Biology subjects

Esvelt, K. M.

Publications and source records attributed to Esvelt, K. M..

14 recordsLinked to original sources

bioRxiv2026

Complementing Biosafety Levels With Societal Safety Levels

Biosafety level (BSL) classifications of biological agents have succeeded at minimizing occupational risk inside laboratories, but largely neglect the potential for onward transmission. As a result, many non-transmissible pathogens that could kill at most one individual per person exposed require greater containment than 1918 influenza, a virus that killed 50-100 million and might cause a new pandemic today. Laboratory workers are consenting professionals; the public is not. We recommend complementing BSLs with explicit thresholds for expected societal harm. Here we formalize Societal Safety Levels (SSLs) based on expected public fatalities per year, which we quantify from (i) estimated probability of laboratory release, (ii) likelihood of societal transmission, and (iii) consequence. SSLs would apply specifically to laboratory research with replication-competent potential pandemic pathogens, and would not restrict field surveillance, sequencing, or countermeasure development using non-replicating systems or pandemic-incapable agents. We find that applying the 0.1 expected deaths per facility-year standard common across multiple major-hazard industries to potential pandemic pathogen research would require marked safety improvements. Complementing BSLs with SSLs would establish enforceable accident-safety thresholds for pandemic-capable pathogens, bringing high-risk biological research into alignment with the quantitative safety standards that help other hazardous industries operate with public acceptance.

microbiology↗

bioRxiv2025

Increasing the effective gene drive homing rate by targeting the haploinsufficient spermatogenesis gene KLHL10

CRISPR-based gene drives represent a powerful new technology for limiting disease transmission and controlling invasive populations. These systems rely on homology-directed repair (HDR) to drive a genetic element through a population. However, mammals tend to favor non-homologous end joining (NHEJ), which generates mutations that halt further drive propagation. Here, we describe the experimental characterization of a gene drive system targeting the haploinsufficient spermatogenesis gene KLHL10 in the laboratory mouse. Using a newly designed coding sequence cassette we introduce downstream guide RNAs within the gene, ensuring that sperm undergoing NHEJ are selectively removed from the population. As a proof of principle, we demonstrate that targeting KLHL10 with constitutively expressed LbCas12a results in strong selection against frameshift-containing sperm, validating the core purification mechanism required for this drive strategy. Unexpectedly, we also observed that female offspring lacked most frameshift mutations, suggesting a previously unrecognized role for KLHL10 in oogenesis or early embryonic development.

synthetic biology↗

bioRxiv2025

Engineering gene drive docking sites in a haplolethal locus in Anopheles gambiae

Gene drives are selfish genetic elements which promise to be powerful tools in the fight against vector-borne diseases such as malaria. We previously proposed population replacement gene drives designed to better withstand the evolution of resistance by homing through haplolethal loci. Because most mutations in the wild-type allele that would otherwise confer resistance are lethal, only successful drive homing permits the cell to survive. Here we outline the development and characterization of two {Phi}C31-Recombination mediated cassette exchange (RMCE) gene drive docking lines with these features in Anopheles gambiae, a first step towards construction of robust gene drives in this important malaria vector. We outline adaption of the technique HACK (Homology Assisted CRISPR knockin) to knock-in two docking site sequences into a paired haplolethal-haplosufficient (Ribosome-Proteasome) locus, and confirm that these docking lines permit insertion of drive-relevant transgenes. We report the first anopheline proteasome knockouts, and identify ribosome mutants that reveal a major hurdle that such designs must overcome to develop robust drives in the future. Although we do not achieve drive, this work provides a new tool for constructing future evolution-robust drive systems and reveals critical challenges that must be overcome for future development of gene drives designed to target haplolethal loci in anophelines and, potentially, other metazoans.

