Systematic review and meta-analysis of Chinese coach leadership and athlete satisfaction and cohesion.

Introduction: This meta-analysis investigates the relationship between coach leadership behaviors and athlete satisfaction and group cohesion within the realm of Chinese sports. The study also explores player sex and player classification as potential moderating variables. The primary focus is on evaluating the impact of coaching behaviors, as measured by the Leadership Scale for Sports, on athlete satisfaction and group cohesion. Methods: Standard literature searches from China National Knowledge Infrastructure and Wanfang academic databases produced 26 studies encompassing a total of 319 effect sizes and a participant pool of 7,121 athletes across various sports. Results: Using the Comprehensive Meta-Analysis (CMA) to examine relevant data, results reveal a moderate and positive association between coach leadership and athlete satisfaction (ES = 0.412). Specifically, training and instruction (ES = 0.531), positive feedback (ES = 0.526), social support, and democratic decision-making exhibit positive effects, while autocratic behavior demonstrates a marginal positive effect. Similarly, a moderate positive relationship is identified between coach leadership and overall group cohesion (ES = 0.275), with training and instruction (ES = 0.396), social support (ES = 0.356), positive feedback, and democratic behavior positively influencing cohesion. Conversely, autocratic behavior has a small negative impact on cohesion. Furthermore, female athletes (ES = 0.603) and professional players (ES = 0.544) display stronger positive associations between coach leadership and satisfaction. Conclusion: These findings highlight the significance of diverse coaching behaviors aligned with player characteristics for fostering positive athlete satisfaction and group cohesion within the Chinese sports context, offering valuable guidance to Chinese coaches aiming to enhance their coaching strategies.

Impact of neighborhood context on self-rated health among very old adults living in Germany: a cross-sectional representative study.

BACKGROUND: Increasingly, evidence has shown that different aspects of neighborhood context play a significant role in self-rated health, one of the key health indicators in advanced age. Nevertheless, very old adults are often under represented or excluded from such research. Therefore, the first aim of this study was to examine whether social, socioeconomic, and physical neighborhood context is associated with self-rated health in the very old population of Germany. The second objective was to explore whether the link of socioeconomic and physical neighborhood context with self-rated health is moderated by availability of social resources in neighborhoods. METHODS: Data from the representative survey, "Old Age in Germany" (D80+) were employed. In total, the study sample of D80+ included 10,578 individuals aged 80 years and over. Additionally, the D80+ data were matched with the freely accessible regional dataset of the Federal Institute for Research on Building, Urban Affairs, and Spatial Development. Two self-rated items (place attachment and social cohesion) were used to assess social neighborhood context. Socioeconomic context of neighborhoods was operationalized by German index of socioeconomic deprivation. To evaluate physical context, perceived measures of building conditions and walkability were included. Using the maximum likelihood estimator with robust standard errors, logistic regression models were estimated to analyze the relationship between neighborhood context (social, socioeconomic, and physical context, as well as their interactions) and self-rated health. RESULTS: Including 8,066 participants in the analysis, the findings showed that better condition of residential building, higher walkability, being closely attached to outdoor places, and higher social cohesion were associated with higher chance to report good self-rated health of very old adults. In the adjusted models, the German socioeconomic deprivation index was not related to self-rated health. The effect of socioeconomic and physical neighborhood context on self-rated health did not differ according available neighborhood social resources. CONCLUSIONS: The results indicate that especially more favorable conditions in social and physical neighborhood context are associated with good self-rated health in the very old population of Germany. Further studies should consider multiple aspects of neighborhood context as well as their interplay when examining the neighborhood impact on self-rated health in older populations.

The association between team behaviors and competitive anxiety among team-handball players: the mediating role of achievement goals.

