No abstract

Type I IFN is a major player in innate and adaptive immune responses. Besides, it is involved in organogenesis and tumor development. Generally, IFN responses are amplified by an autocrine loop with IFN-β as the priming cytokine. However, due to the lack of sensitive detection systems, where and how type I IFN is produced in vivo is still poorly understood. In this study, we describe a luciferase reporter mouse, which allows tracking of IFN-β gene induction in vivo. Using this reporter mouse, we reveal strong tissue-specific induction of IFN-β following infection with influenza or La Crosse virus. Importantly, this reporter mouse also allowed us to visualize that IFN-β is expressed constitutively in several tissues. As suggested before, low amounts of constitutively produced IFN might maintain immune cells in an activated state ready for a timely response to pathogens. Interestingly, thymic epithelial cells were the major source of IFN-β under noninflammatory conditions. This relatively high constitutive expression was controlled by the NF Aire and might influence induction of tolerance or T cell development.

The integrin ␣ 2 -subunit was ablated in mice by targeted deletion of the ITGA2 gene. ␣ 2 -Deficient animals develop normally, are fertile, and reproduce. Surprisingly, no obvious anatomical or histological differences were observed in mutant mice. Besides its significance in tissue morphogenesis, integrin ␣ 2 ␤ 1 has been reported to play a major role in hemostasis by mediating platelet adhesion and activation on subendothelial collagen. To define its role in hemostasis, ␣ 2 -deficient platelets were analyzed for their capacity to adhere to and aggregate in response to fibrillar or soluble collagen type I. We show that aggregation of ␣ 2 -deficient platelets to fibrillar collagen is delayed but not reduced, whereas aggregation to enzymatically digested soluble collagen is abolished. Furthermore, ␣ 2 -deficient platelets normally adhere to fibrillar collagen. However, in the presence of an antibody against GPVI (activating platelet collagen receptor), adhesion of ␣ 2 -deficient but not wild type platelets is abrogated. These results demonstrate that integrin ␣ 2 ␤ 1 significantly contributes to platelet adhesion to (fibrillar) collagen, which is further confirmed by the abolished adhesion of ␣ 2 -deficient platelets to soluble collagen. Thus, ␣ 2 ␤ 1 plays a supportive rather than an essential role in platelet-collagen interactions. These results are in agreement with the observation that ␣ 2 ␤ 1 -deficient animals suffer no bleeding anomalies.Integrins are a large family of heterodimeric transmembrane receptors composed of noncovalently associated ␣-and ␤-subunits that function as receptors for extracellular matrix components and also bind to counter receptors on other cells (1-3). Integrin receptors modulate critical cellular processes, including adhesion and spreading, migration, survival, gene expression, and differentiation. These processes are physiologically relevant to growth and development, angiogenesis, and hemostasis but may also be significant in pathological conditions such as tumor metastasis and thrombosis (4 -6).The essential role of ␤ 1 integrins for development and differentiation was clearly demonstrated by the peri-implantation lethality of mouse embryos lacking ␤ 1 integrin (7). Four collagen-binding ␤ 1 integrin receptors have been identified, ␣ 1 ␤ 1 , ␣ 2 ␤ 1 , ␣ 10 ␤ 1 , and ␣ 11 ␤ 1 (8), which interact with collagens via their individual I domains (9 -12).␣ 2 ␤ 1 integrin (VLA-2, platelet GPIaIIa) was thought to play a pivotal role in development, differentiation, and tissue morphogenesis. It is widely expressed, especially on cell types entering the final stages of differentiation (13,14). ␣ 2 ␤ 1 receptors bind with high affinity to collagen I (15) and also to collagens 17), and they mediate adhesion to laminins- 1 and -5 (18, 19). Contact with collagen of ␣ 2 ␤ 1 on fibroblasts and epithelial cells induces synthesis and activation of several matrix metalloproteinases (20 -22) and is therefore thought to play an essential role in connective tissue remodeling and resurfacing of wound...

No abstract

Vacuolar-vesicular protein sorting (Vps) factors are involved in vesicular trafficking in eukaryotic cells. We identified the missense mutation L967Q in Vps54 in the wobbler mouse, an animal model of amyotrophic lateral sclerosis, and also characterized a lethal allele, Vps54(beta-geo). Motoneuron survival and spermiogenesis are severely compromised in the wobbler mouse, indicating that Vps54 has an essential role in these processes.

No abstract

Three mouse lines expressing Cre recombinase under the control of the human K14 promoter induced specific deletion of loxP flanked target sequences in the epidermis, in tongue, and thymic epithelium of the offspring where the Cre allele was inherited from the father. Where the mother carried the Cre allele, loxP flanked sequences were completely deleted in all tissues of the offspring, even in littermates that did not inherit the Cre allele. This maternally inherited phenotype indicates that the human K14 promoter is transcriptionally active in murine oocytes and that the enzyme remains active until after fertilization, even when the Cre allele becomes transmitted to the polar bodies during meiosis. Detection of K14 mRNA by RT-PCR in murine ovaries and immunohistochemical identification of the K14 protein in oocytes demonstrates that the human K14 promoter behaves like its murine homolog, thus identifying K14 as an authentic oocytic protein.

The unfolded protein response (UPR) is a conserved eukaryotic signaling pathway regulating endoplasmic reticulum (ER) homeostasis during ER stress, which results, for example, from an increased demand for protein secretion. Here, we characterize the homologs of the central UPR regulatory proteins Hac1 (for Homologous to ATF/CREB1) and Inositol Requiring Enzyme1 in the plant pathogenic fungus Ustilago maydis and demonstrate that the UPR is tightly interlinked with the b mating-type-dependent signaling pathway that regulates pathogenic development. Exact timing of UPR is required for virulence, since premature activation interferes with the b-dependent switch from budding to filamentous growth. In addition, we found crosstalk between UPR and the b target Clampless1 (Clp1), which is essential for cell cycle release and proliferation in planta. The unusual C-terminal extension of the U. maydis Hac1 homolog, Cib1 (for Clp1 interacting bZIP1), mediates direct interaction with Clp1. The interaction between Clp1 and Cib1 promotes stabilization of Clp1, resulting in enhanced ER stress tolerance that prevents deleterious UPR hyperactivation. Thus, the interaction between Cib1 and Clp1 constitutes a checkpoint to time developmental progression and increased secretion of effector proteins at the onset of biotrophic development. Crosstalk between UPR and the b mating-type regulated developmental program adapts ER homeostasis to the changing demands during biotrophy.