Genome-wide associations, polygenic risk, and Mendelian randomization reveal limited interactions between John Henryism and cynicism

BACKGROUND

John Henryism (JH) is a strategy for dealing with chronic psychological stress characterized by high levels of physical effort and work. Cynicism is a belief that people are motivated primarily by self-interest. High scores on the JH scale and cynicism measures correlate with an increased risk of cardiovascular disease. High cynicism is also a hallmark of burnout syndrome, another known risk factor for heart disease.

AIM

To evaluate possible interactions between JH and cynicism hoping to clarify risk factors of burnout.

METHODS

We analyzed genetic and psychological data available from the Database of Genotypes and Phenotypes for genome-wide associations with these traits. We split the total available samples and used plink to perform the association studies on the discovery set (n = 1852, 80%) and tested for replication using the validation set (n = 465). We used scikit-learn to perform supervised machine learning for developing genetic risk algorithms.

RESULTS

We identified 2, 727, and 204 genetic associations for scores on the JH, cynicism and cynical distrust (CD) scales, respectively. We also found 173 associations with high cynicism, 109 with high CD, but no associations with high JH. We also produced polygenic classifiers for high cynicism using machine learning with areas under the receiver operator characteristics curve greater than 0.7.

CONCLUSION

We found significant genetic components to these traits but no evidence of an interaction. Therefore, while there may be a genetic risk, JH is not likely a burnout risk factor.

Genetic Markers of Atopic Dermatitis Risk for Screening Aviation Applicants

INTRODUCTION: Atopic dermatitis (AD) is a skin condition with many genetic risk factors. In this review, we summarize the different genetic variants for AD from the perspective of screening purposes within the U.S. Air Force aviation community. Using a PRISMA-informed systematic review approach, we found 13 papers reporting genetic associations with AD. We report 98 genetic associations with AD, of which 4 had a greater than twofold increased odds of developing the condition when present. These 98 variants were found in 45 associated genes, including LRRC32, OVOL1, and IL13, which were each replicated in 3 studies; as well as RTEL1 and ZNF365, which were each replicated in 2 studies. A polygenic risk model created based upon these variants or genes could contribute to a risk screening protocol for military aviation candidates, potentially helping minimize risk for candidates at increased genetic risk for AD or other atopic diseases (e.g., asthma, allergic rhinitis).Gregory ID, Collie J, Chapleau RR. Genetic markers of atopic dermatitis risk for screening aviation applicants. Aerosp Med Hum Perform. 2022; 93(11):806–810.

Using a pilot-centric, qualitative drug risk assessment model to identify opportunities for implementing pharmacogenetics

Background

Risk assessment models are at the core of flight medicine, weighing both the impact of the flight environment on an aviator and the potential impact of medical events in aviators on flight operations. Pharmacogenetics is the application of a patient’s genetic information to reduce medication risk. Here, we use three medical conditions commonly encountered by the U.S. Air Force’s flight medicine community (asthma, diabetes, and hypertension) to demonstrate a framework for implementing occupationally relevant pharmacogenetics. We identified medications approved by the U.S. Food & Drug Administration for each condition, obtained adverse effects and frequencies, scored each adverse effect’s impact on work duties from 0 to 4 in increasing severity, and used control theory to stratify the medications by occupational risk. For those medications within 10% of the control limits, pharmacogenetic information was collected from PharmGKb.

Results

We observed a correlation of 0.557 between our risk scores and previous reports for 20 medications, demonstrating robustness of our scoring. Using average risks for those 20 medications, we set control theory acceptable and tolerable thresholds at 601,109.5 and 2,097,721, respectively. The majority of medications for the three conditions were below the thresholds (66 and 26, respectively). Three medications have pharmacogenetic guidance provided by regulatory bodies.

Conclusions

By focusing first on risk to performing occupational tasks and then on genetic implementation, our work presents a framework by which pharmacogenetics can be selectively applied by considering specific occupational and environmental risks, thereby saving costs and reducing possible psychological burdens on patients.

