Circadian and Brain State Modulation of Network Hyperexcitability in Alzheimer’s Disease

Abstract Network hyperexcitability is a feature of Alzheimer’ disease (AD) as well as numerous transgenic mouse models of AD. While hyperexcitability in AD patients and AD animal models share certain features, the mechanistic overlap remains to be established. We aimed to identify features of network hyperexcitability in AD models that can be related to epileptiform activity signatures in AD patients. We studied network hyperexcitability in mice expressing amyloid precursor protein (APP) with mutations that cause familial AD, and compared a transgenic model that overexpresses human APP (hAPP) (J20), to a knock-in model expressing APP at physiological levels (APPNL/F). We recorded continuous long-term electrocorticogram (ECoG) activity from mice, and studied modulation by circadian cycle, behavioral, and brain state. We report that while J20s exhibit frequent interictal spikes (IISs), APPNL/F mice do not. In J20 mice, IISs were most prevalent during daylight hours and the circadian modulation was associated with sleep. Further analysis of brain state revealed that IIS in J20s are associated with features of rapid eye movement (REM) sleep. We found no evidence of cholinergic changes that may contribute to IIS-circadian coupling in J20s. In contrast to J20s, intracranial recordings capturing IIS in AD patients demonstrated frequent IIS in non-REM (NREM) sleep. The salient differences in sleep-stage coupling of IIS in APP overexpressing mice and AD patients suggests that different mechanisms may underlie network hyperexcitability in mice and humans. We posit that sleep-stage coupling of IIS should be an important consideration in identifying mouse AD models that most closely recapitulate network hyperexcitability in human AD

Adaptation of HIV-1 Depends on the Host-Cell Environment

Many viruses have the ability to rapidly develop resistance against antiviral drugs and escape from the host immune system. To which extent the host environment affects this adaptive potential of viruses is largely unknown. Here we show that for HIV-1, the host-cell environment is key to the adaptive potential of the virus. We performed a large-scale selection experiment with two HIV-1 strains in two different T-cell lines (MT4 and C8166). Over 110 days of culture, both virus strains adapted rapidly to the MT4 T-cell line. In contrast, when cultured on the C8166 T-cell line, the same strains did not show any increase in fitness. By sequence analyses and infections with viruses expressing either yellow or cyan fluorescent protein, we were able to show that the absence of adaptation was linked to a lower recombination rate in the C8166 T-cell line. Our findings suggest that if we can manipulate the host-cellular factors that mediate viral evolution, we may be able to significantly retard viral adaptability

Imaging of Biological Materials and Cells by X-ray Scattering and Diffraction

Cells and biological materials are large objects in comparison to the size of internal components such as organelles and proteins. An understanding of the functions of these nanoscale elements is key to elucidating cellular function. In this review, we describe the advances in X-ray scattering and diffraction techniques for imaging biological systems at the nanoscale. We present a number of principal technological advances in X-ray optics and development of sample environments. We identify radiation damage as one of the most severe challenges in the field, thus rendering the dose an important parameter when putting different X-ray methods in perspective. Furthermore, we describe different successful approaches, including scanning and full-field techniques, along with prominent examples. Finally, we present a few recent studies that combined several techniques in one experiment in order to collect highly complementary data for a multidimensional sample characterization

Implication de nouvelles cibles microgliales, Cst7 et Clec7a/Dectin-1, dans le développement et la progression de la maladie d'Alzheimer

