Biology subjects

Davidson, R.

Publications and source records attributed to Davidson, R..

9 recordsLinked to original sources

bioRxiv2026

Overcoming Daraxonrasib Resistance: Allele-Specific Mechanisms Guide Salvage Therapy in Pancreatic Cancer

Clinical-grade RAS inhibitors raise an unresolved question as to whether KRAS-alleles impose constraints on adaptive resistance that can be exploited therapeutically. Using daraxonrasib (RMC-6236), a multi-selective RAS(ON) inhibitor, we compared resistance mechanisms between KRASG12D and KRASG12R, alleles with fundamentally different RAS network dynamics. Daraxonrasib inhibited KRASMUT primarily through steric occlusion of effector binding, while engaging RASWT only modestly ([~]20%). KRASG12R is marked by its inability to transactivate RASWT, and it was observed that daraxonrasib resistant KRASG12R PDAC cells utilize EGFR/RASWT-GTP signaling as the dominant adaptive route. In contrast, KRASG12D resistance arose through retained KRASG12D-GTP signaling, with a decrease of cyclophilin A (CypA) protein, the binding partner required for daraxonrasib activity. The shift from KRASG12R dependence to the EGFR/RASWT conferred sensitivity to trametinib. We confirmed this clinically: a KRASG12R PDAC patient who progressed after 10 months on daraxonrasib showed intratumoral EGFR/RASWT activation, and rapid 3D-bioprinted patient-derived toroid modeling predicted sensitivity to trametinib-based combination therapy. Given the aggressive disease trajectory and lack of response to the two immediately preceding lines of therapy, sixth-line trametinib-based combination therapy achieved approximately 5 months of disease control. This patient ultimately achieved 40 months of overall survival, far exceeding the 8-12 month median for metastatic PDAC. Collectively, these data establish a framework in which allele-specific RAS network topology dictates the adaptive resistance landscape, enabling rational selection of targeted therapies with meaningful clinical benefit in metastatic PDAC. STATEMENT OF SIGNIFICANCEDaraxonrasib resistance mechanisms have allele-specific routes: CypA becomes downregulated in KRASG12D and reliance on EGFR/RASWT in KRASG12R. Rapid patient-derived toroids identified sixth-line targeted therapy strategies with an overall survival of 40 months.

cancer biology↗

bioRxiv2026

Improving Turnaround Times with Artificial Intelligence in Microbiology

This dual-center study evaluated the impact of artificial intelligence (AI) on urine culture turnaround times in Canadian diagnostic laboratories employing full microbiology laboratory automation. Data were collected before and after the implementation of PhenoMATRIX (PM), an AI-based software designed to support culture sorting and result interpretation. In both a low-volume tertiary care hospital and a high-volume community laboratory, PM reduced the time to final culture reporting, with decreases of approximately 1.5 hours and 3.9 hours, respectively. Implementation of PM+, which automatically releases defined results to patient charts, further improved turnaround time. These findings indicate that microbiology laboratories with full laboratory automation can achieve further improvements in turnaround time by integrating AI-culture assessment and results release.

microbiology↗

bioRxiv2025

Palaeogenomics reveals 1,500 years of population history of the peoples of the Chonos Archipelago, Chile.

The Chonos archipelago, located in northwestern Chilean Patagonia, was historically inhabited by an Indigenous sea-faring population known to the European colonists as the "Chono". Previous research has contextualized the human occupation of this region with radiocarbon dates and ancient mitochondrial genomes, offering a partial perspective on the history of its inhabitants. Here we present a paleogenomic analysis of 20 ancient human individuals from 6 archaeological sites, dated between 1,600-50 years before present (BP). We successfully captured over 100,000 SNPs from 15 of 20 individuals and recovered 12 full mitogenomes. All individuals presented unadmixed Indigenous South American ancestry and formed a separated genetic cluster relative to other ancient and modern South American genomes, indicating a unique Chonos ancestry. This Chonos ancestry falls within a broader cluster of late-Holocene Patagonian ancestry, most similar to the Kawesqar peoples who neighbour to the south. Within the Chonos, we distinguish a northern and southern ancestry cluster. The northern Chonos cluster exhibits some genetic connections to the present-time inhabitants of the neighbouring island of Chiloe, who are connected to Huilliche Indigenous history. Our findings reveal a point of contact between southern Chonos/Patagonian ancestry to the south and Mapuche ancestry to the north, and confirm that sea-faring subsistence was a knowledge transferred between Patagonian peoples.

