A comprehensive antibody panel for immunohistochemical analysis of formalin-fixed, paraffin-embedded hematopoietic neoplasms of mice: analysis of mouse specific and human antibodies cross-reactive with murine tissue

Increased estrogen to androgen ratio enhances immunoglobulin levels and impairs B cell function in male mice

Sex steroids, such as estrogens and androgens, are important regulators of the humoral immune response. Studies in female mice have demonstrated that alteration of circulating estrogen concentration regulates antibody-mediated immunity. As males have normally little endogenous estrogen, we hypothesized that in males high estrogens and low androgens affect the immune system and enhance the allergic inflammatory response. Here, we studied transgenic male mice expressing human aromatase (AROM+). These animals have a high circulating estrogen to androgen ratio (E/A), causing female traits such as gynecomastia. We found that AROM+ male mice had significantly higher plasma immunoglobulin levels, particularly IgE. Flow cytometry analyses of splenocytes revealed changes in mature/immature B cell ratio together with a transcriptional upregulation of the Igh locus. Furthermore, higher proliferation rate and increased IgE synthesis after IgE class-switching was found. Subsequently, we utilized an ovalbumin airway challenge model to test the allergic response in AROM+ male mice. In line with above observations, an increase in IgE levels was measured, albeit no impact on immune cell infiltration into the lungs was detected. Together, our findings suggest that high circulating E/A in males significantly alters B cell function without any significant enhancement in allergic inflammation.

High-Resolution Histological Landscape of AAV DNA Distribution in Cellular Compartments and Tissues following Local and Systemic Injection

Adeno-associated virus (AAV) is one of the most important gene delivery vehicles for in vivo gene therapy. Intramuscular (i.m.) and intravascular (i.v.) injection are commonly used for AAV gene transfer. Unfortunately, the fate of AAV vectors following administration remains unclear at the histological level. Taking advantage of RNAscope, a recently developed in situ hybridization technique that can reveal high-resolution viral DNA localization information, in this study, we evaluated body-wide distribution of an AAV9 vector in the context of the cell and tissue microenvironments. We observed distinctive kinetics of cell and nuclear entry of the AAV DNA in striated muscle and liver following i.m. and i.v. injection. We also found characteristic distribution patterns of the AAV DNA in various histological structures in internal organs, including gonads and lymph nodes, following i.v. injection. Finally, we showed significantly body-wide spreading of the AAV DNA following i.m. injection. These results add a new dimension to our understanding of AAV transduction biology and provide a basis for assessing the full impact of AAV gene therapy.

Immunohistochemical identification of T and B lymphocytes in formalin-fixed paraffin-embedded chicken tissues using commercial antibodies

Immunohistochemical method to detect avian lymphocytes is an efficient and reliable tool for accurate diagnosis, and immunological analysis of avian diseases. However, there are scarce studies reporting immunohistochemistry (IHC) using commercially available antibodies in formalin-fixed paraffin-embedded (FFPE) chicken tissues. In the present study, we established an immunohistochemical method to identify chicken T and B lymphocytes in FFPE chicken tissues using commercial antibodies against chicken or human antigens. For this IHC method, the five tested anti-T lymphocyte antibodies reacted with chicken T lymphocytes on the FFPE sections. Further, 10 commercial anti-B lymphocyte antibodies were tested; of these, three successfully detected chicken B lymphocytes for IHC. In particular, anti-human CD3 (clone F7.2.38) antibody was most suitable for the detection of chicken T lymphocytes, whereas anti-chicken B cell activating factor receptor (BAFF-R) antibody (clone 2C4) was most suitable for the detection of chicken B lymphocytes under our IHC staining conditions. These two antibodies reacted with numerous lymphocytes of all representative lymphoid tissues without problematic background staining and nonspecific reactions. Our results indicate that T and B lymphocytes in FFPE chicken tissues can be immunohistochemically detected using commercial antibodies.

