Biology subjects

Edgell, D. R.

Publications and source records attributed to Edgell, D. R..

12 recordsLinked to original sources

bioRxiv2026

An agentic AI environment to support biomedical research in collaborative academic environments

Agentic artificial intelligence (AAI) is increasingly used by biomedical scientists, where it has substantially lowered the difficulty of integrating computational, statistical and data-science approaches into day-to-day research activities, assisting with project design, analysis and manuscript preparation. Significant barriers remain, however, which are unlikely to be removed solely by releasing more capable AI models. Meaningful use still demands a technical fluency that many biomedical researchers lack: a PI and their lab members must learn how to use the AAI system, establish standard operating procedures (SOPs) for managing, sharing and curating data, and enforce rules that address data privacy and security. Existing commercial AAI systems, which were designed primarily for software engineering purposes, need to be significantly re-purposed for biomedical-related data science. We present Murmurent, shared software that sits beneath the agentic AI and provides the skills, procedures and protections to address the concerns above, removing the need for a lab to develop them independently. This includes (1) infrastructure to support projects and so-called choreographies} involving multiple group members; (2) a set of specialized agents each dedicated to typical biomedical data science tasks including software and statistical development, data visualization, literature search, equity, diversity, inclusion, and decolonization (EDID) review, and others; (3) a tiered memory which can retain important research decisions, intermediate, derived outputs and sensitive data, and which can exploit this information to automatically build better contexts in AAI sessions; (4) traceability records which are used by the AAI session to better plan and execute data analyses and software builds by, for example, helping to avoid repeating decisions that lead to dead-ends; (5) enforcement of SOPs for data maintenance and data governance across all lab members; and (6) multi-user capacity to allow groups to interact and collaborate. We use the system to identify putative inhibitors of Peptidyl-prolyl cis-trans Isomerase NIMA-interacting 1 (Pin1), a protein with a shallow catalytic site making it difficult to target. We describe the construction of several approaches to identify Pin1 inhibitors and the results they yield. Murmurent is open source.

bioinformatics↗

bioRxiv2026

The activity, divergence, and evolutionary degradation of modern-day homing endonucleases and their reconstructed ancestors

Homing endonucleases (HEs) are selfish genetic elements that drive the mobilization of their own coding sequences, often in concert with surrounding introns. Homing endonuclease genes (HEGs) usually display life cycles in which they accumulate inactivating mutations after invading a host genomic target site, leading to eventual removal from the genome. We identified several hundred novel HEGs and determined the distribution of their proteins behaviors and activities. Approximately 10% are expressed as properly folded functional proteins that cleave predictable DNA target sites. Another [~]20% display significant expression but little to no cleavage activity; the remainder display severely reduced expression. Despite the presence of debilitating mutations throughout most HEGs, ancestral reconstructions yielded endonucleases with improved expression and stability. One such reconstruction, at a hypothetical node preceding highly diverged HEs that cleave unique target sites, binds (but does not cleave) their individual targets. It instead cleaves a DNA sequence that represents a hybrid of those modern-day DNA targets, while displaying a specificity profile that resembled those of previously characterized HEs. Its DNA-bound crystal structure adds detail to our understanding of how homing endonuclease DNA contacting surfaces and residues shift and rearrange during evolution, ultimately leading to their action at new target sites.

biochemistry↗

bioRxiv2025

A buffer-tuning strategy to profile domain-specific activity of chimeric I-TevI/CRISPR gene editors in vitro

Protein-DNA interactions can be manipulated in vitro by changing buffer conditions. Here, we develop a methodology to map the cleavage preferences of chimeric gene editors that are fusions of the I-TevI nuclease domain to CRIPSR nucleases by manipulating in vitro salt concentrations. We found that DNA cleavage by the I-TevI (Tev) nuclease domain at CNNNG sites was de-coupled from the gRNA-targeted site in low salt buffers. For TevCas12a, this non-targeted cleavage activity was enriched at Tev CNNNG cleavage motifs optimally positioned within a 30-bp window upstream of a Cas12a TTTV PAM site. Non-targeted cleavage did not require Cas12a nuclease activity or specific Cas12a gRNA targeting. Similar non-targeted products were observed in low salt buffer conditions for TevSaCas9, Tev-meganuclease and Tev-zinc finger editors. Cas12a and SaCas9 activity at gRNA-directed sites and sites with multiple mismatches were also sensitive to buffer salt concentration. Oxford Nanopore sequencing revealed a remarkably similar Tev CNNNG cleavage preference at different salt concentrations and in different fusion contexts, emphasizing the robustness and specificity of Tev activity. More generally, our work highlights the sensitivity of gene editors to in vitro reaction conditions and how these conditions can be leveraged to functionally dissect the activity of individual domains of chimeric gene editors.

