Unraveling the structure of DNA during overstretching by using multicolor, single-molecule fluorescence imaging.

Single-molecule manipulation studies have revealed that double-stranded DNA undergoes a structural transition when subjected to tension. At forces that depend on the attachment geometry of the DNA (65 pN or 110 pN), it elongates ≈1.7-fold and its elastic properties change dramatically. The nature of this overstretched DNA has been under debate. In one model, the DNA cooperatively unwinds, while base pairing remains intact. In a competing model, the hydrogen bonds between base pairs break and two single DNA strands are formed, comparable to thermal DNA melting. Here, we resolve the structural basis of DNA overstretching using a combination of fluorescence microscopy, optical tweezers, and microfluidics. In DNA molecules undergoing the transition, we visualize double- and single-stranded segments using specific fluorescent labels. Our data directly demonstrate that overstretching comprises a gradual conversion from double-stranded to single-stranded DNA, irrespective of the attachment geometry. We found that these conversions favorably initiate from nicks or free DNA ends. These discontinuities in the phosphodiester backbone serve as energetically favorable nucleation points for melting. When both DNA strands are intact and no nicks or free ends are present, the overstretching force increases from 65 to 110 pN and melting initiates throughout the molecule, comparable to thermal melting. These results provide unique insights in the thermodynamics of DNA and DNA-protein interactions

Association between pre-treatment IQ and educational achievement after gender-affirming treatment including puberty suppression in transgender adolescents

Background: Concerns exist regarding effects of puberty suppression on neurodevelopment. Intelligence is strongly correlated with educational achievement in the general population. This study aimed to examine the association between pre-treatment intelligence and educational achievement after gender-affirming treatment including puberty suppression in transgender adolescents to contribute to the emerging understanding of the effect that gender-affirming treatment including puberty suppression may have on cognitive development. Methods: IQ was measured in 72 adolescents (45 trans boys, 27 trans girls) at clinical entry (mean age 12.78 years), educational achievement was evaluated after gender-affirming treatment (mean age 20.40 years). Results: IQ pre-treatment and educational achievement post-treatment were positively associated (Nagelkerke R = 0.71). Discussion: The association between IQ pre-treatment and educational achievement post-treatment in transgender adolescents who received gender-affirming medical treatment including puberty suppression appears to be similar to the general population. This may reflect that gender-affirming medical treatment including puberty suppression does not negatively affect the association between IQ and educational achievement

Impact of the COVID-19 pandemic on children and adolescents with autism spectrum disorder and their families: a mixed-methods study protocol

Background The COVID-19 pandemic is a challenge for everyone, particularly for children and adolescents with autism spectrum disorder (ASD). ASD is a developmental disorder characterised by limitations in social communication, repetitive behavioural patterns, and limited interests, and activities. It is expected that many families with children with ASD will experience more problems due to the COVID-19 pandemic and the related public health restrictions. At the same time, some may experience improved functioning, due to fewer expectations and social demands. Methods/design In a mixed-method study to identify the impact of the COVID-19 pandemic, parents of children with ASD (ages 4-21) who were in care pre-COVID-19 at one of three large mental healthcare institutions in the region of Rotterdam participated (68 for T0, 57 for T1). The aims are (1) to investigate the impact of the COVID-19 pandemic on overall functioning and autistic symptoms of the child/adolescent with ASD, as well as parental and family functioning (QUANT-QUAL), in both the short term and longer term, and (2) to investigate risk and protective factors (in light of resilience) (QUANT-qual) and (3) to investigate care and informational needs (QUAL-quant). Pre-COVID-19 baseline data will be retrieved from clinical records. Participants will fill out two surveys (one during a COVID-19 peak-January-May 2021-and one thereafter). Survey participants were invited to participate in interviews (n=27). Surveys include measures thar were included pre-COVID-19 (ie, overall functioning and autism symptoms) as well as specific measures to identify family functioning and COVID-19 impact. The semistructured interviews focus on child, parent and family functioning and care-and informational needs. Ethics and dissemination The Medical Ethics Committee of the Erasmus MC has approved the study. Findings will be available to families of children with ASD, their care providers, the funders, autism societies, the government and other researchers.New methods for child psychiatric diagnosis and treatment outcome evaluatio

Impact of the COVID-19 pandemic on children and adolescents with autism spectrum disorder and their families: a mixed-methods study protocol