Team sports athletes may encounter significant stress, leading to competitive anxiety. The anxiety levels can be influenced by team behaviors and achievement goals. This study aims to investigate the relationship between team behaviors (i.e., perceptions of controlling coaching behavior and team cohesion) and competitive anxiety, and to examine the mediation effects of achievement goals (i.e., task-oriented and ego-oriented) on the relationship. A total of 298 team-handball players were involved in the study, ages ranging from 16 to 24 years old (M = 18.44, SD = 3.09). A cross-sectional research design was adopted, and structural equation modeling was utilized to analyze path coefficients and mediating effects. Findings indicated that perceptions of controlling coaching behaviors had significant positive predictions for state and somatic anxiety (ß = 0.22, 0.29) and negative predictions for self-confidence (ß = -0.19). Team cohesion had significant negative predictions for state anxiety (ß = -0.31) and positive predictions for self-confidence (ß = 0.58). In addition, ego-oriented goals play a positive mediating role in the relationship between team behaviors and competitive anxiety (ß = 0.03-0.35), while task-oriented goals play a negative mediating role in the relationship between team behaviors and competitive anxiety (ß = -0.18 - -0.03). In conclusion, team behaviors have a significant relationship with competitive anxiety, with achievement goals playing a mediating role among them. Therefore, to alleviate team sports athletes' competitive anxiety, it is recommended to reduce coach control behaviors, enhance team cohesion, and employ psychological training methods (e.g., mindfulness or meditation) to strengthen athletes' task-oriented goals.

Connected communities: Perceived neighborhood social cohesion during adolescence and subsequent health and well-being in young adulthood-An outcome-wide longitudinal approach.

Does higher perceived neighborhood social cohesion in adolescence lead to better health and well-being 10-12 years later? We evaluated this question using data from a large, prospective, and nationally representative sample of US adolescents (Add Health; N = 10,963), and an outcome-wide approach. Across 38 outcomes, perceived neighborhood social cohesion was associated with some: mental health outcomes (i.e., depressive symptoms, suicidal ideation, perceived stress), psychological well-being outcomes (i.e., happiness, optimism), social outcomes (i.e., loneliness, romantic relationship quality, satisfaction with parenting), and civic/prosocial outcomes (i.e., volunteering). However, it was not associated with health behaviors nor physical health outcomes. These results were maintained after robust control for a wide range of potential confounders.

Adapting and testing measures of organizational context in primary care clinics in KwaZulu-Natal, South Africa.

BACKGROUND: Implementation science frameworks situate intervention implementation and sustainment within the context of the implementing organization and system. Aspects of organizational context such as leadership have been defined and measured largely within US health care settings characterized by decentralization and individual autonomy. The relevance of these constructs in other settings may be limited by differences like collectivist orientation, resource constraints, and hierarchical power structures. We aimed to adapt measures of organizational context in South African primary care clinics. METHODS: We convened a panel of South African experts in social science and HIV care delivery and presented implementation domains informed by existing frameworks and prior work in South Africa. Based on panel input, we selected contextual domains and adapted candidate items. We conducted cognitive interviews with 25 providers in KwaZulu-Natal Province to refine measures. We then conducted a cross-sectional survey of 16 clinics with 5-20 providers per clinic (N = 186). We assessed reliability using Cronbach's alpha and calculated interrater agreement (awg) and intraclass correlation coefficient (ICC) at the clinic level. Within clinics with moderate agreement, we calculated correlation of clinic-level measures with each other and with hypothesized predictors - staff continuity and infrastructure - and a clinical outcome, patient retention on antiretroviral therapy. RESULTS: Panelists emphasized contextual factors; we therefore focused on elements of clinic leadership, stress, cohesion, and collective problem solving (critical consciousness). Cognitive interviews confirmed salience of the domains and improved item clarity. After excluding items related to leaders' coordination abilities due to missingness and low agreement, all other scales demonstrated individual-level reliability and at least moderate interrater agreement in most facilities. ICC was low for most leadership measures and moderate for others. Measures tended to correlate within facility, and higher stress was significantly correlated with lower staff continuity. Organizational context was generally more positively rated in facilities that showed consistent agreement. CONCLUSIONS: As theorized, organizational context is important in understanding program implementation within the South African health system. Most adapted measures show good reliability at individual and clinic levels. Additional revision of existing frameworks to suit this context and further testing in high and low performing clinics is warranted.