biochemistry↗

bioRxiv2025

Better data for better predictions: data curation improves deep learning for sgRNA/Cas9 prediction

The Cas9 enzyme along with a single guide RNA molecule is a modular tool for genetic engineering and has shown effectiveness as a species-specific anti-microbial. The ability to accurately predict on-target cleavage is critical as activity varies by target. Using the sgRNA nucleotide sequence and an activity score, predictive models have been developed with the best performance resulting from deep learning architectures. Prior work has emphasized robust and novel architectures to improve predictive performance. Here, we explore the impact of a data-centric approach through optimization of the input target site adjacent nucleotide sequence length and the use of data filtering for read counts in the control conditions to improve input data utility. Using the existing crisprHAL architecture, we develop crisprHAL Tev, a best-in-class bacterial SpCas9 prediction model with performance that generalizes between related species and across data types. During this process, we also rebuild two prior E. coli Cas9 datasets, demonstrating the importance of data quality, and resulting in the production of an improved bacterial eSpCas9 prediction model. The crisprHAL models are available through GitHub (https://github.com/tbrowne/crisprHAL).

bioinformatics↗

bioRxiv2025

Ku suppresses RNA-mediated innate immune responses in human cells to accommodate primate-specific Alu expansion.

Ku70 and Ku80 form Ku, a ring-shaped protein that initiates the non-homologous end-joining (NHEJ) DNA repair pathway.1 Specifically, Ku binds to double-stranded DNA (dsDNA) ends and recruits other NHEJ factors (e.g., DNA-PKcs and LIG4). While Ku binds to double-stranded RNA (dsRNA)2 and traps mutated-DNA-PKcs on ribosomal RNA in vivo,3,4 the physiological significance of Ku-dsRNA interactions in otherwise wild-type cells remains elusive. Intriguingly, while dispensable for murine development,5,6 Ku is essential in human cells.7 Despite similar genome sizes, human cells express [~]100-fold more Ku than mouse cells, implying functions beyond NHEJ, possibly through a dose-sensitive interaction with dsRNA, which is [~]100 times weaker than with dsDNA.2,8 While investigating the essentiality of Ku in human cells, we found that depletion of Ku - unlike LIG4 - induces profound interferon (IFN) and NF-kB responses reliant on the dsRNA-sensor MDA5/RIG-I and adaptor MAVS. Prolonged Ku-degradation also activates other dsRNA-sensors, e.g. PKR that suppresses protein translation, and OAS/RNaseL that cleaves rRNAs and eventually induces growth arrest and cell death. MAVS, RIG-I, or MDA5 knockouts suppressed IFN signaling and, together with PKR knockouts, partially rescued Ku-depleted human cells. Ku-irCLIP analyses revealed that Ku binds to diverse dsRNA, predominantly stem-loops in primate-specific Alu elements9 at anti-sense orientation in introns and 3-UTRs. Ku expression rose sharply in higher primates tightly correlating with Alu-expansion (r = 0.94/0.95). Together, our study identified a vital role of Ku in accommodating Alu-expansion in primates by mitigating a dsRNA-induced innate immune response, explaining the rise of Ku levels and its essentiality in human cells.

genetics↗

bioRxiv2023

De novo synthesis of a conjugative system from human gut metagenomic data for targeted delivery of Cas9 antimicrobials

Metagenomic sequence represents an untapped source of genetic novelty, particularly for conjugative systems that could be used for plasmid-based delivery of Cas9-derived antimicrobial agents. However, unlocking the functional potential of conjugative systems purely from metagenomic sequence requires the identification of suitable candidate systems as starting scaffolds for de novo DNA synthesis. Here, we developed a bioinformatics approach that searches through the metagenomic trash bin for conjugative systems present on contigs that are typically excluded from common metagenomic analysis pipelines. Using a human metagenomic gut dataset representing 2805 taxonomically distinct units, we identified 1598 contigs containing conjugative systems with a differential distribution in human cohorts. We synthesized de novo an entire Citrobacter spp. conjugative system of 54 kb and containing at least 47 genes, pCitro, and found that pCitro conjugates from Escherichia coli to Citrobacter rodentium with a 30-fold higher frequency than to E. coli, and is compatible with Citrobacter resident plasmids. Mutations in the traV and traY conjugation components of pCitro inhibited conjugation. We showed that pCitro can be re-purposed as an antimicrobial delivery agent by programming it with the TevCas9 nuclease and Citrobacter -specific sgRNAs to kill C. rodentium. Our study reveals a trove of uncharacterized conjugative systems in metagenomic data and describes an experimental framework to animate these large genetic systems as novel target-adapted delivery vectors for Cas9-based editing of bacterial genomes.

synthetic biology↗

bioRxiv2023

A generalizable Cas9/sgRNA prediction model using machine transfer learning with small high-quality datasets