synthetic biology↗

bioRxiv2024

Heritable Immunization Establishes a New Model for Pathogen Control

Heritable immunization represents a promising approach for controlling infectious diseases by embedding immunity directly into the genomes of wild species that spread human pathogens. Here, we report the genetic engineering of Mus musculus to produce a neutralizing, protective single-chain antibody against Borrelia burgdorferi, the causative agent of Lyme disease. Engineered mice stably produced a LA-2 scFv-albumin fusion protein across multiple generations, demonstrating robust heritability and stability of gene expression. Following sequential challenges with infected and uninfected ticks, heterozygous mice exhibited strong resistance to infection, effectively interrupting the Borrelia burgdorferi disease transmission cycle. Having recently established novel protocols to genetically engineer the white-footed mouse, Peromyscus leucopus, a key reservoir of Lyme disease, these findings demonstrate the feasibility of heritable immunization as a potential strategy for mitigating Lyme disease transmission in the environment. More broadly, engineered reservoir immunity may offer a generalizable approach to controlling vector-borne and zoonotic disease with profound potential to improve human health.

bioengineering↗

bioRxiv2024

Modeling the benefits of virus discovery and pandemic virus identification

Preventing and mitigating future zoonotic pandemics are global health priorities, but there are few quantitative estimates of how best to target interventions. Here we construct a mathematical model to evaluate the benefits of 1) virus discovery and sequencing (VDS) in animals and 2) pandemic virus identification (PVI) via laboratory characterization of pandemic potential. Drawing on historical data and expert surveys of One Health and vaccine researchers, we estimate that intensifying virus discovery efforts by three-fold could prevent between 0 and 1.46 million expected deaths per decade by improving non-pharmaceutical interventions and broad-spectrum vaccines. In contrast, because researchers estimate that there are well over a hundred pandemic-capable viruses in nature, identification through laboratory characterization would prevent 48,000 deaths per decade [10,500; 93,600], or just [~]0.62% of expected pandemic deaths. Further identifications would offer diminishing returns. Given wide-ranging survey responses and limited cost-effectiveness compared to proven global health interventions such as insecticide-treated bed nets, our model suggests that health establishments aiming to mitigate future pandemics should focus on monitoring spillover hotspots and empowering local communities to detect, sequence, and suppress nascent epidemics rather than characterizing pandemic potential in laboratories.

ecology↗

bioRxiv2024

Random adversarial threshold search enables automated DNA screening

Custom DNA synthesis underpins modern biology, but controlled genes in the wrong hands could threaten many lives and public trust in science. In .1992, a virology-trained mass murderer tried and failed to obtain physical samples of Ebola; today, viruses can be assembled from synthetic DNA fragments. Screening orders for controlled sequences is unreliable and expensive because current similarity search algorithms yield false alarms requiring expert human review. Exact-match search can achieve perfect specificity among short known sequences by detecting subsequences unique to controlled genes, but can be trivially evaded by incorporating mutations. Here we rescue exact-match search by additionally screening for predicted functional variants of pseudo-randomly chosen subsequences that arent found in known unregulated genes. To experimentally assess robustness, we protected nine windows from the M13 bacteriophage virus, then invited a "red team" to launch up to 21,000 attacks at each window and measure the fitness of their designed mutants. We identified defensible windows from regulated pathogens, built a test database that our experiments indicate will block 99.999% of functional attacks, and verified its sensitivity against redesigned enzymes. Exact-match search with functional variant prediction offers a promising way to safeguard biotechnology by automating DNA synthesis screening. SummarySearching for exact matches to pre-computed functional variants unique to controlled genes enables sensitive, secure, and automated DNA synthesis screening.

synthetic biology↗

bioRxiv2023

Virus-like DNA tracers for characterizing wastewater-based pathogen monitoring systems

