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Found 35817 matches. Displaying 81-90
Alonso RG, Tobin M, Martin P, Hudspeth AJ
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Fast recovery of disrupted tip links induced by mechanical displacement of hair bundles

Hearing and balance rely on the capacity of mechanically sensitive hair bundles to transduce vibrations into electrical signals that are forwarded to the brain. Hair bundles possess tip links that interconnect the mechanosensitive stereocilia and convey force to the transduction channels. A dimer of dimers, each of these links comprises two molecules of protocadherin 15 (PCDH15) joined to two of cadherin 23 (CDH23). The "handshake" that conjoins the four molecules can be disrupted in vivo by intense stimulation and in vitro by exposure to Ca2+ chelators. Using hair bundles from the rat's cochlea and the bullfrog's sacculus, we observed that extensive recovery of mechanoelectrical transduction, hair bundle stiffness, and spontaneous bundle oscillation can occur within seconds after Ca2+ chelation, especially if hair bundles are deflected toward their short edges. Investigating the phenomenon in a two-compartment ionic environment that mimics natural conditions, we combined iontophoretic application of a Ca2+ chelator to selectively disrupt the tip links of individual frog hair bundles with displacement clamping to control hair bundle motion and measure forces. Our observations suggest that, after the normal Ca2+ concentration has been restored, mechanical stimulation facilitates the reconstitution of functional tip links.
Campbell C, Marchildon F, Michaels AJ, Takemoto N, van der Veeken J, Schizas M, Pritykin Y, Leslie CS, Intlekofer AM, Cohen P, Rudensky AY
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FXR mediates T cell-intrinsic responses to reduced feeding during infection

Reduced nutrient intake is a widely conserved manifestation of sickness behavior with poorly characterized effects on adaptive immune responses. During infectious challenges, naive T cells encountering their cognate antigen become activated and differentiate into highly proliferative effector T cells. Despite their evident metabolic shift upon activation, it remains unclear how effector T cells respond to changes in nutrient availability in vivo. Here, we show that spontaneous or imposed feeding reduction during infection decreases the numbers of splenic lymphocytes. Effector T cells showed cell-intrinsic responses dependent on the nuclear receptor Farnesoid X Receptor (FXR). Deletion of FXR in T cells prevented starvation-induced loss of lymphocytes and increased effector T cell fitness in nutrient-limiting conditions, but imparted greater weight loss to the host. FXR deficiency increased the contribution of glutamine and fatty acids toward respiration and enhanced cell survival under low-glucose conditions. Provision of glucose during anorexia of infection rescued effector T cells, suggesting that this sugar is a limiting nutrient for activated lymphocytes and that alternative fuel usage may affect cell survival in starved animals. Altogether, we identified a mechanism by which the host scales immune responses according to food intake, featuring FXR as a T cell-intrinsic sensor.
Altenberg L, Cohen JE
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Nonconcavity of the spectral radius in Levinger's theorem

Let A is an element of R-n x n be a nonnegative irreducible square matrix and let r (A) be its spectral radius and Perron-Frobenius eigenvalue. Levinger asserted and several have proven that r(t) := r((1-t)A + tA(T) ) increases over t is an element of [0, 1/2] and decreases over t is an element of [1/2, 1]. It has further been stated that r(t) is concave over t is an element of (0, 1). Here we show that the latter claim is false in general through a number of counterexamples, but prove it is true for A is an element of R-2 x 2, weighted shift matrices (but not cyclic weighted shift matrices), tridiagonal Toeplitz matrices, and the 3-parameter Toeplitz matrices from Fiedler, but not Toeplitz matrices in general. A general characterization of the range of t, or the class of matrices, for which the spectral radius is concave in Levinger's homotopy remains an open problem. (C) 2020 Elsevier Inc. All rights reserved.
Hatten ME
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Adding cognitive connections to the cerebellum

SCIENCE 2020 DEC 18; 370(6523):1411-1412
Yang R, Mele F, Worley L, Langlais D, Rosain J, Benhsaien I, Elarabi H, Croft CA, Doisne JM, Zhang P, Weisshaar M, Jarrossay D, Latorre D, Shen YC, Han J, Ogishi M, Gruber C, Markle J, Al Ali F, Rahman M, Khan T, Seeleuthner Y, Kerner G, Husquin LT, Maclsaac JL, Jeljeli M, Errami A, Ailal F, Kobor MS, Oleaga-Quintas C, Roynard M, Bourgey M, El Baghdadi J, Boisson-Dupuis S, Puel A, Batteux F, Rozenberg F, Marr N, Pan-Hammarstrom Q, Bogunovic D, Quintana-Murci L, Carroll T, Ma CS, Abel L, Bousfiha A, Di Santo JP, Glimcher LH, Gros P, Tangye SG, Sallusto F, Bustamante J, Casanova JL
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Human T-bet Governs Innate and Innate-like Adaptive IFN-gamma Immunity against Mycobacteria