Background The COVID-19 pandemic is a challenge for everyone, particularly for children and adolescents with autism spectrum disorder (ASD). ASD is a developmental disorder characterised by limitations in social communication, repetitive behavioural patterns, and limited interests, and activities. It is expected that many families with children with ASD will experience more problems due to the COVID-19 pandemic and the related public health restrictions. At the same time, some may experience improved functioning, due to fewer expectations and social demands. Methods/design In a mixed-method study to identify the impact of the COVID-19 pandemic, parents of children with ASD (ages 4-21) who were in care pre-COVID-19 at one of three large mental healthcare institutions in the region of Rotterdam participated (68 for T0, 57 for T1). The aims are (1) to investigate the impact of the COVID-19 pandemic on overall functioning and autistic symptoms of the child/adolescent with ASD, as well as parental and family functioning (QUANT-QUAL), in both the short term and longer term, and (2) to investigate risk and protective factors (in light of resilience) (QUANT-qual) and (3) to investigate care and informational needs (QUAL-quant). Pre-COVID-19 baseline data will be retrieved from clinical records. Participants will fill out two surveys (one during a COVID-19 peak-January-May 2021-and one thereafter). Survey participants were invited to participate in interviews (n=27). Surveys include measures thar were included pre-COVID-19 (ie, overall functioning and autism symptoms) as well as specific measures to identify family functioning and COVID-19 impact. The semistructured interviews focus on child, parent and family functioning and care-and informational needs. Ethics and dissemination The Medical Ethics Committee of the Erasmus MC has approved the study. Findings will be available to families of children with ASD, their care providers, the funders, autism societies, the government and other researchers

Muscle ankyrin repeat protein 1 (MARP1) locks titin to the sarcomeric thin filament and is a passive force regulator

Muscle ankyrin repeat protein 1 (MARP1) is frequently up-regulated in stressed muscle, but its effect on skeletal muscle function is poorly understood. Here, we focused on its interaction with the titin-N2A element, found in titin's molecular spring region. We show that MARP1 binds to F-actin, and that this interaction is stronger when MARP1 forms a complex with titin-N2A. Mechanics and super-resolution microscopy revealed that MARP1 "locks" titin-N2A to the sarcomeric thin filament, causing increased extension of titin's elastic PEVK element and, importantly, increased passive force. In support of this mechanism, removal of thin filaments abolished the effect of MARP1 on passive force. The clinical relevance of this mechanism was established in diaphragm myofibers of mechanically ventilated rats and of critically ill patients. Thus, MARP1 regulates passive force by locking titin to the thin filament. We propose that in stressed muscle, this mechanism protects the sarcomere from mechanical damage. © 2021 van der Pijl et al.Open access articleThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Diaphragm fiber strength is reduced in critically ill patients and restored by a troponin activator

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Positive End-expiratory Pressure Ventilation Induces Longitudinal Atrophy in Diaphragm Fibers

RATIONALE: Diaphragm weakness in critically ill patients prolongs ventilator dependency and duration of hospital stay, and increases mortality and health care costs. The mechanisms underlying diaphragm weakness include cross-sectional fiber atrophy and contractile protein dysfunction, but whether additional mechanisms are at play is unknown. OBJECTIVES: To test the hypothesis that mechanical ventilation with positive end-expiratory pressure (PEEP) induces longitudinal atrophy by displacing the diaphragm in caudal direction and reducing the length of fibers. METHODS: We studied structure and function of diaphragm fibers of mechanically ventilated critically ill patients, and mechanically ventilated rats with normal and increased titin compliance. MEASUREMENTS AND MAIN RESULTS: (1) PEEP causes a caudal movement of the diaphragm, both in critically ill patients and in rats, and this caudal movement reduces fiber length; (2) diaphragm fibers of 18h mechanically ventilated rats (PEEP: 2.5 cmH2O) adapt to the reduced length by absorbing serially-linked sarcomeres, the smallest contractile units in muscle (i.e. longitudinal atrophy); (3) increasing the compliance of titin molecules reduces longitudinal atrophy. CONCLUSION: Mechanical ventilation with PEEP results in longitudinal atrophy of diaphragm fibers, a response which is modulated by the elasticity of the giant sarcomeric protein titin. We postulate that longitudinal atrophy, in concert with the aforementioned cross-sectional atrophy, hampers spontaneous breathing trials in critically ill patients: during these efforts end-expiratory lung volume is reduced, and the shortened diaphragm fibers are stretched to excessive sarcomere lengths. At these lengths, muscle fibers generate less force and diaphragm weakness ensues