[Effects of reductive soil disinfestation and organic fertilizer application on microbial community stability in a facility vegetable soil]. / 强还原处理和施用有机肥对设施蔬菜地土壤微生物群落稳定性的影响.

Reductive soil disinfestation (RSD) is an effective method for remediating degraded facility vegetable soils. However, the effectiveness of RSD using green manure as a carbon source in the field has not yet been clarified. We investigated the effects of RSD and organic fertilizer application on soil microbial community composition, diversity, and stability in a degraded facility vegetable soil. There were six treatments, including no fertilization (CK), no fertilization and soil flooded and mulched with plastic film (FF), soil amended with chicken manure (OM), soil amended with chicken manure and flooded and mulched with plastic film (OMR), soil amended with Sesbania cannabina (TF), and soil amended with S. cannabina and flooded and mulched with plastic film (TR). The results showed that the OMR and TR treatments significantly decreased bacterial Chao1 index, altered bacterial and fungal community structure, and increased the relative abundances of Bacillus, Rhodococcus, Clostridium, and Penicillium. The TR treatment significantly reduced the relative abundance of Fusarium. Results of redundancy analysis and Mantel test analysis suggested that soil ammonium nitrogen and dissolved organic carbon contents were the key factors influencing bacterial community composition, and soil pH was the key factor affecting fungal community composition. Results of cohesion analysis showed that the OMR and TR treatments significantly improved bacterial community stability, and that there was no difference between OMR and TR treatments. The TR treatment enhanced fungal community stability, which was significantly higher than the OMR treatment. Therefore, the RSD with green manure as carbon source could be effective remediation practice to improve soil health.

The impact of social cohesion and risk communication on excess mortality due to COVID-19 in 213 countries: a retrospective analysis.

BACKGROUND: Tools for assessing a country's capacity in the face of public health emergencies must be reviewed, as they were not predictive of the COVID-19 pandemic. Social cohesion and risk communication, which are related to trust in government and trust in others, may have influenced adherence to government measures and mortality rates due to COVID-19. OBJECTIVE: To analyse the association between indicators of social cohesion and risk communication and COVID-19 outcomes in 213 countries. RESULTS: Social cohesion and risk communication, in their dimensions (public trust in politicians, trust in others, social safety nets, and equal distribution of resources index), were associated with lower excess mortality due to COVID-19. The number of COVID-19-related disorder events and government transparency were associated with higher excess mortality due to COVID-19. The lower the percentage of unemployed people, the higher the excess mortality due to COVID-19. Most of the social cohesion and risk communication variables were associated with better vaccination indicators, except for social capital and engaged society, which had no statistically significant association. The greater the gender equality, the better the vaccination indicators, such as the number of people who received all doses. CONCLUSION: Public trust in politicians, trust in others, equal distribution of resources and government that cares about the most vulnerable, starting with the implementation of programs, such as cash transfers and combating food insecurity, were factors that reduced the excess mortality due to COVID-19. Countries, especially those with limited resources and marked by social, economic, and health inequalities, must invest in strengthening social cohesion and risk communication, which are robust strategies to better cope with future pandemics.

Prediction of the Cohesion Energy, Shear Modulus and Hardness of Single-Phase Metals and High-Entropy Alloys.

In order to facilitate the prediction of some physical properties, we propose several simple formulas based on two parameters only, the metallic valence and metallic atomic radii. Knowing the composition, for single-phase alloys, the average parameters can be calculated by the rule of mixture. The input parameters can be obtained from tabulated databases. Adopting from the literature the results of Coulomb crystal model for metals and single-phase high-entropy alloys, we have derived formulas for the shear modulus (G) and the cohesion energy (Ecoh). Based on these parameters separately, we set up two formulas to estimate the hardness in the case of pure metals. For single-phase (solid-solution) HEAs, by simplifying the Maresca and Curtin model, we obtained a formula for estimating the hardness, which takes into account the atomic misfit in addition to G. The maximal hardness for single-phase HEA is approximately 600 kg/mm2 and is obtained for a composition with a valence electron concentration of approximately 6 ÷ 7.