Identification of aspartame-induced haematopoietic and lymphoid tumours in rats after lifetime treatment

Lymphomas and leukaemias involving the lung have in some cases been hard to distinguish from respiratory tract infection in Sprague-Dawley (SD) rats from long-term bioassays. In order to differentiate between tumours and immune cell infiltrates, updated pathological criteria and nomenclature were used and immunohistochemistry (IHC) was applied to haematopoietic and lymphoid tissue tumours (HLTs) in the original prenatal long-term Aspartame (APM) study performed by the Ramazzini Institute (RI). All 78 cases of HLTs from treated and control groups were re-examined based on light microscopic morphological characteristics and subjected to a panel of IHC markers including Ki67, CD3, PAX5, CD20, CD68, TdT, CD45, CD14 and CD33. The analysis confirmed the diagnoses of HLTs in 72 cases, identified 3 cases of preneoplastic lesions (lymphoid hyperplasia), and categorized 3 cases as inflammatory lesions. A statistically significant increase in total HLTs (p = 0.006), total lymphomas (p = 0.032) and total leukaemias (p = 0.031) in treated female rats was confirmed (high dose vs control), and a statistically significant linear trend for each HLT type was also observed. After the HLT cases re-evaluation, the results obtained are consistent with those reported in the previous RI publication and reinforce the hypothesis that APM has a leukaemogenic and lymphomatogenic effect.

Nonproliferative and Proliferative Lesions of the Rat and Mouse Hematolymphoid System

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative changes in rats and mice. The purpose of this publication is to provide a standardized nomenclature for classifying changes observed in the hematolymphoid organs, including the bone marrow, thymus, spleen, lymph nodes, mucosa-associated lymphoid tissues, and other lymphoid tissues (serosa-associated lymphoid clusters and tertiary lymphoid structures) with color photomicrographs illustrating examples of the lesions. Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions as well as lesions induced by exposure to test materials. The nomenclature for these organs is divided into 3 terminologies: descriptive, conventional, and enhanced. Three terms are listed for each diagnosis. The rationale for this approach and guidance for its application to toxicologic pathology are described in detail below.

A quantitative brain map of experimental cerebral malaria pathology

The murine model of experimental cerebral malaria (ECM) has been utilised extensively in recent years to study the pathogenesis of human cerebral malaria (HCM). However, it has been proposed that the aetiologies of ECM and HCM are distinct, and, consequently, no useful mechanistic insights into the pathogenesis of HCM can be obtained from studying the ECM model. Therefore, in order to determine the similarities and differences in the pathology of ECM and HCM, we have performed the first spatial and quantitative histopathological assessment of the ECM syndrome. We demonstrate that the accumulation of parasitised red blood cells (pRBCs) in brain capillaries is a specific feature of ECM that is not observed during mild murine malaria infections. Critically, we show that individual pRBCs appear to occlude murine brain capillaries during ECM. As pRBC-mediated congestion of brain microvessels is a hallmark of HCM, this suggests that the impact of parasite accumulation on cerebral blood flow may ultimately be similar in mice and humans during ECM and HCM, respectively. Additionally, we demonstrate that cerebrovascular CD8+ T-cells appear to co-localise with accumulated pRBCs, an event that corresponds with development of widespread vascular leakage. As in HCM, we show that vascular leakage is not dependent on extensive vascular destruction. Instead, we show that vascular leakage is associated with alterations in transcellular and paracellular transport mechanisms. Finally, as in HCM, we observed axonal injury and demyelination in ECM adjacent to diverse vasculopathies. Collectively, our data therefore shows that, despite very different presentation, and apparently distinct mechanisms, of parasite accumulation, there appear to be a number of comparable features of cerebral pathology in mice and in humans during ECM and HCM, respectively. Thus, when used appropriately, the ECM model may be useful for studying specific pathological features of HCM.

Long-term observation reveals high-frequency engraftment of human acute myeloid leukemia in immunodeficient mice

