Impact of Experimental Tuberculosis on Fertility of Female BALB/c Mice.

The study revealed no effects of pregnancy and childbirth on the course of tuberculosis in female BALB/c mice after aerosol infection with Mycobacterium tuberculosis. However, we demonstrated a negative effect of tuberculosis infection on the fertility of infected females, which manifested in a longer period from mating to pregnancy and in a smaller litter size. Impaired reproductive function in response to the effect of the systemic infectious process was accompanied by the development of immunosuppression confirmed by an immunological test (delayed-type hypersensitivity to tuberculin) and the formation of genital tract dysbiosis during pregnancy and postpartum period.

Effects of Excess Sodium Consumption on Arterial Function in C57BL/6 Mice.

Excess sodium consumption contributes to arterial dysfunction in humans. The C57BL/6 strain of mice have been used to identify mechanisms by which arterial dysfunction occurs after excess sodium consumption. However, there are concerns that C57BL/6 mice have strain-specific resistance to high-sodium (HS) diet-induced hypertension. To address this concern, we performed a meta-analysis to determine if excess sodium consumption in C57BL/6 mice induces arterial dysfunction. Databases were searched for HS vs. standard diet studies that measured arterial function (i.e., systolic blood pressure [BP], endothelium-dependent dilation [EDD], and central arterial stiffness) in C57BL/6 mice. A total of 39 studies were included, demonstrating that HS condition resulted in higher systolic BP than control mice with a mean difference of 9.8 mmHg (95% CI [5.6, 14], P<0.001). Subgroup analysis indicated that the systolic BP was higher in HS compared to the control condition when measured during night compared to daytime with telemetry (P<0.001). We also identified that the difference in systolic BP between HS and control was ~2.5-fold higher when administered through drinking water than through food (P<0.001). A total of 12 studies were included, demonstrating that HS condition resulted in lower EDD than control with a weighted mean difference of -12.0% (95% CI [-20.0, -4.1], P=0.003). It should be noted that there was considerable variability across studies with more than half of the studies showing no effect of HS condition on systolic BP and EDD. In summary, excess sodium consumption elevates systolic BP and impairs EDD in C57BL/6 mice.

The ameliorative effects of choline on ethanol-induced cell death in the neural tube of susceptible BXD strains of mice.

Introduction: Fetal alcohol spectrum disorders (FASD) are the leading preventable cause of intellectual disability, providing the impetus for evaluating various potential treatments to ameliorate ethanol's teratogenic effects, particularly in the nervous system. One treatment is the dietary supplement choline which has been shown to mitigate at least some of ethanol's teratogenic effects. The present study was designed to investigate the effects of genetics on choline's efficacy in ameliorating cell death in the developing neural tube. Previously, we examined BXD recombinant inbred mice, and their parental C57BL/6 J (B6) and DBA/2 J strains, and identified strains that were sensitive to ethanol's teratogenic actions. Thus, we used these strains to identify response to choline treatment. Materials and methods: Timed pregnant mice from 4 strains (B6, BXD51, BXD73, BXD2) were given either ethanol or isocaloric maltose-dextrin (5.8 g/kg in two administrations separated by 2 h) with choline at one of 3 doses: 0, 100 or 250 mg/kg. Subjects were exposed via intragastric gavage on embryonic day 9 and embryos were collected 7 h after the initial ethanol administrations. Cell death was analyzed using TUNEL staining in the developing forebrain and brainstem. Results: Choline ameliorated the ethanol-induced cell death across all 4 strains without causing enhanced cell death in control mice. Choline was effective in both the developing telencephalon and in the brainstem. Both doses diminished cell death, with some differences across strains and brain regions, although the 100 mg/kg dose was most consistent in mitigating ethanol-related cell death. Comparisons across strains showed that there was an effect of strain, particularly in the forebrain at the higher dose. Discussion: These results show that choline is effective in ameliorating ethanol-induced cell death at this early stage of nervous system development. However, there were some strain differences in its efficacy, especially at the high dose, providing further evidence of the importance of genetics in influencing the ability of choline to protect against prenatal alcohol exposure.

Genetic background influences arterial vasomotor function in male and female mice.

