️ Episode 240: CYFIP1 controls cortical axon development by modulating calcium

In this episode of PaperCast Base by Base, we explore Reduction of CYFIP1 delays callosal axon growth and arborization by lowering intracellular calcium and impairing mitochondrial function

Study Highlights:
In vivo, Cyfip1+/- mice show delayed callosal axon growth at P5 and reduced axonal branching during P15 arborization that normalizes by P30. Cyfip1+/- cortical neurons have reduced cytosolic and mitochondrial calcium, larger and elongated mitochondria, increased mitochondrial density and motility, and decreased mitochondrial membrane potential and ATP at early stages. CYFIP1 associates with Hu proteins and binds mRNAs encoding Cav alpha-1 subunits (Cacna1c, Cacna1e, Cacna1i), stabilizing those transcripts and maintaining membrane protein levels in developing neurons and axons. Loss of CYFIP1 accelerates decay of these channel mRNAs, leading to reduced Cav protein abundance in axons and lower calcium availability. Restoring intracellular calcium with ionomycin or activating L-type channels (Bay-K-8644, nefiracetam) rescues axonal growth and mitochondrial defects in Cyfip1+/- neurons

Conclusion:
CYFIP1 ensures timely cortical callosal development by stabilizing mRNAs for voltage-gated calcium channel subunits to maintain intracellular calcium and mitochondrial function, and its haploinsufficiency may contribute to connectivity deficits linked to neurodevelopmental disorders

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Reference:
Ricci C, Midroit MJ, Caicci F, Achsel T, Domínguez-Iturza N, Bagni C. CYFIP1 governs the development of cortical axons by modulating calcium availability. Nature Communications. 2025;16:10764. https://doi.org/10.1038/s41467-025-65801-0

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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/

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On PaperCast Base by Base you’ll discover the latest in genomics, functional genomics, structural genomics, and proteomics.

Keywords: cyfip1, axon development, calcium, mitochondria, callosal connectivity

️ Episode 239: Genomic Adaptations of the Svalbard Reindeer

In this episode of PaperCast Base by Base, we explore Comparative whole-genome analyses identify 150 differentiated genomic regions and candidate genes linked to fat metabolism, energy conservation, cold tolerance, reduced body size, fur morphology, and circadian rhythm that likely underpin Svalbard reindeer adaptation to the High Arctic

Study Highlights:
The authors sequenced and analyzed 62 reindeer genomes from Svalbard, mainland Norway, mainland Russia, and Novaya Zemlya using three complementary approaches: population branch statistic scans, annotation of high-frequency derived coding variants, and copy number variant analysis. They identified 150 genomic regions with 120 annotated candidate genes enriched for functions related to methylglyoxal metabolism, DNA repair, transport, metabolism, and microtubule extension. Candidate genes and structural variants implicate pathways for fat storage and fasting endurance, insulin and leptin-related energy regulation, brown adipose thermogenesis, fur and skin development, eye and circadian function, and genes associated with reduced body and limb size. Results show no single gene set detected by all methods, indicating a complex genomic architecture where selection, drift from historical bottlenecks, and structural variation contribute to the Svalbard phenotype.

Conclusion:
Multiple genomic regions and candidate genes involved in energy metabolism, thermoregulation, and morphology show putative signatures of adaptation that likely enabled Svalbard reindeer to persist in the High Arctic despite low genetic diversity

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Reference:
Dussex N, Ersmark E, Hansen BB, Bieker VC, Sun X, Le Moullec M, Røed KH, Speakman JR, Loe LE, Dalén L, Martin MD. The Genomic Basis of the Svalbard Reindeer’s Adaptation to an Extreme Arctic Environment. Genome Biol Evol. 2025;17(9):evaf160. https://doi.org/10.1093/gbe/evaf160

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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/

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On PaperCast Base by Base you’ll discover the latest in genomics, functional genomics, structural genomics, and proteomics.

Keywords: Svalbard reindeer, genomics, adaptation, thermoregulation, energy metabolism

️ Episode 238: Germline polymorphisms shape antibody light chain repertoires

In this episode of PaperCast Base by Base, we explore Long-read sequencing of IGK and IGL paired with AIRR-seq shows that common germline SNVs, SVs, and alleles drive inter-individual differences in light chain gene usage and CDR3 properties

Study Highlights:
The authors combined targeted long-read genomic sequencing of IGK and IGL in 177 donors with matched AIRR-seq (IGK n=164, IGL n=168) to generate phased SNV, SV, and allele callsets and personalized germline databases. Cis guQTL analysis identified 2,352 variants in the unmutated IGK repertoire linked to usage changes in 21 IGKV and 3 IGKJ genes, and 911 variants in IGL linked to 22 IGLV and 3 IGLJ genes, indicating germline variation affects >70% of light chain genes. Lead variants mapped to intergenic regions, RSSs, coding exons and structural variants, with examples including a premature stop in IGKV2-29, a K50D missense in IGKV1-5, RSS spacer changes in IGLV3-16, and copy-number SVs that alter gene usage. Genetic effects were stronger in the antigen-naïve repertoire, associated with shifts in encoded V/J alleles and CDR3 physicochemical properties, and IGK exhibited larger LD blocks and coordinated multi-gene usage compared with IGL.