Surveying the Genomic Landscape Supporting the Development of Precision Military Aerospace Medicine

INTRODUCTION: Precision medicine is an approach to healthcare that is modifying clinical management by leveraging technological advances in genomics that assess a patient's genetic information to identify unique predispositions. While the civilian sector is integrating genomics widely to personalize diagnosis and treatment, the military medical environment has reacted more slowly. The operational requirements of military service encourage a tailored approach for focusing military precision medicine on occupation-specific conditions. Here, we present a survey of the genomic landscape related to military aerospace medicine.METHODS: We collated observations from genome-wide association studies (GWAS) relating genetic markers to conditions that may negatively influence flight operations and for which the U.S. Air Force School of Aerospace Medicine's Aeromedical Consult Service (ACS) provides aeromedical waiver guidance. Our sources for identifying relevant literature were the GWAS Catalog, the Atlas of GWAS Summary Statistics, and PubMed/Google Scholar searches.RESULTS: Using the ACS guidance as a starting point, we found 1572 papers describing 84 clinical conditions with genetic associations. The earliest aeromedical GWAS publication was in 2006, increasing to 225 publications in 2019. We identified 42,020 polymorphisms from more than 84 million participants across the studies.CONCLUSION: Our study revealed areas where deeper investigations into how genetic markers manifest in clinical diagnosis, prevention, or risk management could lead to increased medical readiness. Additionally, our results show those clinical areas for which guidance could include genetic risk considerations.Chapleau RR, Regn DD, de Castro MJ. Surveying the genomic landscape supporting the development of precision military aerospace medicine. Aerosp Med Hum Perform. 2022; 93(2):89-93.

Variants in SARS-CoV-2 associated with mild or severe outcome

Introduction

The coronavirus disease 2019 (COVID-19) pandemic is a global public health emergency causing a disparate burden of death and disability around the world. The viral genetic variants associated with outcome severity are still being discovered.

Methods

We downloaded 155 958 severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genomes from GISAID. Of these genomes, 3637 samples included useable metadata on patient outcomes. Using this subset, we evaluated whether SARS-CoV-2 viral genomic variants improved prediction of reported severity beyond age and region. First, we established whether including genomic variants as model features meaningfully increased the predictive power of our model. Next, we evaluated specific variants in order to determine the magnitude of association with severity and the frequency of these variants among SARS-CoV-2 genomes.

Results

Logistic regression models that included viral genomic variants outperformed other models (area under the curve = 0.91 as compared with 0.68 for age and gender alone; P < 0.001). We found 84 variants with odds ratios greater than 2 for outcome severity (17 and 67 for higher and lower severity, respectively). The median frequency of associated variants was 0.15% (interquartile range 0.09-0.45%). Altogether 85% of genomes had at least one variant associated with patient outcome.

Conclusion

Numerous SARS-CoV-2 variants have 2-fold or greater association with odds of mild or severe outcome and collectively, these variants are common. In addition to comprehensive mitigation efforts, public health measures should be prioritized to control the more severe manifestations of COVID-19 and the transmission chains linked to these severe cases.Lay summary: This study explores which, if any, SARS-CoV-2 viral genomic variants are associated with mild or severe COVID-19 patient outcomes. Our results suggest that there are common genomic variants in SARS-CoV-2 that are more often associated with negative patient outcomes, which may impact downstream public health measures.

Early Identification of SARS-CoV-2 Emergence in the Department of Defense via Retrospective Analysis of 2019-2020 Upper Respiratory Illness Samples

The first U.S. case of non-travel-related severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection was detected in late February 2020 in California, but the prevailing delay in diagnostic testing and initial stringent testing criteria made it difficult to identify those who could have acquired the virus through community spread. The emergence of the virus in the western Pacific region in late 2019 and the global distribution of Department of Defense (DoD) personnel present the risk that DoD members may have been exposed and contracted the virus earlier then U.S. detections. Here, a retrospective study from residual samples collected from a global DoD Respiratory Surveillance Program was conducted to establish a tentative timeline of when this virus began circulating in the DoD population. Quantitative real-time reverse-transcription polymerase chain reaction testing for SARS-CoV-2 was performed and the specimen collection dates of positive results were compared to the dates of the first infections previously identified in respective states and counties. Twenty-four positive samples were identified out of approximately 7,000 tested. Although this retrospective testing found early cases in 8 locations, there were no results indicative of circulation before late February.

