1,721,132 research outputs found
Cdc42 expression in keratinocytes is required for the maintenance of the basement membrane in skin.
No full textUdgivelsesdato: 2006-OctCdc42 is a small GTPase, which acts as a molecular switch to regulate a wide variety of cellular functions, such as actin cytoskeleton organization, cell proliferation, apoptosis, cell migration and in particular, cell polarity. Formation and maintenance of the basement membrane is a polarized process, which requires directed secretion, deposition and organization of basement membrane components at the basal side of epithelial cells. In the current study, we analyzed the maintenance of skin basement membrane in mice with a keratinocyte-restricted deletion of the Cdc42 gene. In the absence of Cdc42, basement membrane components became aberrantly deposited and the processing of laminin 5 was impaired in parts of the dermal-epidermal junction. These impairments became more severe with age and corresponded to local defects of the basement membrane in 4.5-month-old mutant mice. However, both, structure and number of hemidesomosomes were not significantly changed in the Cdc42 mutant skin compared with the control mice and no blister formation was observed in mutant skin. These data indicate that Cdc42 in keratinocytes is important for maintenance of the basement membrane of skin
The cell membrane of a novel Rhizobium phaseoli strain is the crucial target for Aluminium toxicity and tolerance
Get PDFSoils with low pH and high aluminium (Al) contamination restrict common bean production, mainly due to adverse effects on rhizobia. We isolated a novel rhizobium strain, B3, from Kenyan soil which is more tolerant to Al stress than the widely used commercial strain CIAT899. B3 was resistant to 50 µM Al and recovered from 100 µM Al stress, while CIAT899 did not. Calcein labeling showed that less Al binds to the B3 membranes and less ATP and mScarlet-1 protein, a cytoplasmic marker, leaked out of B3 than CIAT899 cells in Al-containing media. Expression profiles showed that the primary targets of Al are genes involved in membrane biogenesis, metal ions binding and transport, carbohydrate, and amino acid metabolism and transport. The identified differentially expressed genes suggested that the intracellular γ-aminobutyric acid (GABA), glutathione (GSH), and amino acid levels, as well as the amount of the extracellular exopolysaccharide (EPS), might change during Al stress. Altered EPS levels could also influence biofilm formation. Therefore, these parameters were investigated in more detail. The GABA levels, extracellular EPS production, and biofilm formation increased, while GSH and amino acid level decreased. In conclusion, our comparative analysis identified genes that respond to Al stress in R. phaseoli. It appears that a large portion of the identified genes code for proteins stabilizing the plasma membrane. These genes might be helpful for future studies investigating the molecular basis of Al tolerance and the characterization of candidate rhizobial isolates that perform better in Al-contaminated soils than commercial strains
A Novel Pro-Inflammatory Mechanosensing Pathway Orchestrated by the Disintegrin Metalloproteinase ADAM15 in Synovial Fibroblasts
Get PDFMechanotransduction is elicited in cells upon the perception of physical forces transmitted via the extracellular matrix in their surroundings and results in signaling events that impact cellular functions. This physiological process is a prerequisite for maintaining the integrity of diarthrodial joints, while excessive loading is a factor promoting the inflammatory mechanisms of joint destruction. Here, we describe a mechanotransduction pathway in synovial fibroblasts (SF) derived from the synovial membrane of inflamed joints. The functionality of this pathway is completely lost in the absence of the disintegrin metalloproteinase ADAM15 strongly upregulated in SF. The mechanosignaling events involve the Ca2+-dependent activation of c-Jun-N-terminal kinases, the subsequent downregulation of long noncoding RNA HOTAIR, and upregulation of the metabolic energy sensor sirtuin-1. This afferent loop of the pathway is facilitated by ADAM15 via promoting the cell membrane density of the constitutively cycling mechanosensitive transient receptor potential vanilloid 4 calcium channels. In addition, ADAM15 reinforces the Src-mediated activation of pannexin-1 channels required for the enhanced release of ATP, a mediator of purinergic inflammation, which is increasingly produced upon sirtuin-1 induction
Voluntary Wheel Running in Old C57BL/6 Mice Reduces Age-Related Inflammation in the Colon but Not in the Brain
