A user-inspired mobility experience of the future: a qualitative investigation.

Wheelchair users (WCUs) face additional challenges than non-WCU to multi-tasking (i.e. open doors, cook, use a cell-phone) while navigating their environments. While assistive devices have attempted to provide WCUs with mobility solutions that enable multi-tasking capabilities, current devices have been developed without the input of end-users and have proven to be non-usable. More balanced approaches that integrate the end-users' voices may improve current assistive technology usability trends. This study sought to empathically understand the lived experience of WCUs, their needs towards a mobility device, and their perceptions towards hands-free mobility. Full-time WCUs and care providers participated in semi-structured interviews examining wheelchair use and perceptions towards current and future mobility devices. Thematic analysis was used to analyze interview data. 9 WCUs (aged 32.1 ± 7.0 years; wheelchair experience 17.9 ± 11.6 years) and five care providers (years caring for WCU 3.75 ± 0.96 years) participated in the study. The most common disability type was spinal cord injury (WCUs: n = 3; care providers: n = 3). Qualitative analysis revealed four key themes: (1) Current wheelchair usage, (2) WCU and care provider perspectives, (3) Future wheelchair, and (4) Hands-free wheelchair. Accordingly, participants desire bespoke, light-weight mobility devices that can through tight spaces, access uneven terrain, and free the hands during navigation. This study provides meaningful insight into the needs of WCUs and care providers that assistive technology innovators can use to develop more usable assistive technologies. Amongst study participants, the concept of a hands-free mobility device appears to be usable and desirable.

Integrating end-users' voices into the development of assistive technology may improve current usability trendsWheelchair users desire access to their hands and the ability to multi-task while navigating their wheelchairsThe development of a hands-free mobility device may profoundly improve the quality of life of wheelchair users.

Assembly of the Tn7 targeting complex by a regulated stepwise process.

The Tn7 family of transposons is notable for its highly regulated integration mechanisms, including programmable RNA-guided transposition. The targeting pathways rely on dedicated target selection proteins from the TniQ family and the AAA+ adaptor TnsC to recruit and activate the transposase at specific target sites. Here, we report the cryoelectron microscopy (cryo-EM) structures of TnsC bound to the TniQ domain of TnsD from prototypical Tn7 and unveil key regulatory steps stemming from unique behaviors of ATP- versus ADP-bound TnsC. We show that TnsD recruits ADP-bound dimers of TnsC and acts as an exchange factor to release one protomer with exchange to ATP. This loading process explains how TnsC assembles a heptameric ring unidirectionally from the target site. This unique loading process results in functionally distinct TnsC protomers within the ring, providing a checkpoint for target immunity and explaining how insertions at programmed sites precisely occur in a specific orientation across Tn7 elements.

A mixed-methods study examining perceptions of fear of falling among community-dwelling people who use wheelchairs full-time.

Objective: There is growing evidence that fear of falling (FOF) is common in people who use wheelchairs full-time and negatively influence their performance of daily activities and quality of life. The purpose of this study was to gain an in-depth understanding of perceptions related to FOF among people who use wheelchairs full-time.Methods: Mixed-method analysis was conducted using semi-structured interviews and surveys to gain insight into FOF. Surveys included demographic information; Spinal Cord Injury-Fall Concerns Scale (SCI-FCS); a questionnaire that directly assesses FOF and associated activity curtailment; and Fall Control Scale (FCS).Results: Among 39 participants (age = 43.1 ± 15.6 years, disability duration = 21.2 ± 11.1 years), 27 participants (69%) reported FOF. Participants with less perceived ability to control falls indexed by FCS reported higher SCI-FCS scores, indicating greater FOF (rs = -0.384, p = 0.016). Qualitative findings revealed that participants felt that FOF developed due to sustaining fall-related injuries or limited ability to recover from a fall. Some participants perceived falling as a part of their lives. They believed that it was not the cause of developing FOF.Conclusions: Among people who use wheelchairs full-time, FOF is prevalent and may develop due to fears of sustaining injuries or being unable to get up after falling. Developing an evidenced-based education protocol aimed at managing falls (e.g., establishing a fall recovery strategy and education on techniques to reduce injury during falls) is needed to minimize FOF people who use wheelchairs full-time.