Repopulation of immunodeficient mice remains the primary method for functional assessment of human acute myeloid leukemia. Published data report engraftment in ~40–66% of cases, mostly of intermediate- or poor-risk subtypes. Here we report that extending follow-up beyond the standard analysis endpoints of 10 to 16 weeks after transplantation permitted leukemic engraftment from nearly every case of xenotransplanted acute myeloid leukemia (18/19, ~95%). Xenogeneic leukemic cells showed conserved immune pheno-types and genetic signatures when compared to corresponding pre-transplant cells and, furthermore, were able to induce leukemia in re-transplantation assays. Importantly, bone marrow biopsies taken at standardized time points failed to detect leukemic cells in 11/18 of cases that later showed robust engraftment (61%, termed “long-latency engrafters”), indicating that leukemic cells can persist over months at undetectable levels without losing disease-initiating properties. Cells from favorable-risk leukemia subtypes required longer to become detectable in NOD/SCID/IL2Rγ^null mice (27.5±9.4 weeks) than did cells from intermediate-risk (21.9±9.4 weeks, P<0.01) or adverse-risk (17±7.6 weeks; P<0.0001) subtypes, explaining why the engraftment of the first was missed with previous protocols. Mechanistically, leukemic cells engrafting after a prolonged latency showed inferior homing to the bone marrow. Finally, we applied our model to favorable-risk acute myeloid leukemia with inv(16); here, we showed that CD34⁺ (but not CD34⁻) blasts induced robust, long-latency engraftment and expressed enhanced levels of stem cell genes. In conclusion, we provide a model that allows in vivo mouse studies with a wide range of molecular subtypes of acute myeloid leukemia subtypes which were previously considered not able to engraft, thus enabling novel insights into leukemogenesis.

Acute DNA damage activates the tumour suppressor p53 to promote radiation-induced lymphoma

Genotoxic cancer therapies, such as chemoradiation, cause haematological toxicity primarily by activating the tumour suppressor p53. While inhibiting p53-mediated cell death during cancer therapy ameliorates haematologic toxicity, whether it also impacts carcinogenesis remains unclear. Here we utilize a mouse model of inducible p53 short hairpin RNA (shRNA) to show that temporarily blocking p53 during total-body irradiation (TBI) not only ameliorates acute toxicity, but also improves long-term survival by preventing lymphoma development. Using Kras^LA1 mice, we show that TBI promotes the expansion of a rare population of thymocytes that express oncogenic Kras^G12D. However, blocking p53 during TBI significantly suppresses the expansion of Kras^G12D-expressing thymocytes. Mechanistically, bone marrow transplant experiments demonstrate that TBI activates p53 to decrease the ability of bone marrow cells to suppress lymphoma development through a non-cell-autonomous mechanism. Together, our results demonstrate that the p53 response to acute DNA damage promotes the development of radiation-induced lymphoma.

p53 can be activated by oncogenic stress to suppress tumourigenesis, but its role in radiation carcinogenesis has not been studied in p53 wild-type mice. Here, Lee et al. show that knocking down p53 during total-body irradiation not only reduces acute toxicity, but prevents the formation of radiation-induced lymphoma.

SOX2 expression associates with stem cell state in human ovarian carcinoma

The SRY-related HMG-box family of transcription factors member SOX2 regulates stemness and pluripotency in embryonic stem cells and plays important roles during early embryogenesis. More recently, SOX2 expression was documented in several tumor types including ovarian carcinoma, suggesting an involvement of SOX2 in regulation of cancer stem cells (CSC). Intriguingly, however, studies exploring the predictive value of SOX2 protein expression with respect to histopathologic and clinical parameters report contradictory results in individual tumors, indicating that SOX2 may play tumor-specific roles. In this report, we analyze the functional relevance of SOX2 expression in human ovarian carcinoma. We report that in human serous ovarian carcinoma (SOC) cells, SOX2 expression increases the expression of CSC markers, the potential to form tumor spheres, and the in vivo tumor-initiating capacity, while leaving cellular proliferation unaltered. Moreover, SOX2-expressing cells display enhanced apoptosis resistance in response to conventional chemotherapies and TRAIL. Hence, our data show that SOX2 associates with stem cell state in ovarian carcinoma and induction of SOX2 imposes CSC properties on SOC cells. We propose the existence of SOX2-expressing ovarian CSCs as a mechanism of tumor aggressiveness and therapy resistance in human SOC.

An ENU mutagenesis-derived mouse model with a dominant Jak1 mutation resembling phenotypes of systemic autoimmune disease

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.