The purpose of this study was to assess the influence of genetic background and sex on nitric oxide (NO)-mediated vasomotor function in arteries from different vascular territories. Vasomotor function was assessed in thoracic aorta, abdominal aorta, carotid arteries, and femoral arteries from the following mouse strains: SJL/J, DBA/2J, NZW/LacJ, and C57BL/6J. Contractile responses were assessed using the α1-adrenergic receptor agonist phenylephrine (PE, 10-9 -10-5 M). Vasorelaxation responses were assessed by examining relaxation to an endothelium-dependent vasodilator acetylcholine (ACh, 10-9 -10-5 M) and an endothelium-independent vasodilator sodium nitroprusside (SNP, 10-9 -10-5 M). To evaluate the role of NO, relaxation responses to ACh and SNP were assessed in the absence or presence of a nitric oxide synthase inhibitor (N omega-nitro-l-arginine methyl ester hydrochloride: 10-4 M). Vasomotor responses to ACh and PE varied across strains and among the arteries tested with some strains exhibiting artery-specific impairment. Results indicated some concentration-response heterogeneity in response to ACh and SNP between vessels from females and males, but no significant differences in responses to PE. Collectively, these findings indicate that vasomotor responses vary by genetic background, sex, and artery type.

Gene network based analysis identifies a coexpression module involved in regulating plasma lipids with high-fat diet response.

Plasma lipids are modulated by gene variants and many environmental factors, including diet-associated weight gain. However, understanding how these factors jointly interact to influence molecular networks that regulate plasma lipid levels is limited. Here, we took advantage of the BXD recombinant inbred family of mice to query weight gain as an environmental stressor on plasma lipids. Coexpression networks were examined in both nonobese and obese livers, and a network was identified that specifically responded to the obesogenic diet. This obesity-associated module was significantly associated with plasma lipid levels and enriched with genes known to have functions related to inflammation and lipid homeostasis. We identified key drivers of the module, including Cidec, Cidea, Pparg, Cd36, and Apoa4. The Pparg emerged as a potential master regulator of the module as it can directly target 19 of the top 30 hub genes. Importantly, activation of this module is causally linked to lipid metabolism in humans, as illustrated by correlation analysis and inverse-variance weighed Mendelian randomization. Our findings provide novel insights into gene-by-environment interactions for plasma lipid metabolism that may ultimately contribute to new biomarkers, better diagnostics, and improved approaches to prevent or treat dyslipidemia in patients.

Attenuated Strain of Mycobacterium tuberculosis BN: Characteristics.

We evaluated the vaccine properties of a novel attenuated strain of M. tuberculosis BN (Mtb BN) and its impact on the gut microbiota in inbred female mice in comparison with a virulent strain Mtb H37Rv and a vaccine strain BCG. The Mtb BN strain demonstrated the highest anti-tuberculosis vaccine effect in I/St mice highly susceptible to tuberculosis infection and the same effect as BCG in mice of the recombinant strain B6.I-100 and in ß2 microglobulin gene knockout mice. No adverse effects of the new Mtb BN strain on the gut microbiota of BALB/c mice were revealed. The virulent strain Mtb H37Rv and the vaccine strain BCG decreased the main indicators of normocenosis (Bifidobacterium spp., Bifidobacterium animalis subsp. lactis, Akkermansia, and Erysipelotrichaceae) and led to disappearance of Clostridium perfingens, E. coli, Pseudomonas spp., which contributed to reduction of species diversity and the development of dysbiosis.

Lrig1 expression identifies quiescent stem cells in the ventricular-subventricular zone from postnatal development to adulthood and limits their persistent hyperproliferation.

