Characterization of the non-functional Fas ligand of gld mice

Mice homozygous for either the gld or Ipr mutation develop autoimmune diseases and progressive lymphadenopathy. The Ipr mutation Is characterized by the absence of unctional Fas, whereas gld mice exhibit an inactive FasL due to a point mutation proximal to the extracellular C-terminus. The structural repercussions of this amino acid substitution remain unknown. Here we report that FasL Is expressed at similar levels on the surface of activated T lymphocytes from gld and wild-type mice. Using a polyclonal anti-FasL antibody, Indistinguishable amounts of a 40 kDa protein are detected In both gld and wild-type splenocytes. The molecular model of FasL, based on the known structure of TNF-α, predicts that the Phe→Leu gld mutation is located at the protomer interface which Is close to the FasR Interaction site. We conclude that the gld mutation allows normal FasL biosynthesis, surface expression and ollgomerlzatlon, but induces structural alterations to the Fas binding region leading to the phenotypic changes observe

Cytokine expression and regulation in experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease characterized by leukocytic infiltration of the central nervous system (CNS) and demyelination and remission/relapse. It is induced by CD4$sp{+}$ T cells. We used reverse transcriptase/polymerase chain reaction to analyse T cell and cytokine gene expression in the CNS of SJL/J mice with myelin basic protein-induced EAE. Undetectable in normal CNS and cerebrospinal fluid, the expression of CD3, IL-2, IFN-$gamma$, and TNF$alpha$ increased in EAE, correlating with disease severity, then dropped to background levels during remission. IL-2 and IFN-$gamma$ were produced by CD4$sp{+}$ CD45RB$sp{ rm low}$ T cells isolated from LN and CNS. In contrast, TNF$alpha$ was predominately made by macrophages and microglia in the CNS. Purified microglia from normal CNS were induced to express TNF$alpha$ by activated TH1 supernatant, suggesting that TNF$alpha$ expression by cells in the CNS could be regulated by cytokines from infiltrating T cells. IL-4 was not detectable in total CNS or in isolated CD4$sp{+}$ CD45RB$sp{ rm low}$ cells from the CNS, but was readily amplified from CD4$sp{+}$ CD45RB$sp{ rm low}$ LN T cells. This suggests an enrichment of TH1 cells in autoimmune CNS.To determine the effect of IFN-$gamma$ expression in the CNS, we produced transgenic mice using an IFN-$gamma$ cDNA downstream of an MBP promoter. Expression of the transgene was CNS-specific. MHC class I was induced in the CNS of transgenic mice. Transgenic animals that were backcrossed up to 5 generations with SJL/J did not develop spontaneous pathology. However, when they were immunized with MBP in adjuvant, the penetrance of EAE was greater, symptoms were more severe, and the duration of the first episode significantly longer than in non-transgenic littermates, suggesting a role for IFN-$gamma$ in the amplification and perpetuation of EAE

La b-caténine dans les tumeurs sporadiques chez la souris

Nous avons généré un modèle de tumeurs sporadiques chez la souris suite à l'expression aléatoire d'une forme oncogénique de la b-caténine. Cette expression mime les cancers sporadiques chez l'homme et résulte d'une double recombinaison homologue in vitro et in vivo. En effet, les tumeurs dans ce modèle sont issues de cellules isolées exprimant la forme mutante de la b-caténine, contrairement aux modèles classiques où la b-caténine est surexprimée simultanément dans un grand nombre de cellules, facilitant ainsi de façon artificielle le développement de tumeurs. Dans les souris mutantes ainsi générées, nous avons observé des papillomes dans la zone mammaire et, à plus faible fréquence, des lésions gastriques (dysplasie et métaplasie de type intestinal). Ces tumeurs sont classifiées comme précancéreuses, suggérant que la surexpression de la b-caténine dans des cellules isolées active le processus de transformation dans certains tissus, mais n'est pas suffisante pour le développement de tumeurs malignesLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Precancerous Lesions Upon Sporadic Activation of β-Catenin in Mice

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ERK1/2/MAPK pathway-dependent regulation of the telomeric factor TRF2

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