Enhanced safety and efficacy of protease-regulated CAR-T cell receptors.

Regulatable CAR platforms could circumvent toxicities associated with CAR-T therapy, but existing systems have shortcomings including leakiness and attenuated activity. Here, we present SNIP CARs, a protease-based platform for regulating CAR activity using an FDA-approved small molecule. Design iterations yielded CAR-T cells that manifest full functional capacity with drug and no leaky activity in the absence of drug. In numerous models, SNIP CAR-T cells were more potent than constitutive CAR-T cells and showed diminished T cell exhaustion and greater stemness. In a ROR1-based CAR lethality model, drug cessation following toxicity onset reversed toxicity, thereby credentialing the platform as a safety switch. In the same model, reduced drug dosing opened a therapeutic window that resulted in tumor eradication in the absence of toxicity. SNIP CARs enable remote tuning of CAR activity, which provides solutions to safety and efficacy barriers that are currently limiting progress in using CAR-T cells to treat solid tumors.

Optobiochemistry: Genetically Encoded Control of Protein Activity by Light.

Optobiochemical control of protein activities allows the investigation of protein functions in living cells with high spatiotemporal resolution. Over the last two decades, numerous natural photosensory domains have been characterized and synthetic domains engineered and assembled into photoregulatory systems to control protein function with light. Here, we review the field of optobiochemistry, categorizing photosensory domains by chromophore, describing photoregulatory systems by mechanism of action, and discussing protein classes frequently investigated using optical methods. We also present examples of how spatial or temporal control of proteins in living cells has provided new insights not possible with traditional biochemical or cell biological techniques.

Ultrafast Two-Photon Imaging of a High-Gain Voltage Indicator in Awake Behaving Mice.

Optical interrogation of voltage in deep brain locations with cellular resolution would be immensely useful for understanding how neuronal circuits process information. Here, we report ASAP3, a genetically encoded voltage indicator with 51% fluorescence modulation by physiological voltages, submillisecond activation kinetics, and full responsivity under two-photon excitation. We also introduce an ultrafast local volume excitation (ULoVE) method for kilohertz-rate two-photon sampling in vivo with increased stability and sensitivity. Combining a soma-targeted ASAP3 variant and ULoVE, we show single-trial tracking of spikes and subthreshold events for minutes in deep locations, with subcellular resolution and with repeated sampling over days. In the visual cortex, we use soma-targeted ASAP3 to illustrate cell-type-dependent subthreshold modulation by locomotion. Thus, ASAP3 and ULoVE enable high-speed optical recording of electrical activity in genetically defined neurons at deep locations during awake behavior.

A Suite of Transgenic Driver and Reporter Mouse Lines with Enhanced Brain-Cell-Type Targeting and Functionality.

Modern genetic approaches are powerful in providing access to diverse cell types in the brain and facilitating the study of their function. Here, we report a large set of driver and reporter transgenic mouse lines, including 23 new driver lines targeting a variety of cortical and subcortical cell populations and 26 new reporter lines expressing an array of molecular tools. In particular, we describe the TIGRE2.0 transgenic platform and introduce Cre-dependent reporter lines that enable optical physiology, optogenetics, and sparse labeling of genetically defined cell populations. TIGRE2.0 reporters broke the barrier in transgene expression level of single-copy targeted-insertion transgenesis in a wide range of neuronal types, along with additional advantage of a simplified breeding strategy compared to our first-generation TIGRE lines. These novel transgenic lines greatly expand the repertoire of high-precision genetic tools available to effectively identify, monitor, and manipulate distinct cell types in the mouse brain.

Subcellular Imaging of Voltage and Calcium Signals Reveals Neural Processing In Vivo.

