Mouse Colonies Research Articles

BIOLOGICAL RESOURCES FOR AGING RESEARCH AT THE NATIONAL INSITUTE ON AGING

Abstract Research on aging, by its nature, requires the acquisition of data over an organism’s lifespan or at later stages in life. For animals with medium to long lifespans such as rodents and nonhuman primates (NHPs), time is a limiting factor for the acquisition of data and samples. One of the missions of the National Institute on Aging (NIA) is to maintain and manage biological resources needed to support aging research that would be otherwise less accessible or excessively costly or time consuming to the investigators. The resources made available to publicly funded investigators comprise: 1) live rodents (Aging Mouse and Rat Colonies); 2) cells from different species including human, NHP, rodent, and domestic companion animals (Aging Cell Repository); 3) tissues from aged rodents (Rodent Tissue Bank) and NHPs (NHP Tissue Bank); and 4) a database of NHP vital parameters (Primate Aging Database). The NIA also supports two multi-institutional programs investigating interventions with the potential to extend lifespan and delay disease/dysfunction in worms (Caenorhabditis Intervention Testing Program, CITP) and in mice (Interventions Testing Program, ITP). The NIA values feedback to continue to provide valuable resources that will help the field move forward.

Integrating natural commensals and pathogens into preclinical mouse models.

Fundamental discoveries in many aspects of mammalian physiology have been made using laboratory mice as research models. These studies have been facilitated by the genetic tractability and inbreeding of such mice, the large set of immunological reagents that are available, and the establishment of environmentally controlled, high-throughput facilities. Such facilities typically include barriers to keep the mouse colonies free of pathogens and the frequent re-derivation of the mice severely limits their commensal flora. Because humans have co-evolved with microorganisms and are exposed to a variety of pathogens, a growing community of researchers posits that preclinical disease research can be improved by studying mice in the context of the microbiota and pathogens that they would encounter in the natural world. Here, we provide a perspective of how these different approaches can be combined and integrated to improve existing mouse models to enhance our understanding of disease mechanisms and develop new therapies for humans. We also propose that the term 'mice with natural microbiota' is more appropriate for describing these models than existing terms such as 'dirty mice'.

Induction of territorial dominance and subordination behaviors in laboratory mice.

Territorial behaviors comprise a set of coordinated actions and response patterns found across animal species that promote the exclusive access to resources. House mice are highly territorial with a subset of males consistently attacking and chasing competing males to expel them from their territories and performing urine marking behaviors to signal the extent of their territories. Natural variation in territorial behaviors within a mouse colony leads to the formation of dominance hierarchies in which subordinate males can reside within the territory of a dominant male. While the full repertoire of such territorial behaviors and hierarchies has been extensively studied in wild-derived mice in semi-natural enclosures, so far they have not been established in the smaller enclosures and with the genetically-defined laboratory strains required for the application of neural recording and manipulation methods. Here, we present a protocol to rapidly induce an extensive repertoire of territorial behaviors in pairs of laboratory mice in an enclosure compatible with tethered neurocircuit techniques, including a method for the simultaneous tracking of urine marking behavior in mouse pairs. Using this protocol we describe the emergence of robust dominant-subordinate hierarchies between pairs of CD1 outbred or CD1xB6 F1 hybrid mice, but unexpectedly not in C57BL/6 inbred animals. Our behavioral paradigm opens the door for neurocircuit studies of territorial behaviors and social hierarchy in the laboratory.

Corynebacterium bovis Growth in Tissue Culture Conditions and Media.

