolvability); conservation assessments should not rely on these alone and should incorporate trait-based or functionally informed genomic data.

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

Article title:
Nucleotide diversity is a poor predictor of short-term adaptive potential

First author:
Abson KL

Journal:
PNAS

DOI:
10.1073/pnas.2536181123

Reference:
Abson KL, Zijmers L, Mittell EA, Young EA, Postma E, Eyre-Walker A, Hadfield JD. Nucleotide diversity is a poor predictor of short-term adaptive potential. Proc Natl Acad Sci U S A. 2026;123(27):e2536181123. doi:10.1073/pnas.2536181123

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
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/nucleotide-diversity-poor-predictor-adaptive-potential

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-07-08.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited the transcript's coverage of core scientific claims: relationship between π and IA, the π vs He relationship, functional variation (πN/πS), the theoretical basis (stabilizing selection), and conservation implications/policy directions.
- transcript topics: Adaptive potential and evolvability (IA) concept; Nucleotide diversity (π) as predictor of evolvability; Microsatellite diversity (He) and its relation to π and IA; Theoretical mutation–selection–drift framework and stabilizing selection; Functional variation (πN/πS) and its predictive power; Conservation policy implications and IUCN Red List considerations

QC Summary:
- factual score: 10/10
- metadata score: 10/10
- supported core claims: 7
- 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:
- Nucleotide diversity explains 1.1% of interspecific differences in evolvability (IA).
- Doubling nucleotide diversity (π) corresponds to ~11.7% increase in evolvability (IA).
- Microsatellite diversity (He) and nucleotide diversity (π) are not significantly correlated across species.
- Functional diversity (πN/πS) shows little predictive power for IA; doubling πN/πS yields near-zero increase in IA.
- Slope of ln(VA) vs ln(π) is substantially less than 1 (β ≈ 0.160), consistent with stabilizing selection decoupling VA from π.
- Conservation implications: relying on simple molecular proxies (π, He) can misinform management; need genomic annotation and functionally informed approaches.

QC result: Pass.

Shin J et al., PNAS - This episode examines a large transcriptome compendium (PRECISE-NP881) that profiles E. coli K-12 MG1655 across 43 carbon substrates. Independent component analysis resolved 137 iModulons, including 25 carbon-catabolism modules that organize substrates into four activity-defined groups tied to growth rate, substrate chemistry, metabolic entry routes, and proteome allocation. The study integrates growth phenotyping, FBA/ME-modeling, targeted knockouts, and reanalysis of a starvation/refeeding time course to connect transcriptional modules to physiological context. Key terms: carbon response, iModulon, Escherichia coli, carbon catabolite repression, transcriptional regulatory network.

Study Highlights:
The authors assembled PRECISE-NP881 (881 transcriptomes) and used ICA to define 137 iModulons, 25 of which are carbon-catabolism modules whose activities cluster substrates into four groups. Faster-growing sugars showed limited CRP-linked remodeling while slower-growth, non-glycolytic substrates activated CRP-linked, NtrC-1, Propionate, and SgcABCEQX iModulons. Targeted knockouts (e.g., ΔprpC) demonstrated conditional growth defects on Group C/D substrates supporting a role for methylcitrate-mediated propionyl-CoA processing. Proteome-allocation modeling and projection of an independent starvation/refeeding dataset corroborated links between carbon-response modules, growth/stress physiology, and metabolite dynamics.

Conclusion:
The paper provides a quantitative atlas of carbon-responsive transcriptional states in E. coli, decomposing CCR into separable CRP-linked and substrate-specific modules and linking these modules to growth rate, metabolic context, proteome allocation, and conditional physiological relevance.

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

Article title:
A systems-level atlas of carbon-response transcriptional states in Escherichia coli

First author:
Shin J

Journal:
PNAS

DOI:
10.1073/pnas.2531884123

Reference:
Shin J, Son HF, Krishnan J, Hefner Y, Szubin R, Sung J, Patel A, Lou XA, Catoiu EA, Palsson BØ, Zielinski DC. A systems-level atlas of carbon-response transcriptional states in Escherichia coli. PNAS. 2026;123(27):e2531884123. doi:10.1073/pnas.2531884123.