A mechanistic understanding of neural computation requires determining how information is processed as it passes through neurons and across synapses. However, it has been challenging to measure membrane potential changes in axons and dendrites in vivo. We use in vivo, two-photon imaging of novel genetically encoded voltage indicators, as well as calcium imaging, to measure sensory stimulus-evoked signals in the Drosophila visual system with subcellular resolution. Across synapses, we find major transformations in the kinetics, amplitude, and sign of voltage responses to light. We also describe distinct relationships between voltage and calcium signals in different neuronal compartments, a substrate for local computation. Finally, we demonstrate that ON and OFF selectivity, a key feature of visual processing across species, emerges through the transformation of membrane potential into intracellular calcium concentration. By imaging voltage and calcium signals to map information flow with subcellular resolution, we illuminate where and how critical computations arise.

Cell-Type-Specific Optical Recording of Membrane Voltage Dynamics in Freely Moving Mice.

Electrophysiological field potential dynamics are of fundamental interest in basic and clinical neuroscience, but how specific cell types shape these dynamics in the live brain is poorly understood. To empower mechanistic studies, we created an optical technique, TEMPO, that records the aggregate trans-membrane voltage dynamics of genetically specified neurons in freely behaving mice. TEMPO has >10-fold greater sensitivity than prior fiber-optic techniques and attains the noise minimum set by quantum mechanical photon shot noise. After validating TEMPO's capacity to track established oscillations in the delta, theta, and gamma frequency bands, we compared the D1- and D2-dopamine-receptor-expressing striatal medium spiny neurons (MSNs), which are interspersed and electrically indistinguishable. Unexpectedly, MSN population dynamics exhibited two distinct coherent states that were commonly indiscernible in electrical recordings and involved synchronized hyperpolarizations across both MSN subtypes. Overall, TEMPO allows the deconstruction of normal and pathologic neurophysiological states into trans-membrane voltage activity patterns of specific cell types.

A positively tuned voltage indicator for extended electrical recordings in the brain.

Genetically encoded voltage indicators (GEVIs) enable optical recording of electrical signals in the brain, providing subthreshold sensitivity and temporal resolution not possible with calcium indicators. However, one- and two-photon voltage imaging over prolonged periods with the same GEVI has not yet been demonstrated. Here, we report engineering of ASAP family GEVIs to enhance photostability by inversion of the fluorescence-voltage relationship. Two of the resulting GEVIs, ASAP4b and ASAP4e, respond to 100-mV depolarizations with ≥180% fluorescence increases, compared with the 50% fluorescence decrease of the parental ASAP3. With standard microscopy equipment, ASAP4e enables single-trial detection of spikes in mice over the course of minutes. Unlike GEVIs previously used for one-photon voltage recordings, ASAP4b and ASAP4e also perform well under two-photon illumination. By imaging voltage and calcium simultaneously, we show that ASAP4b and ASAP4e can identify place cells and detect voltage spikes with better temporal resolution than commonly used calcium indicators. Thus, ASAP4b and ASAP4e extend the capabilities of voltage imaging to standard one- and two-photon microscopes while improving the duration of voltage recordings.

An optimized bioluminescent substrate for non-invasive imaging in the brain.

Bioluminescence imaging (BLI) allows non-invasive visualization of cells and biochemical events in vivo and thus has become an indispensable technique in biomedical research. However, BLI in the central nervous system remains challenging because luciferases show relatively poor performance in the brain with existing substrates. Here, we report the discovery of a NanoLuc substrate with improved brain performance, cephalofurimazine (CFz). CFz paired with Antares luciferase produces greater than 20-fold more signal from the brain than the standard combination of D-luciferin with firefly luciferase. At standard doses, Antares-CFz matches AkaLuc-AkaLumine/TokeOni in brightness, while occasional higher dosing of CFz can be performed to obtain threefold more signal. CFz should allow the growing number of NanoLuc-based indicators to be applied to the brain with high sensitivity. Using CFz, we achieve video-rate non-invasive imaging of Antares in brains of freely moving mice and demonstrate non-invasive calcium imaging of sensory-evoked activity in genetically defined neurons.

Comparison of Daily versus Admission and Discharge Surveillance Cultures for Multidrug-Resistant Organism Detection in an Intensive Care Unit.

