A combinatorial TIR1/AFB–Aux/IAA co-receptor system for differential sensing of auxin

The plant hormone auxin regulates virtually every aspect of plant growth and development. Auxin acts by binding the F-box protein transport inhibitor response 1 (TIR1) and promotes the degradation of the AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) transcriptional repressors. Here we show that efficient auxin binding requires assembly of an auxin co-receptor complex consisting of TIR1 and an Aux/IAA protein. Heterologous experiments in yeast and quantitative IAA binding assays using purified proteins showed that different combinations of TIR1 and Aux/IAA proteins form co-receptor complexes with a wide range of auxin-binding affinities. Auxin affinity seems to be largely determined by the Aux/IAA. As there are 6 TIR1/AUXIN SIGNALING F-BOX proteins (AFBs) and 29 Aux/IAA proteins in Arabidopsis thaliana, combinatorial interactions may result in many co-receptors with distinct auxin-sensing properties. We also demonstrate that the AFB5–Aux/IAA co-receptor selectively binds the auxinic herbicide picloram. This co-receptor system broadens the effective concentration range of the hormone and may contribute to the complexity of auxin response

Influence des recepteurs alpha-et beta-andrenergiques sur le metabolisme des phosphoinositides : relation avec les reponses physiologiques cellulaires : modele d'etude : la plaquette de rat

SIGLECNRS TD 15319 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Analytical validation of hepatitis B core‐related antigen (HBcrAg) using dried blood spots (DBS)

International audienceLimited access to nucleic acid testing (NAT) to quantify HBV DNA levels, an essential tool to determine anti-HBV treatment eligibility, represents a significant barrier to scale up HBV diagnostic services in resource-limited countries. Hepatitis B core-related antigen (HBcrAg) has the potential to become an affordable alternative because of its low cost (US$ <15/assay) and strong correlation with HBV DNA levels in treatment-naïve patients. However, the current assay requires plasma or serum. To further facilitate its application to decentralized settings, we developed and evaluated a standardized procedure to quantify HBcrAg using dried blood spots as a tool to diagnose HBV-infected people with high viraemia. We evaluated the following elution method optimized to quantify HBcrAg: suspension of a punched blood-soaked disc (11 mm) of Whatman 903 Protein Saver Card in 450 µL of PBS 0.05% Tween 20, followed by an incubation for 4 h at room temperature and a centrifugation at 10,000 g for 10 minutes. 150 µL of DBS eluate was used to quantify HBcrAg using chemiluminescent enzyme immunoassay (LUMIPULSE® G600II, Fujirebio). The limit of detection of dried blood spot HBcrAg in relation with HBV DNA levels was 19,115 IU/mL across the five major HBV genotypes (A/B/C/D/E). A strong linear correlation was confirmed between dried blood spot HBcrAg and HBV DNA levels (r = 0.94, p < 0.0001) in samples with high viral loads (range: 3.7–7.0 log IU/mL). The coefficient of variation ranged between 4.0–11.2% for repeatability and 3.9–12.2% for reproducibility. Analytical specificity was 100% (95% CI: 83.9–100%) in HBV-negative samples. Using our elution method, it may be possible to identify HBV-infected patients with high viraemia who need antiviral therapy using dried blood spot and HBcrAg. A large-scale clinical validation is warranted in resource-limited countries

Biomarqueurs aux phases précoces de développement dans la maladie d’Alzheimer

Le développement clinique de médicaments disease-modifiers dans la maladie d’Alzheimer se heurte à des difficultés méthodologiques dont témoignent plusieurs échecs récents de médicaments en phase III. Compte-tenu des enjeux financiers inhérents au passage en phase III et du risque d’investir en pure perte de l’énergie pour l’évaluation d’un mauvais candidat-médicament, la question cruciale reste la décision de go/no go entre la phase II et la phase III dont l’objectif est certes de sélectionner une molécule susceptible d’être efficace en phase III mais plus encore d’écarter d’un développement ultérieur les candidats aux effets insuffisants. Aucun consensus n’existe aujourd’hui sur la meilleure conception possible des études de phase II pour tenter d’éclairer au mieux la décision de go/nogo. Les difficultés de choix de la meilleure conception d’étude concernent tout aussi bien la population-cible, les critères de jugement en particulier le recours à des biomarqueurs, le plan expérimental ou la durée des études. L’objet de la Table Ronde (TR) a été de rassembler les points de vue d’experts français issus du monde académique, industriel ou réglementaire afin d’arriver à une proposition consensuelle sur la meilleure conception possible que devraient utiliser les études de phase II dans la maladie d’Alzheimer