BACKGROUND: We previously identified Leucine-rich repeats and immunoglobulin-like domains 1 (Lrig1) as a marker of long-term neurogenic stem cells in the lateral wall of the adult mouse brain. The morphology of the stem cells thus identified differed from the canonical B1 type stem cells, raising a question about their cellular origin. Thus, we investigated the development of these stem cells in the postnatal and juvenile brain. Furthermore, because Lrig1 is a known regulator of quiescence, we also investigated the effect(s) of its deletion on the cellular proliferation in the lateral wall. METHODS: To observe the development of the Lrig1-lineage stem cells, genetic inducible fate mapping studies in combination with thymidine analog administration were conducted using a previously published Lrig1T2A-iCreERT2 mouse line. To identify the long-term consequence(s) of Lrig1 germline deletion, old Lrig1 knock-out mice were generated using two different Lrig1 null alleles in the C57BL/6J background. The lateral walls from these mice were analyzed using an optimized whole mount immunofluorescence protocol and confocal microscopy. RESULTS: We observed the Lrig1-lineage labeled cells with morphologies consistent with neurogenic stem cell identity in postnatal, juvenile, and adult mouse brains. Interestingly, when induced at postnatal or juvenile ages, morphologically distinct cells were revealed, including cells with the canonical B1 type stem cell morphology. Almost all of the presumptive stem cells labeled were non-proliferative at these ages. In the old Lrig1 germline knock-out mice, increased proliferation was observed compared to wildtype littermates without concomitant increase in apoptosis. CONCLUSIONS: Once set aside during embryogenesis, the Lrig1-lineage stem cells remain largely quiescent during postnatal and juvenile development until activation in adult age. The absence of premature proliferative exhaustion in the Lrig1 knock-out stem cell niche during aging is likely due to a complex cascade of effects on the adult stem cell pool. Thus, we suggest that the adult stem cell pool size may be genetically constrained via Lrig1.

Investigation of the tissue-damaging effects and mechanisms of neutrophil-derived MMP-8 in Fusarium keratitis / 中华实验眼科杂志

Objective:To investigate the mechanism of tissue damage caused by neutrophil matrix metalloproteinase-8 (MMP-8) in Fusarium keratitis. Methods:A total of 108 male C57BL/6J SPF grade mice, 6-8 weeks old, were selected to establish a model of Fusarium keratitis (FK) in the right eyes.Corneal inflammation in mice was observed and scored under a slit lamp microscope.Based on the corneal inflammation scores, the modeling eyes were divided into 0, 12, 24, 48, and 72-hour groups post-modeling.At the corresponding time points, mice were euthanized, and corneal tissues were collected.The expressions of MMP-8, adenylate-activated protein kinase (AMPKα) and its serine 172-site phosphorylated form (p-AMPKα) proteins in corneal tissues were detected by Western blot.The neutrophil count in mice corneal tissues at each time point was determined using hematoxylin and eosin staining.The co-localization of neutrophils and MMP-8 protein in the cornea was observed by immunofluorescence staining.In the in vitro corneal collagen degradation experiment, corneal tissues were divided into MMP-8 group, buffer group, and normal saline group, which were treated with 100 μl of activated recombinant MMP-8, detection buffer, and normal saline, respectively.Hydroxyproline content in corneal tissues was determined using a hydroxyproline assay kit, and the mass fractions of hydroxyproline were compared among the groups.Peripheral blood neutrophils were isolated from human blood samples, and Fusarium spores were collected for experiments.Human neutrophils were divided into four groups, negative control group (cultured neutrophils), co-culture group (neutrophils co-cultured with spores), AICAR-treated group (neutrophils co-cultured with spores and treated with p-AMPK protein kinase activator AICAR), and compound C-treated group (neutrophils co-cultured with spores and treated with the inhibitor compound C).The MMP-8 protein expression levels in each group of human neutrophils were assessed via immunofluorescence staining.The use and care of animals complied with the ARVO statement and Regulations for the Administration of Affairs Concerning Experimental Animals.The animal experiment protocol was approved by the Animal Ethics Committee of Henan Eye Hospital (No.HNEECA-2017-04-02).One healthy adult volunteer was selected and 10 ml of peripheral venous blood was collected.The clinical study protocol was approved by the Clinical Ethics Committee of Henan Eye Hospital (No.HNEECKY-2019[16]). Results:At 24 hours post-modeling, corneal opacification was observed in the modeling eyes, and corneal perforation occurred in 72-hour post-modeling group.The corneal inflammation scores in 24, 48, and 72-hour post-modeling groups were all higher than those in 12-hour post-modeling group, and the differences were statistically significant (all at P<0.001).The relative expression levels of MMP-8 protein in the cornea were higher in 12, 24, and 48-hour post-modeling groups compared to 0-hour group, with statistically significant differences (all at P<0.001).There was a moderate positive correlation between the relative expression level of MMP-8 protein in the cornea and the inflammation scores of the modeling eye ( rs=0.50, P<0.05).In the cornea, the p-AMPKα (Thr 172)/AMPKα ratio was higher in 24, 48, and 72-hour post-modeling groups than in 0-hour group, and the differences were statistically significant (all at P<0.05).The p-AMPKα(Thr 172)/AMPKα ratio in the cornea was moderately positively correlated with the relative expression level of MMP-8 protein ( r=0.54, P<0.01).The number of neutrophils in the cornea was significantly higher in 24, 48, and 72-hour post-modeling groups than in 0-hour group, with statistically significant differences (all at P<0.001).The number of neutrophils in the cornea was strongly positively correlated with the inflammation score ( rs=0.77, P<0.001), and was moderately positively correlated with the relative expression level of MMP-8 protein ( r=0.56, P<0.05).MMP-8 protein expression in the cornea of the modeling eyes showed a high degree of co-localization with neutrophils.The hydroxyproline content in the cornea was (0.52±0.02)μg/mg, (0.51±0.03)μg/mg, and (0.27±0.02)μg/mg in buffer group, normal saline group and MMP-8 group, respectively, with a significant overall difference among them ( F=156.63, P<0.01).The corneal hydroxyproline content was lower in MMP-8 group compared to buffer and normal saline groups, and the differences were statistically significant (all at P<0.05).In the experiment involving the infection of cultured Fusarium spores with human neutrophils, the fluorescence intensity of MMP-8 expression was significantly higher in AICAR-treated group than in negative control group and compound C-treated group, with statistically significant differences (all at P<0.05). Conclusions:The MMP-8 secreted by neutrophils in mice with fungal keratitis can degrade corneal stromal collagen fibers, leading to corneal opacification or perforation.The variations in MMP-8 protein expression levels in human neutrophils may be associated with AMPK activation.