A common concern in preclinical cancer research is the introduction of Corynebacterium bovis into immunodeficient mouse colonies through cancer cell lines. C. bovis is a known contaminant of patient-derived xenograft tumors passaged horizontally between immunodeficient mice. However, it is unclear if C. bovis can grow in mammalian tissue culture conditions or tissue culture media. We hypothesized that C. bovis would not grow under tissue culture conditions or media, diminishing the risk of transmission from tumor cell lines cultured in vitro. Three C. bovis isolates, CUAMC1, HAC, and ATCC-7715, were used to test our hypothesis in 3 of the most common media used to grow human cancer cell lines including RPMI 1640 + 10% FBS (RPMI), DMEM/high glucose + 10% FBS (DMEM), and DMEM/F-12 + 10% FBS (DMEM/F12). Our results confirmed propagation of each C. bovis isolate in DMEM/F12 media under tissue culture conditions after 72 h. However, these results also demonstrate diminished viability of each C. bovis isolate in RPMI and DMEM after 72 h. To assess whether antibiotics could halt the growth of C. bovis under tissue culture conditions in DMEM/F12, penicillin-streptomycin (pen/strep) was added to the experimental media. This treatment was effective in eliminating all viable C. bovis in the culture system after 72 h. Our data suggest that C. bovis growth under tissue culture conditions is possible and growth in tissue culture media is nuanced. These results highlight the importance of pathogen surveillance for tumor cell lines propagated in vitro and demonstrate the need for further investigation into C. bovis growth requirements.

Single nucleotide polymorphism (SNP) characterisation of mouse inbred strains bred at MRC-National Institute for Medical Research.

Inbred mouse strains have long proved useful as tools for biomedical research. They remove the effects of genetic background as an experimental variable. Within all mouse colonies, genetic drift is a recognised phenomenon and monitoring and documenting changes is important for experimental design and consistency. This communication documents the initial characterisation through SNP analysis of the inbred mouse strains bred and used at the time at the Medical Research Council National Institute for Medical Research (MRC-NIMR), Mill Hill, now The Crick Institute. These inbred strains were part of the foundation colonies for the many genetically modified mouse strains made at Mill Hill. We found small genetic changes in four of the nine inbred strains. Although phenotypic differences have not yet been found between the NIMR and the correspondent parental strains, I cannot discard that these may arise or have already arisen. This work has also authenticated the 129/SvJEvNimr-Gpi1c strain that was widely used at MRC-NIMR for gene targeting. All these inbred strains have been renamed according to The International Committee on Standardized Genetic Nomenclature for Mice.

Working with Miraculous Mice: Mus musculus as a Model Organism.

The laboratory mouse has been described as a "miracle" model organism, providing a window by which we may gain an understanding of ourselves. Since the first recorded mouse experiment in 1664, the mouse has become the most used animal model in biomedical research. Mice are ideally suited as a model organism because of their small size, short gestation period, large litter size, and genetic similarity to humans. This article provides a broad overview of the laboratory mouse as a model organism and is intended for undergraduates and those new to working with mice. We delve into the history of the laboratory mouse and outline important terminology to accurately describe research mice. The types of laboratory mice available to researchers are reviewed, including outbred stocks, inbred strains, immunocompromised mice, and genetically engineered mice. The critical role mice have played in advancing knowledge in the areas of oncology, immunology, and pharmacology is highlighted by examining the significant contribution of mice to Nobel Prize winning research. International mouse mutagenesis programs and accurate phenotyping of mouse models are outlined. We also explain important considerations for working with mice, including animal ethics; the welfare principles of replacement, refinement, and reduction; and the choice of mouse model in experimental design. Finally, we present practical advice for maintaining a mouse colony, which involves adequate training of staff, the logistics of mouse housing, monitoring colony health, and breeding strategies. Useful resources for working with mice are also listed. The aim of this overview is to equip the reader with a broad appreciation of the enormous potential and some of the complexities of working with the laboratory mouse in a quest to improve human health. © 2024 The Author(s). Current Protocols published by Wiley Periodicals LLC.

Chlamydia muridarum Causes Persistent Subclinical Infection and Elicits Innate and Adaptive Immune Responses in C57BL/6J, BALB/cJ, and J:ARC(S) Mice Following Exposure to Shedding Mice