Conclusion:
Germline polymorphisms across IGK and IGL establish reproducible baseline differences in light chain gene availability and amino acid composition that likely influence antibody-mediated responses.

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Reference:
Engelbrecht E, Rodriguez OL, Lees W, Vanwinkle Z, Shields K, Schultze S, Gibson WS, Smith DR, Jana U, Saha S, Peres A, Yaari G, Smith ML, Watson CT. Germline polymorphisms in the immunoglobulin kappa and lambda loci underpinning antibody light chain repertoire variability. Nat Commun. 2025. https://doi.org/10.1038/s41467-025-66759-9

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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/

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Keywords: immunoglobulin-kappa, immunoglobulin-lambda, germline-variation, antibody-repertoire, long-read-sequencing

️ Episode 237: Tracing enteric pathogens in Africa with metagenomics and WGS

In this episode of PaperCast Base by Base, we explore This study combines whole-genome sequencing and metagenomics to map the diversity, abundance, and genomic relationships of enteric foodborne pathogens across human, animal, food and environmental samples in four African LMICs

Study Highlights:
The project sampled 3,417 items across Ethiopia, Mozambique, Nigeria and Tanzania between 2019 and 2023 and applied culture-based WGS and metagenomic sequencing. Of 446 recovered isolates, 380 high-quality genomes were analyzed (207 E. coli, 138 Salmonella spp., 24 Campylobacter spp., 11 Shigella spp.), and 139 metagenomes passed QC for community profiling. Pathogen distributions were geographically stable over time, with genomic clustering showing closely related isolates across distinct sources consistent with potential transmission routes. Metagenomics revealed dominant genera such as Escherichia, Enterococcus and Bifidobacterium, recovered 13 high-quality MAGs (12 E. coli, 1 Campylobacter), and provided complementary population-level insights though MAGs rarely reached strain-level identity with cultured isolates.

Conclusion:
Combining targeted environmental and food-chain sampling with WGS and metagenomic sequencing strengthens surveillance and source-tracing of foodborne enteric pathogens in resource-limited African settings

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Reference:
Thystrup C, Gobena T, Salvador EM, Fayemi OE, Kumburu H, Buys EM, Gichure J, Moiane BT, Belina D, Hugho EA, Faife S, Ogunbiyi TS, Akanni G, Ayolabi CI, Mmbaga B, Thomas KM, Pires SM, Njage PMK, Hald T. Using metagenomics and whole-genome sequencing to characterize enteric pathogens across various sources in Africa. Nat Commun (2025). https://doi.org/10.1038/s41467-025-66400-9

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/

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On PaperCast Base by Base you’ll discover the latest in genomics, functional genomics, structural genomics, and proteomics.

Keywords: metagenomics, whole-genome sequencing, foodborne pathogens, one-health, surveillance

️ Episode 236: XPD translocation and genetic disease etiology

In this episode of PaperCast Base by Base, we explore Computational modeling reveals how ATP-driven conformational cycles of the XPD helicase drive directional 5′→3′ translocation on single-stranded DNA and how mutations disrupt this process to cause disease

Study Highlights:
The authors combined molecular dynamics, partial nudged elastic band path optimization, transition path sampling, and Markov state modeling to map seven metastable on-path states that define XPD’s ATPase cycle. ATP binding and hydrolysis drive reciprocal rotations of the RecA2 and Arch domains, transmitted via a spring helix and spindle helix, that alternate DNA affinity at two defined constrictions at the 5′ and 3′ ends of the DNA-binding groove. Translocation proceeds in two phases: RecA2-driven sliding of ssDNA through Constriction 1 followed by ATP hydrolysis, constriction switching and sliding through Constriction 2, advancing one nucleotide per ATP. Mapping of missense mutations shows clustering of disease-associated residues at DNA- and ATP-binding sites and classifies mutations that impair DNA binding, ATPase function, or allosteric domain dynamics

Conclusion:
A detailed mechanistic map links XPD’s nucleotide-dependent conformational switching to directional ssDNA translocation and explains how perturbations of key residues underlie XP, CS, and TTD phenotypes

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Reference:
Paul T, Yan C, Derdeyn-Blackwell G, Ivanov I. Translocation mechanism of xeroderma pigmentosum group D protein on single-stranded DNA and genetic disease etiology. Nat Commun. 2025. https://doi.org/10.1038/s41467-025-66834-1

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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/

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On PaperCast Base by Base you’ll discover the latest in genomics, functional genomics, structural genomics, and proteomics.