genomics↗

bioRxiv2024

The genetic history of Portugal over the past 5,000 years

BackgroundRecent ancient DNA studies uncovering large-scale demographic events in Iberia have focused primarily on Spain, with limited reports for Portugal, a country located at the westernmost edge of continental Eurasia. Here, we introduce the largest collection of ancient Portuguese genomic datasets (n = 68) to date, spanning 5,000 years, from the Neolithic to the 19th century. ResultsWe found evidence of patrilocality in Neolithic Portugal, with admixture from local hunter-gatherers and Anatolian farmers, and persistence of Upper Paleolithic Magdalenian ancestry. This genetic profile persists into the Chalcolithic, reflecting diverse local hunter- gatherer contributions. During the Bronze Age, local genetic ancestry persisted, particularly in southern Iberia, despite influences from the North Pontic Steppe and early Mediterranean contacts. The Roman period highlights Idanha-a-Velha as a hub of migration and interaction, with a notably diverse genetic profile. The Early Medieval period is marked by Central European ancestry linked to Suebi/Visigoth migrations, adding to coeval local, African, and Mediterranean influences. The Islamic and Christian Conquest periods show strong genetic continuity in northern Portugal and significant African admixture in the south, with persistent Jewish and Islamic ancestries suggesting enduring influences in the post-Islamic period. ConclusionsThis study represents the first attempt to reconstruct the genetic history of Portugal from the analysis of ancient individuals. We reveal dynamic patterns of migration and cultural exchange across millennia, but also the persistence of local ancestries. Our findings integrate genetic information with historical and archaeological data, enhancing our understanding of Iberias ancient heritage.

genomics↗

bioRxiv2024

Overcoming Hemophilia A Gene Therapy Limitations with an Enhanced Function Factor VIII Variant

Durable factor VIII (FVIII) expression that normalizes hemostasis is an unrealized goal of hemophilia A adeno- associated virus (AAV)-mediated gene therapy. Trials with initial normal FVIII activity observed unexplained year-over-year declines in expression while others reported low-level, stable FVIII expression inadequate to restore normal hemostasis. Here we demonstrate that mice recapitulate FVIII expression-level-dependent loss of plasma FVIII levels due to declines in vector copy number. We show that an enhanced function FVIII variant (FVIII-R336Q/R562Q; FVIII-QQ), resistant to inactivation by protein C, normalizes hemostasis at below-normal expression levels without evidence of prothrombotic risk in hemophilia A mice. These data support that FVIII- QQ may restore normal FVIII function at low-levels of expression to permit durability using low AAV vector doses to minimize dose-dependent AAV toxicities. This work informs the mechanism of FVIII durability after AAV gene transfer and supports that incorporating the FVIII-QQ transgene may safely overcome current hemophilia A gene therapy limitations.

pharmacology and toxicology↗

bioRxiv2024

Optimised in-solution enrichment of over a million ancient human SNPs

In-solution hybridisation enrichment of genetic markers is a method of choice in paleogenomic studies, where the DNA of interest is generally heavily fragmented and contaminated with environmental DNA, and where the retrieval of genetic data comparable between individuals is challenging. Here, we benchmarked the commercial "Twist Ancient DNA" reagent from Twist Biosciences using sequencing libraries from ancestrally diverse ancient human samples with low to high endogenous DNA content (0.1-44%). For each library, we tested one and two rounds of enrichment, and assessed performance compared to deep shotgun sequencing. We find that the "Twist Ancient DNA" assay provides robust enrichment of [~]1.2M target SNPs without introducing allelic bias that may interfere with downstream population genetics analyses. Additionally, we show that pooling up to 4 sequencing libraries and performing two rounds of enrichment is both reliable and cost-effective for libraries with less than 27% endogenous DNA content. Above 38% endogenous content, a maximum of one round of enrichment is recommended for cost-effectiveness and to preserve library complexity. In conclusion, we provide researchers in the field of human paleogenomics with a comprehensive understanding of the strengths and limitations of different sequencing and enrichment strategies, and our results offer practical guidance for optimising experimental protocols.

genomics↗

bioRxiv2023

Comparative genomics reveals the emergence of an outbreak-associated Cryptosporidium parvum population in Europe and its spread to the USA