CELL 2020 DEC 23; 183(7):1826-1847.e31
Inborn errors of human interferon gamma (IFN-gamma) immunity underlie mycobacterial disease. We report a patient with mycobacterial disease due to inherited deficiency of the transcription factor T-bet. The patient has extremely low counts of circulating Mycobacterium-reactive natural killer (NK), invariant NKT (iNKT), mucosal-associated invariant T (MATT), and V delta 2(+) gamma delta T lymphocytes, and of Mycobacterium-non reactive classic T(H)1 lymphocytes, with the residual populations of these cells also producing abnormally small amounts of IFN-gamma. Other lymphocyte subsets develop normally but produce low levels of IFN-gamma, with the exception of CD8(+) alpha beta T and non-classic CD4(+) cep T(H)1* lymphocytes, which produce IFN-gamma normally in response to mycobacterial antigens. Human T-bet deficiency thus underlies mycobacterial disease by preventing the development of innate (NK) and innate-like adaptive lymphocytes (iNKT, MATT, and V delta 2(+) gamma delta T cells) and IFN-gamma production by them, with mycobacterium-specific, IFN-gamma-producing, purely adaptive CD8(+) alpha beta T and CD4(+) alpha beta T(H)1* cells unable to compensate for this deficit.
Zouboulis CC, Benhadou F, Byrd AS, Chandran NS, Giamarellos-Bourboulis EJ, Fabbrocini G, Frew JW, Fujita H, Gonzalez-Lopez MA, Guillem P, Gulliver WPF, Hamzavi I, Hayran Y, Horvath B, Hue S, Hunger RE, Ingram JR, Jemec GB, Ju Q, Kimball AB, Kirby JS, Konstantinou MP, Lowes MA, MacLeod AS, Martorell A, Marzano AV, Matusiak L, Nassif A, Nikiphorou E, Nikolakis G, da Costa AN, Okun MM, Orenstein LAV, Pascual JC, Paus R, Perin B, Prens EP, Rohn TA, Szegedi A, Szepietowski JC, Tzellos T, Wang BX, van der Zee HH
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What causes hidradenitis suppurativa ?-15 years after

The 14 authors of the first review article on hidradenitis suppurativa (HS) pathogenesis published 2008 in EXPERIMENTAL DERMATOLOGY cumulating from the 1st International Hidradenitis Suppurativa Research Symposium held March 30-April 2, 2006 in Dessau, Germany with 33 participants were prophetic when they wrote "Hopefully, this heralds a welcome new tradition: to get to the molecular heart of HS pathogenesis, which can only be achieved by a renaissance of solid basic HS research, as the key to developing more effective HS therapy." (Kurzen et al. What causes hidradenitis suppurativa? Exp Dermatol 2008;17:455). Fifteen years later, there is no doubt that the desired renaissance of solid basic HS research is progressing with rapid steps and that HS has developed deep roots among inflammatory diseases in Dermatology and beyond, recognized as "the only inflammatory skin disease than can be healed". This anniversary article of 43 research-performing authors from all around the globe in the official journal of the European Hidradenitis Suppurativa Foundation e.V. (EHSF e.V.) and the Hidradenitis Suppurativa Foundation, Inc (HSF USA) summarizes the evidence of the intense HS clinical and experimental research during the last 15 years in all aspects of the disease and provides information of the developments to come in the near future.
Pulupa J, Prior H, Johnson DS, Simon SM
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Conformation of the nuclear pore in living cells is modulated by transport state

ELIFE 2020 DEC 21; 9(?):? Article e60654
While the static structure of the nuclear pore complex (NPC) continues to be refined with cryo-EM and x-ray crystallography, in vivo conformational changes of the NPC remain under-explored. We developed sensors that report on the orientation of NPC components by rigidly conjugating mEGFP to different NPC proteins. Our studies show conformational changes to select domains of nucleoporins (Nups) within the inner ring (Nup54, Nup58, Nup62) when transport through the NPC is perturbed and no conformational changes to Nups elsewhere in the NPC. Our results suggest that select components of the NPC are flexible and undergo conformational changes upon engaging with cargo.
Al-Hashimi A, Venugopalan V, Sereesongsaeng N, Tedelind S, Pinzaru AM, Hein Z, Springer S, Weber E, Fuhrer D, Scott CJ, Burden RE, Brix K
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Significance of nuclear cathepsin V in normal thyroid epithelial and carcinoma cells