The CRISPR/Cas9 nuclease from Streptococcus pyogenes (SpCas9) can be used with single guide RNAs (sgRNAs) as a sequence-specific antimicrobial agent and as a genome-engineering tool. However, current bacterial sgRNA activity models poorly predict SpCas9/sgRNA activity and are not generalizable, possibly because the underlying datasets used to train the models do not accurately measure SpCas9/sgRNA cleavage activity and cannot distinguish cleavage activity from toxicity. We solved this problem by using a two-plasmid positive selection system to generate high-quality biologically-relevant data that more accurately reports on SpCas9/sgRNA cleavage activity and that separates activity from toxicity. We developed a new machine transfer learning architecture (crisprHAL) that can be trained on existing datasets and that shows marked improvements in sgRNA activity prediction accuracy when transfer learning is used with small amounts of high-quality data. The crisprHAL model recapitulates known SpCas9/sgRNA-target DNA interactions and provides a pathway to a generalizable sgRNA bacterial activity prediction tool.

bioinformatics↗

bioRxiv2022

Noncannonical functions of Ku may underlie essentiality in human cells

The Ku70/80 heterodimer is a key player in non-homologous end-joining DNA repair but has also been involved in other cellular functions like telomere regulation and maintenance, in which Kus role is not fully characterized. It was previously reported that knockout of Ku80 in a human cell line results in lethality, but the underlying cause of Ku essentiality in human cells has yet to be fully explored. Here, we established conditional Ku70 knockout cells to study the essentiality of Ku70 function. Endogenous Ku70 knockout was achieved using CRISPR/Cas9 editing in cells where Ku70 expression was maintained through integration of an HA-tagged Ku70 cDNA under the control of a doxycycline-inducible promoter. Ku70 conditional knockout cell lines were identified via western blotting, and edits were validated by Sanger sequencing. We visually observed cell death in Ku70 knockout cells 8-10 days post Ku70-HA depletion, and loss of viability following Ku depletion was quantified using crystal violet assays. Interestingly, assessment of telomere length in Ku70 knockout cells using telomere restriction fragment analyses did not reveal any changes in average telomere length following Ku70-HA depletion. Immunofluorescence analysis used to assess {gamma}H2AX foci accumulation as a measure of double-stranded DNA breaks following Ku70-HA depletion allowed us to conclude that increased DNA damage is not the driving cause of loss of cell viability. Finally, quantitative proteome analysis of Ku70 knockout cells following Ku70-HA depletion identified a number of pathways and proteins that are significantly dysregulated following the loss of Ku70, including processes which Ku function has been previously associated with such as cell cycle/mitosis, RNA related processes, and translation/ribosome biogenesis. Overall, this conditional Ku70 knockout system reveals that loss of Ku affects multiple cellular processes and pathways and suggests that Ku plays critical roles in other cellular processes beyond DNA repair and telomere maintenance to maintain cell viability. Author SummaryThe Ku70/80 heterodimer is a key player in non-homologous end-joining DNA repair, where it acts as a scaffold for other repair factors needed to process double-stranded DNA breaks. Ku has also been involved in other cellular functions like telomere regulation and maintenance, in which Kus role is not fully characterized. Previous data suggest that while loss of Ku70/80 can be tolerated in other species, Ku is essential to humans. We have established a conditional Ku70 knockout in HEK293 cells to evaluate the basis of Ku essentiality in human cells. While we observed loss of cell viability upon Ku depletion, we did not observe significant changes in telomere length nor did we record lethal levels of DNA damage upon loss of Ku, suggesting that the reasons for the loss of viability is not linked to the functions of Ku in DNA repair or at telomeres. Analysis of global proteome changes following Ku70 depletion revealed dysregulations of several cellular pathways including cell cycle/mitosis, RNA related processes, and translation/ribosome biogenesis. Our study reveals that loss of Ku affects multiple cellular processes and pathways and suggests that Ku plays critical roles in cellular processes beyond DNA repair and telomere maintenance to maintain cell viability.

molecular biology↗

bioRxiv2021

Conjugation-based genome engineering in Deinococcus radiodurans

D. radiodurans has become an attractive microbial platform for the study of extremophile biology and industrial bioproduction. To improve the genomic manipulation and tractability of this species, the development of tools for whole genome engineering and design is necessary. Here, we report the development of a simple and robust conjugation-based transformation system from E. coli to D. radiodurans allowing for the introduction of stable, replicating plasmids expressing antibiotic resistance markers. Using this method with nonreplicating plasmids, we developed a protocol for creating sequential gene deletions in D. radiodurans by targeting re-striction-modification system genes. Importantly, we demonstrated a conjugation-based method for cloning the large (178 kb), high G+C content MP1 megaplasmid from D. radiodurans in E. coli. The conjugation-based tools described here will facilitate the development of D. radiodurans strains with synthetic genomes for biological studies and industrial applications. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=103 SRC="FIGDIR/small/464295v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@128437borg.highwire.dtl.DTLVardef@6669ddorg.highwire.dtl.DTLVardef@1b041eaorg.highwire.dtl.DTLVardef@b77f07_HPS_FORMAT_FIGEXP M_FIG C_FIG