Alternatives to Viral Transport Medium for use in SARS-CoV-2 Sample Preparation

Introduction: As the world struggles to manage and move forward from the clinical effects of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the ability to test for viral genomic RNA in patient samples is critical. Currently, the development and performance of SARS-CoV-2 clinical tests is impaired by a diminished supply chain of reagents needed for the tests, compelling labs to seek alternative, readily-available reagents as substitutes. Aim: To evaluate the suitability of Phosphate-Buffered Saline (PBS) and RNAlater™ as substitutes for sample transport media, to preserve the fidelity of viral RNA for use in a SARS-CoV-2 RT-PCR assay. Materials and Methods: This molecular study was conducted in Dayton, Ohio (USA) using synthetic materials and de-identified remnant patient specimens. Simulated standard clinical laboratory storage conditions were used, including prolonged storage up to 72 hours at 2-8°C and a freeze/thaw cycle. PCR amplification performance was measured for PBS and RNAlater™ against transport medium as a reference using purified viral RNA. Performance differences were determined using repeated-measures two-way ANOVA with a 5% false discovery rate. Results: Results indicate that both solutions were suitable for testing viral RNA in the short term, but the viral RNA stored in PBS began to degrade after just 24 hours at 2-8°C. In contrast, RNAlater™ preserved the viral RNA out to 72 hours when stored at 2-8°C, with no statistically significant decrease in the detection limits compared to freshly-prepared viral RNA dilutions. A single freeze/thaw cycle raised the lower limit of detection for RNAlater™-preserved viral RNA slightly. Conclusion: The current (as of April 2020) CDC sample guidelines permit the use of PBS, but have not published data to support this claim. These results offer an alternative to the transport options outlined in many Emergency Use Authorisations (EUA) currently authorised for use in diagnostic testing and may be used for possible long-term storage solutions for studies investigating SARS-CoV-2.

Apolipoprotein E promoter genotypes are not associated with white matter hyperintensity development in high-altitude careers

OBJECTIVE

This study sought to determine if there is an association between variants in the apolipoprotein E (ApoE) promoter regions and development of white matter hyperintensities (WMH) in military subjects who have been exposed to high altitude. In an earlier study, we found that ApoE status did not correlate with WMH development, and here we hypothesized that regulation of APOE protein expression may be protective.

RESULTS

Our cohort of 92 subjects encountered altitude exposures above 25,000 feet mean sea level through their occupations as pilots or altitude chamber technicians. Using Taqman-style polymerase chain reaction genotyping and t-tests and two-way analyses of variance we found no significant association between ApoE promoter genotypes and the presence, volume, or quantity of WMHs after high altitude exposure. Taken together, the observations that neither ApoE genotype status nor promoter status are associated with WMH properties, we believe that the mechanism of action for developing WMH does not derive from ApoE, nor would therapies for ApoE-mediated neurodegeneration likely benefit high altitude operators.

Comparing DNA quantity and quality using saliva collection following food and beverage consumption

Objective

With the democratization of genetic testing, researchers, clinicians, and educators must consider the varying degree of field conditions when collecting samples for genetic analyses. For genotyping or sequencing studies, study designers have multiple options from which to choose, including cheek swabs and saliva sampling. One significant benefit of saliva collection is that it can be done remotely, in the privacy of one’s home. This same benefit adds a risk of compliance. Therefore, our goal with this study was to see if the quality and quantity of the saliva collection by a saliva DNA collection kit would be affected by not following the manufacturer’s directions, i.e., drinking or eating right before collection.

Results

We asked five participants to collect saliva samples according to the manufacturer’s guidance and also after consuming five food items or beverages. We evaluated DNA quantity and quality post-purification using spectroscopy, electrophoresis, and polymerase chain reaction genotyping. Consistent with our hypothesis, we did not see a difference in quantity or quality of the isolated DNA. From our results, we conclude that the manufacturer’s instructions serve as an ideal guideline, but the collection devices are robust enough to permit flexibility in sampling at home or in the field.

Electronic supplementary material

The online version of this article (10.1186/s13104-019-4211-6) contains supplementary material, which is available to authorized users.

Evaluating apolipoprotein E genotype status and neuroprotective effects against white matter hyperintensity development in high-altitude careers

Objective

This study considers the use of a rapid molecular assay to evaluate apolipoprotein E (ApoE) status in military subjects who have been exposed to high altitude. We hypothesize that ApoE status may be protective against developing brain white matter hyperintensities (WMHs) after high altitude exposure.