T-helper-1-cell cytokines drive cancer into senescence

Cancer control by adaptive immunity involves a number of defined death and clearance mechanisms. However, efficient inhibition of exponential cancer growth by T cells and interferon-γ (IFN-γ) requires additional undefined mechanisms that arrest cancer cell proliferation. Here we show that the combined action of the T-helper-1-cell cytokines IFN-γ and tumour necrosis factor (TNF) directly induces permanent growth arrest in cancers. To safely separate senescence induced by tumour immunity from oncogene-induced senescence, we used a mouse model in which the Simian virus 40 large T antigen (Tag) expressed under the control of the rat insulin promoter creates tumours by attenuating p53- and Rb-mediated cell cycle control. When combined, IFN-γ and TNF drive Tag-expressing cancers into senescence by inducing permanent growth arrest in G1/G0, activation of p16INK4a (also known as CDKN2A), and downstream Rb hypophosphorylation at serine 795. This cytokine-induced senescence strictly requires STAT1 and TNFR1 (also known as TNFRSF1A) signalling in addition to p16INK4a. In vivo, Tag-specific T-helper 1 cells permanently arrest Tag-expressing cancers by inducing IFN-γ- and TNFR1-dependent senescence. Conversely, Tnfr1(-/-)Tag-expressing cancers resist cytokine-induced senescence and grow aggressively, even in TNFR1-expressing hosts. Finally, as IFN-γ and TNF induce senescence in numerous murine and human cancers, this may be a general mechanism for arresting cancer progression.

Mast cells and inflammation-associated colorectal carcinogenesis

Close association between chronic inflammation and cancer has been recently highlighted. Indeed, inflammatory bowel disease (IBD) has been strongly linked with an increased risk of development of colorectal cancer (CRC). Inflammatory cell-produced inflammatory mediators, such as proinflammatory cytokines and inducible enzymes, contribute to this association. In an inflammatory microenvironment, infiltrating macrophages and mast cells mediate production of these inflammatory mediators to promote growth of tumors in target tissues. In contrast to macrophages, contribution of mast cells to CRC development in inflamed colon is not well understood. This study aimed to determine the role of mast cells in inflammation-associated colorectal carcinogenesis. CRC was induced by administration of the colonic carcinogen, azoxymethane (AOM), and the tumor promoter dextran sodium sulfate (DSS) in male mast cell-deficient WBBF(1)-kit (W/W-v) (W/W(v)) and mast cell-normal WBB6F(1)-+/+(WT) mice. At week 12, the W/W(v) mice had markedly lower inflammation scores in the colon when compared with WT mice. The mRNA levels of colonic proinflammatory cytokines and inducible enzymes were also decreased in W/W(V) mice at weeks 12 and 20, when compared with WT counterparts. Colorectal tumors, including CRC, were identified by histopathological analysis performed 20 weeks thereafter. Importantly, there were less neoplastic and preneoplastic colonic lesions in the W/W(v) mice compared with the WT mice. Thus, for the first time, our study shows that mice lacking mast cells are less susceptible to inflammation-associated colorectal carcinogenesis. Our findings also suggest that mast cells and their selected cytokines could play an important role in inflammation-mediated tumorigenesis through regulation of proinflammatory cytokines and inducible inflammatory enzymes.

The utility of immunohistochemistry for the identification of hematopoietic and lymphoid cells in normal tissues and interpretation of proliferative and inflammatory lesions of mice and rats

Expression of antigens in cells and tissues can be readily studied immunohistochemically with the use of antibodies. A panel of antibodies to cell-specific markers can be used to diagnose lesions, including tumors, in the hematopoietic and lymphoid systems. This review discusses the use of readily available antibodies and procedures to identify antigens expressed in normal tissues and in proliferative and inflammatory lesions in formalin-fixed, paraffin-embedded (FFPE) murine specimens.

The feed-forward loop between YB-1 and MYC is essential for multiple myeloma cell survival

Y-box binding protein 1 (YB-1) functions as a translational regulator and has been suggested to elevate MYC mRNA translation via an internal ribosome entry segment (IRES) point mutation in multiple myeloma (MM). We show that YB-1-mediated translation of MYC mRNA occurs independently of the reported IRES mutation, as 87 MM patients (n=88) and all tested human MM cell lines (HMCLs) were negative for the mutation. We show for the first time that positive MYC staining predicts YB-1 co-expression in malignant plasma cells and YB-1/MYC co-expression increases from 30% in medullary to 70% in extramedullary MM. YB-1 knockdown in HMCLs reduced both MYC protein levels and MYC mRNA in the polysomal fraction, providing a mechanism by which YB-1 controls MYC translation. MYC transcription of YB-1 is demonstrated in HMCLs as MYC knockdown resulted in reduced YB-1 protein and mRNA levels. Furthermore, MYC activation in non-malignant mouse embryonic fibroblasts (MEFs) increased YB-1 mRNA, clearly indicating that MYC drives YB-1 transcription. Importantly, perturbation of the MYC/YB-1 oncogenic circuit leads to apoptosis in HMCLs. Here, we demonstrate that these two proteins co-regulate each other via combined transcriptional/translational activity establishing their pivotal role in MM cell survival. We therefore suggest that targeting the YB-1/mRNA interaction provides a new strategy for MM drug development.

