Research Article
Abstract
Oligodendrocyte precursor cells (OPCs) persist near the demyelinated axons arising in MS but inefficiently differentiate into oligodendrocytes and remyelinate these axons. The pathogenesis of differentiation failure remains elusive. We initially hypothesized that injured axons fail to present Contactin, a positive ligand for the oligodendroglial Notch1 receptor to induce myelination, and thus tracked axoglial Contactin/Notch1 signaling in situ, using immunohistochemistry in brain tissue from MS patients containing chronic demyelinated lesions. Instead, we found that Contactin was saturated on demyelinated axons, Notch1-positive OPCs accumulated in Contactin-positive lesions, and the receptor was engaged, as demonstrated by cleavage to Notch1-intracellular domain (NICD). However, nuclear translocalization of NICD, required for myelinogenesis, was virtually absent in these cells. NICD and related proteins carrying nuclear localization signals were associated with the nuclear transporter Importin but were trapped in the cytoplasm. Abnormal expression of TIP30, a direct inhibitor of Importin, was observed in these OPCs. Overexpression of TIP30 in a rat OPC cell line resulted in cytoplasmic entrapment of NICD and arrest of differentiation upon stimulation with Contactin-Fc. Our results suggest that extracellular inhibitory factors as well as an intrinsic nucleocytoplasmic transport blockade within OPCs may be involved in the pathogenesis of remyelination failure in MS.
Authors
Jin Nakahara, Kohsuke Kanekura, Mikiro Nawa, Sadakazu Aiso, Norihiro Suzuki
Abstract
Pulmonary fibrosis, in particular idiopathic pulmonary fibrosis (IPF), results from aberrant wound healing and scarification. One population of fibroblasts involved in the fibrotic process is thought to originate from lung epithelial cells via epithelial-mesenchymal transition (EMT). Indeed, alveolar epithelial cells (AECs) undergo EMT in vivo during experimental fibrosis and ex vivo in response to TGF-β1. As the ECM critically regulates AEC responses to TGF-β1, we explored the role of the prominent epithelial integrin α3β1 in experimental fibrosis by generating mice with lung epithelial cell–specific loss of α3 integrin expression. These mice had a normal acute response to bleomycin injury, but they exhibited markedly decreased accumulation of lung myofibroblasts and type I collagen and did not progress to fibrosis. Signaling through β-catenin has been implicated in EMT; we found that in primary AECs, α3 integrin was required for β-catenin phosphorylation at tyrosine residue 654 (Y654), formation of the pY654–β-catenin/pSmad2 complex, and initiation of EMT, both in vitro and in vivo during the fibrotic phase following bleomycin injury. Finally, analysis of lung tissue from IPF patients revealed the presence of pY654–β-catenin/pSmad2 complexes and showed accumulation of pY654–β-catenin in myofibroblasts. These findings demonstrate epithelial integrin–dependent profibrotic crosstalk between β-catenin and Smad signaling and support the hypothesis that EMT is an important contributor to pathologic fibrosis.
Authors
Kevin K. Kim, Ying Wei, Charles Szekeres, Matthias C. Kugler, Paul J. Wolters, Marla L. Hill, James A. Frank, Alexis N. Brumwell, Sarah E. Wheeler, Jordan A. Kreidberg, Harold A. Chapman
Abstract
Parkinson disease (PD) is a neurodegenerative disorder characterized by a loss of dopamine-containing neurons. Mounting evidence suggests that dopaminergic cell death is influenced by the innate immune system. However, the pathogenic role of the adaptive immune system in PD remains enigmatic. Here we showed that CD8+ and CD4+ T cells but not B cells had invaded the brain in both postmortem human PD specimens and in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD during the course of neuronal degeneration. We further demonstrated that MPTP-induced dopaminergic cell death was markedly attenuated in the absence of mature T lymphocytes in 2 different immunodeficient mouse strains (Rag1–/– and Tcrb–/– mice). Importantly, similar attenuation of MPTP-induced dopaminergic cell death was seen in mice lacking CD4 as well as in Rag1–/– mice reconstituted with FasL-deficient splenocytes. However, mice lacking CD8 and Rag1–/– mice reconstituted with IFN-γ–deficient splenocytes were not protected. These data indicate that T cell–mediated dopaminergic toxicity is almost exclusively arbitrated by CD4+ T cells and requires the expression of FasL but not IFNγ. Further, our data may provide a rationale for targeting the adaptive arm of the immune system as a therapeutic strategy in PD.