BACKGROUND: Admission and discharge screening of patients for asymptomatic gut colonization with multidrug-resistant organisms (MDROs) is a traditional approach to active surveillance, but its sensitivity for detecting colonization is uncertain. METHODS: Daily rectal or fecal swab samples and clinical data were collected over 12 months from patients in one 25-bed intensive care unit (ICU) in Chicago, IL USA and tested for the following multidrug-resistant organisms (MDROs): vancomycin-resistant enterococci (VRE); third-generation cephalosporin-resistant Enterobacterales, including extended-spectrum ß-lactamase-producing Enterobacterales (ESBL); and carbapenem-resistant Enterobacterales (CRE). MDRO detection by (1) admission/discharge surveillance cultures or (2) clinical cultures were compared to daily surveillance cultures. Samples underwent 16S rRNA gene sequencing to measure the relative abundance of operational taxonomic units (OTUs) corresponding to each MDRO. RESULTS: Compared with daily surveillance cultures, admission/discharge cultures detected 91% of prevalent MDRO colonization and 63% of incident MDRO colonization among medical ICU patients. Only a minority (7%) of MDRO carriers were identified by clinical cultures. Higher relative abundance of MDRO-associated OTUs and specific antibiotic exposures were independently associated with higher probability of MDRO detection by culture. CONCLUSION: Admission and discharge surveillance cultures underestimated MDRO acquisitions in an ICU. These limitations should be considered when designing sampling strategies for epidemiologic studies that use culture-based surveillance.

Effectiveness of mRNA Covid-19 Vaccine among U.S. Health Care Personnel.

BACKGROUND: The prioritization of U.S. health care personnel for early receipt of messenger RNA (mRNA) vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (Covid-19), allowed for the evaluation of the effectiveness of these new vaccines in a real-world setting. METHODS: We conducted a test-negative case-control study involving health care personnel across 25 U.S. states. Cases were defined on the basis of a positive polymerase-chain-reaction (PCR) or antigen-based test for SARS-CoV-2 and at least one Covid-19-like symptom. Controls were defined on the basis of a negative PCR test for SARS-CoV-2, regardless of symptoms, and were matched to cases according to the week of the test date and site. Using conditional logistic regression with adjustment for age, race and ethnic group, underlying conditions, and exposures to persons with Covid-19, we estimated vaccine effectiveness for partial vaccination (assessed 14 days after receipt of the first dose through 6 days after receipt of the second dose) and complete vaccination (assessed ≥7 days after receipt of the second dose). RESULTS: The study included 1482 case participants and 3449 control participants. Vaccine effectiveness for partial vaccination was 77.6% (95% confidence interval [CI], 70.9 to 82.7) with the BNT162b2 vaccine (Pfizer-BioNTech) and 88.9% (95% CI, 78.7 to 94.2) with the mRNA-1273 vaccine (Moderna); for complete vaccination, vaccine effectiveness was 88.8% (95% CI, 84.6 to 91.8) and 96.3% (95% CI, 91.3 to 98.4), respectively. Vaccine effectiveness was similar in subgroups defined according to age (<50 years or ≥50 years), race and ethnic group, presence of underlying conditions, and level of patient contact. Estimates of vaccine effectiveness were lower during weeks 9 through 14 than during weeks 3 through 8 after receipt of the second dose, but confidence intervals overlapped widely. CONCLUSIONS: The BNT162b2 and mRNA-1273 vaccines were highly effective under real-world conditions in preventing symptomatic Covid-19 in health care personnel, including those at risk for severe Covid-19 and those in racial and ethnic groups that have been disproportionately affected by the pandemic. (Funded by the Centers for Disease Control and Prevention.).

Usability of Patient Education-Oriented Cataract Surgery Websites.