Fear of falling and associated activity curtailment are prevalent among people who use wheelchairs full-time.Fear of falling often develops as a result of prior fall-related injuries or the inability to recover from a fall independently.Evidence-based education protocols to reduce fear of falling among people who use wheelchairs full-time should contain content related to fall recovery and injury prevention.

Natural and Engineered Guide RNA-directed Transposition with CRISPR-Associated Tn7-like Transposons.

CRISPR-Cas (clustered regularly interspaced short palindromic repeats-CRISPR-associated nuclease) defense systems have been naturally coopted for guide RNA-directed transposition on multiple occasions. In all cases, cooption occurred with diverse elements related to the bacterial transposon Tn7. Tn7 tightly controls transposition; the transposase is activated only when special targets are recognized by dedicated target-site selection proteins. Tn7 and the Tn7-like elements that coopted CRISPR-Cas systems evolved complementary targeting pathways: one that recognizes a highly conserved site in the chromosome and a second pathway that targets mobile plasmids capable of cell-to-cell transfer. Tn7 and Tn7-like elements deliver a single integration into the site they recognize and also control the orientation of the integration event, providing future potential for use as programmable gene-integration tools. Early work has shown that guide RNA-directed transposition systems can be adapted to diverse hosts, even within microbial communities, suggesting great potential for engineering these systems as powerful gene-editing tools.

Dual-Task Assessments for Predicting Future Falls in Neurologic Conditions: A Systematic Review.

ABSTRACT: This review investigated the ability of dual-task tests to predict falls in people with neurological disorders. Databases were searched to identify prospective cohort studies that analyzed dual-task testing and falls in people with neurological disorders. Reviewers screened studies for eligibility and extracted key information like participant characteristics, intervention details, outcome measures, and significant outcomes. Reviewers assessed methodological quality of eligible studies using the Standard Quality Assessment Criteria. Eighteen studies of strong methodological qualified with 1750 participants were included in the review. Dual-task performances were predictive of future falls in people with Huntington's disease, spinal cord injury, and moderate cognitive impairment, although only one independent study was included for each disability type. In people with stroke, 37% of eligible studies showed dual-task assessments to be predictive of future falls. No dual-task tests predicted prospective falling in people with Alzheimer's or Parkinson's disease. Complex dual tasks seemed to be more predictive of fall risk than simpler dual tasks. Results suggest that disability type, severity of disability, and task complexity play a role in the predictive ability of dual-task assessments and future falling in neurological disorders. Future studies may benefit from using this review to guide the design of effective dual-task assessments and fall interventions.

Fear of falling and common symptoms of multiple sclerosis: Physical function, cognition, fatigue, depression, and sleep - A systematic review.

BACKGROUND: Fear of falling (FOF) is a common concern among persons with multiple sclerosis (MS) and affects the performance of their daily living activities. Falls may result in FOF, leading to worsening of symptoms of MS, physical deconditioning, and exposure to future falls. This may trigger a vicious cycle between FOF and falls. A better understanding of the relationship between FOF and symptoms of MS may be helpful to develop a conceptual model to guide fall prevention interventions. OBJECTIVE: To synthesize the correlational and predictive relationships between FOF and common symptoms of MS. METHODS: Databases including PubMed, Embase, Web of Science, Scopus, CINHAL, PsycINFO, and SPORTDiscuss were searched from inception to October 2023. Studies examining correlations and/or predictions between FOF and common MS symptoms that include measures of gait, postural control, fatigue, cognition, pain, sleep, depression, and anxiety were identified by two independent reviewers. Both reviewers also conducted the methodological quality assessment of the included studies. RESULTS: Twenty-three studies with a total of 2819 participants were included in the review. Correlational findings indicated that increased FOF was significantly associated with greater walking deficits (lower gait speed, smaller steps), reduced mobility, and poorer balance. Increased FOF was also significantly correlated with higher cognitive impairments, more fatigue, sleep disturbances, and depression. Decreased gait parameters, reduced balance, lower physical functions, cognitive impairments, and sleep deficits were found as significant predictors of increased FOF. CONCLUSION: Evidence indicates significant correlational and bidirectional predictive relationships exist between FOF and common MS symptoms. A comprehensive conceptual framework accounting for the interaction between FOF and MS symptoms is needed to develop effective falls prevention strategies.