Differentiation of rodent immune and hematopoietic system reactive lesions from neoplasias

The immune and hematopoietic systems play an important role in the normal homeostasis of blood and blood cells and for immune responses to endogenous and exogenous processes and insults. In order to interpret histopathologic changes in the immune and hematopoietic systems, it is important to understand the normal anatomy and histology of the thymus, spleen, lymph nodes, bone marrow, and other tissues. The thymus, spleen, and lymph nodes can be categorized by anatomical compartments, each of which contributes to specific immune functions. Lesions may be diagnosed by interpretive or descriptive (semiquantitative) methods. The interpretation of these tissues by lesion in anatomical compartments should allow for better understanding of these reactions and more definitive pathologic findings. Proliferative lesions may be difficult to differentiate from lymphomas and leukemias. The use of immunohistochemistry, compartmental pathology, and methods for the evaluation of clonality will make interpretation easier.

Inhibition of PPARγ in myeloid-lineage cells induces systemic inflammation, immunosuppression, and tumorigenesis

Peroxisome proliferator-activated receptor-γ (PPARγ) is an anti-inflammatory molecule. To study its biologic function in myeloid cells, dominant-negative PPARγ (dnPPARγ) was overexpressed in a myeloid-specific bitransgenic mouse model. In this bitransgenic system, overexpression of the dnPPARγ-Flag fusion protein in myeloid-lineage cells abnormally elevated frequencies and total numbers of IL-7Rα(-)Lin(-)c-Kit(+)Sca-1(-), Lin(-)/Scal(+)/c-Kit(+), common myeloid, and granulocyte-monocyte progenitor populations in the BM. dnPPARγ overexpression led to up-regulation of IL-1β, IL-6, and TNFα in the blood plasma. As a result, CD11b(+)Ly6G(+) cells were systemically increased in association with activation of Stat3, NF-κB, Erk1/2, and p38 molecules. Myeloid-derived suppressor cells (MDSCs) inhibited the proliferation and lymphokine production of wild-type CD4+ T cells in vitro. CD4+ T cells from doxycycline-treated bitransgenic mice displayed reduced proliferation and lymphokine release. Both CD4+ and CD8+ T-cell populations were decreased in doxycycline-treated bitransgenic mice. Multiple forms of carcinoma and sarcoma in the lung, liver, spleen, and lymph nodes were observed in doxycycline-treated bitransgenic mice. BM transplantation revealed that a myeloid-autonomous defect was responsible for MDSC expansion, immunosuppression, and tumorigenesis in these mice. These studies suggest that anti-inflammatory PPARγ in myeloid-lineage cells plays a key role in controlling pro-inflammatory cytokine synthesis, MDSC expansion, immunosuppression, and the development of cancer.

Prevention of multiple low-dose streptozotocin (MLD-STZ) diabetes in mice by an extract from gum resin of Boswellia serrata (BE)