Chlamydia muridarum (Cm) has reemerged as a moderately prevalent infectious agent in research mouse colonies. Despite its experimental use, few studies evaluate Cm’s effects on immunocompetent mice following its natural route of infection. A Cm field isolate was administered (orogastric gavage) to 8-wk-old female BALB/cJ (C) mice. After shedding was confirmed (through 95 d), these mice were cohoused with naïve C57BL/6J (B6), C, and Swiss (J:ARC[S]) mice (n = 28/strain) for 30 d. Cohoused mice (n = 3 to 6 exposed and 1 to 6 control/strain) were evaluated 7, 14, 21, 63, 120, and 180 d post-cohousing (DPC) via hemograms, serum biochemistry analysis, fecal quantitative PCR, histopathology, and Cm major outer membrane protein immunohistochemistry. Immunophenotyping was performed on spleen (B6, C, and S; n = 6/strain) and intestines (B6; n = 6) at 14 and 63 DPC. Serum cytokine concentrations were measured (B6; n = 6 exposed and 2 control) at 14 and 63 DPC. All B6 mice were shedding Cm by 3 through 180 DPI. One of 3 C and 1 of 6 S mice began shedding Cm at 3 and 14 DPC, respectively, with the remaining shedding thereafter. Clinical pathology was nonremarkable. Minimal-to-moderate enterotyphlocolitis and gastrointestinal-associated lymphoid tissue (GALT) hyperplasia were observed in 15 and 47 of 76 Cm-infected mice, respectively. Cm antigen was frequently detected in GALT-associated surface intestinal epithelial cells. Splenic immunophenotyping revealed increased monocytes and shifts in T-cell population subsets in all strains/time points. Gastrointestinal immunophenotyping (B6) revealed sustained increases in total inflammatory cells and elevated cytokine expression in innate lymphoid and effector T cells (large intestine). Elevated concentrations of proinflammatory cytokines were detected in the serum (B6). Results demonstrate that while clinical disease was not appreciated, 3 commonly used strains of mice are susceptible to chronic enteric Cm infection which may alter various immune responses. Considering the widespread use of mice to model gastrointestinal disease, institutions should consider excluding Cm from their colonies.

Риск-ориентированный подход к мониторингу здоровья лабораторных грызунов

Health monitoring of laboratory rodents is essential to ensure the health and welfare of the animals and to standardize biomedical research. Recently, progress in the field of housing and hygiene programs has led to significant improvements in the microbiological quality of laboratory animals. At the same time, traditional methods of health monitoring and pathogen detection continue to serve as powerful tools for diagnosing common animal diseases. Constant monitoring and strict barrier breeding and husbandry of laboratory rodents have resulted in colonies that are free of previously common pathogens and even most opportunistic microorganism with means limited diversity in the animal microbiome. Moreover, the application of the well-known international list of pathogens to the monitoring of animals raised in a completely different territory based on epidemiological characteristics seems inappropriate. In this regard, approaches to health monitoring have to be reviewed and reformed in order to increase the reliability and relevance of all data obtained. This article discusses a method for selecting relevant and indicative microorganisms (risk-based approach) for monitoring the health of laboratory rodents in Russia. Based on the results of the assessment, a current list was identified for isolated colonies of laboratory mice, rats, guinea pigs, gerbils and hamsters. The resulting list of pathogens differs from international recommendations and is more applicable to animals used in Russian testing centers.

Chlamydia muridarum Causes Persistent Subclinical Infection and Elicits Innate and Adaptive Immune Responses in C57BL/6J, BALB/cJ and J:ARC(S) Mice Following Exposure to Shedding Mice.

