The haematopoietic‐specific RhoGTPase, Rac2, has been indirectly implicated in T‐lymphocyte development and function, and as a pivotal regulator of T Helper 1 (T
H
1) responses. In other ...haematopoietic cells it regulates cytoskeletal rearrangement downstream of extracellular signals. Here we demonstrate that Rac2 deficiency results in an abnormal distribution of T lymphocytes
in vivo
and defects in T‐lymphocyte migration and filamentous actin generation in response to chemoattractants
in vitro
. To investigate the requirement for Rac2 in IFN‐γ production and T
H
1 responses
in vivo
, Rac2‐deficient mice were challenged with
Leishmania major
and immunized with ovalbumin‐expressing cytomegalovirus. Despite a minor skewing towards a T
H
2 phenotype, Rac2‐deficient mice displayed no increased susceptibility to
L. major
infection. Cytotoxic T‐lymphocyte responses to cytomegalovirus and ovalbumin were also normal. Although Rac2 is required for normal T‐lymphocyte migration, its role in the generation of T
H
1 responses to infection
in vivo
is largely redundant.
Objectives The aim of this study was to examine the value of native and post-contrast T1 relaxation in the differentiation between healthy and diffusely diseased myocardium in 2 model conditions, ...hypertrophic cardiomyopathy and nonischemic dilated cardiomyopathy. Background T1 mapping has been proposed as potentially valuable in the quantitative assessment of diffuse myocardial fibrosis, but no studies to date have systematically evaluated its role in the differentiation of healthy myocardium from diffuse disease in a clinical setting. Methods Consecutive subjects undergoing routine clinical cardiac magnetic resonance at King's College London were invited to participate in this study. Groups were based on cardiac magnetic resonance findings and consisted of subjects with known hypertrophic cardiomyopathy (n = 25) and nonischemic dilated cardiomyopathy (n = 27). Thirty normotensive subjects with low pre-test likelihood of cardiomyopathy, not taking any regular medications and with normal cardiac magnetic resonance findings including normal left ventricular mass indexes, served as controls. Single equatorial short-axis slice T1 mapping was performed using a 3-T scanner before and at 10, 20, and 30 minutes after the administration of 0.2 mmol/kg of gadobutrol. T1 values were quantified within the septal myocardium (T1native ), and extracellular volume fractions (ECV) were calculated. Results T1native was significantly longer in patients with cardiomyopathy compared with control subjects (p < 0.01). Conversely, post-contrast T1 values were significantly shorter in patients with cardiomyopathy at all time points (p < 0.01). ECV was significantly higher in patients with cardiomyopathy compared with controls at all time points (p < 0.01). Multivariate binary logistic regression revealed that T1native could differentiate between healthy and diseased myocardium with sensitivity of 100%, specificity of 96%, and diagnostic accuracy of 98% (area under the curve 0.99; 95% confidence interval: 0.96 to 1.00; p < 0.001), whereas post-contrast T1 values and ECV showed lower discriminatory performance. Conclusions This study demonstrates that native and post-contrast T1 values provide indexes with high diagnostic accuracy for the discrimination of normal and diffusely diseased myocardium.
T1 imaging based on pixel-wise quantification of longitudinal relaxation has the potential to differentiate between normal and abnormal myocardium. The accuracy of T1 measurement has not been ...established nor systematically tested in the presence of health and disease.
Intra-observer, inter-observer and inter-study reproducibility of T1 imaging was assessed in subjects with left ventricular hypertrophy (LVH, n = 25) or dilated cardiomyopathy (DCM, n = 43). Thirty-eight subjects with low-pretest likelihood of cardiomyopathy served as a control group. T1 values were acquired in a single mid-ventricular short axis slice using modified Look-Locker imaging prior and after the application of gadolinium contrast at 1.5 and 3 T. Analysis was performed with regions of interest (ROI) placed conservatively within the septum or to include the whole short axis (SAX) myocardium.
Intra-observer, inter-observer and inter-study repeated measurements within the septum showed smaller mean differences and narrower 95% confidence intervals than repeated short axis ROI measurements. Native T1 values were higher in septal ROIs compared with SAX values at both field strengths (1.5 T: 976 ± 37 vs. 952 ± 41, p < 0.01; 3 T: 1108 ± 67 vs. 1087 ± 60, p < 0.01). Native T1 values revealed significant mean differences between controls and patients with LVH for both septal (1.5 T: 26 ± 9, p < 0.01; 3 T: 50 ± 13, p < 0.01) and SAX ROIs (1.5 T: 19 ± 11, p < 0.05; 3 T: 47 ± 19, p < 0.05) with greater differences observed at 3 T versus 1.5 T field strength. Native T1 values revealed significant mean differences between controls and patients with DCM for septal ROI (1.5 T: 29 ± 15, p < 0.05; 3 T: 55 ± 16, p < 0.01) at both 1.5 T and 3 T, but only for SAX ROIs at 3 T (49 ± 17, p < 0.01). There were no significant differences in post-contrast T1 values or partition coefficient (λ) between controls and patients.
Conservative septal ROI T1 measurement is a robust technique with excellent intra-observer, inter-observer and inter-study reproducibility for native and post-contrast T1 value and partition coefficient measurements. Moreover, native septal T1 values reveal the greatest difference between normal and abnormal myocardium, which is independent of geometrical alterations of cardiac chamber and wall thickness. We propose the use of native T1 measurements using conservative septal technique as the standardized approach to distinguish health from disease assuming diffuse myocardial involvement.