Novel mechanisms of diversity generation in Acinetobacter baumannii resistance islands driven by Tn7-like elements.

Mobile genetic elements play an important role in the acquisition of antibiotic and biocide resistance, especially through the formation of resistance islands in bacterial chromosomes. We analyzed the contribution of Tn7-like transposons to island formation and diversification in the nosocomial pathogen Acinetobacter baumannii and identified four separate families that recognize different integration sites. One integration site is within the comM gene and coincides with the previously described Tn6022 elements suggested to account for the AbaR resistance island. We established Tn6022 in a heterologous E. coli host and confirmed basic features of transposition into the comM attachment site and the use of a novel transposition protein. By analyzing population features within Tn6022 elements we identified two potential novel transposon-encoded diversification mechanisms with this dynamic genetic island. The activities of these diversification features were confirmed in E. coli. One was a novel natural gain-of-activity allele that could function to broaden transposition targeting. The second was a transposon-encoded hybrid dif-like site that parasitizes the host dimer chromosome resolution system to function with its own tyrosine recombinase. This work establishes a highly active Tn7-like transposon that harnesses novel features allowing the spread and diversification of genetic islands in pathogenic bacteria.

Perceptions of High-Intensity Interval Training Among People With Spinal Cord Injury: A Mixed-Methods Analysis.

This mixed-method project investigated how people with spinal cord injury perceive high-intensity interval training (HIIT). Using a recumbent hand cycle, 11 active men and 9 active women with spinal cord injury or related disease participated in a single HIIT and moderate-intensity continuous training (MICT) session. Following exercise, participants completed surveys assessing enjoyment, self-efficacy, and outcome expectations. Ten participants were randomly selected to participate in a semistructured interview to assess perceptions toward HIIT. Quantitative survey data revealed that participants trended toward enjoying HIIT over MICT (p = .06) with similar levels of self-efficacy and outcome expectations toward HIIT and MICT (p > .05). Qualitative data revealed that participants believed HIIT would enhance long-term physical and self-evaluative outcomes; several barriers emerged that could prevent widespread adoption among the general population with spinal cord injury. Results support HIIT as a viable exercise option, although research should begin exploring ways to remove HIIT-related barriers that people with spinal cord injury may encounter.

Cardiorespiratory Responses to an Acute Bout of High Intensity Interval Training and Moderate Intensity Continuous Training on a Recumbent Handcycle in People With Spinal Cord Injury: A Within-Subject Design.