Keywords: XPD, DinG, ssDNA translocation, nucleotide excision repair, disease mutations

️ Episode 235: Maternal H3K9 methyltransferases control aRMAE in C. elegans

In this episode of PaperCast Base by Base, we explore Using dual-color reporters in C. elegans, the study shows maternal H3K9 methyltransferases MET-2 and SET-25 antagonistically regulate autosomal random monoallelic expression initiated in the early embryo

Study Highlights:
Dual-color fluorescent reporter alleles in C. elegans intestine cells enabled single-cell quantification of allele expression and a targeted screen for aRMAE regulators. MET-2/SETDB1, with LIN-65 and ARLE-14, acts maternally in the 8-cell E-cell to prevent monoallelic expression, while SET-25/SUV39 with HPL-2 and LIN-61 promotes allele silencing. Catalytic SET domains of both MET-2 and SET-25 are required for their opposing activities, and loss of MET-2 increases persistent but non-heritable monoallelic expression whereas loss of SET-25 causes biallelic expression. Reciprocal crosses and genetic interactions indicate these maternal H3K9 HMTs set early embryonic histone states that are propagated through somatic divisions to shape tissue-wide allele expression.

Conclusion:
Maternal MET-2 and SET-25 establish competing H3K9-related chromatin states in the early embryo that bias autosomal alleles toward persistent somatic monoallelic or biallelic expression

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Reference:
Sands, B., Yun, S.R., Oshima, J. et al. Maternal histone methyltransferases antagonistically regulate autosomal random monoallelic expression (aRMAE) in C. elegans. Nat Commun (2025). https://doi.org/10.1038/s41467-025-66501-5

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/

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On PaperCast Base by Base you’ll discover the latest in genomics, functional genomics, structural genomics, and proteomics.

Keywords: histone-methyltransferase, aRMAE, MET-2, SET-25, c-elegans

️ Episode 234: MTHFR genotype and methionine metabolism predict COVID-19 severity

In this episode of PaperCast Base by Base, we explore IMPACC longitudinal metabolomics and genomics analyses show that disruptions in one‑carbon/methionine metabolism together with MTHFR C677T genotype at hospital admission improve prediction of severe COVID‑19 and long COVID risk

Study Highlights:
IMPACC profiled plasma metabolites (global and targeted) from over 1,000 hospitalized COVID-19 patients and identified early alterations in one‑carbon metabolism, with emphasis on the methionine cycle. Methionine‑sulfoxide and S‑adenosylhomocysteine (SAH) were elevated in patients with more severe clinical trajectories and changed over serial visits. The common hypomorphic MTHFR C677T (AA) genotype associated with distinct methionine‑cycle metabolite profiles and, when combined with baseline methionine, methionine‑sulfoxide, and SAH levels, significantly improved mortality prediction versus genotype alone. The combined genotype–metabolite factor also stratified risk of long COVID across patient‑reported outcome clusters.

Conclusion:
Integrating MTHFR C677T status with early plasma methionine‑cycle metabolite measurements can enhance early risk stratification for severe COVID‑19 and long COVID.

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Reference:
Petrova B, Syphur C, Montgomery RR, Levy O, Diray‑Arce J, Kleinstein SH, Kanarek N, Culhane AJ, Chen J, et al. MTHFR allele and one‑carbon metabolic profile predict severity of COVID‑19. Proc Natl Acad Sci U S A. 2025;122(51):e2509118122. https://doi.org/10.1073/pnas.2509118122

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/

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Episode link: https://basebybase.castos.com/episodes/mthfr-methionine-covid-risk

Episode Slug: mthfr-methionine-covid-risk

Keywords: mthfr, one-carbon metabolism, methionine, metabolomics, long covid

️ Episode 233: Mechanistic basis of NuA3 recognition and H3K14 acetylation

In this episode of PaperCast Base by Base, we explore Cryo-EM structures of the yeast NuA3 complex reveal how a cooperative Sas3–Nto1 binding cleft recognizes the H3 tail and directs acetylation of H3K14

Study Highlights:
The authors report cryo-EM structures of NuA3 in apo, acetyl-CoA-bound, and acetyl-CoA plus H3 tail-bound states at ~3.7, 3.1, and 3.2 Å resolution respectively. The histone H3 tail binding cleft is formed cooperatively by the catalytic subunit Sas3 and the non-catalytic subunit Nto1, with a hydrophobic pocket engaging H3 residues 9–12 and a polar network contacting the backbone of residues 12–15, notably Gly13. Acetyl-CoA binding induces conformational changes in a histone-engaging loop and a CoA-engaging helix that expand the cleft and position catalytic residues Cys418 and Glu452 between H3K14 and the acetyl donor. Mutational and biochemical assays show L369R abolishes HAT activity, N354A partially reduces activity, and a G13R peptide is poorly acetylated, supporting the structural basis for H3K14 specificity and recruitment by H3K4me3/H3K36me3 readers.