The zoonotic parasite Cryptosporidium parvum is a global cause of gastrointestinal disease in humans and ruminants. Sequence analysis of the highly polymorphic gp60 gene enabled the classification of C. parvum isolates into multiple groups (e.g. IIa, IIc, Id) and a large number of subtypes. In Europe, subtype IIaA15G2R1 is largely predominant and has been associated with many water-and food-borne outbreaks. In this study, we generated new whole genome sequence (WGS) data from 123 human-and ruminant-derived isolates collected in 13 European countries and included other available WGS data from Europe, Egypt, China and the USA (n=72) in the largest comparative genomics study to date. We applied rigorous filters to exclude mixed infections and analysed a dataset from 141 isolates from the zoonotic groups IIa (n=119) and IId (n=22). Based on 28,047 high quality, biallelic genomic SNPs, we identified three distinct and strongly supported populations: isolates from China (IId) and Egypt (IIa and IId) formed population 1, a minority of European isolates (IIa and IId) formed population 2, while the majority of European (IIa, including all IIaA15G2R1 isolates) and all isolates from the USA (IIa) clustered in population 3. Based on analyses of the population structure, population genetics and recombination, we show that population 3 has recently emerged and expanded throughout Europe to then, possibly from the UK, reach the USA where it also expanded. In addition, genetic exchanges between different populations led to the formation of mosaic genomes. The reason(s) for the successful spread of population 3 remained elusive, although genes under selective pressure uniquely in this population were identified.

genomics↗

bioRxiv2023

Allelic bias when performing in-solution enrichment of ancient human DNA

In-solution hybridisation enrichment of genetic variation is a valuable methodology in human paleogenomics. It allows enrichment of endogenous DNA by targeting genetic markers that are comparable between sequencing libraries. Many studies have used the 1240k reagent--which enriches 1,237,207 genome-wide SNPs--since 2015, though access was restricted. In 2021, Twist Biosciences and Daicel Arbor Biosciences independently released commercial kits that enabled all researchers to perform enrichments for the same 1240k SNPs. We used the Daicel Arbor Biosciences Prime Plus kit to enrich 132 ancient samples from three continents. We identified a systematic assay bias that increases genetic similarity between enriched samples and that cannot be explained by batch effects. We present the impact of the bias on population genetics inferences (e.g., Principal Components Analysis, [f]-statistics) and genetic relatedness (READ). We compare the Prime Plus bias to that previously reported of the legacy 1240k enrichment assay. In [f]-statistics, we find that all Prime-Plus-generated data exhibit artefactual excess shared drift, such that within-continent relationships cannot be correctly determined. The bias is more subtle in READ, though interpretation of the results can still be misleading in specific contexts. We expect the bias may affect analyses we have not yet tested. Our observations support previously reported concerns for the integration of different data types in paleogenomics. We also caution that technological solutions to generate 1240k data necessitate a thorough validation process before their adoption in the paleogenomic community.

genomics↗

bioRxiv2019

Motif V acts as a Regulator of Energy Transduction Between the Flavivirus NS3 ATPase and RNA Binding Cleft

The unwinding of double-stranded RNA intermediates is a critical component for the replication of flavivirus RNA genomes. This function is achieved by the C-terminal helicase domain of nonstructural protein 3 (NS3). As a member of the superfamily 2 (SF2) helicases, NS3 is known to require the binding and hydrolysis of ATP/NTP to translocate along and unwind double-stranded nucleic acids. However, the mechanism of energy transduction between the ATP and RNA binding pockets is not well understood. Previous molecular dynamics simulations published by our group have identified Motif V as a potential "communication hub" for this energy transduction pathway. In order to investigate the role of Motif V in this process, a study combining molecular dynamics, biochemistry and virology has been employed. Mutations of Motif V were tested in both replicon and recombinant protein systems to investigate viral genome replication, RNA binding affinity, ATP hydrolysis activity and helicase unwinding activity. Using these analyses, we found that T407A and S411A in Motif V demonstrated increased turnover rates, suggesting that the mutations causes the helicase to unwind dsRNA more quickly than WT. Additionally, simulations of each mutant were used to probe structural changes within NS3 caused by each mutation. These simulations indicate that Motif V controls communication between the ATP binding pocket and the helical gate. These data help define the linkage between ATP hydrolysis and helicase activity within NS3 and provide insight into the biophysical mechanisms for ATPase driven NS3 helicase function.

biochemistry↗