Objectives: To compare acute cardiorespiratory responses during high intensity interval training (HIIT) and moderate intensity continuous training (MICT) on a recumbent handcycle in persons with spinal cord injury (PwSCI). Methods: Eleven males and nine females with chronic SCI (T3 - L5), aged 23 (9) years, participated in this within-subject design. Based off peak power outputs from an incremental test to exhaustion, participants engaged in a HIIT and MICT session at matched workloads on a recumbent handcycle. Workloads (Joules), time, oxygen uptake (VO2), metabolic equivalent of task (MET), heart rate (HR), and energy expenditure (kcal) were recorded during HIIT and MICT. Results: Total workload was similar across HIIT (87820 ± 24021 Joules) and MICT sessions (89044 ± 23696 Joules; p > .05). HIIT (20.00 [.03] minutes) was shorter in duration than MICT (23.20 [2.56]; p < .01). Average VO2 (20.96 ± 4.84 vs. 129.38 ± 19.13 mL/kg/min O2), MET (7.54 ± 2.00 vs. 6.21 ± 1.25), and HR (146.26 ± 13.80 vs. 129.38 ± 19.13 beats per minute) responses were significantly greater during HIIT than MICT (p < .01). Participants burned significantly more kilocalories during HIIT (128.08 ± 35.65) than MICT (118.93 ± 29.58; p < .01) and at a faster rate (6.40 ± 1.78 [HIIT] vs. 5.09 ± 1.14 [MICT] kcal/min; p < .01). Conclusion: HIIT elicits greater increases in oxygen uptake and HR than MICT in PwSCI. In significantly less time, HIIT also burned more calories than MICT.

Moving forward: A review of continuous kinetics and kinematics during handcycling propulsion.

Wheelchair users (WCUs) face high rates of shoulder overuse injuries. As exercise is recommended to reduce cardiovascular disease prevalent among WCUs, it is becoming increasingly important to understand the mechanisms behind shoulder soft-tissue injury in WCUs. Understanding the kinetics and kinematics during upper-limb propulsion is the first step toward evaluating soft-tissue injury risk in WCUs. This paper examines continuous kinetic and kinematic data available in the literature. Attach-unit and recumbent handcycling are examined and compared. Athletic modes of propulsion such as recumbent handcycling are important considering the higher contact forces, speed, and power outputs experienced during these activities that could put users at increased risk of injury. Understanding the underlying kinetics and kinematics during various propulsion modes can lend insight into shoulder loading, and therefore injury risk, during these activities and inform future exercise guidelines for WCUs.

Propulsion kinetics of recumbent handcycling during high and moderate intensity exercise.

People with spinal cord injuries (PwSCI) are at high risk of developing cardiovascular disease (CVD). While regular exercise can reduce risk of CVD, PwSCI face various barriers to exercise, including high rates of upper limb injuries, especially in the shoulder. Handcycling high intensity interval training (HIIT), which consists of periods of high intensity exercise followed by rest, is a potential exercise solution, but the musculoskeletal safety of HIIT is still unknown. In this study, we characterized three-dimensional continuous applied forces at the handle during handcycling HIIT and moderate intensity continuous training (MICT). These applied forces can give an early indication of joint loading, and therefore injury risk, at the shoulder. In all three directions (tangential, radial, and lateral), the maximum applied forces during HIIT were larger than those in MICT at all timepoints, which may indicate higher contact forces and loads on the shoulder during HIIT compared to MICT. The tangential and radial forces peaked twice in a propulsion cycle, while the lateral forces peaked once. Throughout the exercises, the location of tangential peak 2 and radial peak 1 was later in HIIT compared to MICT. This difference in maximum force location could indicate either altered kinematics or muscular fatigue at the end of the exercise protocol. These changes in kinematics should be more closely examined using motion capture or other modeling techniques. If we combine this kinetic data with kinematic data during propulsion, we can create musculoskeletal models that more accurately predict contact forces and injury risk during handcycling HIIT in PwSCI.

Multiple adaptations underly co-option of a CRISPR surveillance complex for RNA-guided DNA transposition.

CRISPR-associated transposons (CASTs) are natural RNA-directed transposition systems. We demonstrate that transposon protein TniQ plays a central role in promoting R-loop formation by RNA-guided DNA-targeting modules. TniQ residues, proximal to CRISPR RNA (crRNA), are required for recognizing different crRNA categories, revealing an unappreciated role of TniQ to direct transposition into different classes of crRNA targets. To investigate adaptations allowing CAST elements to utilize attachment sites inaccessible to CRISPR-Cas surveillance complexes, we compared and contrasted PAM sequence requirements in both I-F3b CAST and I-F1 CRISPR-Cas systems. We identify specific amino acids that enable a wider range of PAM sequences to be accommodated in I-F3b CAST elements compared with I-F1 CRISPR-Cas, enabling CAST elements to access attachment sites as sequences drift and evade host surveillance. Together, this evidence points to the central role of TniQ in facilitating the acquisition of CRISPR effector complexes for RNA-guided DNA transposition.