Results

We tested 92 subjects who had been exposed to altitudes above 25,000 ft mean sea level, either as pilots or as altitude chamber technicians. We determined subject genetic status using rapid Taqman-style polymerase chain reaction genotyping and evaluated the association of ApoE subtype versus brain lesions using t-tests and two-way analyses of variance. Our results indicate that there is no significant association between ApoE genotype status and the presence of WMHs after high altitude exposure. We did observe a significantly higher number of hours spent at altitude for subjects with the ApoE E2 allele; however, the mechanism by which this may occur is not determined in this study. To more fully elucidate this effect, larger populations would be required to observe greater numbers of subjects with the E2 and E4 alleles.

Patient-Centric Side Effect Risk Assessment for Medications Used During Aeromedical Evacuations

BACKGROUND

The U.S. Air Force performs more than 6000 aeromedical transport flights annually, both internationally and domestically. Many of these flights include patients requiring pain relief medications. The risk of side effects from such medications administered at altitude is unknown, but understanding these risks is vital when selecting the safest pain management strategies to achieve optimal postflight outcomes.

METHODS

Using an evidence-based medication side effect risk assessment model, we compared our patient-centric approach to an aircrew-centric approach using medications approved for use in U.S. Navy aircrew. We then determined the patient-centric side effect risk of medications commonly used during Air Force aeromedical evacuation (AE).

RESULTS

The patient-centric approach to medication side effect risk assessment demonstrates that the majority of medications currently approved for use during AE have an acceptable side effect risk for the patient (18/22, 82%). Four approved drugs displayed significantly elevated patient risk, with risk scores between 2.0- and 3.2-fold greater than the statistically determined upper allowable ("acceptable") limit and between 1.2- and 2.0-fold above the upper control ("tolerable") limit.

DISCUSSION

Our results suggest that pain management strategies during AE should be tailored individually to minimize the risk associated with pain medications administered en route.Huntsberger SA, Butler WP, Chapleau RR. Patient-centric side effect risk assessment for medications used during aeromedical evacuations. Aerosp Med Hum Perform. 2017; 88(4):423-426.

Organophosphorus Inhibition and Characterization of Recombinant Guinea Pig Acetylcholinesterase

Organophosphorus (OP) pesticides and nerve agents have been designed to inhibit the hydrolysis of the neurotransmitter acetylcholine by covalently binding to the active site serine of acetylcholinesterase while Alzheimer drugs and prophylactics, such as tacrine, are characterized by reversible binding. Historically, the guinea pig has been believed to be the best non-primate model for OP toxicology and medical countermeasure development because, similarly to humans, guinea pigs have low amounts of circulating OP metabolizing carboxylesterase. To explore the hypothesis that guinea pigs are the appropriate responder species for OP toxicology and medical countermeasure development, guinea pig acetylcholinesterase (gpAChE) was cloned into pENTR/D-TOPO, recombined into pT-Rex-DEST30 and expressed in Human Embryonic Kidney 293 cells. Recombinant gpAChE was purified to a specific activity of 800 U/mg using size exclusion and immobilized nickel affinity chromatography, with purity confirmed by gel electrophoresis. Ellman's assay was used to enzymatically characterize gpAChE, identifying a K(M) of 154±18.7 µmol L(-1) and a k(cat) of 4.79x10(4)±5.26x10(2) /sec. Apparent gpAChE IC50's for diisopropylfluorophosphate, dicrotophos, paraoxon, and an Alzheimer's drug, tacrine, were found to be 10.1±1.98, 337±108, 1.02±0.29 and 0.30±0.01 µmol L(-1), respectively. Apparent gpAChE inhibition constants for diisopropylfluorophosphate, dicrotophos, paraoxon, and tacrine were found to be 8.40±0.60, 4.50±0.30, 0.29±0.01 and 0.42±0.07 µmol L(-1), respectively. Lineweaver-Burk plots confirmed tacrine as a mixed inhibitor and paraoxon, dicrotophos and diisopropylfluorophosphate as irreversible non-competitive inhibitors. gpAChE bimolecular rate constants for diisopropylfluorophosphate, dicrotophos and paraoxon were found to be 1.44±0.33x10(4), 1.56±0.12x10(3) and 4.57± 0.23x10(5) L µmol(-1) min(-1), respectively. Although the blood levels of OP metabolizing carboxylesterases in the guinea pig are similar to the low levels in human blood, the gpAChE is different in its enzymology. Therefore, medical countermeasures against OP intoxication should be tested for efficacy with the recombinant form of gpAChE prior to initiating animal studies.