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
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/atlas-carbon-response-transcriptional-states-e-coli

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-07-07.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited the transcript sections describing PRECISE-NP881 atlas construction ( ICA/iModulons ), four substrate groups (A–D), CRP decomposition into Crp-1/Crp-2/Crp-3, NtrC-1 and Propionate iModulons linked to propionyl-CoA stress, methylcitrate pathway (prpC/astC), SgcABCEQX prophage iModulon, starvation/refeeding dynam
- transcript topics: ICA-based iModulon analysis; CRP-linked iModulons decomposition (Crp-1, Crp-2, Crp-3); Four substrate groups (A–D) and growth phenotypes; NtrC-1 and Propionate iModulons and propionyl-CoA stress; Methylcitrate pathway and prpC/astC functional evidence; SgcABCEQX prophage iModulon

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:
- 25 carbon-catabolism iModulons identified (out of 137 total iModulons)
- four activity-defined substrate groups (A–D) with distinct growth and metabolic patterns
- CRP network decomposes into Crp-1, Crp-2, Crp-3 iModulons
- NtrC-1 and Propionate iModulons associated with Group C/D substrates and methylcitrate pathway
- prpC (methylcitrate synthase) deletion reduces growth on Group C/D substrates but not on glucose
- SgcABCEQX prophage iModulon induced under nitrogen-containing, slower-growth conditions; not required for growth in tested conditions

QC result: Pass.

Tsakiria E et al., Proceedings of the National Academy of Sciences (PNAS) - Using Tau knockout mice and the C. elegans PTL-1 deletion, this study shows that loss of wild-type Tau promotes a conserved shift toward mitochondrial fusion, increases respiratory activity, membrane potential and mitophagy, raises ROS, and enhances stress resilience. The adaptive phenotypes depend on mitofusin/FZO-1 and are phenocopied by FZO-1 overexpression. Key terms: Tau protein, mitochondrial fusion, mitofusin (FZO-1), mitophagy, neurodegeneration.

Study Highlights:
Across mouse and nematode models, Tau/PTL-1 deficiency increased basal and ATP-linked respiration, mitochondrial membrane potential, and ROS while enhancing mitophagy. Loss of Tau shifted mitochondrial morphology toward a pro-fusion state with increased mitofusin (Mfn1/2/FZO-1) localization and reduced Drp1 recruitment. Genetic removal of the mitofusin FZO-1 abolished the enhanced bioenergetics, motility, longevity under stress, and stress resistance, whereas FZO-1 overexpression phenocopied key Tau-loss features. These results identify a conserved, mitofusin-dependent mechanism by which wild-type Tau restrains mitochondrial fusion and functional adaptation.

Conclusion:
Wild-type Tau acts as a conserved negative regulator of mitochondrial fusion and functional adaptation; its loss triggers FZO-1/mitofusin-dependent mitochondrial remodeling that elevates bioenergetics and stress resilience in a context-dependent manner.

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

Article title:
Tau protein as a regulator of mitochondrial function and dynamics

First author:
Tsakiria E

Journal:
Proceedings of the National Academy of Sciences (PNAS)

DOI:
10.1073/pnas.2521642123

Reference:
Tsakiria E., Campos-Marques C., Ferreira I.L., Trougakos I.P., Dioli C., Gianniou D.D., Silva J.M., Skourti K., Roussos A., Samiotaki M., Sotiropoulos I., Palikaras K., et al. Tau protein as a regulator of mitochondrial function and dynamics. Proc Natl Acad Sci U S A. 2026; doi:10.1073/pnas.2521642123.

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
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/tau-mitochondrial-fusion-episode-408

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-07-06.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Substantively audited sections covering: WT Tau localization and baseline role; Tau/PTL-1 deficiency effects on respiration and mitophagy; pro-fusion shift and changes in fission/fusion proteins; ROS dynamics and hormetic effects; dependency on FZO-1 and rescue via FZO-1 overexpression; implications for Tau-lowering th
- transcript topics: Tau deficiency and mitochondrial respiration (Seahorse data in Tau-KO mice and PTL-1 KO worms); Mitochondrial morphology and fusion/fission regulators (DRP-1, MFN1/MFN2, form factor); Mitophagy dynamics in Tau/PTL-1 deficiency; ROS production and membrane potential changes; ROS-mediated hormesis and antioxidant effects (NAC) across conditions; Genetic dissection: role of FZO-1 (fusion) and DRP-1 (fission)

QC Summary:
- factual score: 10/10
- metadata score: 10/10
- supported core claims: 5
- 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:
- Tau deficiency increases mitochondrial respiration (basal and ADP-stimulated OCR) in Tau-KO mice and PTL-1 KO C. elegans neurons
- Loss of Tau/PTL-1 promotes pro-fusion mitochondrial state with decreased DRP-1 at mitochondria and increased MFN1/MFN2
- Mitophagy is enhanced in Tau-KO and PTL-1 KO models
- Mitochondrial membrane potential increases and ROS production rises with Tau deficiency
- Under mild stress, Tau/PTL-1-deficient animals show improved survival; antioxidant NAC modulates lifespan depending on temperature/condition
- Fusion is required for Tau/PTL-1–deficiency–mediated benefits; FZO-1 loss suppresses phenotypes; FZO-1 overexpression phenocopies Tau loss

QC result: Pass.

