Age-related decline in white matter integrity in a mouse model of tauopathy: an in vivo diffusion tensor magnetic resonance imaging study

Elevated expression of human hyperphosphorylated tau is associated with neuronal loss and white matter (WM) pathology in Alzheimer's disease (AD) and related neurodegenerative disorders. Using in vivo diffusion tensor magnetic resonance imaging (DT-MRI) at 11.1 Tesla we measured age-related alterations in WM diffusion anisotropy indices in a mouse model of human tauopathy (rTg4510) and nontransgenic (nonTg) control mice at the age of 2.5, 4.5, and 8 months. Similar to previous DT-MRI studies in AD subjects, 8-month-old rTg4510 mice showed lower fractional anisotropy (FA) values in WM structures than nonTg. The low WM FA in rTg4510 mice was observed in the genu and splenium of the corpus callosum, anterior commissure, fimbria, and internal capsule and was associated with a higher radial diffusivity than nonTg. Interestingly, rTg4510 mice showed lower estimates for the mode of anisotropy than controls at 2.5 months suggesting that changes in this diffusivity metric are detectable at an early stage preceding severe tauopathy. Immunogold electron microscopy partly supports our diffusion tensor imaging findings. At the age of 4 months, rTg4510 mice show axonal tau inclusions and unmyelinated processes. At later ages (12 months and 14 months) we observed inclusions in myelin sheath, axons, and unmyelinated processes, and a “disorganized” pattern of myelinated fiber arrangement with enlarged inter-axonal spaces in rTg4510 but not in nonTg mice. Our data support a role for the progression of tau pathology in reduced WM integrity measured by DT-MRI. Further in vivo DT-MRI studies in the rTg4510 mouse should help better discern the detailed mechanisms of reduced FA and anisotropy mode, and the specific role of tau during neurodegeneration.     

A Lifecycle Approach to HIV Prevention in African Women and Children

Effective biomedical and structural HIV prevention approaches are being implemented throughout sub-Saharan Africa. A “lifecycle approach” to HIV prevention recognizes the interconnectedness of the health of women, children and adolescents, and prioritizes interventions that have benefits across these populations. We review new biomedical prevention strategies for women, adolescents and children, structural prevention approaches, and new modalities for eliminating infant HIV infection, and discuss the implications of a lifecycle approach for the success of these methods. Some examples of the lifecycle approach include evaluating education and HIV prevention strategies among adolescent girls not only for their role in reducing risk of HIV infection and early pregnancy, but also to promote healthy adolescents who will have healthier future children. Similarly, early childhood interventions such as exclusive breastfeeding not only prevent HIV, but also contribute to better child and adolescent health outcomes. The most ambitious biomedical infant HIV prevention effort, Option B+, also represents a lifecycle approach by leveraging the prevention benefits of optimal HIV treatment for mothers; maternal survival benefits from Option B+ may have ultimately more health impact on children than the prevention of infant HIV in isolation. The potential for synergistic and additive benefits of lifecycle interventions should be considered when scaling up HIV prevention efforts in sub-Saharan Africa.     

Action research: A mechanism for active engagement of clinical nurses in a program of research

This study aimed to explore the outcomes of active participation in an action research project on building the research capacity of clinical nurses. In this qualitative research study, six registered nurses volunteered to participate in the action research team. None of the nurses reported having any prior research experience. This study was part of a larger three‐phase project. The nurses were required to reflect on the data about their medication practice of phase 1, develop and implement a bundle of interventions in phase 2 to improve medication safety, and evaluate the effectiveness of these interventions in phase 3. We report the nurses' participation in Action Research during phase 2. Meeting minutes and six semistructured interviews were thematically analyzed. The results showed that after receiving support to enhance their research skills from the research team, the nurses were empowered to perform and lead clinical nursing research project. Nurses were able to take ownership of the research process and outcomes and were then able to translate their new research knowledge and skills into their clinical practice by building their own research capacity.     

A tool for translating polygenic scores onto the absolute scale using summary statistics

There is growing interest in the clinical application of polygenic scores as their predictive utility increases for a range of health-related phenotypes. However, providing polygenic score predictions on the absolute scale is an important step for their safe interpretation. We have developed a method to convert polygenic scores to the absolute scale for binary and normally distributed phenotypes. This method uses summary statistics, requiring only the area-under-the-ROC curve (AUC) or variance explained (R²) by the polygenic score, and the prevalence of binary phenotypes, or mean and standard deviation of normally distributed phenotypes. Polygenic scores are converted using normal distribution theory. We also evaluate methods for estimating polygenic score AUC/R² from genome-wide association study (GWAS) summary statistics alone. We validate the absolute risk conversion and AUC/R² estimation using data for eight binary and three continuous phenotypes in the UK Biobank sample. When the AUC/R² of the polygenic score is known, the observed and estimated absolute values were highly concordant. Estimates of AUC/R² from the lassosum pseudovalidation method were most similar to the observed AUC/R² values, though estimated values deviated substantially from the observed for autoimmune disorders. This study enables accurate interpretation of polygenic scores using only summary statistics, providing a useful tool for educational and clinical purposes. Furthermore, we have created interactive webtools implementing the conversion to the absolute (https://opain.github.io/GenoPred/PRS_to_Abs_tool.html). Several further barriers must be addressed before clinical implementation of polygenic scores, such as ensuring target individuals are well represented by the GWAS sample.Subject terms: Personalized medicine, Medical genomics