Chlamydia muridarum (Cm) has reemerged as a moderately prevalent infectious agent in research mouse colonies. Despite its' experimental use, few studies evaluate Cm's effects on immunocompetent mice following its natural route of infection. A Cm field isolate was administered (orogastric gavage) to 8-week-old female BALB/cJ (C) mice. After confirming shedding (through 95d), these mice were cohoused with naïve C57BL/6J (B6), C, and Swiss (J:ARC[S]) mice (n=28/strain) for 30 days. Cohoused mice (n=3-6 exposed and 1-6 control/strain) were evaluated 7, 14, 21, 63, 120, and 180 days post-cohousing (DPC) via hemograms, serum biochemistry analysis, fecal qPCR, histopathology, and Cm MOMP immunohistochemistry. Immunophenotyping was performed on spleen (B6, C, S; n=6/strain) and intestines (B6; n=6) at 14 and 63 DPC. Serum cytokine concentrations were measured (B6; n=6 exposed and 2 control) at 14 and 63 DPC. All B6 mice were shedding Cm by 3 through 180 DPI. One of 3 C and 1 of 6 S mice began shedding Cm at 3 and 14 DPC, respectively, with the remaining shedding thereafter. Clinical pathology was nonremarkable. Minimal-to-moderate enterotyphlocolitis and gastrointestinal associated lymphoid tissue (GALT) hyperplasia was observed in 15 and 47 of 76 Cm-infected mice, respectively. Cm antigen was frequently detected in GALT-associated surface intestinal epithelial cells. Splenic immunophenotyping revealed increased monocytes and shifts in T cell population subsets in all strains/timepoints. Gastrointestinal immunophenotyping (B6) revealed sustained increases in total inflammatory cells and elevated cytokine production in innate lymphoid cells and effector T cells (large intestine). Elevated concentrations of pro-inflammatory cytokines were detected in the serum (B6). Results demonstrate that while clinical disease was not appreciated, 3 commonly utilized strains of mice are susceptible to chronic enteric Cm infection which may alter various immune responses. Considering the widespread use of mice to model GI disease, institutions should consider excluding Cm from their colonies.

Examining Intercage Transmission of Chlamydia muridarum: Impact of Barrier Husbandry and Cage Sanitization.

Chlamydia muridarum (Cm) has reemerged as a prevalent bacterial contaminant of academic research mouse colonies. A study was conducted to assess the effectiveness of husbandry and cage sanitization methods in preventing intercage transmission of Cm. To assess intercage transmission during cage change, a cage housing 2 Cm-free Swiss Webster (SW; Tac:SW) sentinel mice was placed randomly on each of 12 individually ventilated cage racks, housing cages with Cm-shedding mice, located in one of 2 animal holding rooms. Husbandry staff blinded to the study cages changed all cages in the animal holding rooms weekly using a microisolation cage technique. PCR testing performed at 180 d postplacement confirmed all mice remained negative for Cm. To assess the effectiveness of cage sanitization to eliminate Cm, we investigated transmission of Cm to a naive Cm-free SW and NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mouse cohoused for 7 d (repeated weekly for 4 wk) in cages assigned to one of 3 groups (n = 10 pairs of mice/group). Cages that previously housed 2 Cm-shedding BALB/c mice were either washed in a tunnel washer (82.2 °C [180 °F] final rinse for an average of 16 s per run; n = 10) with and without postwashing autoclaving (121 °C for 20 min; n = 10), or were untreated (bedding change only; n = 10). Pre- and postsanitization swabs of each cage were assayed for Cm by PCR. All pretreatment swabs tested positive, while posttreatment swabs from all cages (excluding bedding change) tested negative. All SW and NSG mice, irrespective of group, remained negative for Cm as determined by PCR. These findings suggest that infectious Cm does not persist in untreated cages or after mechanical washing with and without autoclaving. Collectively, these findings suggest that neither our husbandry protocols nor inadequate cage sanitization methods likely contributed to the observed prevalence of Cm in contemporary research mouse colonies.

Multi-objective optimal reconfiguration of distribution networks using a novel meta-heuristic algorithm

Reconfiguration strategies are used to reduce power losses and increase the reliability of the distribution systems. Since the optimal reconfiguration problem is a multi-objective optimization problem with non-convex functions and constraints, meta-heuristic algorithms are the most suitable choice for the problem-solving approach. One of the new meta-heuristic algorithms that exhibits excellent performance in solving multi-objective problems is the wild mice colony (WMC) algorithm, which is implemented based on aggressive and mating strategies of wild mice. In this paper, the distribution network reconfiguration problem is solved to reduce power losses, improve reliability, and increase the voltage profile of network buses using the WMC algorithm. In addition, the obtained results are compared with conventional multi-objective algorithms. The optimal reconfiguration problem is applied to the IEEE 33-bus and 69-bus test systems. The comparative study confirms the superior performance of the proposed algorithm in terms of convergence speed, execution time, and the final solution.