synthetic biology↗

bioRxiv2021

Telomere-to-telomere genome assembly of Phaeodactylum tricornutum

Phaeodactylum tricornutum is a marine diatom with a growing genetic toolbox available and is being used in many synthetic biology applications. While most of the genome has been assembled, the currently available genome assembly is not a completed telomere-to-telomere assembly. Here, we used Oxford Nanopore long reads to build a telomere-to-telomere genome for Phaeodactylum tricornutum. We developed a graph-based approach to extract all unique telomeres, and used this information to manually correct assembly errors. In total, we found 25 nuclear chromosomes that comprise all previously assembled fragments, in addition to the chloroplast and mitochondrial genomes. We found that chromosome 19 has filtered long-read coverage and a quality estimate that suggests significantly less haplotype sequence variation than the other chromosomes. This work improves upon the previous genome assembly and provides new opportunities for genetic engineering of this species, including creating designer synthetic chromosomes.

genomics↗

bioRxiv2021

Separation of cohorts on the basis of bacterial type IV conjugation systems identified from metagenomic assemblies

Conjugation enables the exchange of genetic elements throughout environments, including the human gut microbiome. Conjugative elements can carry and transfer clinically relevant metabolic pathways which makes precise identification of these systems in metagenomic samples clinically important. Here, we outline two distinct methods to identify conjugative systems in the human gut microbiome. We first show that conjugative systems exhibit strong population and age-level stratification. Additionally, we find that the total relative abundance of all conjugative systems present in a sample is not an informative metric to use, regardless of the method of identifying the systems. Finally, we demonstrate that the majority of assembled conjugative systems are not included within metagenomic bins, and that only a small proportion of the binned conjugative systems are included in "high-quality" metagenomic bins. Our findings highlight that conjugative systems differ between general North Americans and a cohort of North American pre-term infants, revealing a potential use as an age-related biomarker. Furthermore, conjugative systems can distinguish between other geographical-based cohorts. Our findings emphasize the need to identify and analyze conjugative systems outside of standard metagenomic binning pipelines. ImportanceThe human gut microbiome is increasingly being associated with human health outcomes through shotgun metagenomic sequencing. The usual approach of metagenomic-level analyses is to bin assembled sequences into approximations of bacterial genomes and perform further investigations on the resultant bins. Here, we show that type IV conjugative systems differ between age and geographically-based cohorts and that these systems are systematically excluded by binning algorithms. We suggest that analysis of type IV conjugative systems should be added to the current metagenomic analysis approaches as they contain much information that could explain differences between cohorts beyond those we investigated.

bioinformatics↗

bioRxiv2019

Rapid method for generating designer algal mitochondrial genomes

With synthetic biology, we can turn algae into bio-factories that produce high-value molecules (e.g. medicines or biofuels) or tackle global challenges (e.g. malnutrition and climate change). This realization has provoked rapid progress towards the creation of genetic tools for multiple algal species, notably Phaeodactylum tricornutum. The power of synthetic biology to generate more useful or productive organisms is contingent on the ability to produce diverse DNA molecules and rapidly screen them for beneficial variants. However, it is still relatively expensive to synthesize DNA, and delivering large DNA (>50 kbp) to eukaryotic cellular compartments remains challenging. In this study, we establish a robust system for building algal mitochondrial genomes as a practical alternative to DNA synthesis. Our approach permits an inexpensive and rapid generation of mitochondrial derivatives designed for testing targeted DNA delivery. First, we cloned the mitochondrial genome of P. tricornutum into the eukaryotic host organism S. cerevisiae using two different techniques: transformation-associated recombination; and PCR-based cloning. Next, we analyzed the cloned genomes by multiplex PCR, and correct genomes were transferred to prokaryotic host E. coli. Then these genomes were again analyzed by multiplex PCR, followed by diagnostic digest and complete-plasmid sequencing to evaluate the fidelity of each cloning method. Finally, we assessed the burden on eukaryotic and prokaryotic hosts to propagate the cloned genomes. We conclude that our system can reliably generate variants for genome-level engineering of algal mitochondria. HIGHLIGHTSO_LITAR-cloned mitochondrial genome of P. tricornutum in yeast C_LIO_LIDeveloped PCR-based cloning method to create designer algal mitochondrial genomes C_LIO_LIStably propagated algal mitochondrial genomes in S. cerevisiae and E. coli hosts C_LI

synthetic biology↗