9 research outputs found
Neurog2 Deficiency Uncovers a Critical Period of Cell Fate Plasticity and Vulnerability among Neural-Crest-Derived Somatosensory Progenitors.
No full textFunctionally distinct classes of dorsal root ganglia (DRG) somatosensory neurons arise from neural crest cells (NCCs) in two successive phases of differentiation assumed to be respectively and independently controlled by the proneural genes Neurog2 and Neurog1. However, the precise role of Neurog2 during this process remains unclear, notably because no neuronal loss has been reported hitherto in Neurog2-/- mutants. Here, we show that at trunk levels, Neurog2 deficiency impairs the production of subsets of all DRG neuron subtypes. We establish that this phenotype is highly dynamic and reflects multiple defects in NCC-derived progenitors, including somatosensory-to-melanocyte fate switch, apoptosis, and delayed differentiation which alters neuronal identity, all occurring during a narrow time window when Neurog2 temporarily controls onset of Neurog1 expression and neurogenesis. Collectively, these findings uncover a critical period of cell fate plasticity and vulnerability among somatosensory progenitors and establish that Neurog2 function in the developing DRG is broader than initially envisaged.info:eu-repo/semantics/publishe
No H- and L-type cases in Belgium in cattle diagnosed with bovine spongiform encephalopathy (1999-2008) aging seven years and older
No full textAbstract Background The bovine spongiform encephalopathy (BSE) epidemic presented homogeneity of the phenotype. This classical BSE (called C-type) was probably due to the contamination of the food chain by a single prion strain. However, due to the active surveillance and better techniques, two rare variants of BSE have been recently reported in different continents without a clear correlation to the BSE epidemic. These emerging types behave as different strains of BSE and were named H-type and L-type according to the high and low molecular mass of the unglycosylated fragment of their proteinase K resistant prion protein (PrPres). In these types, the proportion of the un-, mono- and di-glycosylated fragments of PrP (glycoprofile) is also atypical and represents an effective diagnostic parameter. This study evaluated the presence of such types in bovine of 7 years and older in Belgium. Results The Belgian BSE archive contained 41 bovines of at least 7 years of age. The biochemical features of their PrPres were analyzed by Western blot with five antibodies recognising different regions of PrPres, from N- to C-terminus: 12B2, 9A2, Sha31, SAF84 and 94B4. All antibodies clearly detected PrPres except 12B2 antibody, which is specific for N-terminal region 101-105, a PrP region that is only retained in H-types. The glycoprofiles did correspond to that of C-type (with more than 55% of diglycosylated PrPres using antibody 94B4). Therefore, all cases have the features of C-type BSE. Conclusions This study supports that, among the BSE cases of 7 years and older identified in Belgium, none was apparently of the H- or L- type. This is consistent with the very rare occurrence of atypical BSE and the restricted dimension of Belgium. These results shed some light on the worldwide prevalence of atypical BSE.</p
Atypical status of bovine spongiform encephalopathy in Poland: a molecular typing study
No full textThe aim of this study was to analyze molecular features of protease-resistant prion protein (PrPres) in Western blots of BSE cases diagnosed in Poland with respect to a possible atypical status. Confirmed cases were analyzed by Western blotting with several monoclonal antibodies directed at N-terminal and core epitopes of prion protein (PrP). Most cases showed the classical glycoprofile characterized by the dominance of the di- over the monoglycosylated PrPres band, yielding di-/mono- ratios well above 2 and by reactivity with antibodies having their epitopes in bovine PrP region 110-242 (C-type cases). Surprisingly, seven cases of BSE were atypical. Six were classified as L-type based on a slightly lower molecular mass (M-r) of the non- glycosylated band with respect to C-types and a conspicuously low di-/mono- ratio of glycosylated PrPres bands approaching unity. One case was classified as H-type because of a higher M-r of PrPres bands on the blot when compared with C-type cases. A characteristic epitope of H-type PrPres occurred in the 101-110 region of PrP for which only antibody 12B2 had a sufficient affinity. The occurrence of atypical cases only in animals 9 years of age and older raises questions about the mechanisms of prion diseases and the origin of BSE
A mechano-osmotic feedback couples cell volume to the rate of cell deformation
No full textMechanics has been a central focus of physical biology in the past decade. In comparison, how cells manage their size is less understood. Here, we show that a parameter central to both the physics and the physiology of the cell, its volume, depends on a mechano-osmotic coupling. We found that cells change their volume depending on the rate at which they change shape, when they spontaneously spread or when they are externally deformed. Cells undergo slow deformation at constant volume, while fast deformation leads to volume loss. We propose a mechanosensitive pump and leak model to explain this phenomenon. Our model and experiments suggest that volume modulation depends on the state of the actin cortex and the coupling of ion fluxes to membrane tension. This mechano-osmotic coupling defines a membrane tension homeostasis module constantly at work in cells, causing volume fluctuations associated with fast cell shape changes, with potential consequences on cellular physiology
Adaptive motility enables neutrophils to rapidly navigate confined capillaries