PURPOSE: To assess the web accessibility and readability of patient-oriented educational websites for cataract surgery. DESIGN: Cross-sectional electronic survey. PARTICIPANTS: Websites with information dedicated to educating patients about cataract surgery. METHODS: An incognito search for "cataract surgery" was performed using a popular search engine. The top 100 patient-oriented cataract surgery websites that came up were included and categorized as institutional, private practice, or medical organization according to authorship. Each site was assessed for readability using 4 standardized reading grade-level formulas. Accessibility was assessed through multilingual availability, accessibility menu availability, complementary educational video availability, and conformance and adherence to the Web Content Accessibility Guidelines (WCAG) 2.0. A standard t test and chi-square analysis were performed to assess the significance of differences with regard to readability and accessibility among the 3 authorship categories. MAIN OUTCOME MEASURES: The main outcome measures were the website's average reading grade level, number of accessibility violations, multilingual availability, accessibility menu availability, complementary educational video availability, accessibility conformance level, and violation of the perceivable, operable, understandable, and robust (POUR) principles according to the WCAG 2.0. RESULTS: A total of 32, 55, and 13 sites were affiliated with institutions, private practice, and other medical organizations, respectively. The overall mean reading grade was 11.8 ± 1.6, with higher reading levels observed in private practice websites compared with institutions and medical organizations combined (12.1 vs. 11.4; P = 0.03). Fewer private practice websites had multiple language options compared with institutional and medical organization websites combined (5.5% vs. 20.0%; P = 0.03). More private practice websites had accessibility menus than institutions and medical organizations combined (27.3% vs. 8.9%; P = 0.038). The overall mean number of WCAG 2.0 POUR principle violations was 17.1 ± 23.1 with no significant difference among groups. Eighty-five percent of websites violated the perceivable principle. CONCLUSIONS: Available patient-oriented online information for cataract surgery may not be comprehensible to the general public. Readability and accessibility aspects should be considered when designing these resources. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Dexamethasone Intracanalicular Insert for Clinically Significant Aqueous-Deficient Dry Eye: A Randomized Controlled Trial.

PURPOSE: To evaluate a commercially available dexamethasone intracanalicular insert to treat dry eye. DESIGN: Single-center, double-masked randomized controlled trial. PARTICIPANTS: Patients with clinically significant aqueous-deficient dry eye (combined ocular surface staining score, ≥ 3 [0-12]; corneal fluorescein staining score, ≥ 2 [0-6]; and Schirmer's wetting, < 10 mm at 5 minutes in both eyes) with symptoms (dryness, eye discomfort, or visual fatigue, ≥ 30 [0-100]) despite treatment with at least 1 prescription drop and deemed candidates for topical steroid therapy. METHODS: Seventy-five adult patients were enrolled. A 1:1 randomization sequence was used to determine which eye of each patient would receive the treatment (dexamethasone 0.4-mg intracanalicular insert with 30-day elution time) or sham (collagen plug). The fellow eye received the opposite treatment. Patients were masked to treatment assignment. Follow-up visits (at weeks 2, 4, and 6) were performed by a masked investigator. MAIN OUTCOME MEASURES: Dry eye parameters and patient symptoms were used for efficacy, and intraocular pressure (IOP) was used for safety assessment. RESULTS: The severity of dry eye was comparable between the treatment arms (fellow eyes) at baseline. Eyes that received the dexamethasone insert showed significantly less corneal staining at week 4 (mean difference [MD], -0.55; 95% confidence interval [CI], -0.91 to -0.19) and conjunctival staining at week 4 (MD, -0.68; 95% CI, -1.05 to -0.30) and week 6 (MD, -0.34; 95% CI, -0.65 to -0.02). Schirmer's wetting was comparable between the two treatment arms. Although the patients reported less dryness in eyes that received the insert at week 4 (MD, -5.5; 95% CI, -11.4 to 0.4), no statistically significant differences were found in any patient-reported symptoms. At week 4, dexamethasone-treated eyes were more likely to show an IOP increase (by 5-10 mmHg; 9 eyes vs. 1 eye; relative risk, 9.00; 95% CI, 1.14-71.0). All cases of increased IOP were managed with short-term topical ß-blockers and subsided. CONCLUSIONS: The dexamethasone intracanalicular insert may be considered a dropless dual treatment for clinically significant aqueous-deficient dry eye when topical steroid treatment is deemed appropriate. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

A Systematic Review of Ophthalmology Education in Medical Schools: The Global Decline.