Optical Whole-Genome Restriction Mapping as a Tool for Rapidly Distinguishing and Identifying Bacterial Contaminants in Clinical Samples

INTRODUCTION

Optical restriction genome mapping is a technology in which a genome is linearized on a surface and digested with specific restriction enzymes, giving an arrangement of the genome with gaps whose order and size are unique for a given organism. Current applications of this technology include assisting with the correct scaffolding and ordering of genomes in conjunction with whole-genome sequencing, observation of genetic drift and evolution using comparative genomics and epidemiological monitoring of the spread of infections. Here, we investigated the suitability of genome mapping for use in clinical labs as a potential diagnostic tool.

MATERIALS AND METHODS

Using whole genome mapping, we investigated the basic performance of the technology for identifying two bacteria of interest for food-safety (Lactobacilli spp. and Enterohemorrhagic Escherichia coli). We further evaluated the performance for identifying multiple organisms from both simple and complex mixtures.

RESULTS

We were able to successfully generate optical restriction maps of four Lactobacillus species as well as a strain of Enterohemorrhagic Escherichia coli from within a mixed solution, each distinguished using a common compatible restriction enzyme. Finally, we demonstrated that optical restriction maps were successfully obtained and the correct organism identified within a clinical matrix.

CONCLUSION

With additional development, whole genome mapping may be a useful clinical tool for rapid invitro diagnostics.

High-Throughput Screening for Positive Allosteric Modulators Identified Potential Therapeutics against Acetylcholinesterase Inhibition

The current standard of care for treatment of organophosphate (OP) poisoning includes pretreatment with the weak reversible acetylcholinesterase (AChE) inhibitor pyridostigmine bromide. Because this drug is an AChE inhibitor, similar side effects exist as with OP poisoning. In an attempt to provide a therapeutic capable of mitigating AChE inhibition without such side effects, high-throughput screening was performed to identify a compound capable of increasing the catalytic activity of AChE. Herein, two such novel positive allosteric modulators (PAMs) of AChE are presented. These PAMs increase AChE activity threefold, but they fail to upshift the apparent IC50 of a variety of OPs. Further development and optimization of these compounds may lead to pre- and/or postexposure therapeutics with broad-spectrum efficacy against pesticide and nerve agent poisoning. In addition, they could be used to complement the current therapeutic standard of care to increase the activity of uninhibited AChE, potentially increasing the efficacy of current therapeutics in addition to altering the therapeutic window.

Potential new therapeutic modality revealed through agent-based modeling of the neuromuscular junction and acetylcholinesterase inhibition

Background

One of the leading causes of death and illness within the agriculture industry is through unintentionally ingesting or inhaling organophosphate pesticides. OP intoxication directly inhibits acetylcholinesterase, resulting in an excitatory signaling cascade leading to fasciculation, loss of control of bodily fluids, and seizures.

Methods

Our model was developed using a discrete, rules-based modeling approach in NetLogo. This model includes acetylcholinesterase, the nicotinic acetylcholine receptor responsible for signal transduction, a single release of acetylcholine, organophosphate inhibitors, and a theoretical novel medical countermeasure. We have parameterized the system considering the molecular reaction rate constants in an agent-based approach, as opposed to apparent macroscopic rates used in differential equation models.

Results

Our model demonstrates how the cholinergic crisis can be mitigated by therapeutic intervention with an acetylcholinesterase activator. Our model predicts signal rise rates and half-lives consistent with in vitro and in vivo data in the absence and presence of inhibitors. It also predicts the efficacy of theoretical countermeasures acting through three mechanisms: increasing catalytic turnover of acetylcholine, increasing acetylcholine binding affinity to the enzyme, and decreasing binding rates of inhibitors.

Conclusion

We present a model of the neuromuscular junction confirming observed acetylcholine signaling data and suggesting that developing a countermeasure capable of reducing inhibitor binding, and not activator concentration, is the most important parameter for reducing organophosphate (OP) intoxication.

Electronic supplementary material

The online version of this article (doi:10.1186/1742-4682-11-42) contains supplementary material, which is available to authorized users.