Limited bedding nesting paradigm alters maternal behavior and pup's early developmental milestones but did not induce anxiety- or depressive-like behavior in two different inbred mice.

Animal models are crucial to understanding the mechanisms underlying the deleterious consequences of early-life stress. Here, we aimed to examine the effect of the limited bedding nesting (LBN) paradigm on early life development milestones and anxiety- and/or depression-like behavior in adolescent and adult mice from two inbred mice of both sexes. C57BL/6NCrl and BALB/c litters were exposed to the LBN paradigm postnatal day (PND) 2-9. Maternal behavior recording occurred on PND 3-9, and pups were weighed daily and examined to verify the eye-opening on PND 10-22. The male and female offspring underwent evaluation in the open field test, elevated plus-maze, and the forced swimming test during adolescence (PND 45-49) and adulthood (PND 75-79). We found that LBN impaired the maternal behavior patterns of both strain dams, mainly on C57BL/6NCrl strain. Also, LBN delayed the pup's eye-opening time and reduced body weight gain, impacting C57BL/6NCrl pups more. We also found that LBN decreased anxiety-related indices in adolescent and adult male but not female mice of both strains. Furthermore, LBN decreased depression-related indices only adolescent female and male BALB/c and female but not male C57BL/6NCrl mice. These findings reinforce the evidence that the LBN paradigm impairs the maternal behavior pattern and pup's early developmental milestones but does not induce anxiety- or depressive-like behavior outcomes during later life.

Standing on the shoulders of mice.

While inbred mice have informed most of what we know about the immune system in the modern era, they have clear limitations with respect to their ability to be informative regarding genetic heterogeneity or microbial influences. They have also not been very predictive as models of human disease or vaccination results. Although there are concerted attempts to compensate for these flaws, the rapid rise of human studies, driven by both technical and conceptual advances, promises to fill in these gaps, as well as provide direct information about human diseases and vaccination responses. Work on human immunity has already provided important additional perspectives on basic immunology such as the importance of clonal deletion to self-tolerance, and while many challenges remain, it seems inevitable that "the human model" will continue to inform us about the immune system and even allow for the discovery of new mechanisms.

Inbred Mice Again at Stake: How the Cognitive Profile of the Wild-Type Mouse Background Discloses Pathogenic Effects of APP Mutations.