Alzheimer’s Disease (AD) is the most common form of dementia in the elderly. Effective threapeutics are still very needed for this neurodegenerative disorder. Interestingly, almost all risk genes for sporadic AD are highly expressed in microglia demonstrating their crucial role in this disorder.Microglial cells are brain resident immune cells. They play pivotal roles in neuroinflammatory processes. However, whether microglia play beneficial and/or detrimental roles in AD progression remains heavily debated and, in addition, their roles in the early stages of the pathology are still poorly understood.Previous study from our lab identified several microglial genes dysregulated in AD early stages. We focused our work on two main targets : Cst7 and Clec7a. Indeed, while the microglial roles of these two genes are poorly known, their peripheral functions (cytokines production, phagocytosis and protein degradation) put them under the spotlight for early involvment in AD.The main objectives of this thesis project were : (i) to caracterize AD early stage development in the APP(swe)/PS1(dE9) model; then (ii) to study the targets’ implication in AD initiation, (iii) to unravel their microglial functions, and finally (iv) to demonstrate their relevance in Humans.As a whole our data support an early contribution of microglia to AD progression in the APP(swe)/PS1(dE9) mouse model and point to two specific genes that may represent potential early biomarkers and/or therapeutic targets.La maladie d’Alzheimer (MA), première cause de démence chez les personnes âgées, est une maladie neurodégénérative pour laquelle il n'existe toujours pas de stratégie thérapeutique efficace. Singulièrement, une grande partie des facteurs de risques des formes sporadiques de la MA sont associés à des gènes microgliaux. Les microglies sont les cellules immunitaires résidentes du cerveau, et jouent un rôle pivot dans les processus neuroinflammatoires. Néanmoins, leurs rôles dans les différentes phases de la MA, et en particulier durant la phase précoce constituant un enjeu thérapeutique majeur, restent encore très mal connus.Des travaux réalisés dans notre laboratoire ont permis d'identifier deux cibles moléculaires particulières, Cst7 et Clec7a, qui du fait de leur dérégulation précoce et de leurs rôles à la périphérie (production de cytokines, phagocytose et dégradation de protéines) représentent des cibles pertinentes dans les phases précoces de la MA.Les objectifs de mon projet de thèse ont donc été : (i) de caractériser le modèle d'étude APP(swe)/PS1(dE9) au stade précoce; puis (ii) de déterminer l'implication des deux cibles dans le développement de la MA et (iii) d'élucider leurs rôles microgliaux; enfin (iv) j'ai cherché à démontrer l’intérêt de ces cibles chez l'Homme.L'ensemble de ces travaux ont permis de démontrer l'existence d'une réaction microgliale précoce dans le modèle APP(swe)/PS1(dE9) et de mettre en avant deux gènes microgliaux, pour l'instant peu étudiés, qui pourraient représenter des biomarqueurs précoces et/ou des cibles thérapeutiques innovantes

Rôle de la phosphorylation des protéines virales dans le cycle de rétrovirus VIH-1 et HTLV-1

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Involvment of new microglial genes in Alzheimer's disease development, focus on Cst7 and Clec7a/Dectin-1

La maladie d’Alzheimer (MA), première cause de démence chez les personnes âgées, est une maladie neurodégénérative pour laquelle il n'existe toujours pas de stratégie thérapeutique efficace. Singulièrement, une grande partie des facteurs de risques des formes sporadiques de la MA sont associés à des gènes microgliaux. Les microglies sont les cellules immunitaires résidentes du cerveau, et jouent un rôle pivot dans les processus neuroinflammatoires. Néanmoins, leurs rôles dans les différentes phases de la MA, et en particulier durant la phase précoce constituant un enjeu thérapeutique majeur, restent encore très mal connus.Des travaux réalisés dans notre laboratoire ont permis d'identifier deux cibles moléculaires particulières, Cst7 et Clec7a, qui du fait de leur dérégulation précoce et de leurs rôles à la périphérie (production de cytokines, phagocytose et dégradation de protéines) représentent des cibles pertinentes dans les phases précoces de la MA.Les objectifs de mon projet de thèse ont donc été : (i) de caractériser le modèle d'étude APP(swe)/PS1(dE9) au stade précoce; puis (ii) de déterminer l'implication des deux cibles dans le développement de la MA et (iii) d'élucider leurs rôles microgliaux; enfin (iv) j'ai cherché à démontrer l’intérêt de ces cibles chez l'Homme.L'ensemble de ces travaux ont permis de démontrer l'existence d'une réaction microgliale précoce dans le modèle APP(swe)/PS1(dE9) et de mettre en avant deux gènes microgliaux, pour l'instant peu étudiés, qui pourraient représenter des biomarqueurs précoces et/ou des cibles thérapeutiques innovantes.Alzheimer’s Disease (AD) is the most common form of dementia in the elderly. Effective threapeutics are still very needed for this neurodegenerative disorder. Interestingly, almost all risk genes for sporadic AD are highly expressed in microglia demonstrating their crucial role in this disorder.Microglial cells are brain resident immune cells. They play pivotal roles in neuroinflammatory processes. However, whether microglia play beneficial and/or detrimental roles in AD progression remains heavily debated and, in addition, their roles in the early stages of the pathology are still poorly understood.Previous study from our lab identified several microglial genes dysregulated in AD early stages. We focused our work on two main targets : Cst7 and Clec7a. Indeed, while the microglial roles of these two genes are poorly known, their peripheral functions (cytokines production, phagocytosis and protein degradation) put them under the spotlight for early involvment in AD.The main objectives of this thesis project were : (i) to caracterize AD early stage development in the APP(swe)/PS1(dE9) model; then (ii) to study the targets’ implication in AD initiation, (iii) to unravel their microglial functions, and finally (iv) to demonstrate their relevance in Humans.As a whole our data support an early contribution of microglia to AD progression in the APP(swe)/PS1(dE9) mouse model and point to two specific genes that may represent potential early biomarkers and/or therapeutic targets