Authors
Vanessa Brochard, Béhazine Combadière, Annick Prigent, Yasmina Laouar, Aline Perrin, Virginie Beray-Berthat, Olivia Bonduelle, Daniel Alvarez-Fischer, Jacques Callebert, Jean-Marie Launay, Charles Duyckaerts, Richard A. Flavell, Etienne C. Hirsch, Stéphane Hunot
Abstract
Familial hemiplegic migraine type 1 (FHM1) is an autosomal dominant subtype of migraine with aura that is associated with hemiparesis. As with other types of migraine, it affects women more frequently than men. FHM1 is caused by mutations in the CACNA1A gene, which encodes the α1A subunit of Cav2.1 channels; the R192Q mutation in CACNA1A causes a mild form of FHM1, whereas the S218L mutation causes a severe, often lethal phenotype. Spreading depression (SD), a slowly propagating neuronal and glial cell depolarization that leads to depression of neuronal activity, is the most likely cause of migraine aura. Here, we have shown that transgenic mice expressing R192Q or S218L FHM1 mutations have increased SD frequency and propagation speed; enhanced corticostriatal propagation; and, similar to the human FHM1 phenotype, more severe and prolonged post-SD neurological deficits. The susceptibility to SD and neurological deficits is affected by allele dosage and is higher in S218L than R192Q mutants. Further, female S218L and R192Q mutant mice were more susceptible to SD and neurological deficits than males. This sex difference was abrogated by ovariectomy and senescence and was partially restored by estrogen replacement, implicating ovarian hormones in the observed sex differences in humans with FHM1. These findings demonstrate that genetic and hormonal factors modulate susceptibility to SD and neurological deficits in FHM1 mutant mice, providing a potential mechanism for the phenotypic diversity of human migraine and aura.
Authors
Katharina Eikermann-Haerter, Ergin Dileköz, Chiho Kudo, Sean I. Savitz, Christian Waeber, Michael J. Baum, Michel D. Ferrari, Arn M.J.M. van den Maagdenberg, Michael A. Moskowitz, Cenk Ayata
Abstract
The clear association of Th17 cells with autoimmune pathogenicity implicates Th17 cytokines as critical mediators of chronic autoimmune diseases such as EAE. To study the impact of IL-17A on CNS inflammation, we generated transgenic mice in which high levels of expression of IL-17A could be initiated after Cre-mediated recombination. Although ubiquitous overexpression of IL-17A led to skin inflammation and granulocytosis, T cell–specific IL-17A overexpression did not have a perceptible impact on the development and health of the mice. In the context of EAE, neither the T cell–driven overexpression of IL-17A nor its complete loss had a major impact on the development of clinical disease. Since IL-17F may be able to compensate for the loss of IL-17A, we also generated IL-17F–deficient mice. This strain was fully susceptible to EAE and displayed unaltered emergence and expansion of autoreactive T cells during disease. To eliminate potential compensatory effects of either cytokine, we treated IL-17F–deficient mice with antagonistic monoclonal antibodies specific for IL-17A and found again only a minimal beneficial impact on disease development. We conclude therefore that both IL-17A and IL-17F, while prominently expressed by an encephalitogenic T cell population, may only marginally contribute to the development of autoimmune CNS disease.