Increasing efforts have been made in the last decades to increase the face validity of Alzheimer's disease (AD) mouse models. Main advancements have consisted in generating AD mutations closer to those identified in humans, enhancing genetic diversity of wild-type backgrounds, and choosing protocols much apt to reveal AD-like cognitive dysfunctions. Nevertheless, two aspects remain less considered: the cognitive specialization of inbred strains used as recipient backgrounds of mutations and the heuristic importance of studying destabilization of memory circuits in pre-symptomatic mice facing cognitive challenges. This article underscores the relevance of these behavioral/experimental aspects by reviewing data which show that (i) inbred mice differ in their innate predisposition to rely on episodic vs. procedural memory, which implicates differential sensitivity to mutations aimed at disrupting temporal lobe-dependent memory, and that (ii) investigating training-driven neural alterations in asymptomatic mutants unveils early synaptic damage, which considerably anticipates detection of AD first signs.

Genetic dissection of glutathione S-transferase omega-1: identification of novel downstream targets and Alzheimer's disease pathways.

Alzheimer's disease (AD) is affected by genetic factors. Polymorphisms in the glutathione S-transferase omega-1 (Gsto1) gene have been shown by genetic correlation analyses performed in different ethnic populations to be genetic risk factors for AD. Gene expression profile data from BXD recombinant inbred mice were used in combination with genetic and bioinformatic analyses to characterize the mechanisms underlying regulation of Gsto1 variation regulation and to identify network members that may contribute to AD risk or progression. Allele-specific assays confirmed that variation in Gsto1 expression is controlled by cis-expression quantitative trait loci. We found that Gsto1 mRNA levels were related to several central nervous system traits, such as glial acidic fibrillary protein levels in the caudate putamen, cortical gray matter volume, and hippocampus mossy fiber pathway volume. We identified 2168 genes whose expression was highly correlated with that of Gsto1. Some genes were enriched for the most common neurodegenerative diseases. Some Gsto1-related genes identified in this study had previously been identified as susceptibility genes for AD, such as APP, Grin2b, Ide, and Psenen. To evaluate the relationships between Gsto1 and candidate network members, we transfected astrocytes with Gsto1 siRNA and assessed the effect on putative downstream effectors. We confirmed that knockdown of Gsto1 had a significant influence on Pa2g4 expression, suggesting that Pa2g4 may be a downstream effector of Gsto1, and that both genes interact with other genes in a network during AD pathogenesis.

Feeding role of mouse embryonic fibroblast cells is influenced by genetic background, cell passage and day of isolation.

Mouse embryonic fibroblast (MEF) cells are commonly used as feeder cells to maintain the pluripotent state of stem cells. MEFs produce growth factors and provide adhesion molecules and extracellular matrix (ECM) compounds for cellular binding. In the present study, we compared the expression levels of Fgf2, Bmp4, ActivinA, Lif and Tgfb1 genes at the mRNA level and the level of Fgf2 protein secretion and Lif cytokine secretion at passages one, three and five of MEFs isolated from 13.5-day-old and 15.5-day-old embryos of NMRI and C57BL/6 mice using real-time PCR and enzyme-linked immunosorbent assay. We observed differences in the expression levels of the studied genes and secretion of the two growth factors in the three passages of MEFs isolated from 13.5-day-old and 15.5-day-old embryos, respectively. These differences were also observed between the NMRI and C57BL/6 strains. The results of this study suggested that researchers should use mice embryos that have different genetic backgrounds and ages, in addition to different MEF passages, when producing MEFs based on the application and type of their study.

Systematic Review and Meta-Analysis of Endurance Exercise Training Protocols for Mice.