La place du pharmacien vétérinaire en milieu rural

DIJON-BU Médecine Pharmacie (212312103) / SudocSudocFranceF

Image Processing for Bioluminescence Resonance Energy Transfer Measurement—BRET-Analyzer

A growing number of tools now allow live recordings of various signaling pathways and protein-protein interaction dynamics in time and space by ratiometric measurements, such as Bioluminescence Resonance Energy Transfer (BRET) Imaging. Accurate and reproducible analysis of ratiometric measurements has thus become mandatory to interpret quantitative imaging. In order to fulfill this necessity, we have developed an open source toolset for Fiji—BRET-Analyzer—allowing a systematic analysis, from image processing to ratio quantification. We share this open source solution and a step-by-step tutorial at https://github.com/ychastagnier/BRET-Analyzer. This toolset proposes (1) image background subtraction, (2) image alignment over time, (3) a composite thresholding method of the image used as the denominator of the ratio to refine the precise limits of the sample, (4) pixel by pixel division of the images and efficient distribution of the ratio intensity on a pseudocolor scale, and (5) quantification of the ratio mean intensity and standard variation among pixels in chosen areas. In addition to systematize the analysis process, we show that the BRET-Analyzer allows proper reconstitution and quantification of the ratiometric image in time and space, even from heterogeneous subcellular volumes. Indeed, analyzing twice the same images, we demonstrate that compared to standard analysis BRET-Analyzer precisely define the luminescent specimen limits, enlightening proficient strengths from small and big ensembles over time. For example, we followed and quantified, in live, scaffold proteins interaction dynamics in neuronal sub-cellular compartments including dendritic spines, for half an hour. In conclusion, BRET-Analyzer provides a complete, versatile and efficient toolset for automated reproducible and meaningful image ratio analysis

Image Processing for Bioluminescence Resonance Energy Transfer Measurement—BRET-Analyzer

International audienceA growing number of tools now allow live recordings of various signaling pathways and protein-protein interaction dynamics in time and space by ratiometric measurements, such as Bioluminescence Resonance Energy Transfer (BRET) Imaging. Accurate and reproducible analysis of ratiometric measurements has thus become mandatory to interpret quantitative imaging. In order to fulfill this necessity, we have developed an open source toolset for Fiji—BRET-Analyzer—allowing a systematic analysis, from image processing to ratio quantification. We share this open source solution and a step-by-step tutorial at https://github.com/ychastagnier/BRET-Analyzer. This toolset proposes (1) image background subtraction, (2) image alignment over time, (3) a composite thresholding method of the image used as the denominator of the ratio to refine the precise limits of the sample, (4) pixel by pixel division of the images and efficient distribution of the ratio intensity on a pseudocolor scale, and (5) quantification of the ratio mean intensity and standard variation among pixels in chosen areas. In addition to systematize the analysis process, we show that the BRET-Analyzer allows proper reconstitution and quantification of the ratiometric image in time and space, even from heterogeneous subcellular volumes. Indeed, analyzing twice the same images, we demonstrate that compared to standard analysis BRET-Analyzer precisely define the luminescent specimen limits, enlightening proficient strengths from small and big ensembles over time. For example, we followed and quantified, in live, scaffold proteins interaction dynamics in neuronal sub-cellular compartments including dendritic spines, for half an hour. In conclusion, BRET-Analyzer provides a complete, versatile and efficient toolset for automated reproducible and meaningful image ratio analysis

Microglia in Alzheimer Disease: Well-Known Targets and New Opportunities

International audienceMicroglia are the resident macrophages of the central nervous system. They play key roles in brain development, and physiology during life and aging. Equipped with a variety of molecular sensors and through the various functions they can fulfill, they are critically involved in maintaining the brain's homeostasis. In Alzheimer disease (AD), microglia reaction was initially thought to be incidental and triggered by amyloid deposits and dystrophic neurites. However, recent genome-wide association studies have established that the majority of AD risk loci are found in or near genes that are highly and sometimes uniquely expressed in microglia. This leads to the concept of microglia being critically involved in the early steps of the disease and identified them as important potential therapeutic targets. Whether microglia reaction is beneficial, detrimental or both to AD progression is still unclear and the subject of intense debate. In this review, we are presenting a state-of-knowledge report intended to highlight the variety of microglial functions and pathways shown to be critically involved in AD progression. We first address both the acquisition of new functions and the alteration of their homeostatic roles by reactive microglia. Second, we propose a summary of new important parameters currently emerging in the field that need to be considered to identify relevant microglial targets. Finally, we discuss the many obstacles in designing efficient therapeutic strategies for AD and present innovative technologies that may foster our understanding of microglia roles in the pathology. Ultimately, this work aims to fly over various microglial functions to make a general and reliable report of the current knowledge regarding microglia's involvement in AD and of the new research opportunities in the field