Wastewater-based pathogen monitoring has recently become a ubiquitous method for tracking the abundance and evolution of pathogens in a community or port of entry. But accurate inference of disease incidence from wastewater remains challenging, in large part due to noise and bias arising from wastewater transport and measurement. We developed a new system of tracer particles designed to enhance wastewater monitoring of viral pathogens. These tracers, which consist of synthetic DNA barcodes packaged into non-infectious viral capsids, can be deposited at known amounts and times into the sewer system and measured in wastewater samples to assess features such as assay sensitivity, and the decay and delay in viral signal arising from a shedding event. Here we describe the design, construction, and initial characterization of a 25-plex tracer library. Our tracer library supports simultaneous measurement of up to 5 distinct tracers by qPCR and up to 25 distinct tracers by amplicon or metagenomic sequencing. We demonstrate experimentally that the tracers are biologically inert and exhibit good stability and qPCR-assay performance in wastewater. These features collectively suggest that barcoded, virus-like tracers have the required properties for high-accuracy, high-resolution characterization of wastewater monitoring systems.

synthetic biology↗

bioRxiv2023

Low-cost camera-based estrous tracking enables transgenesis in Peromyscus leucopus, the primary reservoir for Lyme disease

CRISPR/Cas9 technology has revolutionized the production of animal models by reducing experimental timelines, slashing costs and streamlining gene editing, leading to a rapid expansion in the number of unique models for the study of human disease and gene function. However, most non-model animals, many of which are important in cancer and aging research, remain recalcitrant to genome engineering due to our limited understanding of their reproductive biology. Many wild rodents that transmit human diseases remain particularly challenging to engineer due to low pregnancy rates, the lack of external copulatory plugs, and susceptibility to premature termination of pregnancy. Here, we present low-cost activity-based estrous tracking for the efficient generation of timed pregnant and pseudopregnant white-footed mice and extend this tracking method to both lab mice and hamsters. Leveraging this technology, we demonstrate the generation of engineered Peromyscus leucopus, the primary reservoir for Lyme disease-causing bacteria and a putative model organism for studies of aging. These tools have broad implications for biomedical research and ecological engineering. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=107 SRC="FIGDIR/small/563285v1_ufig1.gif" ALT="Figure 1"> View larger version (45K): org.highwire.dtl.DTLVardef@19a3fb2org.highwire.dtl.DTLVardef@1cbce4corg.highwire.dtl.DTLVardef@1551e0corg.highwire.dtl.DTLVardef@127c028_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2021

Measuring the tolerance of the genetic code to altered codon size

Protein translation using four-base codons occurs in both natural and synthetic systems. What constraints contributed to the universal adoption of a triplet-codon, rather than quadruplet-codon, genetic code? Here, we investigate the tolerance of the E. coli genetic code to tRNA mutations that increase codon size. We found that tRNAs from all twenty canonical isoacceptor classes can be converted to functional quadruplet tRNAs (qtRNAs), many of which selectively incorporate a single amino acid in response to a specified four-base codon. However, efficient quadruplet codon translation often requires multiple tRNA mutations, potentially constraining evolution. Moreover, while tRNAs were largely amenable to quadruplet conversion, only nine of the twenty aminoacyl tRNA synthetases tolerate quadruplet anticodons. These constitute a functional and mutually orthogonal set, but one that sharply limits the chemical alphabet available to a nascent all-quadruplet code. Our results illuminate factors that led to selection and maintenance of triplet codons in primordial Earth and provide a blueprint for synthetic biologists to deliberately engineer an all-quadruplet expanded genetic code.

synthetic biology↗

bioRxiv2020

Attribution of genetic engineering: a practical and accurate machine learning toolkit for biosecurity

The promise of biotechnology is tempered by its potential for accidental or deliberate misuse. Reliably identifying telltale signatures characteristic to different genetic designers, termed genetic engineering attribution, would deter misuse, yet is still considered unsolved. Here, we show that recurrent neural networks trained on DNA motifs and basic phenotype can reach 70% attribution accuracy distinguishing between over 1,300 labs. To make these models usable in practice, we introduce a framework for weighing predictions against other investigative evidence using calibration, and bring our model to within 1.6% of perfect calibration. Additionally, we demonstrate that simple models can accurately predict both the nation-state-of-origin and ancestor labs, forming the foundation of an integrated attribution toolkit which should promote responsible innovation and international security alike.