Inbred and genetically modified mice are frequently used to investigate the molecular mechanisms responsible for the beneficial adaptations to exercise training. However, published paradigms for exercise training in mice are variable, making comparisons across studies for training efficacy difficult. The purpose of this systematic review and meta-analysis was to characterize the diversity across published treadmill-based endurance exercise training protocols for mice and to identify training protocol parameters that moderate the adaptations to endurance exercise training in mice. Published studies were retrieved from PubMed and EMBASE and reviewed for the following inclusion criteria: inbred mice; inclusion of a sedentary group; and exercise training using a motorized treadmill. Fifty-eight articles met those inclusion criteria and also included a "classical" marker of training efficacy. Outcome measures included changes in exercise performance, V ˙ O2max, skeletal muscle oxidative enzyme activity, blood lactate levels, or exercise-induced cardiac hypertrophy. The majority of studies were conducted using male mice. Approximately 48% of studies included all information regarding exercise training protocol parameters. Meta-analysis was performed using 105 distinct training groups (i.e., EX-SED pairs). Exercise training had a significant effect on training outcomes, but with high heterogeneity (Hedges' g=1.70, 95% CI=1.47-1.94, Tau2=1.14, I2 =80.4%, prediction interval=-0.43-3.84). Heterogeneity was partially explained by subgroup differences in treadmill incline, training duration, exercise performance test type, and outcome variable. Subsequent analyses were performed on subsets of studies based on training outcome, exercise performance, or biochemical markers. Exercise training significantly improved performance outcomes (Hedges' g=1.85, 95% CI=1.55-2.15). Subgroup differences were observed for treadmill incline, training duration, and exercise performance test protocol on improvements in performance. Biochemical markers also changed significantly with training (Hedges' g=1.62, 95% CI=1.14-2.11). Subgroup differences were observed for strain, sex, exercise session time, and training duration. These results demonstrate there is a high degree of heterogeneity across exercise training studies in mice. Training duration had the most significant impact on training outcome. However, the magnitude of the effect of exercise training varies based on the marker used to assess training efficacy.

Efficacy of BCG Vaccination Depends on Host Genetics.

We studied the effectiveness of anti-tuberculosis vaccination with BCG in mice of inbred strains and F1 hybrids (highly resistant to tuberculosis infection) that represent a wide range of genetically determined differences in susceptibility to infection with virulent Mycobacterium tuberculosis. The greatest relative effect was found in susceptible mice, with the exception of highly susceptible I/St mice that were practically not protected by vaccination. Despite significant effect of vaccination in inbred mice, their resistance to M. tuberculosis infection did not exceed that of non-vaccinated highly resistant F1 hybrids.

Inter-individual variability in habituation of anxiety-related responses within three mouse inbred strains.

Inter-individual variability in behavioral and physiological response has become a well-established phenomenon in animal models of anxiety and other disorders. Such variability is even demonstrated within mouse inbred strains. A recent study showed that adaptive and non-adaptive anxiety phenotypes (measured as habituation and/or sensitization of anxiety responses) may differ within cohorts of 129 mice. This variability was expressed across both anxiety- and activity-related behavioral dimensions. These findings were based however on re-analysis of previously published data. The present study therefore aimed to empirically validate these findings in 129 mice. In addition, we assessed such inter-individuality in two other strains: BALB/c and C57BL/6. Males of three mouse inbred strains (BALB/c, C57BL/6 and 129S2) were behaviorally characterized through repeated exposure to a mild aversive stimulus (modified Hole Board, 4 consecutive trials). Behavioral observations were supplemented with assessment of circulating corticosterone levels. Clustering the individual response trajectories of behavioral and endocrine responses yielded two multidimensional response types of different adaptive value. Interestingly, these response types were displayed by individuals of all three strains. The response types differed significantly on anxiety and activity related behavioral dimensions but not on corticosterone concentrations. This study empirically confirms that adaptive capacities may differ within 129 cohorts. In addition, it extends this inter-individual variability in behavioral profiles to BALB/c and C57BL/6. Whether these two sub-types constitute differential anxiety phenotypes may differ per strain and requires further study.

Drug Resistance of Mouse Somatic Cells to Rifampicin in Experimental Tuberculosis.

We have demonstrated that long-term exposure of intact mice to rifampicin (6 months) induces resistance to this drug, which manifested in inability of rifampicin to suppress the growth of Mycobacterium tuberculosis in the lungs and spleen during subsequent infection. It the same time, isoniazid is still effective in these mice. In this case, the phenomenon of somatic resistance to rifampicin in mice was observed if the treatment was started in a short period (within 4 days) after infection with M. tuberculosis. If the interval between infection and rifampicin administration was longer (3 weeks), the resistance disappeared.

The Japanese Wild-Derived Inbred Mouse Strain, MSM/Ms in Cancer Research.