TOPIC: This systematic review examined geographical and temporal trends in medical school ophthalmology education in relationship to course and student outcomes. CLINICAL RELEVANCE: Evidence suggesting a decline in ophthalmology teaching in medical schools is increasing, raising concern for the adequacy of eye knowledge across the rest of the medical profession. METHODS: Systematic review of Embase and SCOPUS, with inclusion of studies containing data on medical school ophthalmic course length; 1 or more outcome measures on student ophthalmology knowledge, skills, self-evaluation of knowledge or skills, or student course appraisal; or both. The systematic review was registered prospectively on the International Prospective Register of Systematic Reviews (identifier, CRD42022323865). Results were aggregated with outcome subgroup analysis and description in relationship to geographical and temporal trends. Descriptive statistics, including nonparametric correlations, were used to analyze data and trends. RESULTS: Systematic review yielded 4596 publication titles, of which 52 were included in the analysis, with data from 19 countries. Average course length ranged from 12.5 to 208.7 hours, with significant continental disparity among mean course lengths. Africa reported the longest average course length at 103.3 hours, and North America reported the shortest at 36.4 hours. On average, course lengths have been declining over the last 2 decades, from an average overall course length of 92.9 hours in the 2000s to 52.9 hours in the 2020s. Mean student self-evaluation of skills was 51.3%, and mean student self-evaluation of knowledge was 55.4%. Objective mean assessment mark of skills was 57.5% and that of knowledge was 71.7%, compared with an average pass mark of 66.7%. On average, 26.4% of students felt confident in their ophthalmology knowledge and 34.5% felt confident in their skills. DISCUSSION: Most evidence describes declining length of courses devoted to ophthalmology in the last 20 years, significant student dissatisfaction with courses and content, and suboptimal knowledge and confidence. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Reducing Hospitalizations and Multidrug-Resistant Organisms via Regional Decolonization in Hospitals and Nursing Homes.

Importance: Infections due to multidrug-resistant organisms (MDROs) are associated with increased morbidity, mortality, length of hospitalization, and health care costs. Regional interventions may be advantageous in mitigating MDROs and associated infections. Objective: To evaluate whether implementation of a decolonization collaborative is associated with reduced regional MDRO prevalence, incident clinical cultures, infection-related hospitalizations, costs, and deaths. Design, Setting, and Participants: This quality improvement study was conducted from July 1, 2017, to July 31, 2019, across 35 health care facilities in Orange County, California. Exposures: Chlorhexidine bathing and nasal iodophor antisepsis for residents in long-term care and hospitalized patients in contact precautions (CP). Main Outcomes and Measures: Baseline and end of intervention MDRO point prevalence among participating facilities; incident MDRO (nonscreening) clinical cultures among participating and nonparticipating facilities; and infection-related hospitalizations and associated costs and deaths among residents in participating and nonparticipating nursing homes (NHs). Results: Thirty-five facilities (16 hospitals, 16 NHs, 3 long-term acute care hospitals [LTACHs]) adopted the intervention. Comparing decolonization with baseline periods among participating facilities, the mean (SD) MDRO prevalence decreased from 63.9% (12.2%) to 49.9% (11.3%) among NHs, from 80.0% (7.2%) to 53.3% (13.3%) among LTACHs (odds ratio [OR] for NHs and LTACHs, 0.48; 95% CI, 0.40-0.57), and from 64.1% (8.5%) to 55.4% (13.8%) (OR, 0.75; 95% CI, 0.60-0.93) among hospitalized patients in CP. When comparing decolonization with baseline among NHs, the mean (SD) monthly incident MDRO clinical cultures changed from 2.7 (1.9) to 1.7 (1.1) among participating NHs, from 1.7 (1.4) to 1.5 (1.1) among nonparticipating NHs (group × period interaction reduction, 30.4%; 95% CI, 16.4%-42.1%), from 25.5 (18.6) to 25.0 (15.9) among participating hospitals, from 12.5 (10.1) to 14.3 (10.2) among nonparticipating hospitals (group × period interaction reduction, 12.9%; 95% CI, 3.3%-21.5%), and from 14.8 (8.6) to 8.2 (6.1) among LTACHs (all facilities participating; 22.5% reduction; 95% CI, 4.4%-37.1%). For NHs, the rate of infection-related hospitalizations per 1000 resident-days changed from 2.31 during baseline to 1.94 during intervention among participating NHs, and from 1.90 to 2.03 among nonparticipating NHs (group × period interaction reduction, 26.7%; 95% CI, 19.0%-34.5%). Associated hospitalization costs per 1000 resident-days changed from $64 651 to $55 149 among participating NHs and from $55 151 to $59 327 among nonparticipating NHs (group × period interaction reduction, 26.8%; 95% CI, 26.7%-26.9%). Associated hospitalization deaths per 1000 resident-days changed from 0.29 to 0.25 among participating NHs and from 0.23 to 0.24 among nonparticipating NHs (group × period interaction reduction, 23.7%; 95% CI, 4.5%-43.0%). Conclusions and Relevance: A regional collaborative involving universal decolonization in long-term care facilities and targeted decolonization among hospital patients in CP was associated with lower MDRO carriage, infections, hospitalizations, costs, and deaths.