Conclusion:
The structures define a cooperative Sas3–Nto1 recognition mechanism and Gly13-dependent substrate geometry that underlie NuA3 specificity for H3K14 acetylation

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Reference:
Shi, W., Zhao, L., Wang, Y. et al. Mechanistic insights into histone recognition and H3K14 acetylation by the NuA3 histone acetyltransferase complex. Nat Commun (2025). https://doi.org/10.1038/s41467-025-67049-0

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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/

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On PaperCast Base by Base you’ll discover the latest in genomics, functional genomics, structural genomics, and proteomics.

Keywords: NuA3, histone acetylation, H3K14, cryo-EM, Sas3-Nto1

️Episode 232: Lamin A/C steers fork restart via H3K9me3 and PARylation

In this episode of PaperCast Base by Base, we explore Nucleoplasmic Lamin A/C, together with LAP2α, enforces active replication fork slowing during mild replication stress by promoting local H3K9me3 and ADP-ribosylation to restrain RECQ1-mediated restart and protect genome stability

Study Highlights:
Lamin A/C dynamically associates with replication factories throughout the nucleus and its acute depletion abolishes stress-induced fork slowing and increases chromosomal breakage. Loss of nucleoplasmic Lamin A/C or LAP2α reduces poly-ADP-ribosylation (PAR) at nascent DNA, leading to untimely RECQ1-dependent restart of reversed forks. Mild replication stress induces accumulation of H3K9me3 at replication forks, and Lamin A/C is required to maintain this mark by preventing its removal by the demethylase KDM3A/JMJD1A. Inhibiting G9a to prevent H3K9 methylation phenocopies Lamin A/C loss, reducing PAR at forks and deregulating RECQ1 restart, whereas PARG inhibition or KDM3A downregulation restores PAR levels and fork slowing.

Conclusion:
Nucleoplasmic Lamin A/C maintains local chromatin compaction and PARylation at replication factories to limit RECQ1 activity, enforce fork slowing under mild stress, and preserve genome stability

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Reference:
Cherdyntseva V, Paulson J, González-Acosta D, Ubieto-Capella P, Rodrigues M, Aouami M, Adakli S, Gagné J-P, Bakker C, Poirier GG, Taneja N, Lopes M. Nucleoplasmic Lamin A/C controls replication fork restart upon stress by modulating local H3K9me3 and ADP-ribosylation levels. Nat Commun. 2025. https://doi.org/10.1038/s41467-025-66098-9

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On PaperCast Base by Base you’ll discover the latest in genomics, functional genomics, structural genomics, and proteomics.

️Episode 231: Transcription start sites as a germline mutational hotspot

In this episode of PaperCast Base by Base, we explore This study identifies a pronounced germline mutational hotspot centered on transcription start sites (TSSs) driven in part by early embryonic mosaic variants and transcription-associated DNA damage

Study Highlights:
Extremely rare variants show a localized excess of non(CpG > TpG) mutations around TSSs extending several hundred base pairs, reaching ~35% enrichment at the 100-bp scale and ~14% at 1 kb. The hotspot is largely absent from de novo mutation calls because early mosaic variants are significantly enriched downstream of the TSS and are often filtered from family sequencing data. Regression and feature analyses link the TSS excess to divergent transcription, RNA polymerase II stalling, R-loop formation and somatic (mitotic) double-strand breaks rather than meiotic PRDM9-associated breaks. Mutational signature decomposition implicates non-canonical DSB repair (including TMEJ) and transcription-associated processes, and the hotspot preferentially affects genes related to cancer and developmental phenotypes.

Conclusion:
Transcription initiation regions are focal points of heritable variation shaped by early-development mosaicism and transcription-linked mitotic DNA damage, with implications for disease genetics and evolutionary constraint

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Reference:
Cortés Guzmán M, Castellano D, Serrano Colomé C, Seplyarskiy V, Weghorn D. Transcription start sites experience a high influx of heritable variants fueled by early development. Nat Commun. 2025;16:10120. https://doi.org/10.1038/s41467-025-66201-0

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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/

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On PaperCast Base by Base you’ll discover the latest in genomics, functional genomics, structural genomics, and proteomics.