Widespread CRISPR-derived RNA regulatory elements in CRISPR-Cas systems.

CRISPR-cas loci typically contain CRISPR arrays with unique spacers separating direct repeats. Spacers along with portions of adjacent repeats are transcribed and processed into CRISPR(cr) RNAs that target complementary sequences (protospacers) in mobile genetic elements, resulting in cleavage of the target DNA or RNA. Additional, standalone repeats in some CRISPR-cas loci produce distinct cr-like RNAs implicated in regulatory or other functions. We developed a computational pipeline to systematically predict crRNA-like elements by scanning for standalone repeat sequences that are conserved in closely related CRISPR-cas loci. Numerous crRNA-like elements were detected in diverse CRISPR-Cas systems, mostly, of type I, but also subtype V-A. Standalone repeats often form mini-arrays containing two repeat-like sequence separated by a spacer that is partially complementary to promoter regions of cas genes, in particular cas8, or cargo genes located within CRISPR-Cas loci, such as toxins-antitoxins. We show experimentally that a mini-array from a type I-F1 CRISPR-Cas system functions as a regulatory guide. We also identified mini-arrays in bacteriophages that could abrogate CRISPR immunity by inhibiting effector expression. Thus, recruitment of CRISPR effectors for regulatory functions via spacers with partial complementarity to the target is a common feature of diverse CRISPR-Cas systems.

Widespread CRISPR repeat-like RNA regulatory elements in CRISPR-Cas systems.

CRISPR- cas loci typically contain CRISPR arrays with unique spacers separating direct repeats. Spacers along with portions of adjacent repeats are transcribed and processed into CRISPR(cr) RNAs that target complementary sequences (protospacers) in mobile genetic elements, resulting in cleavage of the target DNA or RNA. Additional, standalone repeats in some CRISPR- cas loci produce distinct cr-like RNAs implicated in regulatory or other functions. We developed a computational pipeline to systematically predict crRNA-like elements by scanning for standalone repeat sequences that are conserved in closely related CRISPR- cas loci. Numerous crRNA-like elements were detected in diverse CRISPR-Cas systems, mostly, of type I, but also subtype V-A. Standalone repeats often form mini-arrays containing two repeat-like sequence separated by a spacer that is partially complementary to promoter regions of cas genes, in particular cas8 , or cargo genes located within CRISPR-Cas loci, such as toxins-antitoxins. We show experimentally that a mini-array from a type I-F1 CRISPR-Cas system functions as a regulatory guide. We also identified mini-arrays in bacteriophages that could abrogate CRISPR immunity by inhibiting effector expression. Thus, recruitment of CRISPR effectors for regulatory functions via spacers with partial complementarity to the target is a common feature of diverse CRISPR-Cas systems.

The influence of gender on shoulder kinematics and head-hip technique during non-level transfers in full-time wheelchair users.