Tunable stringency aptamer selection and gold nanoparticle assay for detection of cortisol

The first-known aptamer for the stress biomarker cortisol was selected using a tunable stringency magnetic bead selection strategy. The capture DNA probe immobilized on the beads was systematically lengthened to increase the number of bases bound to the complementary pool primer regions following selection enrichment. This resulted in a single sequence (15-1) dominating the final round 15 pool, where the same sequence was the second-highest copy number candidate in the enriched pool with the shorter capture DNA probe (round 13). A thorough analysis of the next-generation sequencing results showed that a high copy number may only correlate with enhanced affinity under certain stringency and enrichment conditions, in contrast with prior published reports. Aptamer 15-1 demonstrated enhanced binding to cortisol (K(d) = 6.9 ± 2.8 μM by equilibrium dialysis; 16.1 ± 0.6 μM by microscale thermophoresis) when compared with the top sequence from round 13 and the negative control progesterone. Whereas most aptamer selections terminate at the selection round demonstrating the highest enrichment, this work shows that extending the selection with higher stringency conditions leads to lower amounts eluted by the target but higher copy numbers of a sequence with enhanced binding. The structure-switching aptamer was applied to a gold nanoparticle assay in buffer and was shown to discriminate between cortisol and two other stress biomarkers, norepinephrine and epinephrine, and a structurally analogous biomarker of liver dysfunction, cholic acid. We believe this approach enhances aptamer selection and serves as proof-of-principle work toward development of point-of-care diagnostics for medical, combat, or bioterrorism targets.

Using affinity chromatography to engineer and characterize pH-dependent protein switches

Conformational changes play important roles in the regulation of many enzymatic reactions. Specific motions of side chains, secondary structures, or entire protein domains facilitate the precise control of substrate selection, binding, and catalysis. Likewise, the engineering of allostery into proteins is envisioned to enable unprecedented control of chemical reactions and molecular assembly processes. We here study the structural effects of engineered ionizable residues in the core of the glutathione-S-transferase to convert this protein into a pH-dependent allosteric protein. The underlying rational of these substitutions is that in the neutral state, an uncharged residue is compatible with the hydrophobic environment. In the charged state, however, the residue will invoke unfavorable interactions, which are likely to induce conformational changes that will affect the function of the enzyme. To test this hypothesis, we have engineered a single aspartate, cysteine, or histidine residue at a distance from the active site into the protein. All of the mutations exhibit a dramatic effect on the protein's affinity to bind glutathione. Whereas the aspartate or histidine mutations result in permanently nonbinding or binding versions of the protein, respectively, mutant GST50C exhibits distinct pH-dependent GSH-binding affinity. The crystal structures of the mutant protein GST50C under ionizing and nonionizing conditions reveal the recruitment of water molecules into the hydrophobic core to produce conformational changes that influence the protein's active site. The methodology described here to create and characterize engineered allosteric proteins through affinity chromatography may lead to a general approach to engineer effector-specific allostery into a protein structure.

Design of a highly specific and noninvasive biosensor suitable for real-time in vivo imaging of mercury (II) uptake

Mercury is a ubiquitous pollutant that when absorbed is extremely toxic to a wide variety of biochemical processes. Mercury (II) is a strong, "invisible" poison that is rapidly absorbed by tissues of the intestinal tract, kidneys, and liver upon ingestion. In this study, a novel fluorescence-based biosensor is presented that allows for the direct monitoring of the uptake and distribution of the metal under noninvasive in vivo conditions. With the introduction of a cysteine residue at position 205, located in close proximity to the chromophore, the green fluorescent protein (GFP) from Aequorea victoria was converted into a highly specific biosensor for this metal ion. The mutant protein exhibits a dramatic absorbance and fluorescence change upon mercuration at neutral pH. Absorbance and fluorescence properties with respect to the metal concentration exhibit sigmoidal binding behavior with a detection limit in the low nanomolar range. Time-resolved binding studies indicate rapid subsecond binding of the metal to the protein. The crystal structures obtained of mutant eGFP205C indicate a possible access route of the metal into the core of the protein. To our knowledge, this engineered protein is a first example of a biosensor that allows for noninvasive and real-time imaging of mercury uptake in a living cell. A major advantage is that its expression can be genetically controlled in many organisms to enable unprecedented studies of tissue specific mercury uptake.