Impact of Mandatory Infectious Disease Specialist Approval on Hospital-Onset Clostridioides difficile Infection Rates and Testing Appropriateness.

BACKGROUND: Inappropriate Clostridioides difficile testing is common in the hospital setting, leading to potential overdiagnosis of infection when single-step nucleic acid amplification testing is used. The potential role of infectious diseases (ID) specialists in enforcing appropriate C. difficile testing is unclear. METHODS: At a single 697-bed academic hospital, we performed a retrospective study from 1 March 2012 to 31 December 2019 comparing hospital-onset C. difficile infection (HO-CDI) rates during 3 consecutive time periods: baseline 1 (37 months, no decision support), baseline 2 (32 months, computer decision support), and intervention period (25 months, mandatory ID specialist approval for all C. difficile testing on hospital day 4 or later). We used a discontinuous growth model to assess the impact of the intervention on HO-CDI rates. RESULTS: During the study period, we evaluated C. difficile infections across 331 180 admission and 1 172 015 patient-days. During the intervention period, a median of 1 HO-CDI test approval request per day (range, 0-6 alerts/day) was observed; adherence by providers with obtaining approval was 85%. The HO-CDI rate was 10.2, 10.4, and 4.3 events per 10 000 patient-days for each consecutive time period, respectively. In adjusted analysis, the HO-CDI rate did not differ significantly between the 2 baseline periods (P = .14) but did differ between the baseline 2 period and intervention period (P < .001). CONCLUSIONS: An ID-led C. difficile testing approval process was feasible and was associated with a >50% decrease in HO-CDI rates, due to enforcement of appropriate testing.

Duration of Replication-Competent Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Shedding Among Patients With Severe or Critical Coronavirus Disease 2019 (COVID-19).