Increased systemic inflammation has been linked to myocardial dysfunction and heart failure in patients with systemic lupus erythematosus (SLE). Accurate detection of early myocardial changes may be ...able to guide preventive intervention. We investigated whether multiparametric imaging by cardiovascular magnetic resonance can detect differences between controls and asymptomatic SLE patients.
A total of 33 SLE predominantly female patients (mean age, 40±9 years) underwent cardiovascular magnetic resonance for routine assessment of myocardial perfusion, function, and late gadolinium enhancement. T1 mapping was performed in single short-axis slice before and after 15 minutes of gadolinium administration. Twenty-one subjects with a low pretest probability and normal cardiovascular magnetic resonance served as a control group. Both groups had similar left ventricular volumes and mass and normal global systolic function. SLE patients had significantly reduced longitudinal strain (controls versus SLE, -20±2% versus -17±3%; P<0.01) and showed intramyocardial and pericardial late gadolinium enhancement. SLE patients had significantly increased native myocardial T1 (1056±27 versus 1152±46 milliseconds; P<0.001) and extracellular volume fraction (26±5% versus 30±6%; P=0.007) and reduced postcontrast myocardial T1 (454±53 versus 411±62 milliseconds; P=0.01). T1-derived indices were associated with longitudinal strain (r=0.37-0.47) but not with the presence of late gadolinium enhancement. Native myocardial T1 values showed the greatest concordance with the presence of clinical diagnosis of SLE.
In patients with SLE and free of cardiac symptoms, there is evidence of subclinical perimyocardial impairment. We further demonstrate that T1 mapping may have potential to detect subclinical myocardial involvement in patients with SLE.
Several proteins have been linked to neurodegenerative disorders (NDDs), but their molecular function is not completely understood. Here, we used quantitative interaction proteomics to identify ...binding partners of Amyloid beta precursor protein (APP) and Presenilin-1 (PSEN1) for Alzheimer’s disease (AD), Huntingtin (HTT) for Huntington’s disease, Parkin (PARK2) for Parkinson’s disease, and Ataxin-1 (ATXN1) for spinocerebellar ataxia type 1. Our network reveals common signatures of protein degradation and misfolding and recapitulates known biology. Toxicity modifier screens and comparison to genome-wide association studies show that interaction partners are significantly linked to disease phenotypes in vivo. Direct comparison of wild-type proteins and disease-associated variants identified binders involved in pathogenesis, highlighting the value of differential interactome mapping. Finally, we show that the mitochondrial protein LRPPRC interacts preferentially with an early-onset AD variant of APP. This interaction appears to induce mitochondrial dysfunction, which is an early phenotype of AD.
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•Quantitative interactomics of proteins involved in four neurodegenerative diseases•Differential interaction mapping of wild-type and disease-associated proteins•Interaction partners are significantly linked to disease phenotypes in vivo•Interaction of APP and LRPPRC appears to induce mitochondrial dysfunction in AD
Hosp et al. show that quantitative interaction proteomics of neurodegenerative disease proteins captures interactions relevant to pathogenesis. Differential interactome mapping reveals preferential binding of the mitochondrial protein LRPPRC with an early-onset Alzheimer’s disease (AD) variant of APP, potentially contributing to mitochondrial dysfunction observed in AD.
Cerebral Amyloid Angiopathy (CAA) disease course is highly variable even in hereditary forms. Sex may be a possible modifying factor. We investigated biological sex differences in clinical disease ...course and magnetic resonance imaging-markers in sporadic (sCAA) and Dutch-type hereditary CAA (D-CAA).
Patients with D-CAA and sCAA were included from hospital and research databases of the Leiden University Medical Center (2012-2020) and Massachusetts General Hospital (1994-2012). Key outcomes were: sex differences in symptomatic intracerebral hemorrhage (sICH) onset, recurrence and survival (analyzed using Kaplan Meier survival and regression analyses), and sex differences in magnetic resonance imaging-markers in D-CAA (explored using scatterplots), and in sCAA (investigated using regression analysis).
We included 136 patients with D-CAA (mean age 57 years, 56% women, 64% with previous sICH) and 370 patients with sCAA (mean age 76 years, 51% women, all with previous sICH). Men and women with D-CAA did not differ for sICH onset (median age 54 in men and 56 in women
=0.13). Men with D-CAA had a slightly higher number of sICH compared with women (median 2 versus 1; adjusted RR, 1.5 95% CI, 1.1-1.9) and a shorter interval between the first and second sICH (median 1.8 years for men and 3.1 years for women,
=0.02). Men with sCAA had their first sICH at an earlier age (median 75 versus 78 years, respectively,
=0.003) and more lobar microbleeds (median 1 versus 0,
=0.022) compared with women with sCAA. No substantial differences were found in the other magnetic resonance imaging markers. Survival after first sICH was comparable between sexes for D-CAA (
=0.12) and sCAA (
=0.23).
Men with CAA seem to have an earlier onset (sCAA) and more hemorrhagic disease course (sCAA and D-CAA) compared with women. Future studies are necessary to confirm these findings and determine the underlying role of sex-related factors.
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