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Within the Munich, Germany, N-ethyl-N-nitrosourea mouse mutagenesis program, we isolated a dominant Jak1 mouse model resembling phenotypic characteristics related to autoimmune disease. Chromosomal sequencing revealed a new Jak1 (p.Ser645Pro) point mutation at the conserved serine of the pseudokinase domain, corresponding to a somatic human mutation (p.Ser646Phe) inducing a constitutive activation of the Janus kinase (JAK)/STAT pathway. Morphologically, all Jak1(S645P+/-) mice showed a progressive structural deterioration of ears starting at the age of 4 months, with mononuclear cell infiltration into the dermis. Female mutant mice, in particular, developed severe skin lesions in the neck from 7 months of age. The IHC analysis of these lesions showed an activation of Stat3 downstream to Jak1(S645P) and elevated tissue levels of IL-6. Histopathological analysis of liver revealed a nodular regenerative hyperplasia. In the spleen, the number of Russell bodies was doubled, correlating with significant increased levels of all immunoglobulin isotypes and anti-DNA antibodies in serum. Older mutant mice developed thrombocytopenia and altered microcytic red blood cell counts. Jak1(S645P+/-) mice showed phenotypes related to impaired bone metabolism as increased carboxy-terminal collagen cross-link-1 levels and alkaline phosphatase activities in plasma, hypophosphatemia, and strongly decreased bone morphometric values. Taken together, Jak1(S645P+/-) mice showed an increased activation of the IL-6-JAK-STAT pathway leading to a systemic lupus erythematosus-like phenotype and offering a new valuable tool to study the role of the JAK/STAT pathway in disease development.

Hodgkin’s lymphoma (HL) is among the most frequent nodal lymphomas in the Western world and is classified into two disease entities: nodular lymphocyte-predominant Hodgkin’s lymphoma (NLPHL) and classical Hodgkin’s lymphoma (cHL, 95 % of all HL). HL lesions are characterised by a minority of clonal neoplastic cells, namely Hodgkin and Reed-Sternberg (HRS) cells and their variants in cHL and lymphocyte-predominant (LP) cells in NLPHL, both occurring within a microenvironment of, for example, reactive T and B cells, macrophages and granulocytes that are assumed to support the proliferation and maintenance of neoplastic cells through cytokines, chemokines and growth factors. Insulin-like growth factor I (IGF-I) is an important growth factor involved in proliferation, differentiation, apoptosis and cell survival of numerous (including immune) tissues and probably has a role in tumour pathogenesis and maintenance. Although HL is characterised by disturbed cell differentiation and apoptosis mechanisms, with the involvement of the IGF-I receptor (IGF-1R), the distinct location of IGF-I in HL has not yet been defined. We localise IGF-I by double-immunofluorescence in frequent neoplastic cells of all cHL and NLPHL cases investigated. Additionally, IGF-I immunoreactivity is detected in high endothelial venules and various immune cells within the surrounding tissue of cHL including neutrophils and macrophages. IGF-1R immunoreactivity of variable intensity is found in HRS cells and high endothelial venules within the microenvironment in cHL. We assume that autocrine and paracrine IGF-I plays an anti-apoptotic role in tumour pathogenesis and in shaping the tumour microenvironment.

The transcription factor Zscan10 had been attributed a role as a pluripotency factor in embryonic stem cells based on its interaction with Oct4 and Sox2 in in vitro assays. Here we suggest a potential role of Zscan10 in controlling progenitor cell populations in vivo. Mice homozygous for a Zscan10 mutation exhibit reduced weight, mild hypoplasia in the spleen, heart and long bones and phenocopy an eye malformation previously described for Sox2 hypomorphs. Phenotypic abnormalities are supported by the nature of Zscan10 expression in midgestation embryos and adults suggesting a role for Zscan10 in either maintaining progenitor cell subpopulation or impacting on fate choice decisions thereof.

Penicillin-binding proteins (PBPs) are involved in the regulation of β-lactamase expression by determining the level of anhydromuramylpeptides in the periplasmatic space. It was hypothesized that one or more PBPs act as a sensor in the β-lactamase induction pathway. We have performed induction studies with Escherichia coli mutants lacking one to four PBPs with dd -carboxypeptidase activity. Therefore, we conclude that a strong β-lactamase inducer must inhibit all dd -carboxypeptidases as well as the essential PBPs 1a, 1b, and/or 2.

Under the label of the German Mouse Clinic (GMC), a concept has been developed and implemented that allows the better understanding of human diseases on the pathophysiological and molecular level. This includes better understanding of the crosstalk between different organs, pleiotropy of genes, and the systemic impact of envirotypes and drugs. In the GMC, experts from various fields of mouse genetics and physiology, in close collaboration with clinicians, work side by side under one roof. The GMC is an open-access platform for the scientific community by providing phenotypic analysis in bilateral collaborations ("bottom-up projects") and as a partner and driver in international large-scale biology projects ("top-down projects"). Furthermore, technology development is a major topic in the GMC. Innovative techniques for primary and secondary screens are developed and implemented into the phenotyping pipelines (e.g., detection of volatile organic compounds, VOCs).

CD20 is a B-lymphocyte-specific integral membrane protein, implicated in the regulation of transmembrane calcium conductance, cell-cycle progression and B-lymphocyte proliferation. CD20 is proposed to function as a SOCC (store-operated calcium channel). SOCCs are activated by receptor-stimulated calcium depletion of intracellular stores. Sustained calcium conductivity across the plasma membrane mediated by SOCC activity is required for long-term calcium-dependent processes, such as transcriptional control and gene expression. Cross-linking of CD20 by antibodies (e.g. Rituxan) has been reported to induce a rapid redistribution of CD20 into specialized microdomains at the plasma membrane, known as lipid rafts. Recruitment of CD20 into lipid rafts and its homo-oligomerization are suggested to be crucial for CD20 activity and regulation. This review outlines recent biochemical studies characterizing the role of CD20 in calcium signalling in B-lymphocytes and evaluates an engagement of lipid rafts in the regulation of CD20-mediated calcium conductivity.

The ABC transporter Mdl1p, a structural and functional homologue of the transporter associated with antigen processing (TAP) plays an important role in intracellular peptide transport from the mitochondrial matrix of Saccharomyces cerevisiae. To characterize the ATP hydrolysis cycle of Mdl1p, the nucleotide-binding domain (NBD) was overexpressed in Escherichia coli and purified to homogeneity. The isolated NBD was active in ATP binding and hydrolysis with a turnover of 25 ATP per minute and a Km of 0.6 mm and did not show cooperativity in ATPase activity. However, the ATPase activity was non-linearly dependent on protein concentration (Hill coefficient of 1.7), indicating that the functional state is a dimer. Dimeric catalytic transition states could be trapped either by incubation with orthovanadate or beryllium fluoride, or by mutagenesis of the NBD. The nucleotide composition of trapped intermediate states was determined using [α-32P]ATP and [γ-32P]ATP. Three different dimeric intermediate states were isolated, containing either two ATPs, one ATP and one ADP, or two ADPs. Based on these experiments, it was shown that: (i) ATP binding to two NBDs induces dimerization, (ii) in all isolated dimeric states, two nucleotides are present, (iii) phosphate can dissociate from the dimer, (iv) both nucleotides are hydrolyzed, and (v) hydrolysis occurs in a sequential mode. Based on these data, we propose a processive-clamp model for the catalytic cycle in which association and dissociation of the NBDs depends on the status of bound nucleotides.