Optimizing domestic energy management with a wild Mice colony-inspired algorithm: Enhancing efficiency and coordination in smart grids through dynamic distributed energy storage

Energy management (EM) is a critical strategy that spans the production and consumption of electricity, enhancing the stability of the electricity network. Smart grid technology significantly improves the electrical system's energy efficiency (EE), facilitating a transformation from a conventional power grid (PG) to a smart PG. This paper presents a key strategy for modeling the EE of the smart grid tailored to domestic demand, establishing smart coordination between domestic demand, energy production, and storage to reduce energy waste and costs. Our model integrates various energy sources, including renewable energy (RE), photovoltaic (PV) systems, wind power, and an energy storage system (ESS), interconnected with the PG. The model's structure ensures the coordinated flow of electricity in a residential house through an optimal control method (OCM). To develop a robust closed-loop control model, we employ Demand Response (DR) schemes within the Real-Time Electricity Pricing (RTEP) framework. We construct a dynamic model of the ESS to compute the System Performance Index (SPI), corresponding to energy costs. To enhance our model, we introduce a Dynamic Distributed Energy Storage Strategy (DDESS). Additionally, we introduce a novel optimization algorithm inspired by the behavioral patterns of wild mice, called the Wild Mice Colony (WMC). By analyzing the targeted and advantageous behaviors of wild mice in colonies, we propose that these behaviors can serve as a model for addressing complex, uncertain problems. This strategy is highly advantageous, capable of reducing total energy consumption (EC) from the main grid by over 100 % of the load demand, optimizing the energy system, and ensuring synchronization. The performance of DDESS optimizes energy flow (EF) during the repayment plan, leading to minimized EC costs from the PG.

Polygenic TB control and the sequence of innate/adaptive immune responses to infection: MHC-II alleles determine the size of the S100A8/9-producing neutrophil population.

Among several quantitative trait loci involved in tuberculosis (TB) control in mice, one was mapped within the chromosome 17 segment occupied by the H2 complex and another within the chromosome 3 segment comprising the S100A8/9 genes, which encode neutrophil inflammatory factor S100A8/9. Previously, we developed a panel of H2-congenic mouse strains differing by small segments of the major histocompatibility complex Class II (MHC-II) region from TB-susceptible H2j mice transferred onto the genetic background of the TB-resistant C57BL/6 (H2b) strain. Susceptible B6.I-9.3 mice differ from B6 progenitors by the alleles of their only classical MHC-II H2-Aβ gene. The goals of the present study were to: (i) comprehensively characterise the differences in TB-related phenotypes between mice of the two strains and (ii) decipher interactions between the H2-Aβ and S100A8/9 genes. Here, we describe the dynamics of TB-related phenotypes differentiating B6.I-9.3 and B6 mice (colony forming unitscounts, histopathology, lung immune cell infiltration and cytokine profiles). We show that disproportionally diminished CD4+ T-cell population, an enlarged S100A8/9-positive neutrophil population and higher S100A8/9 serum levels in B6.I-9.3 mice collectively form the 'susceptible' phenotype before infection. An increase in IL-17 and a decrease in intrferon-gamma production by CD4+ T-cells in these mice provide a mechanistic explanation of this phenotype. Using F2 segregation analysis, we show that the number of S100A8/9-producing neutrophils in lungs and spleens and the proportion of Th17 CD4+ T-cells in lungs are significantly lower in the presence of the MHC-II dominant 'resistant' b allele compared to the recessive 'susceptible' j/j genotype. This provides direct genetic evidence that MHC-II-regulated CD4+ T-cell landscapes determine neutrophil abundance before infection, an important pathogenic factor in TB immunity.

