Comparative analytical performance of multiple plasma Aβ42 and Aβ40 assays and their ability to predict positron emission tomography amyloid positivity

INTRODUCTION: This report details the approach taken to providing a dataset allowing for analyses on the performance of recently developed assays of amyloid beta (Aβ) peptides in plasma and the extent to which they improve the prediction of amyloid positivity. METHODS: Alzheimer's Disease Neuroimaging Initiative plasma samples with corresponding amyloid positron emission tomography (PET) data were run on six plasma Aβ assays. Statistical tests were performed to determine whether the plasma Aβ measures significantly improved the area under the receiver operating characteristic curve for predicting amyloid PET status compared to age and apolipoprotein E (APOE) genotype. RESULTS: The age and APOE genotype model predicted amyloid status with an area under the curve (AUC) of 0.75. Three assays improved AUCs to 0.81, 0.81, and 0.84 (P < .05, uncorrected for multiple comparisons). DISCUSSION: Measurement of Aβ in plasma contributes to addressing the amyloid component of the ATN (amyloid/tau/neurodegeneration) framework and could be a first step before or in place of a PET or cerebrospinal fluid screening study. HIGHLIGHTS: The Foundation of the National Institutes of Health Biomarkers Consortium evaluated six plasma amyloid beta (Aβ) assays using Alzheimer's Disease Neuroimaging Initiative samples. Three assays improved prediction of amyloid status over age and apolipoprotein E (APOE) genotype. Plasma Aβ42/40 predicted amyloid positron emission tomography status better than Aβ42 or Aβ40 alone

Molecular basis for ion current heterogeneity in normal and diseased hearts

Cardiac action potential characteristics are known to vary in different species, but also in the different regions of the heart within a given species and in cardiovascular disease. The heterologous expression of voltage-gated ion currents is believed to underlie these differences. The purpose of this thesis is to elucidate the molecular mechanisms which may underlie some of the observed current changes in different species, as well as regions and diseases of the heart.Here, we describe the variable dependence on repolarizing K+ currents in different species as being the result of the lack of Ito subunits in guinea pig heart with a greater expression of IK subunits, while rabbits express all hypothesized Ito subunits, but express IK subunits at low levels. Humans are found to lie in between these two species in terms of the expression of these voltage-gated K+ channel subunits. The specialized function of certain regions of the heart, such as the ventricles and the SAN, have been attributed to the heterologous expression of Ito and the pacemaker current (I f) respectively. Here were demonstrate that both Kv4.3 and KchIP2 gradients underlie an observed Ito transmural gradient and contribute to the dispersion of repolarization, while a greater expression of HCN2 and HCN4 subunits in the SAN compared to the right atrium account for the larger I f current in this region. Cardiovascular diseases such as congestive heart failure (CHF) have been associated with ion channel remodelling. Here, we report the finding of changes in Nav1.5, Kv4.3, HCN2 and HCN4 expression which may underlie some of the electrophysiological changes associated with this disease. Furthermore, we characterise a genetic polymorphism which is associated with another disease, atrial fibrillation.The heterologous expression of voltage-gated ion channel subunits may account for many of the species-, region- and disease-specific differences which have been observed in the heart. Such heterogeneity contributes to the proper functioning of the heart under normal conditions, but may also contribute to the pathogenesis of cardiovascular disease

Endothelial FAK is required for tumour angiogenesis

Focal adhesion kinase (FAK) is a cytoplasmic tyrosine kinase that plays a fundamental role in integrin and growth factor mediated signalling and is an important player in cell migration and proliferation, processes vital for angiogenesis. However, the role of FAK in adult pathological angiogenesis is unknown. We have generated endothelial-specific tamoxifen-inducible FAK knockout mice by crossing FAK-floxed (FAKfl/fl) mice with the platelet derived growth factor b (Pdgfb)-iCreER mice. Tamoxifen-treatment of Pdgfb-iCreER;FAKfl/fl mice results in FAK deletion in adult endothelial cells (ECs) without any adverse effects. Importantly however, endothelial FAK-deletion in adult mice inhibited tumour growth and reduced tumour angiogenesis. Furthermore, in in vivo angiogenic assays FAK deletion impairs vascular endothelial growth factor (VEGF)-induced neovascularization. In addition, in vitro deletion of FAK in ECs resulted in reduced VEGF-stimulated Akt phosphorylation and correlating reduced cellular proliferation as well as increased cell death. Our data suggest that FAK is required for adult pathological angiogenesis and validates FAK as a possible target for anti-angiogenic therapies