BACKGROUND: Non-level transfers are some of the most demanding tasks for manual wheelchair users. Safely performing these transfer tasks may be needed for maintaining long-term upper limb health. This cross-sectional study aimed to examine the influence of gender on the head-hip technique and lead arm kinematics during multi-height transfers in manual wheelchair users. METHODS: Motion analysis was used to obtain lead-arm shoulder kinematics (flexion/extension and abduction/adduction) and trunk flexion during level, uphill, and floor-to-table transfers in full-time manual wheelchair users. FINDINGS: Twelve male (N = 12) and fifteen female (N = 15) manual wheelchair users with a mean age of 23 ± 5 years and no signs of shoulder pain participated in the study. Lead-arm shoulder flexion and abduction increased as vertical displacement requirements increased during the various transfer tasks (p < 0.01). Women displaced greater trunk flexion during level transfers at approaching significant levels (p = 0.07). During uphill transfers, women displayed significantly greater trunk flexion than men (p < 0.05). INTERPRETATION: Manual wheelchair users use unique kinematic requirements when using the head-hip during level and non-level transfers. Women may be at decreased risk of chronic shoulder pain due to a greater use of the head-hip technique during non-level transfers. Nonetheless, more research that integrates kinetics and strength assessments during non-level transfer biomechanical analyses is needed to better understand technical requirements of non-level transfers in manual wheelchair users.

Discovery and characterization of novel type I-D CRISPR-guided transposons identified among diverse Tn7-like elements in cyanobacteria.

CRISPR-Cas defense systems have been naturally coopted for guide RNA-directed transposition by Tn7 family bacterial transposons. We find cyanobacterial genomes are rich in Tn7-like elements, including most of the known guide RNA-directed transposons, the type V-K, I-B1, and I-B2 CRISPR-Cas based systems. We discovered and characterized an example of a type I-D CRISPR-Cas system which was naturally coopted for guide RNA-directed transposition. Multiple novel adaptations were found specific to the I-D subtype, including natural inactivation of the Cas10 nuclease. The type I-D CRISPR-Cas transposition system showed flexibility in guide RNA length requirements and could be engineered to function with ribozyme-based self-processing guide RNAs removing the requirement for Cas6 in the heterologous system. The type I-D CRISPR-Cas transposon also has naturally fused transposase proteins that are functional for cut-and-paste transposition. Multiple attributes of the type I-D system offer unique possibilities for future work in gene editing. Our bioinformatic analysis also revealed a broader understanding of the evolution of Tn7-like elements. Extensive swapping of targeting systems was identified among Tn7-like elements in cyanobacteria and multiple examples of convergent evolution, including systems targeting integration into genes required for natural transformation.

Motor Cognitive Dual-Task Testing to Predict Future Falls in Multiple Sclerosis: A Systematic Review.

BACKGROUND: Mobility and cognitive impairments are often associated with increased fall risk among people with multiple sclerosis (PwMS). However, evidence on the concurrent assessment of gait or balance and cognitive tasks (dual-task) to predict falls appears to be inconsistent. OBJECTIVE: To summarize the ability of gait or balance dual-task testing to predict future falls among PwMS. METHODS: Seven databases including PubMed, Embase, Web of Science, Scopus, CINHAL, SPORTDiscuss, and PsycINFO were searched from inception to May 2022. Two independent reviewers identified studies that performed a dual-task testing among adults with multiple sclerosis and monitored falls prospectively for at least 3 months. Both reviewers also evaluated the quality assessment of the included studies. RESULTS: Eight studies with 484 participants were included in the review. Most studies (75%) indicated that dual-task testing and dual-task cost did not discriminate prospective fallers (⩾1 fall) and non-fallers (0 fall) and were not found as predictors of future falls. However, dual-task cost of walking velocity (OR = 1.23, 95% CI 0.98-4.45, P = .05) and dual-task of correct response rate of serial 7 subtraction (OR = 1.34, 95% CI 1.04-3.74, P = .02) were significantly associated with increased risk of recurrent falls (≥2 falls). Pattern of cognitive-motor interference was also associated with an increased risk of falling. All studies presented with strong quality. CONCLUSION: The scarce evidence indicates that dual-task testing is not able to predict future falls among PwMS. Further research with more complex motor and cognitive tasks and longer-term fall monitoring is required before dual-task testing can be recommended as a predictor of future falls in this population.

Mechanistic details of CRISPR-associated transposon recruitment and integration revealed by cryo-EM.