Microenvironment M1/M2 macrophages and tumoral progression vary within C57BL/6 mice from same substrain in prostate cancer model

Cancer mice models are critical for immune-oncology research; they provide conditions to explore tumor immunoenviroment aiming to advance knowledge and treatment development. Often, research groups breed their own mice colonies. To assess the effect of C57BL/6 mice breeding nuclei in prostate cancer development and intratumoral macrophage populations, an isotransplantation experiment was performed. C57BL/6J mice from two breeding nuclei (nA and nB) were employed for prostate adenocarcinoma TRAMP-C1 cell implantation; tumor growth period and intratumoral macrophage profile were measured. BL/6nB mice (54%) showed tumor implantation after 69-day growth period while BL/6nA implantation reached 100% across tumor growth period (28 days). No difference in total macrophage populations was observed between groups within several tumoral regions; significantly higher M2 macrophage profile was observed in tumor microenvironments from both mice groups. Nevertheless, BL/6nB tumors showed around twice the population of M1 profile (11–27%) than BL6nA (4–15%) and less non-polarized macrophages. The M1:M2 average ratio was 1:8 for group A and 1:4 for B. Our results demonstrate different tumor progression and intratumoral macrophage populations among mice from the same substrain. Data obtained in this study shows the relevance of animal source renewal for better control of murine cancer model variables.

Polymerase Chain Reaction on In-cage Filter Paper at Different Time Points to Detect Helicobacter spp.

Helicobacter spp. infections in mice can have broad-ranging effects on gastrointestinal, reproductive, and immune systems. This can introduce significant confounding variables for research and may reduce scientific rigor. Screening mouse colonies for Helicobacter species can be accomplished via noninvasive PCR testing on filter paper placed in animal-free dirty bedding sentinel cages. In our facility, one tablespoon of dirty bedding from each cage on a rack is added to a designated sentinel cage every 3 wk at cage change, and PCR testing is performed on in-cage filter paper quarterly. We hypothesized that cages that received Helicobacter spp.-positive bedding at later time points would have a lower detection rate of Helicobacter spp. with PCR testing compared with cages that received positive bedding at earlier time points due to the filter paper becoming saturated. To determine if screening would be able to detect one positive row of cages on a rack, 9 tablespoons of Helicobacter- positive bedding and 71 tablespoons of negative bedding were added at the 3-, 6-, or 9-wk time points to 14 empty sentinel cages per time point. Negative bedding was added every 3 wk to cages not scheduled to receive positive bedding. Negative controls received 80 tablespoons of negative bedding and positive controls received 80 tablespoons of positive bedding at each time point. Filter paper was tested via PCR for Helicobacter spp. at 12 wk. All positive controls tested positive, and all negative controls tested negative. Two 3-wk cages, two 6-wk cages, and three 9-wk cages were positive, indicating no difference between time points. This resulted in a 16.7% Helicobacter spp. detection rate. These results indicate that PCR on in-cage filter paper may not be reliable in detecting low levels of Helicobacter spp. nucleic acid in dirty bedding.

A side-by-side comparison of different capacitation media in developing mouse sperm fertilizing ability

To acquire the ability to fertilize the egg, mammalian spermatozoa must undergo a series of changes occurring within the highly synchronized and specialized environment of the female reproductive tract, collectively known as capacitation. In an attempt to replicate this process in vitro, various culture media for mouse sperm were formulated over the past decades, sharing a similar overall composition but differing mainly in ion concentrations and metabolic substrates. The widespread use of the different media to study the mechanisms of capacitation might hinder a comprehensive understanding of this process, as the medium could become a confounding variable in the analysis. In this context, the present side-by-side study compares the influence of four commonly used culture media (FD, HTF and two TYH versions) on mouse sperm capacitation. We evaluated the induction of protein kinase A phosphorylation pathway, motility, hyperactivation and acrosome reaction. Additionally, in vitro fertilization and embryo development were also assessed. By analyzing these outcomes in two mouse colonies with different reproductive performance, our study provides critical insights to improve the global understanding of sperm function. The results obtained highlight the importance of considering variations in medium composition, and their potential implications for the future interpretation of results.

Examining Intercage Transmission of Chlamydia muridarum : Impact of Barrier Husbandry and Cage Sanitization.