Safety climate and seat belt use in the fire service.

OBJECTIVE: Motor vehicle incidents or apparatus crashes are a leading cause of firefighter fatalities in the United States. Nonuse of seat belts has been linked to some of these fatalities. This research seeks to understand the relationship between safety climate and seat belt use among firefighters, as findings will provide insights into factors that may bolster seat belt use and protect firefighters. METHODS: Data were collected from 208 career firefighters working for a city fire department in the southeastern United States. Structural equation modeling was used to test a hypothesized model and to assess the relationships between organizational safety climate, work group safety climate and seat belt use. RESULTS: It was determined that positive perceptions of workgroup safety climate, as a higher order factor, comprised of supervisor support, horizontal cohesion, and vertical cohesion, was positively associated with seat belt use within a sample of firefighters. Organizational level safety climate did not have a significant relationship with seat belt use but did positively influence workgroup safety climate perceptions. CONCLUSIONS: Safety climate has been associated with safety compliance and participation behaviors, but more research was needed to specifically examine the impact of safety climate on seat belt use in firefighters. The findings point to the importance of safety climate as a leading indicator and predictor of seat belt use. Bolstering safety climate through safety programs, commitment to safety, effective communication, supportive supervisors and cohesion should ultimately aid in bolstering seat belt use among firefighters, which is important to curtailing firefighter injuries and fatalities.

Pregnant Women's Dyadic Coping and Associated Factors: A Cross-Sectional Study Utilizing Latent Profile Analysis.

Background: The problem of maternal mental health is a priority issue of global concern. Dyadic coping refers to the co-managing and making decisions between two parties in response to a joint stressful event. At present, china has limited focus on dyadic coping for pregnant women during pregnancy. This study aimed to investigate different categories and characteristics of dyadic coping in pregnant women throughout pregnancy and to analyze the factors that influence these categories. Methods: This study was a cross-sectional, and 376 pregnant women who visited the obstetric clinic at a tertiary hospital in Sichuan province from June to September 2023 were interviewed face-to-face using convenience sampling. Data were collected using a sociodemographic questionnaire, dyadic coping scale, and family adaptability and cohesion evaluation scale. The data were imported into excel and exported to spss 27.0 to analyze the potential characteristics of pregnant women's dyadic coping during pregnancy and to explore the effects of this using univariate analysis and multifactorial logistic regression. Results: A total of 376 valid questionnaires were collected. The results of the potential profile analysis showed that the dyadic coping of pregnant women during pregnancy could be categorized into three different groups: the "low coping group" (21.3%), the "general coping group" (67.5%), and the "high coping group" (11.2%). Multiple logistic regression analyses revealed that low monthly family income, early pregnancy, primipara, family adaptability and cohesion were the factors influencing the dyadic coping of pregnant women during pregnancy. Conclusion: During pregnancy, pregnant women exhibit moderate levels of dyadic coping. Three different categories of dyadic coping patterns were exhibited: low coping group, general coping group, and high coping group, with significant heterogeneity. Therefore, there is a need to focus on the dyadic coping status of various categories of pregnant women and implement targeted couple and family-wide interventions.

Sexual Debut in Early Adolescence and Individual, School, and Neighborhood Social Capital.