Type 1-diabetes is an autoimmune disease, where a chronic inflammatory process finally causes β-cell death and insulin deficiency. Extracts from gum resin of Boswellia serrata (BE) have been shown to posses anti-inflammatory properties especially by targeting factors/mediators related to autoimmune diseases. Multiple low dose-streptozotocin (MLD-STZ) treatment is a method to induce diabetes in animals similar to Type 1 diabetes in humans. It was aimed to study whether or not a BE could prevent hyperglycemia, inflammation of pancreatic islets and increase of proinflammatory cytokines in the blood in MLD-STZ treated mice. In BK+/+ wild type mice, 5 days of daily treatment with 40 mg/kg STZ i.p. produced permanent increase of blood glucose, infiltration of lymphocytes into pancreatic islets (CD3-stain), apoptosis of periinsular cells (staining for activated caspase 3) after 10 days as well as shrinking of islet tissue after 35 days (H&E staining). This was associated with an increase of granulocyte colony stimulating factor (G-CSF), granulocyte/macrophage colony stimulating factor (GM-CSF) and proinflammatory cytokines (IL-1A, IL-1B, IL-2, IL-6, IFN-γ, TNF-α) in the blood. Whereas BE alone did not affect blood glucose in non diabetic mice, in STZ treated mice simultaneous i.p. injection of 150 mg/kg of BE over 10 days prevented animals from increase of blood glucose levels. Histochemical studies showed, that i.p. injection of 150 mg/kg BE for 10 days starting with STZ treatment, avoided lymphocyte infiltration into islets, apoptosis of periinsular cells and shrinking of islet size 35 days after STZ. As far as the cytokines tested are concerned, there was a significant inhibition of the increase of G-CSF and GM-CSF. BE also significantly prevented the increase of IL-1A, IL-1B, IL-2, IL-6, IFN-γ and TNF-α. It is concluded that extracts from the gum resin of Boswellia serrata prevent islet destruction and consequent hyperglycemia in an animal model of type 1 diabetes probably by inhibition of the production/action of cytokines related to induction of islet inflammation in an autoimmune process.

A novel N-ethyl-N-nitrosourea-induced mutation in phospholipase Cγ2 causes inflammatory arthritis, metabolic defects, and male infertility in vitro in a murine model

OBJECTIVE

It is difficult to identify a single causative factor for inflammatory arthritis because of the multifactorial nature of the disease. This study was undertaken to dissect the molecular complexity of systemic inflammatory disease, utilizing a combined approach of mutagenesis and systematic phenotype screening in a murine model.

METHODS

In a large-scale N-ethyl-N-nitrosourea mutagenesis project, the Ali14 mutant mouse strain was established because of dominant inheritance of spontaneous swelling and inflammation of the hind paws. Genetic mapping and subsequent candidate gene sequencing were conducted to find the causative gene, and systematic phenotyping of Ali14/+ mice was performed in the German Mouse Clinic.

RESULTS

A novel missense mutation in the phospholipase Cγ2 gene (Plcg2) was identified in Ali14/+ mice. Because of the hyperreactive external entry of calcium observed in cultured B cells and other in vitro experiments, the Ali14 mutation is thought to be a novel gain-of-function allele of Plcg2. Findings from systematic screening of Ali14/+ mice demonstrated various phenotypic changes: an abnormally high T cell:B cell ratio, up-regulation of Ig, alterations in body composition, and a reduction in cholesterol and triglyceride levels in peripheral blood. In addition, spermatozoa from Ali14/+ mice failed to fertilize eggs in vitro, despite the normal fertility of the Ali14/+ male mice in vivo.

CONCLUSION

These results suggest that the Plcg2-mediated pathways play a crucial role in various metabolic and sperm functions, in addition to initiating and maintaining the immune system. These findings may indicate the importance of the Ali14/+ mouse strain as a model for systemic inflammatory diseases and inflammation-related metabolic changes in humans.

Hematopoietic proliferative lesions in the spleen of rasH2 transgenic mice treated with MNU

In this study, rasH2-Tg mice treated with N-methyl-N-nitrosurea (MNU) developed exuberant hematoproliferative changes in the spleen that included dysplasia and features of neoplasia. Hematoproliferative change was characterized as exuberant proliferation of hematopoietic cells within the spleen that distorted but did not displace normal splenic morphologic features. The hematopoietic cells were of mixed lineage, but one type, often erythroid, predominated. Cellular atypia was present in all mice with hematoproliferative change, and dysplasia was present in five of eight examined. Hematoproliferative neoplasia was characterized by similar cytologic features but also resulted in displacement/disruption of normal splenic architecture and increased numbers of unidentified blast cells. One case was differentiated toward myeloid proliferation, suggesting granulocytic leukemia. Affected mice had other neoplasms, such as lymphoma and anemia. These proliferative and dysplastic lesions of the spleen in rasH2-Tg mice treated with MNU require additional characterization to definitively differentiate them from the reactive hematopoiesis that can occur in response to inflammatory, neoplastic, or hematopoietic insults in mice.