synthetic biology↗

bioRxiv2020

Flexible open-source automation for robotic bioengineering

INTRODUCTIONLiquid handling robots have become a biotechnology staple1,2, allowing laborious or repetitive protocols to be executed in high-throughput. However, software narrowly designed to automate traditional hand-pipetting protocols often struggles to harness the full capabilities of robotic manipulation. Here we present Pyhamilton, an open-source Python package that eliminates these constraints, enabling experiments that could never be done by hand. We used Pyhamilton to double the speed of automated bacterial assays over current software and execute complex pipetting patterns to simulate population dynamics. Next, we incorporated feedback-control to maintain hundreds of remotely monitored bacterial cultures in log-phase growth without user intervention. Finally, we applied these capabilities to comprehensively optimize bioreactor protein production by maintaining and monitoring fluorescent protein expression of nearly 500 different continuous cultures to explore the carbon, nitrogen, and phosphorus fitness landscape. Our results demonstrate Pyhamiltons empowerment of existing hardware to new applications ranging from biomanufacturing to fundamental biology.

bioengineering↗

bioRxiv2020

Low-N protein engineering with data-efficient deep learning

Protein engineering has enormous academic and industrial potential. However, it is limited by the lack of experimental assays that are consistent with the design goal and sufficiently high-throughput to find rare, enhanced variants. Here we introduce a machine learning-guided paradigm that can use as few as 24 functionally assayed mutant sequences to build an accurate virtual fitness landscape and screen ten million sequences via in silico directed evolution. As demonstrated in two highly dissimilar proteins, avGFP and TEM-1 {beta}-lactamase, top candidates from a single round are diverse and as active as engineered mutants obtained from previous multi-year, high-throughput efforts. Because it distills information from both global and local sequence landscapes, our model approximates protein function even before receiving experimental data, and generalizes from only single mutations to propose high-functioning epistatically non-trivial designs. With reproducible >500% improvements in activity from a single assay in a 96-well plate, we demonstrate the strongest generalization observed in machine-learning guided protein function optimization to date. Taken together, our approach enables efficient use of resource intensive high-fidelity assays without sacrificing throughput, and helps to accelerate engineered proteins into the fermenter, field, and clinic.

synthetic biology↗

bioRxiv2017

Current CRISPR gene drive systems are likely to be highly invasive in wild populations

Recent reports have suggested that CRISPR-based gene drives are unlikely to invade wild populations due to drive-resistant alleles that prevent cutting. Here we develop mathematical models based on existing empirical data to explicitly test this assumption. We show that although resistance prevents drive systems from spreading to fixation in large populations, even the least effective systems reported to date are highly invasive. Releasing a small number of organisms often causes invasion of the local population, followed by invasion of additional populations connected by very low gene flow rates. Examining the effects of mitigating factors including standing variation, inbreeding, and family size revealed that none of these prevent invasion in realistic scenarios. Highly effective drive systems are predicted to be even more invasive. Contrary to the National Academies report on gene drive, our results suggest that standard drive systems should not be developed nor field-tested in regions harboring the host organism.

synthetic biology↗

bioRxiv2017

Daisyfield gene drive systems harness repeated genomic elements as a generational clock to limit spread

Methods of altering wild populations are most useful when inherently limited to local geographic areas. Here we describe a novel form of gene drive based on the introduction of multiple copies of an engineered daisy sequence into repeated elements of the genome. Each introduced copy encodes guide RNAs that target one or more engineered loci carrying the CRISPR nuclease gene and the desired traits. When organisms encoding a drive system are released into the environment, each generation of mating with wild-type organisms will reduce the average number of the guide RNA elements per daisyfield organism by half, serving as a generational clock. The loci encoding the nuclease and payload will exhibit drive only as long as a single copy remains, placing an inherent limit on the extent of spread.

synthetic biology↗