CRISPR-associated transposons (CASTs) are Tn7-like elements that are capable of RNA-guided DNA integration. Although structural data are known for nearly all core transposition components, the transposase component, TnsB, remains uncharacterized. Using cryo-electron microscopy (cryo-EM) structure determination, we reveal the conformation of TnsB during transposon integration for the type V-K CAST system from Scytonema hofmanni (ShCAST). Our structure of TnsB is a tetramer, revealing strong mechanistic relationships with the overall architecture of RNaseH transposases/integrases in general, and in particular the MuA transposase from bacteriophage Mu. However, key structural differences in the C-terminal domains indicate that TnsB's tetrameric architecture is stabilized by a different set of protein-protein interactions compared with MuA. We describe the base-specific interactions along the TnsB binding site, which explain how different CAST elements can function on cognate mobile elements independent of one another. We observe that melting of the 5' nontransferred strand of the transposon end is a structural feature stabilized by TnsB and furthermore is crucial for donor-DNA integration. Although not observed in the TnsB strand-transfer complex, the C-terminal end of TnsB serves a crucial role in transposase recruitment to the target site. The C-terminal end of TnsB adopts a short, structured 15-residue "hook" that decorates TnsC filaments. Unlike full-length TnsB, C-terminal fragments do not appear to stimulate filament disassembly using two different assays, suggesting that additional interactions between TnsB and TnsC are required for redistributing TnsC to appropriate targets. The structural information presented here will help guide future work in modifying these important systems as programmable gene integration tools.

SARS-CoV-2 Brain Regional Detection, Histopathology, Gene Expression, and Immunomodulatory Changes in Decedents with COVID-19.

Brains of 42 COVID-19 decedents and 107 non-COVID-19 controls were studied. RT-PCR screening of 16 regions from 20 COVID-19 autopsies found SARS-CoV-2 E gene viral sequences in 7 regions (2.5% of 320 samples), concentrated in 4/20 subjects (20%). Additional screening of olfactory bulb (OB), amygdala (AMY) and entorhinal area for E, N1, N2, RNA-dependent RNA polymerase, and S gene sequences detected one or more of these in OB in 8/21 subjects (38%). It is uncertain whether these RNA sequences represent viable virus. Significant histopathology was limited to 2/42 cases (4.8%), one with a large acute cerebral infarct and one with hemorrhagic encephalitis. Case-control RNAseq in OB and AMY found more than 5000 and 700 differentially expressed genes, respectively, unrelated to RT-PCR results; these involved immune response, neuronal constituents, and olfactory/taste receptor genes. Olfactory marker protein-1 reduction indicated COVID-19-related loss of OB olfactory mucosa afferents. Iba-1-immunoreactive microglia had reduced area fractions in cerebellar cortex and AMY, and cytokine arrays showed generalized downregulation in AMY and upregulation in blood serum in COVID-19 cases. Although OB is a major brain portal for SARS-CoV-2, COVID-19 brain changes are more likely due to blood-borne immune mediators and trans-synaptic gene expression changes arising from OB deafferentation.

Structural basis of transposon end recognition explains central features of Tn7 transposition systems.

Tn7 is a bacterial transposon with relatives containing element-encoded CRISPR-Cas systems mediating RNA-guided transposon insertion. Here, we present the 2.7 Å cryoelectron microscopy structure of prototypic Tn7 transposase TnsB interacting with the transposon end DNA. When TnsB interacts across repeating binding sites, it adopts a beads-on-a-string architecture, where the DNA-binding and catalytic domains are arranged in a tiled and intertwined fashion. The DNA-binding domains form few base-specific contacts leading to a binding preference that requires multiple weakly conserved sites at the appropriate spacing to achieve DNA sequence specificity. TnsB binding imparts differences in the global structure of the protein-bound DNA ends dictated by the spacing or overlap of binding sites explaining functional differences in the left and right ends of the element. We propose a model of the strand-transfer complex in which the terminal TnsB molecule is rearranged so that its catalytic domain is in a position conducive to transposition.