Norberg ES et al., Proceedings of the National Academy of Sciences - Using metal‑responsive fluorescent Salmonella reporters, calf intestinal loops, and CRISPR edited epithelial cells, this study shows that the divalent metal transporter SLC11A2 is recruited to Salmonella‑containing vacuoles and restricts Fe2+ and Mn2+, limiting intracellular bacterial replication. Key terms: SLC11A2, nutritional immunity, Salmonella enterica, iron and manganese, intestinal epithelium.

Study Highlights:
The authors used metal‑sensing GFP reporters in Salmonella and a calf ligated ileal loop model to map metal availability and found a subpopulation of bacteria in IECs and lamina propria cells exposed to ≤0.1 µM Fe2+ and Zn2+, and possibly Mn2+, early in infection. SLC11A2 localized to the apical surface and endosomal network of IECs and was recruited to maturing Salmonella‑containing vacuoles; CRISPR knockout of SLC11A2 in HCT116 epithelial cells increased bacterial replication. Fluorescent reporters and ICP‑MS indicate vacuolar STm are less starved for Fe2+ and Mn2+ in the absence of SLC11A2, while Zn2+ and Mg2+ sensing was unchanged. Salmonella counters SLC11A2‑mediated restriction through the Mn2+/Fe2+ transporter MntH and siderophore production.

Conclusion:
SLC11A2 mediates epithelial nutritional immunity by sequestering Fe2+ and Mn2+ in Salmonella‑containing vacuoles, reducing vacuolar metal availability and limiting intracellular Salmonella replication.

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

Article title:
SLC11A2 withholds divalent metals from
Salmonella
in the gut epithelium

First author:
Norberg ES

Journal:
Proceedings of the National Academy of Sciences

DOI:
10.1073/pnas.2532675123

Reference:
Norberg ES, Knodler LA, et al. SLC11A2 withholds divalent metals from Salmonella in the gut epithelium. PNAS. 2026;123:e2532675123. doi:10.1073/pnas.2532675123

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
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/slc11a2-withholds-divalent-metals-from-salmonella

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-07-05.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited transcript sections covering nutritional immunity concepts, IEC-localized SLC11A2 function, calf ileal loop in vivo model, metal-responsive STm reporters, SLC11A2 recruitment to SCVs, SLC11A2 knockout effects in HCT116 cells, bacterial countermeasures (MntH and siderophores), intracellular niches (SCV vs cytoso
- transcript topics: Nutritional immunity and trace metal tug-of-war; SLC11A2 (NRAMP2) in intestinal epithelial cells; Calf ligated ileal loop model and metal availability; Metal-responsive Salmonella reporters (iroN, sitA, zinT); SLC11A2 recruitment to Salmonella-containing vacuoles; SLC11A2 knockout in HCT116 cells and impact on Salmonella replication

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:
- SLC11A2 is recruited to Salmonella-containing vacuoles (SCV) in intestinal epithelial cells and restricts Fe2+ and Mn2+ availability within SCVs, limiting intracellular Salmonella
- Deletion of SLC11A2 in HCT116 cells increases Salmonella replication intracellularly, notably at 8 and 16 hours post-infection in 1% fetal calf serum conditions.
- Salmonella counteracts SLC11A2 through MntH and siderophores; entC deletion reduces replication in WT and complementation rescues replication, indicating competition for Fe2+/Mn2+
- Metal-reporter data show early metal starvation in a subpopulation of intracellular Salmonella (≈38% Zn2+-limited at 2 h; regional shifts by 8 h toward lamina propria).
- Calf ligated ileal loop model demonstrates metal restriction at IECs and lamina propria during acute infection.
- SLC11A2 knockout reduces ferritin (FTH1/FTL) levels in cells, suggesting reduced cytosolic iron availability.

QC result: Pass.