Authors
Stefan Haak, Andrew L. Croxford, Katharina Kreymborg, Frank L. Heppner, Sandrine Pouly, Burkhard Becher, Ari Waisman
Abstract
Radiosensitive T–B– severe combined immunodeficiency (RS-SCID) is caused by defects in the nonhomologous end-joining (NHEJ) DNA repair pathway, which results in failure of functional V(D)J recombination. Here we have identified the first human RS-SCID patient to our knowledge with a DNA-PKcs missense mutation (L3062R). The causative mutation did not affect the kinase activity or DNA end-binding capacity of DNA-PKcs itself; rather, the presence of long P-nucleotide stretches in the immunoglobulin coding joints indicated that it caused insufficient Artemis activation, something that is dependent on Artemis interaction with autophosphorylated DNA-PKcs. Moreover, overall end-joining activity was hampered, suggesting that Artemis-independent DNA-PKcs functions were also inhibited. This study demonstrates that the presence of DNA-PKcs kinase activity is not sufficient to rule out a defect in this gene during diagnosis and treatment of RS-SCID patients. Further, the data suggest that residual DNA-PKcs activity is indispensable in humans.
Authors
Mirjam van der Burg, Hanna IJspeert, Nicole S. Verkaik, Tuba Turul, Wouter W. Wiegant, Keiko Morotomi-Yano, Pierre-Olivier Mari, Ilhan Tezcan, David J. Chen, Malgorzata Z. Zdzienicka, Jacques J.M. van Dongen, Dik C. van Gent
Abstract
TLR9 activation is important for the maintenance of mycobacteria-elicited pulmonary granulomatous responses, hallmarks of protective immune responses following mycobacterial infection. However, the mechanism or mechanisms underlying this effect of TLR9 are not clear. Here, we show that Tlr9-deficient mice challenged with a Mycobacterium antigen display an altered Th17 cytokine profile, decreased accumulation of granuloma-associated myeloid DCs, and profoundly impaired delta-like 4 (dll4) Notch ligand expression. Mechanistic analysis revealed that WT bone marrow–derived DCs but not macrophages promoted the differentiation of Th17 cells from bacillus Calmette-Guérin–challenged (BCG-challenged) lung CD4+ T cells. Both lung and bone marrow DCs isolated from Tlr9-deficient mice inoculated with Mycobacterium antigen expressed lower levels of dll4 Notch ligand than the same cells isolated from WT mice. Passively immunizing WT mice with neutralizing antibodies specific for dll4 during granuloma formation resulted in larger granulomas and lower levels of Th17-related cytokines. In addition, dll4 specifically regulated Th17 activation in vitro. Together, these results suggest dll4 plays an important role in promoting Th17 effector activity during a mycobacterial challenge. Furthermore, TLR9 seems to be required for optimal dll4 expression and the regulation of Mycobacterium antigen–elicited granuloma formation in mice.
Authors
Toshihiro Ito, Matthew Schaller, Cory M. Hogaboam, Theodore J. Standiford, Matyas Sandor, Nicholas W. Lukacs, Stephen W. Chensue, Steven L. Kunkel
IL-21R is essential for epicutaneous sensitization and allergic skin inflammation in humans and mice
Abstract
Atopic dermatitis (AD) is a common allergic inflammatory skin disease caused by a combination of intense pruritus, scratching, and epicutaneous (e.c.) sensitization with allergens. To explore the roles of IL-21 and IL-21 receptor (IL-21R) in AD, we examined skin lesions from patients with AD and used a mouse model of allergic skin inflammation. IL-21 and IL-21R expression was upregulated in acute skin lesions of AD patients and in mouse skin subjected to tape stripping, a surrogate for scratching. The importance of this finding was highlighted by the fact that both Il21r–/– mice and WT mice treated with soluble IL-21R–IgG2aFc fusion protein failed to develop skin inflammation after e.c. sensitization of tape-stripped skin. Adoptively transferred OVA-specific WT CD4+ T cells accumulated poorly in draining LNs (DLNs) of e.c. sensitized Il21r–/– mice. This was likely caused by both DC-intrinsic and nonintrinsic effects, because trafficking of skin DCs to DLNs was defective in Il21r–/– mice and, to a lesser extent, in WT mice reconstituted with Il21r–/– BM. More insight into this defect was provided by the observation that skin DCs from tape-stripped WT mice, but not Il21r–/– mice, upregulated CCR7 and migrated toward CCR7 ligands. Treatment of epidermal and dermal cells with IL-21 activated MMP2, which has been implicated in trafficking of skin DCs. These results suggest an important role for IL-21R in the mobilization of skin DCs to DLNs and the subsequent allergic response to e.c. introduced antigen.