PURPOSE: Sexual debut in early adolescence is associated with poor health outcomes in adulthood. We examined the associations of social capital within families, schools, and neighborhoods with early sexual debut. METHODS: Using data from the Healthy Passages cohort, a longitudinal multilevel study of adolescents, we performed a series of cross-classified multilevel logistic regression models to examine (1) the relative contribution of schools and neighborhoods to the variance and (2) the association of markers of social cohesion/social capital in families, schools, and neighborhoods with sexual debut by 10th grade. RESULTS: There were 4,001 youth participants nested in 115 schools and 751 neighborhoods, with a high degree of cross-classification (1,340 unique combinations of school and neighborhoods). In models adjusting for individual demographics, neighborhoods contributed more to the variance (log odds U [95% confidence interval {CI}] [intra class correlation {ICC}%]) in sexual debut than schools: Uneighborhoods = 0.11 (0.02, 0.23) [3.2%] versus Uschools = 0.07 (0.01, 0.16) [2%]. Restriction of dating and family cohesion, markers of family social capital, were associated with reduced odds of sexual debut by 10th grade (odds ratio = 0.45 95% CI: 0.41-0.49 and 0.93, 95% CI: 0.86, 1.00). Neighborhood cohesion and education level were associated with early debut. Although reduced, there remained significant, unexplained variance in both the school and neighborhood level in the fully adjusted model (Uschool = 0.08 [0.01, 0.17] [2.3%], Uneighborhood = 0.08 [0.02, 0.17] [2.2%]). DISCUSSION: Markers of social capital at the family and neighborhood levels were associated with sexual debut by 10th grade. Developers of public health programs aiming to delay sexual debut should consider family-focused and neighborhood-focused interventions.

The role of unit cohesion and perceived resilience in substance use disorder.

Soldiers have high rates of substance use disorders (SUD), often in the aftermath of stressors experienced during military deployments. There are several factors that protect against SUD. For example, individual factors like perceived resilience and group factors such as unit cohesion may make someone less likely to abuse substances. However, there is little research on the differential influence of these resilience factors on SUD over and above deployment stressors. In this study, we examined the relative effects of perceived resilience, unit cohesion, and deployment stressors on SUD in a sample of 21,449 active duty and reserve soldiers from the U.S. Army (primarily White and male, mean age = 28.66, SD = 7.41) using structural equation modeling. We found that unit cohesion (ß = -.17) and perceived resilience (ß = -.16) had negative effects on SUD over and above deployment stressors. The study findings clarify research on resilience to SUD and have implications for addressing substance use in the military, specifically regarding the importance of building unit cohesion.

Social cohesion among healthcare workers during COVID-19: Qualitative research in Indonesia, Nepal, and Vietnam.

Existing literature has portrayed numerous challenges that healthcare workers (HCWs) faced during the COVID-19 pandemic, such as heightened risks of transmission against the scarcity of protective equipment, burgeoning workload, and emotional distress, to name a few. However, most studies explored HCWs' experiences at the individual level rather than examining the collective responses. Exploring these experiences could reveal the social-cultural locality of the pandemic while identifying the system constraints in public health emergencies. As part of a mixed-method study on COVID-19 pandemic impacts, we analysed qualitative interview data with 129 HCWs and health-related staff to explore their experiences during the pandemic between 2020 and 2021 in Vietnam, Indonesia, and Nepal. Using Bahers' sociological framework, Community of Fate, we describe five themes reflecting the formation of a community of HCWs and the social cohesion underlying their efforts to survive hardship. The first three themes characterise the HCW community of fate, including (1) Recognition of extreme work-related danger, (2) physical and figurative closures where HCWs restrict themselves from the outside world, (3) chronic ordeals with overwhelming workload and responsibilities, encompassing recurrent mental health challenges. Against such extreme hardship, cohesive bonding and social resilience are reflected through two additional themes: (4) a mutual sense of moral and professional duty to protect communities, (5) the vertical and horizontal convergence among HCWs across levels and among government departments. We discuss these HCWs' challenges in relation to systemic vulnerabilities while advocating for increasing investment in public health and collaboration across government sectors to prepare for emergency situations.

Three-dimensional chromatin mapping of sensory neurons reveals that cohesin-dependent genomic domains are required for axonal regeneration.

The in vivo three-dimensional genomic architecture of adult mature neurons at homeostasis and after medically relevant perturbations such as axonal injury remains elusive. Here we address this knowledge gap by mapping the three-dimensional chromatin architecture and gene expression programme at homeostasis and after sciatic nerve injury in wild-type and cohesin-deficient mouse sensory dorsal root ganglia neurons via combinatorial Hi-C and RNA-seq. We find that cohesin is required for the full induction of the regenerative transcriptional program, by organising 3D genomic domains required for the activation of regenerative genes. Importantly, loss of cohesin results in disruption of chromatin architecture at regenerative genes and severely impaired nerve regeneration. Together, these data provide an original three-dimensional chromatin map of adult sensory neurons in vivo and demonstrate a role for cohesin-dependent chromatin interactions in neuronal regeneration.