Investigation of genetic determinants of cognitive change in later life

Cognitive decline is a major health concern and identification of genes that may serve as drug targets to slow decline is important to adequately support an aging population. Whilst genetic studies of cross-sectional cognition have been carried out, cognitive change is less well-understood. Here, using data from the TOMMORROW trial, we investigate genetic associations with cognitive change in a cognitively normal older cohort. We conducted a genome-wide association study of trajectories of repeated cognitive measures (using generalised estimating equation (GEE) modelling) and tested associations with polygenic risk scores (PRS) of potential risk factors. We identified two genetic variants associated with change in attention domain scores, rs534221751 (p = 1 × 10−8 with slope 1) and rs34743896 (p = 5 × 10−10 with slope 2), implicating NCAM2 and CRIPT/ATP6V1E2 genes, respectively. We also found evidence for the association between an education PRS and baseline cognition (at &gt;65 years of age), particularly in the language domain. We demonstrate the feasibility of conducting GWAS of cognitive change using GEE modelling and our results suggest that there may be novel genetic associations for cognitive change that have not previously been associated with cross-sectional cognition. We also show the importance of the education PRS on cognition much later in life. These findings warrant further investigation and demonstrate the potential value of using trial data and trajectory modelling to identify genetic variants associated with cognitive change.<br/

Motogenic substrata and chemokinetic growth factors for human skin cells

Extracellular matrix remodelling and accurate spatio-temporal coordination of growth factor expression are two factors that are believed to regulate mitoses and cell migration in developing and regenerating tissues. The present quantitative videomicroscopical study examined the influence of some of the principal components of extracellular matrix and several growth factors that are known to be expressed in dermal wounds on three important facets of human skin cell behaviour in culture. Keratinocytes, melanocytes and dermal fibroblasts (and myofibroblast controls) exhibited varying degrees of substrate adhesion, division and migration depending on the composition of the culture substrate. Substrates that are recognized components of transitional matrices generally accentuated cell adhesion and proliferation, and were motogenic, when compared with serum-treated control surfaces, whereas components of more stable structures such as basement membrane had less influence. Platelet-derived growth factor (PDGF), epidermal growth factor (EGF) and α fibroblastic growth factor (αFGF) all promoted cell proliferation and were chemokinetic to dermal fibroblasts, but not keratinocyte growth factor (KGF) or transforming growth factor β (TGFβ). PDGF, EGF and KGF, but not TGFβ or αFGF, all enhanced proliferation of dermal keratinocytes. The same growth factors, and in addition KGF, all stimulated motility in keratinocytes, but TGFβ and αFGF again had no effect. Developing a better understanding of the interdependency of factors that control crucial cell behaviour may assist those who are interested in the regulation of histogenesis and also inform the development of rational therapeutic strategies for the management of chronic and poorly healed wounds

Alpha v 3 integrin spatially regulates VASP and RIAM to control adhesion dynamics and migration

Integrins are fundamental to the control of protrusion and motility in adherent cells. However, the mechanisms by which specific members of this receptor family cooperate in signaling to cytoskeletal and adhesion dynamics are poorly understood. Here, we show that the loss of ß3 integrin in fibroblasts results in enhanced focal adhesion turnover and migration speed but impaired directional motility on both 2D and 3D matrices. These motility defects are coupled with an increased rate of actin-based protrusion. Analysis of downstream signaling events reveals that loss of ß3 integrin results in a loss of protein kinase A–dependent phosphorylation of the actin regulatory protein vasodilator-stimulated phosphoprotein (VASP). Dephosphorylated VASP in ß3-null cells is preferentially associated with Rap1-GTP–interacting adaptor molecule (RIAM) both in vitro and in vivo, which leads to enhanced formation of a VASP–RIAM complex at focal adhesions and subsequent increased binding of talin to ß1 integrin. These data demonstrate a novel mechanism by which avß3 integrin acts to locally suppress ß1 integrin activation and regulate protrusion, adhesion dynamics, and persistent migration