BACKGROUND: Patterns of shedding replication-competent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in severe or critical COVID-19 are not well characterized. We investigated the duration of replication-competent SARS-CoV-2 shedding in upper and lower airway specimens from patients with severe or critical coronavirus disease 2019 (COVID-19). METHODS: We enrolled patients with active or recent severe or critical COVID-19 who were admitted to a tertiary care hospital intensive care unit (ICU) or long-term acute care hospital (LTACH) because of COVID-19. Respiratory specimens were collected at predefined intervals and tested for SARS-CoV-2 using viral culture and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Clinical and epidemiologic metadata were reviewed. RESULTS: We collected 529 respiratory specimens from 78 patients. Replication-competent virus was detected in 4 of 11 (36.3%) immunocompromised patients up to 45 days after symptom onset and in 1 of 67 (1.5%) immunocompetent patients 10 days after symptom onset (P = .001). All culture-positive patients were in the ICU cohort and had persistent or recurrent symptoms of COVID-19. Median time from symptom onset to first specimen collection was 15 days (range, 6-45) for ICU patients and 58.5 days (range, 34-139) for LTACH patients. SARS-CoV-2 RNA was detected in 40 of 50 (80%) ICU patients and 7 of 28 (25%) LTACH patients. CONCLUSIONS: Immunocompromise and persistent or recurrent symptoms were associated with shedding of replication-competent SARS-CoV-2, supporting the need for improving respiratory symptoms in addition to time as criteria for discontinuation of transmission-based precautions. Our results suggest that the period of potential infectiousness among immunocompetent patients with severe or critical COVID-19 may be similar to that reported for patients with milder disease.

On the cutting edge: protease-based methods for sensing and controlling cell biology.

Sequence-specific proteases have proven to be versatile building blocks for tools that report or control cellular function. Reporting methods link protease activity to biochemical signals, whereas control methods rely on engineering proteases to respond to exogenous inputs such as light or chemicals. In turn, proteases have inherent control abilities, as their native functions are to release, activate or destroy proteins by cleavage, with the irreversibility of proteolysis allowing sustained downstream effects. As a result, protease-based synthetic circuits have been created for diverse uses such as reporting cellular signaling, tuning protein expression, controlling viral replication and detecting cancer states. Here, we comprehensively review the development and application of protease-based methods for reporting and controlling cellular function in eukaryotes.

Kilohertz two-photon fluorescence microscopy imaging of neural activity in vivo.

Understanding information processing in the brain requires monitoring neuronal activity at high spatiotemporal resolution. Using an ultrafast two-photon fluorescence microscope empowered by all-optical laser scanning, we imaged neuronal activity in vivo at up to 3,000 frames per second and submicrometer spatial resolution. This imaging method enabled monitoring of both supra- and subthreshold electrical activity down to 345 µm below the brain surface in head-fixed awake mice.

Novel NanoLuc substrates enable bright two-population bioluminescence imaging in animals.

Sensitive detection of two biological events in vivo has long been a goal in bioluminescence imaging. Antares, a fusion of the luciferase NanoLuc to the orange fluorescent protein CyOFP, has emerged as a bright bioluminescent reporter with orthogonal substrate specificity to firefly luciferase (FLuc) and its derivatives such as AkaLuc. However, the brightness of Antares in mice is limited by the poor solubility and bioavailability of the NanoLuc substrate furimazine. Here, we report a new substrate, hydrofurimazine, whose enhanced aqueous solubility allows delivery of higher doses to mice. In the liver, Antares with hydrofurimazine exhibited similar brightness to AkaLuc with its substrate AkaLumine. Further chemical exploration generated a second substrate, fluorofurimazine, with even higher brightness in vivo. We used Antares with fluorofurimazine to track tumor size and AkaLuc with AkaLumine to visualize CAR-T cells within the same mice, demonstrating the ability to perform two-population imaging with these two luciferase systems.

Optical control of fast and processive engineered myosins in vitro and in living cells.

Precision tools for spatiotemporal control of cytoskeletal motor function are needed to dissect fundamental biological processes ranging from intracellular transport to cell migration and division. Direct optical control of motor speed and direction is one promising approach, but it remains a challenge to engineer controllable motors with desirable properties such as the speed and processivity required for transport applications in living cells. Here, we develop engineered myosin motors that combine large optical modulation depths with high velocities, and create processive myosin motors with optically controllable directionality. We characterize the performance of the motors using in vitro motility assays, single-molecule tracking and live-cell imaging. Bidirectional processive motors move efficiently toward the tips of cellular protrusions in the presence of blue light, and can transport molecular cargo in cells. Robust gearshifting myosins will further enable programmable transport in contexts ranging from in vitro active matter reconstitutions to microfabricated systems that harness molecular propulsion.