Cadmium contamination decreased bacterial network complexity and stability in coastal reclamation areas.

Cadmium(Cd) contamination can exert significantly adverse effects on soil microbiota in reclaimed areas, however, its effects on bacterial network structure are still limitedly understood. Here we collected soil samples from typical reclaimed wetlands (RW) and ditch wetlands (DW) in coastal reclamation areas and examined the effects of Cd contamination on the bacterial network complexity and stability. The results showed that the bacterial networks were destabilized by the Cd contamination, while bacteria in DW soils showed robust invulnerability characterized by higher node constancy and compositional stability compared with RW soils. Soil bacteria resisted Cd stress by forming a network with intensive connections in the module but sparser connections among the modules. Especially, network modularity was higher in DW soils than in RW soils, but made it more vulnerable to nodes removal. In addition, Cd contamination promoted bacterial positive cohesion but decreased negative cohesion in RW soils. Flavobacteriaceae, Xanthomonadaceae, and Alcaligenaceae were identified as core phylotypes, which played pivotal roles in regulating interspecies interactions due to higher contributions to cohesion and significant correlations with soil nutrients. The findings of this work indicate the changes of bacterial network structure and the indispensable role of core phylotypes in regulating interactions and maintaining network sustainability under Cd contamination.

The influence of nativity/birthplace, neighborhood cohesion, and duration lived in the neighborhood on psychological distress.

Introduction: Nativity/birthplace and neighborhood cohesion are potential contributing factors to psychological distress. This study explores the impact of nativity/birthplace and neighborhood cohesion on moderate-severe psychological distress among United States (US) adults, considering the duration lived in a neighborhood. Methods: Using the 2013-2018 National Health Interview Survey data, we conducted a stratified analysis based on years lived in the neighborhood (≤10 years [n = 96,175] and >10 years [n = 68,187]). Bivariate chi-square tests and multivariable logistic regression models were used to assess the statistical differences and associations between moderate-severe psychological distress and nativity/birthplace, and neighborhood cohesion, while adjusting for other covariates. Results: Individuals with 10 years or less of residence reported higher levels of moderate-severe psychological distress than those with more than 10 years (22.3 % vs. 18.1 %). Low or medium neighborhood cohesion, regardless of duration of residence, was associated with significantly higher odds of moderate-severe psychological distress compared to high cohesion. Foreign-born individuals had higher odds of psychological distress after more than 10 years in a neighborhood, although this difference was not statistically significant. However, they had lower odds of psychological distress after 10 years or less in the neighborhood compared to US-born individuals. Similarly, the interaction of foreign-born status and 10 years or less of residence in a neighborhood showed decreased odds of psychological distress. Conclusions: These findings underscore the importance of strong social cohesion in neighborhoods for positive mental well-being. Establishing community initiatives to enhance neighborhood social cohesion is crucial.

An RNAi screen to identify proteins required for cohesion rejuvenation during meiotic prophase in Drosophila oocytes.

Accurate chromosome segregation during meiosis requires maintenance of sister chromatid cohesion, initially established during premeiotic S phase. In human oocytes, DNA replication and cohesion establishment occur decades before chromosome segregation and deterioration of meiotic cohesion is one factor that leads to increased segregation errors as women age. Our previous work led us to propose that a cohesion rejuvenation program operates to establish new cohesive linkages during meiotic prophase in Drosophila oocytes and depends on the cohesin loader Nipped-B and the cohesion establishment factor Eco. In support of this model, we recently demonstrated that chromosome-associated cohesin turns over extensively during meiotic prophase and failure to load cohesin onto chromosomes after premeiotic S phase results in arm cohesion defects in Drosophila oocytes. To identify proteins required for prophase cohesion rejuvenation but not S phase establishment, we conducted a Gal4-UAS inducible RNAi screen that utilized two distinct germline drivers. Using this strategy, we identified 29 gene products for which hairpin expression during meiotic prophase, but not premeiotic S phase, significantly increased segregation errors. Prophase knockdown of Brahma or Pumilio, two positives with functional links to the cohesin loader, caused a significant elevation in the missegregation of recombinant homologs, a phenotype consistent with premature loss of arm cohesion. Moreover, fluorescence in situ hybridization confirmed that Brahma, Pumilio and Nipped-B are required during meiotic prophase for maintenance of arm cohesion. Our data support the model that Brahma and Pumilio regulate Nipped-B dependent cohesin loading during rejuvenation. Future analyses will better define the mechanism(s) that govern meiotic cohesion rejuvenation and whether additional prophase-specific positives function in this process.