Authors
Haoli Jin, Michiko K. Oyoshi, Yi Le, Teresa Bianchi, Suresh Koduru, Clinton B. Mathias, Lalit Kumar, Séverine Le Bras, Deborah Young, Mary Collins, Michael J. Grusby, Joerg Wenzel, Thomas Bieber, Marianne Boes, Leslie E. Silberstein, Hans C. Oettgen, Raif S. Geha
Abstract
The relative activity of lipoprotein lipase (LPL) in different tissues controls the partitioning of lipoprotein-derived fatty acids between sites of fat storage (adipose tissue) and oxidation (heart and skeletal muscle). Here we used a reverse genetic strategy to test the hypothesis that 4 angiopoietin-like proteins (ANGPTL3, -4, -5, and -6) play key roles in triglyceride (TG) metabolism in humans. We re-sequenced the coding regions of the genes encoding these proteins and identified multiple rare nonsynonymous (NS) sequence variations that were associated with low plasma TG levels but not with other metabolic phenotypes. Functional studies revealed that all mutant alleles of ANGPTL3 and ANGPTL4 that were associated with low plasma TG levels interfered either with the synthesis or secretion of the protein or with the ability of the ANGPTL protein to inhibit LPL. A total of 1% of the Dallas Heart Study population and 4% of those participants with a plasma TG in the lowest quartile had a rare loss-of-function mutation in ANGPTL3, ANGPTL4, or ANGPTL5. Thus, ANGPTL3, ANGPTL4, and ANGPTL5, but not ANGPTL6, play nonredundant roles in TG metabolism, and multiple alleles at these loci cumulatively contribute to variability in plasma TG levels in humans.
Authors
Stefano Romeo, Wu Yin, Julia Kozlitina, Len A. Pennacchio, Eric Boerwinkle, Helen H. Hobbs, Jonathan C. Cohen
Abstract
Individuals with the birth defect synpolydactyly (SPD) have 1 or more digit duplicated and 2 or more digits fused together. One form of SPD is caused by polyalanine expansions in homeobox d13 (Hoxd13). Here we have used the naturally occurring mouse mutant that has the same mutation, the SPD homolog (Spdh) allele, and a similar phenotype, to investigate the molecular pathogenesis of SPD. A transgenic approach and crossing experiments showed that the Spdh allele is a combination of loss and gain of function. Here we identify retinaldehyde dehydrogenase 2 (Raldh2), the rate-limiting enzyme for retinoic acid (RA) synthesis in the limb, as a direct Hoxd13 target and show decreased RA production in limbs from Spdh/Spdh mice. Intrauterine treatment with RA restored pentadactyly in Spdh/Spdh mice. We further show that RA and WT Hoxd13 suppress chondrogenesis in mesenchymal progenitor cells, whereas Hoxd13 encoded by Spdh promotes cartilage formation in primary cells isolated from Spdh/Spdh limbs, and that this was associated with increased expression of Sox6/9. Increased Sox9 expression and ectopic cartilage formation in the interdigital mesenchyme of limbs from Spdh/Spdh mice suggest uncontrolled differentiation of these cells into the chondrocytic lineage. Thus, we propose that mutated Hoxd13 causes polydactyly in SPD by inducing extraneous interdigital chondrogenesis, both directly and indirectly, via a reduction in RA levels.
Authors
Pia Kuss, Pablo Villavicencio-Lorini, Florian Witte, Joachim Klose, Andrea N. Albrecht, Petra Seemann, Jochen Hecht, Stefan Mundlos
No posts were found with this tag.
Copyright © 2025 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)