Chlamydia muridarum (Cm) has reemerged as a prevalent bacterial contaminant of academic research mouse colonies. A study was conducted to assess the effectiveness of husbandry and cage sanitization methods in preventing intercage transmission of Cm. To assess intercage transmission during cage change, a cage housing 2 Cm-free Swiss Webster (Tac:SW; SW) sentinel mice was placed randomly on each of 12 individually ventilated cage racks, housing cages with Cm-shedding mice, located in 1 of 2 animal holding rooms. Husbandry staff blinded to the study cages, changed all cages in the animal holding rooms weekly using microisolator cage technique. PCR testing performed 180 days post-placement confirmed all mice remained negative for Cm. To assess the effectiveness of cage sanitization to eliminate Cm, we investigated transmission of Cm to a naïve Cm-free SW and NOD.Cg- Prkdc scid Il2rg tm1Wjl /SzJ (NSG) mouse co-housed for 7 days (repeated weekly for 4 weeks) in cages assigned to 1 of 3 groups (n=10 pairs of mice/group). Cages that previously housed 2 Cm-shedding BALB/c mice were either washed in a tunnel washer (82.2°C [180°F] final rinse for an average of 16 seconds per run; n=10) with and without post-washing autoclaving (121°C for 20 minutes; n=10), or were untreated (bedding change only; n=10). Pre- and post-sanitization swabs of each cage were assayed for Cm by PCR. All pre-treatment swabs tested positive, while post-treatment swabs from all cages (excluding bedding change) tested negative. All SW and NSG mice, irrespective of group, remained negative for Cm as determined by PCR. These findings suggest that infectious Cm does not persist in untreated cages nor after mechanical washing with and without autoclaving. Collectively, these findings suggest that neither our husbandry protocols nor inadequate cage sanitization methods likely contributed to the observed prevalence of Cm in contemporary research mouse colonies.

Spontaneous Akt2 deficiency in a colony of NOD mice exhibiting early diabetes.

Diabetes constitutes a major public health problem, with dramatic consequences for patients. Both genetic and environmental factors were shown to contribute to the different forms of the disease. The monogenic forms, found both in humans and in animal models, specially help to decipher the role of key genes in the physiopathology of the disease. Here, we describe the phenotype of early diabetes in a colony of NOD mice, with spontaneous invalidation of Akt2, that we called HYP. The HYP mice were characterised by a strong and chronic hyperglycaemia, beginning around the age of one month, especially in male mice. The phenotype was not the consequence of the acceleration of the autoimmune response, inherent to the NOD background. Interestingly, in HYP mice, we observed hyperinsulinemia before hyperglycaemia occurred. We did not find any difference in the pancreas' architecture of the NOD and HYP mice (islets' size and staining for insulin and glucagon) but we detected a lower insulin content in the pancreas of HYP mice compared to NOD mice. These results give new insights about the role played by Akt2 in glucose homeostasis and argue for the ß cell failure being the primary event in the course of diabetes.

Chlamydia muridarum Associated Pulmonary and Urogenital Disease and Pathology in a Colony of Enzootically Infected Il12rb2 Deficient and Stat1 Knockout Mice.

Chlamydia muridarum (Cm), an intracellular bacterium of historical importance, was recently rediscovered as moderately prevalent in research mouse colonies. Cm was first reported as a causative agent of severe pneumonia in mice about 80 y ago, and while it has been used experimentally to model Chlamydia trachomatis infection of humans, there have been no further reports of clinical disease associated with natural infection. We observed clinical disease and pathology in 2 genetically engi- neered mouse (GEM) strains, Il12rb2 KO and STAT1 KO, with impaired interferon-γ signaling and Th1 CD4+ T cell responses in a colony of various GEM strains known to be colonized with and shedding Cm. Clinical signs included poor condition, hunched posture, and poor fecundity. Histopathology revealed disseminated Cm with lesions in pulmonary, gastrointestinal, and urogenital tissues. The presence of Cm was confirmed using both immunohistochemistry for Cm major outer membrane protein-1 antigen and in situ hybridization using a target probe directed against select regions of Cm strain Nigg. Cm was also found in association with a urothelial papilloma in one mouse. These cases provide additional support for excluding Cm from research mouse colonies.

Establishing Control Frequency of Embryonic and Fetal Loss in a Mutant Mouse Colony.

In the analysis of prenatal lethal recessive mutations, one must account for embryonic losses that are not related to the mutant phenotype. This protocol details the way to determine what the background level of unrelated embryonic loss is by a simple backcrossing strategy in the particular mouse strain that carries the lethal recessive mutation.