Biomarkers for the Early Stages of Clinical Development in Alzheimer’s Disease

As the failure of several recent Phase III drug development programmes bears witness, the clinical development of “disease-modifying” drugs in Alzheimer’s disease has been confronted with challenging methodological difficulties. Taking into account the financial stakes involved taking drug candidates to the Phase III stage of development, and the risk of investing time and resources fruitlessly in the evaluation of poor candidate drugs, the crucial decision remains whether to proceed from Phase II to Phase III (Go/Nogo). The aim of Phase II studies is to select a molecule likely to be effective in Phase III, but also to eliminate candidate-drugs with an inadequate effect. No consensus currently exists on the best possible design of Phase II studies to inform the Go/Nogo decision optimally. The challenges in choosing the best study design relate to the target population, the end-point criteria used, in particular the use of biomarkers, the experimental protocol, and the study duration. The objective of the Round Table (RT) was to gather the opinions of French experts from the academic, industrial, and regulatory world in order to arrive at a consensus recommendation for the best possible design to be used in Phase II studies in Alzheimer’s disease

bHLH heterodimer complex variations regulate cell proliferation activity in the meristems of Arabidopsis thaliana

International audienceRoot, shoot, and lateral meristems are the main regions of cell proliferation in plants. It has been proposed that meristems might have evolved dedicated transcriptional networks to balance cell proliferation. Here, we show that basic helixloop-helix (bHLH) transcription factor heterodimers formed by members of the TARGET OF MONOPTEROS5 (TMO5) and LONESOME HIGHWAY (LHW) subclades are general regulators of cell proliferation in all meristems. Yet, genetics and expression analyses suggest specific functions of these transcription factors in distinct meristems, possibly due to their expression domains determining heterodimer complex variations within meristems, and to a certain extent to the absence of some of them in a given meristem. Target gene specificity analysis for heterodimer complexes focusing on the LONELY GUY gene targets further suggests differences in transcriptional responses through heterodimer diversification that could allow a common bHLH heterodimer complex module to contribute to cell proliferation control in multiple meristems

Microglial-glucocorticoid receptor depletion alters the response of hippocampal microglia and neurons in a chronic unpredictable mild stress paradigm in female mice

Chronic psychological stress is one of the most important triggers and environmental risk factors for neuropsychiatric disorders. Chronic stress can influence all organs via the secretion of stress hormones, including glucocorticoids by the adrenal glands, which coordinate the stress response across the body. In the brain, glucocorticoid receptors (GR) are expressed by various cell types including microglia, which are its resident immune cells regulating stress-induced inflammatory processes. To study the roles of microglial GR under normal homeostatic conditions and following chronic stress, we generated a mouse model in which the GR gene is depleted in microglia specifically at adulthood to prevent developmental confounds. We first confirmed that microglia were depleted in GR in our model in males and females among the cingulate cortex and the hippocampus, both stress-sensitive brain regions. Then, cohorts of microglial-GR depleted and wild-type (WT) adult female mice were housed for 3 weeks in a standard or stressful condition, using a chronic unpredictable mild stress (CUMS) paradigm. CUMS induced stress-related behavior in both microglial-GR depleted and WT animals as demonstrated by a decrease of both saccharine preference and progressive ratio breakpoint. Nevertheless, the hippocampal microglial and neural mechanisms underlying the adaptation to stress occurred differently between the two genotypes. Upon CUMS exposure, microglial morphology was altered in the WT controls, without any apparent effect in microglial-GR depleted mice. Furthermore, in the standard environment condition, GR depleted-microglia showed increased expression of pro-inflammatory genes, and genes involved in microglial homeostatic functions (such as Trem2, Cx3cr1 and Mertk). On the contrary, in CUMS condition, GR depleted-microglia showed reduced expression levels of pro-inflammatory genes and increased neuroprotective as well as anti-inflammatory genes compared to WT-microglia. Moreover, in microglial-GR depleted mice, but not in WT mice, CUMS led to a significant reduction of CA1 long-term potentiation and paired-pulse ratio. Lastly, differences in adult hippocampal neurogenesis were observed between the genotypes during normal homeostatic conditions, with microglial-GR deficiency increasing the formation of newborn neurons in the dentate gyrus subgranular zone independently from stress exposure. Together, these findings indicate that, although the deletion of microglial GR did not prevent the animal’s ability to respond to stress, it contributed to modulating hippocampal functions in both standard and stressful conditions, notably by shaping the microglial response to chronic stress