Get PDFInflammation is considered a possible cause of cognitive decline during aging. This study investigates the influence of physical activity and social isolation in old mice on their cognitive functions and inflammation. The Barnes maze task was performed to assess spatial learning and memory in 3, 9, 15, 24, and 28 months old male C57BL/6 mice as well as following voluntary wheel running (VWR) and social isolation (SI) in 20 months old mice. Inflammatory gene expression was analyzed in hippocampal and colonic samples by qPCR. Cognitive decline occurs in mice between 15 and 24 months of age. VWR improved cognitive functions while SI had negative effects. Expression of inflammatory markers changed during aging in the hippocampus (Il1a/Il6/S100b/Iba1/Adgre1/Cd68/Itgam) and colon (Tnf/Il6/Il1ra/P2rx7). VWR attenuates inflammaging specifically in the colon (Ifng/Il10/Ccl2/S100b/Iba1), while SI regulates intestinal Il1b and Gfap. Inflammatory markers in the hippocampus were not altered following VWR and SI. The main finding of our study is that both the hippocampus and colon exhibit an increase in inflammatory markers during aging, and that voluntary wheel running in old age exclusively attenuates intestinal inflammation. Based on the existence of the gut-brain axis, our results extend therapeutic approaches preserving cognitive functions in the elderly to the colon
Analysis of N-WASP function in keratinocytes in vivo
No full textN-WASP is a ubiquitously expressed cytoplasmic molecule mediating Arp2/3 nucleated actin polymerization.
We found that mice with a keratinocyte-specific deletion of N-WASP showed normal interfollicular epidermis but delayed hair follicle morphogenesis and abnormal hair follicle cycling associated with cyclic alopecia and prolonged catagen and telogen phases. The delayed anagen onset correlated with an increased expression of the cell cycle inhibitor p21CIP and increased activity of the TGFβ pathway, a known inducer of p21CIP expression. We also found increased apoptosis during the catagen stage, which likely contributes to the hair loss. Differentiation of the hair follicle layers was not altered in absence of N-WASP.
Primary N-WASP null keratinocytes showed reduced growth compared to control cells and enhanced expression of the cell cycle inhibitor p15INK4B, a TGFβ target gene. Inhibition of TGFβ signaling blocked overexpression of p15INK4B and restored proliferation of N-WASP-deficient keratinocytes in vitro. However, induction of N-WASP gene deletion in vitro did not result in obvious changes in TGFβ signaling or growth of keratinocytes, indicating that the in vivo environment is required for the phenotype development.
These data identify the actin nucleation regulator N-WASP as a novel element in hair follicle morphogenesis and hair cycle control, which modulates the antiproliferative and pro-apoptotic TGFβ pathway in keratinocytes in vivo and in vitro
Rac1 is crucial for hair follicle integrity but is not essential for maintenance of the epidermis.
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50328.pdf (Publisher’s version ) (Open Access)Rac1 is a small GTPase that regulates the actin cytoskeleton but also other cellular processes. To investigate the function of Rac1 in skin, we generated mice with a keratinocyte-restricted deletion of the rac1 gene. Rac1-deficient mice lost nearly all of their hair within a few weeks after birth. The nonpermanent part of mutant hair follicles developed constrictions; lost expression of hair follicle-specific keratins, E-cadherin, and alpha6 integrin; and was eventually removed by macrophages. The permanent part of hair follicles and the sebaceous glands were maintained, but no regrowth of full-length hair follicles was observed. In the skin of mutant mice, epidermal keratinocytes showed normal differentiation, proliferation, cell-cell contacts, and basement membrane deposition, demonstrating no obvious defects of Rac1-deficient epidermis in vivo. In vitro, Rac1-null keratinocytes displayed a strong spreading defect and slightly impaired adhesion. These data show that Rac1 plays an important role in sustaining the integrity of the lower part of hair follicles but not in maintenance of the epidermis
Genetically Modified Mice in Medical and Pharmaceutical Research
No full textGenetically altered mice are important models to study the mechanism of inherited and acquired diseases. Furthermore, these mice are extremely useful to test the efficacy of new therapies and to validate potential drug targets. Although the generation of mice carrying point mutations or deletions of specific genes is quite well established, it is still a relatively long procedure. Careful planning of the gene targeting is therefore essential. In this chapter we describe the general procedure of generating genetically altered mice and discuss potential problems that could be encountered and their solution.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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