No full textAs the first responders of the immune system, neutrophils rapidly and abundantly reach inflamed tissues through blood capillaries. The diameter of capillaries can be as narrow as two microns, imposing considerable deformations on neutrophils. Notably, capillary obstruction due to neutrophil retention causes vascular dysfunction and contributes to the pathogenesis of several diseases. However, the cellular mechanisms that allow neutrophils to migrate into small capillaries and to avoid retention remain unknown. In this study, we demonstrate, both in vivo and in vitro , that capillary size does not influence neutrophil migration velocity. During migration into capillaries of different sizes, neutrophils maintain high speed, a phenomenon associated with a global actomyosin cytoskeleton rearrangement in response to confinement strength. In irregular capillaries, neutrophils rapidly adapt their cell contractility via the ROCK-MyoII pathway, which allows them to sustain their migration speed along the vessels despite changes in confinement. At the single cell level, inhibition of ROCK impairs actomyosin cytoskeleton rearrangement and reduces neutrophil migration speed within confined capillaries. At the collective level, ROCK inhibition hampers efficient neutrophil trafficking in a network of small capillaries, resulting in vessel obstruction. These findings reveal a unique capacity of neutrophils to rapidly and dynamically adapt their migration to the confinement strength of capillaries, an ability that might limit vascular dysfunction during inflammation
Actin dynamics regulation by TTC7A/PI4KIIIα limits DNA damage and cell death under confinement
No full textBackground: The actin cytoskeleton has a crucial role in the maintenance of the immune homeostasis by controlling various cellular processes, including cell migration. Mutations in TTC7A have been described as the cause of a primary immunodeficiency associated to different degrees of gut involvement and alterations in the actin cytoskeleton dynamics. Objectives: This study investigates the impact of TTC7A deficiency in immune homeostasis. In particular, the role of the TTC7A/phosphatidylinositol 4 kinase type III α pathway in the control of leukocyte migration and actin dynamics. Methods: Microfabricated devices were leveraged to study cell migration and actin dynamics of murine and patient-derived leukocytes under confinement at the single-cell level. Results: We show that TTC7A-deficient lymphocytes exhibit an altered cell migration and reduced capacity to deform through narrow gaps. Mechanistically, TTC7A-deficient phenotype resulted from impaired phosphoinositide signaling, leading to the downregulation of the phosphoinositide 3-kinase/AKT/RHOA regulatory axis and imbalanced actin cytoskeleton dynamics. TTC7A-associated phenotype resulted in impaired cell motility, accumulation of DNA damage, and increased cell death in dense 3-dimensional gels in the presence of chemokines. Conclusions: These results highlight a novel role of TTC7A as a critical regulator of lymphocyte migration. Impairment of this cellular function is likely to contribute to the pathophysiology underlying progressive immunodeficiency in patients.</p
Imaging of mice and men; adventures in multispectral imaging
No full textCancer of the brain and CNS account for only 2% of new cancer cases in the UK however it is responsible for 7% of cancer deaths of those aged under 70 years of age. Although surgery falls short of a cure it is the primary method of treatment. Two of the key problems in tumour surgery in the brain are a) that many tumours are visually indistinguishable from normal tissue even for experienced surgeons and b) that the risk of post-surgical neurological deficit is related to the proximity of functional (or 'eloquent') neurological tissue. In collaboration with surgeons at the Southampton University NHS Hospitals Trust we seek to address both of these problems. Firstly there is literature evidence that normal and neoplastic tissue have different spectral characteristics in the visible and near-infrared region. We investigate whether these can be practically imaged intraoperatively to establish disease state. Secondly the redox state of haemoglobin is known to affect it's visible and near-infrared spectral characteristics. This project investigates whether it is possible to identify the haemodynamic response associated with functional activity intraoperatively in the human brain. Prion diseases are fatal chronic neurodegenerative diseases of animals and man. They have gained notoriety due to recent outbreaks of Bovine Spongiform Encephalopathy (BSE) and the evidence that they can be transmitted between species, including to man. Exposure to BSE infected material has been shown to cause variant Creutzfeldt-Jacob disease in man. Prion disease is also used as a model of other neurodegenerative diseases, such as Alzheimers disease. Remarkably little is known about this class of disease including the specific cause of the neurodegeneration. Prions are a mis-folded protein which have a different conformation than the normal protein. Certain spectral features in the mid infrared region are associated with protein conformation. In collaboration with neuro-biologists within the university and using a synchrotron light source we investigate the application of multispectral imaging in early stage prion disease. By analysis of the protein conformation sensitivity of the mid infrared spectra (with particular interest in the Amide I band) we seek to identify structurally relevant markers in a mouse model before clinical symptoms of the disease are evident. This may lead to better understanding of the disease progression and the neurotoxic element
Human inherited CCR2 deficiency underlies progressive polycystic lung disease.
No full textWe describe a human lung disease caused by autosomal recessive, complete deficiency of the monocyte chemokine receptor C-C motif chemokine receptor 2 (CCR2). Nine children from five independent kindreds have pulmonary alveolar proteinosis (PAP), progressive polycystic lung disease, and recurrent infections, including bacillus Calmette Gue ́ rin (BCG) disease. The CCR2 variants are homozygous in six patients and compound heterozygous in three, and all are loss-of-expression and loss-of-function. They abolish CCR2- agonist chemokine C-C motif ligand 2 (CCL-2)-stimulated Ca2+ signaling in and migration of monocytic cells. All patients have high blood CCL-2 levels, providing a diagnostic test for screening children with unexplained lung or mycobacterial disease. Blood myeloid and lymphoid subsets and interferon (IFN)-g- and granulocyte- macrophage colony-stimulating factor (GM-CSF)-mediated immunity are unaffected. CCR2-deficient mono- cytes and alveolar macrophage-like cells have normal gene expression profiles and functions. By contrast, alveolar macrophage counts are about half. Human complete CCR2 deficiency is a genetic etiology of PAP, polycystic lung disease, and recurrent infections caused by impaired CCL2-dependent monocyte migration to the lungs and infected tissues