Short-term impact of a combination intervention on family cohesion: Results from a pilot cluster-randomized clinical trial in Northern Ghana.

Child labor remains a concern in sub-Saharan Africa. Yet, evidence-based preventive efforts are limited. We analyzed longitudinal data from Ghanaian adolescent girls in a pilot randomized clinical trial testing the preliminary impact of a combination intervention on family cohesion as a protective factor against child labor and school dropout. While there was no statistical difference between the control and intervention groups at 9 months, the results show that family cohesion scores improved significantly from baseline to 9 months for the ANZANSI intervention group. Qualitative results indicated improved family cohesion in the intervention group. Hence, future studies should further examine this promising social work intervention.

Chromatin-associated cohesin turns over extensively and forms new cohesive linkages in Drosophila oocytes during meiotic prophase.

In dividing cells, accurate chromosome segregation depends on sister chromatid cohesion, protein linkages that are established during DNA replication. Faithful chromosome segregation in oocytes requires that cohesion, first established in S phase, remain intact for days to decades, depending on the organism. Premature loss of meiotic cohesion in oocytes leads to the production of aneuploid gametes and contributes to the increased incidence of meiotic segregation errors as women age (maternal age effect). The prevailing model is that cohesive linkages do not turn over in mammalian oocytes. However, we have previously reported that cohesion-related defects arise in Drosophila oocytes when individual cohesin subunits or cohesin regulators are knocked down after meiotic S phase. Here, we use two strategies to express a tagged cohesin subunit exclusively during mid-prophase in Drosophila oocytes and demonstrate that newly expressed cohesin is used to form de novo linkages after meiotic S phase. Cohesin along the arms of oocyte chromosomes appears to completely turn over within a 2-day window during prophase, whereas replacement is less extensive at centromeres. Unlike S-phase cohesion establishment, the formation of new cohesive linkages during meiotic prophase does not require acetylation of conserved lysines within the Smc3 head. Our findings indicate that maintenance of cohesion between S phase and chromosome segregation in Drosophila oocytes requires an active cohesion rejuvenation program that generates new cohesive linkages during meiotic prophase.

Cohesin Complex: Structure and Principles of Interaction with DNA.

Accurate duplication and separation of long linear genomic DNA molecules is associated with a number of purely mechanical problems. SMC complexes are key components of the cellular machinery that ensures decatenation of sister chromosomes and compaction of genomic DNA during division. Cohesin, one of the essential eukaryotic SMC complexes, has a typical ring structure with intersubunit pore through which DNA molecules can be threaded. Capacity of cohesin for such topological entrapment of DNA is crucial for the phenomenon of post-replicative association of sister chromatids better known as cohesion. Recently, it became apparent that cohesin and other SMC complexes are, in fact, motor proteins with a very peculiar movement pattern leading to formation of DNA loops. This specific process has been called loop extrusion. Extrusion underlies multiple functions of cohesin beyond cohesion, but molecular mechanism of the process remains a mystery. In this review, we summarized the data on molecular architecture of cohesin, effect of ATP hydrolysis cycle on this architecture, and known modes of cohesin-DNA interactions. Many of the seemingly disparate facts presented here will probably be incorporated in a unified mechanistic model of loop extrusion in the not-so-distant future.