Mouse phenotyping

Model organisms like the mouse are important tools to learn more about gene function in man. Within the last 20 years many mutant mouse lines have been generated by different methods such as ENU mutagenesis, constitutive and conditional knock-out approaches, knock-down, introduction of human genes, and knock-in techniques, thus creating models which mimic human conditions. Due to pleiotropic effects, one gene may have different functions in different organ systems or time points during development. Therefore mutant mouse lines have to be phenotyped comprehensively in a highly standardized manner to enable the detection of phenotypes which might otherwise remain hidden. The German Mouse Clinic (GMC) has been established at the Helmholtz Zentrum München as a phenotyping platform with open access to the scientific community (www.mousclinic.de; [1]). The GMC is a member of the EUMODIC consortium which created the European standard workflow EMPReSSslim for the systemic phenotyping of mouse models (http://www.eumodic.org/[2]).

Diverse hematological malignancies including hodgkin-like lymphomas develop in chimeric MHC class II transgenic mice

A chimeric HLA-DR4-H2-E (DR4) homozygous transgenic mouse line spontaneously develops diverse hematological malignancies with high frequency (70%). The majority of malignancies were distributed equally between T and B cell neoplasms and included lymphoblastic T cell lymphoma (LTCL), lymphoblastic B cell lymphoma (LBCL), diffuse large B cell lymphoma (DLBCL), the histiocyte/T cell rich variant of DLBCL (DLBCL-HA/T cell rich DLBCL), splenic marginal zone lymphoma (SMZL), follicular B cell lymphoma (FBL) and plasmacytoma (PCT). Most of these neoplasms were highly similar to human diseases. Also, some non-lymphoid malignancies such as acute myeloid leukemia (AML) and histiocytic sarcoma were found. Interestingly, composite lymphomas, including Hodgkin-like lymphomas, were also detected that had CD30(+) Hodgkin/Reed-Sternberg (H/RS)-like cells, representing a tumor type not previously described in mice. Analysis of microdissected H/RS-like cells revealed their origin as germinal center B cells bearing somatic hypermutations and, in some instances, crippled mutations, as described for human Hodgkin lymphoma (HL). Transgene integration in an oncogene was excluded as an exclusive driving force of tumorigenesis and age-related lymphoma development suggests a multi-step process. Thus, this DR4 line is a useful model to investigate common molecular mechanisms that may contribute to important neoplastic diseases in man.

Systemic first-line phenotyping

With the completion of the mouse genome sequence an essential task for biomedical sciences in the twenty-first century will be the generation and functional analysis of mouse models for every gene in the mammalian genome. More than 30,000 mutations in ES cells will be engineered and thousands of mouse disease models will become available over the coming years by the collaborative effort of the International Mouse Knockout Consortium. In order to realize the full value of the mouse models proper characterization, archiving and dissemination of mouse disease models to the research community have to be performed. Phenotyping centers (mouse clinics) provide the necessary capacity, broad expertise, equipment, and infrastructure to carry out large-scale systemic first-line phenotyping. Using the example of the German Mouse Clinic (GMC) we will introduce the reader to the different aspects of the organization of a mouse clinic and present selected methods used in first-line phenotyping.

Npm1 is a haploinsufficient suppressor of myeloid and lymphoid malignancies in the mouse

Nucleophosmin (NPM1) gene has been heavily implicated in cancer pathogenesis both as a putative proto-oncogene and tumor suppressor gene. NPM1 is the most frequently mutated gene in acute myeloid leukemia (AML), while deletion of 5q, where NPM1 maps, is frequent in patients with myelodysplastic syndromes (MDS). We have previously shown that mice heterozygous for Npm1 (Npm1+/-) develop a hematologic syndrome with features of human MDS. Here we analyzed Npm1+/- mutants to determine their susceptibility to cancer. Npm1+/- mice displayed a greater propensity to develop malignancies compared with Npm1+/+ mice. The Npm1+/- cohort frequently developed hematologic malignancies of both myeloid and lymphoid origin with myeloid malignancies displaying the highest incidence. Malignant cells retained the wild-type allele with normal localization and expression of Npm1 at the protein level, suggesting that complete Npm1 loss is not a prerequisite for tumorigenesis. Our results conclusively demonstrate that Npm1 acts as a haploinsufficient tumor suppressor in the hematopoietic compartment.