Altered expression and/or localization of cysteine cathepsins is believed to involve in thyroid diseases including cancer. Here, we examined the localization of cathepsins B and V in human thyroid tissue sections of different pathological conditions by immunolabeling and morphometry. Cathepsin B was mostly found within endo-lysosomes as expected. In contrast, cathepsin V was detected within nuclei, predominantly in cells of cold nodules, follicular and papillary thyroid carcinoma tissue, while it was less often detected in this unusual localization in hot nodules and goiter tissue. To understand the significance of nuclear cathepsin V in thyroid cells, this study aimed to establish a cellular model of stable nuclear cathepsin V expression. As representative of a specific form lacking the signal peptide and part of the propeptide, N-terminally truncated cathepsin V fused to eGFP recapitulated the nuclear localization of endogenous cathepsin V throughout the cell cycle in Nthy-ori 3-1 cells. Interestingly, the N-terminally truncated cathepsin V-eGFP was more abundant in the nuclei during S phase. These findings suggested a possible contribution of nuclear cathepsin V forms to cell cycle progression. Indeed, we found that N-terminally truncated cathepsin V-eGFP expressing cells were more proliferative than those expressing full-length cathepsin V-eGFP or wild type controls. We conclude that a specific molecular form of cathepsin V localizes to the nucleus of thyroid epithelial and carcinoma cells, where it might involve in deregulated pathways leading to hyperproliferation. These findings highlight the necessity to better understand cathepsin trafficking in health and disease. In particular, cell type specificity of mislocalization of cysteine cathepsins, which otherwise act in a functionally redundant manner, seems to be important to understand their non-canonical roles in cell cycle progression.
Radtke AJ, Kandov E, Lowekamp B, Speranza E, Chu CJ, Gola A, Thakur N, Shih R, Yao L, Yaniv ZR, Beuschel RT, Kabat J, Croteau J, Davis J, Hernandez JM, Germain RN
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IBEX: A versatile multiplex optical imaging approach for deep phenotyping and spatial analysis of cells in complex tissues

The diverse composition of mammalian tissues poses challenges for understanding the cell-cell interactions required for organ homeostasis and how spatial relationships are perturbed during disease. Existing methods such as single-cell genomics, lacking a spatial context, and traditional immunofluorescence, capturing only two to six molecular features, cannot resolve these issues. Imaging technologies have been developed to address these problems, but each possesses limitations that constrain widespread use. Here we report a method that overcomes major impediments to highly multiplex tissue imaging. "Iterative bleaching extends multiplexity" (IBEX) uses an iterative staining and chemical bleaching method to enable high-resolution imaging of >65 parameters in the same tissue section without physical degradation. IBEX can be employed with various types of conventional microscopes and permits use of both commercially available and user-generated antibodies in an "open" system to allow easy adjustment of staining panels based on ongoing marker discovery efforts. We show how IBEX can also be used with amplified staining methods for imaging strongly fixed tissues with limited epitope retention and with oligonucleotide-based staining, allowing potential cross-referencing between flow cytometry, cellular indexing of transcriptomes and epitopes by sequencing, and IBEX analysis of the same tissue. To facilitate data processing, we provide an open-source platform for automated registration of iterative images. IBEX thus represents a technology that can be rapidly integrated into most current laboratory workflows to achieve high-content imaging to reveal the complex cellular landscape of diverse organs and tissues.
Jain SU, Khazaei S, Marchione DM, Lundgren SM, Wang XS, Weinberg DN, Deshmukh S, Juretic N, Lu C, Allis CD, Garcia BA, Jabado N, Lewis PW
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Histone H3.3 G34 mutations promote aberrant PRC2 activity and drive tumor progression

A high percentage of pediatric gliomas and bone tumors reportedly harbor missense mutations at glycine 34 in genes encoding histone variant H3.3. We find that these H3.3 G34 mutations directly alter the enhancer chromatin landscape of mesenchymal stem cells by impeding methylation at lysine 36 on histone H3 (H3K36) by SETD2, but not by the NSD1/2 enzymes. The reduction of H3K36 methylation by G34 mutations promotes an aberrant gain of PRC2-mediated H3K27me2/3 and loss of H3K27ac at active enhancers containing SETD2 activity. This altered histone modification profile promotes a unique gene expression profile that supports enhanced tumor development in vivo. Our findings are mirrored in G34W-containing giant cell tumors of bone where patient-derived stromal cells exhibit gene expression profiles associated with early osteoblastic differentiation. Overall, we demonstrate that H3.3 G34 oncohistones selectively promote PRC2 activity by interfering with SETD2-mediated H3K36 methylation. We propose that PRC2-mediated silencing of enhancers involved in cell differentiation represents a potential mechanism by which H3.3 G34 mutations drive these tumors.