MSM/Ms is a unique inbred mouse strain derived from the Japanese wild mouse, Mus musculus molossinus, which has been approximately 1 million years genetically distant from standard inbred mouse strains mainly derived from M. m. domesticus. Due to its genetic divergence, MSM/Ms has been broadly used in linkage studies. A bacterial artificial chromosome (BAC) library was constructed for the MSM/Ms genome, and sequence analysis of the MSM/Ms genome showed approximately 1% of nucleotides differed from those in the commonly used inbred mouse strain, C57BL/6J. Therefore, MSM/Ms mice are thought to be useful for functional genome studies. MSM/Ms mice show unique characteristics of phenotypes, including its smaller body size, resistance to high-fat-diet-induced diabetes, high locomotive activity, and resistance to age-onset hearing loss, inflammation, and tumorigenesis, which are distinct from those of common inbred mouse strains. Furthermore, ES (Embryonic Stem) cell lines established from MSM/Ms allow the MSM/Ms genome to be genetically manipulated. Therefore, genomic and phenotypic analyses of MSM/Ms reveal novel insights into gene functions that were previously not obtained from research on common laboratory strains. Tumorigenesis-related MSM/Ms-specific genetic traits have been intensively investigated in Japan. Furthermore, radiation-induced thymic lymphomas and chemically-induced skin tumors have been extensively examined using MSM/Ms.

Population and subspecies diversity at mouse centromere satellites.

BACKGROUND: Mammalian centromeres are satellite-rich chromatin domains that execute conserved roles in kinetochore assembly and chromosome segregation. Centromere satellites evolve rapidly between species, but little is known about population-level diversity across these loci. RESULTS: We developed a k-mer based method to quantify centromere copy number and sequence variation from whole genome sequencing data. We applied this method to diverse inbred and wild house mouse (Mus musculus) genomes to profile diversity across the core centromere (minor) satellite and the pericentromeric (major) satellite repeat. We show that minor satellite copy number varies more than 10-fold among inbred mouse strains, whereas major satellite copy numbers span a 3-fold range. In contrast to widely held assumptions about the homogeneity of mouse centromere repeats, we uncover marked satellite sequence heterogeneity within single genomes, with diversity levels across the minor satellite exceeding those at the major satellite. Analyses in wild-caught mice implicate subspecies and population origin as significant determinants of variation in satellite copy number and satellite heterogeneity. Intriguingly, we also find that wild-caught mice harbor dramatically reduced minor satellite copy number and elevated satellite sequence heterogeneity compared to inbred strains, suggesting that inbreeding may reshape centromere architecture in pronounced ways. CONCLUSION: Taken together, our results highlight the power of k-mer based approaches for probing variation across repetitive regions, provide an initial portrait of centromere variation across Mus musculus, and lay the groundwork for future functional studies on the consequences of natural genetic variation at these essential chromatin domains.

Morphine and ethanol pretreatment effects on expression and extinction of ethanol-induced conditioned place preference and aversion in mice.

RATIONALE: Opioid receptor antagonists reliably alter the expression or extinction of ethanol's conditioned motivational effects as indexed by the place conditioning procedure, suggesting endogenous opioids are normally involved. These studies examined how exogenous stimulation of opioid receptors alters ethanol's conditioned rewarding and aversive effects. OBJECTIVES: Drugs that either directly (morphine) or indirectly (ethanol) stimulate opioid receptors were tested for their effects on the expression and extinction of ethanol-induced conditioned place preference (CPP) and conditioned place aversion (CPA). METHODS: Male DBA/2J mice were exposed to unbiased ethanol (2 g/kg) conditioning procedures that produced either CPP (experiments 1-2) or CPA (experiments 3-4). Morphine (0, 2.5, 5, or 10 mg/kg) was injected before three post-conditioning tests in experiments 1 and 3, whereas ethanol (0, 1, 2, or 3 g/kg) was injected before tests in experiments 2 and 4. All groups received vehicle on test 4 to determine whether the drug pretreatments altered the course of extinction. RESULTS: Morphine dose-dependently enhanced CPP expression (experiment 1), but ethanol dose-dependently reduced CPP expression (experiment 2). Test 4 showed no differences between drug-treated mice and mice given vehicle on all tests. Morphine had no effect on expression or extinction of ethanol-induced CPA (experiment 3). The highest ethanol dose (3 g/kg) interfered with CPA expression, but not extinction (experiment 4). CONCLUSIONS: Pretreatment drug effects on ethanol CPP and CPA expression were most likely a byproduct of their activity altering effects rather than opioid-receptor mediated modulation of ethanol's conditioned motivational effects. Neither drug affected the course of extinction.