Recommended housing densities for research mice: filling the gap in data-driven alternatives.

Space recommendations for mice made in the Guide for Care and Use of Laboratory Animals have not changed since 1972, despite important improvements in husbandry and caging practices. The 1996 version of the Guide put forth a challenge to investigators to produce new data evaluating the effects of space allocation on the well-being of mice. In this review, we summarize many studies published in response to this challenge. We distinguish between studies using ventilated or nonventilated caging systems and those evaluating reproductive performance or general well-being of adult mice. We discuss how these studies might affect current housing density considerations in both production and research settings and consider gaps in mouse housing density research. Additionally, we discuss reliable methods used to monitor and quantify general well-being of research mice. Collectively, this large body of new data suggests that husbandry practices dictating optimal breeding schemes and space allocation per mouse can be reconsidered. Specifically, these data demonstrate that prewean culling of litters has no benefit, trio breeding is an effective production strategy without adversely affecting pup survival and well-being, and housing of adult mice at densities of up to twice current Guide recommendations does not compromise well-being for most strains.-Svenson, K. L., Paigen, B. Recommended housing densities for research mice: filling the gap in data-driven alternatives.

Physician-diagnosed eczema is an independent risk factor for incident mouse skin test sensitization in adults.

BACKGROUND: The disrupted skin barrier in eczema has been associated with an increased risk of immunoglobulin E (IgE) sensitization in childhood. However, it is unclear whether eczema, independent of atopy, is a risk factor for the development of allergic sensitization in adulthood. OBJECTIVE: To determine if skin barrier dysfunction, independent of atopy, is a risk factor for incident sensitization in adult workers at a mouse production and research facility. METHODS: New employees at The Jackson Laboratory enrolled in a cohort study and underwent skin-prick testing (SPT) at baseline and every 6 months to mouse and to a panel of aeroallergens (net wheal ≥3 mm indicated a positive SPT result). Mouse allergen exposure was measured every 6 months by using personal air monitors. Physician-diagnosed eczema was defined as self-reported physician-diagnosed eczema. Cox proportional hazard modeling was used to examine the association between baseline physician-diagnosed eczema and incident mouse skin test sensitization and adjusted for potential confounders. RESULTS: The participants (N = 394) were followed up for a median of 24 months. Fifty-four percent were women, 89% were white, and 64% handled mice. At baseline, 7% of the participants reported physician-diagnosed eczema and 9% reported current asthma; 61% had at least one positive skin test result. At 30 months, 36% of those with eczema versus 14% of those without eczema had developed a positive mouse skin test result (p = 0.02, log-rank test). After adjusting for age, race, sex, smoking status (current, former, never), current asthma, hay fever, the number of positive SPT results at baseline, and mouse allergen exposure, physician-diagnosed eczema was an independent risk factor for incident mouse SPT sensitization (hazard ratio 5.6 [95% confidence interval, 2.1-15.2]; p = 0.001). CONCLUSION: Among adult workers at a mouse production and research facility, physician-diagnosed eczema was a risk factor for incident mouse sensitization, independent of atopy, which indicated that a defect in skin barrier alone may increase the risk of skin sensitization, not just in childhood, but throughout life.

Atopy as a Modifier of the Relationships Between Endotoxin Exposure and Symptoms Among Laboratory Animal Workers.

BACKGROUND: Exposure to endotoxin is known to trigger airway inflammation and symptoms, and atopy may modify the relationship between endotoxin exposure and symptom development. OBJECTIVE: To test the a priori hypothesis that atopic status modifies the relationship between endotoxin exposure and respiratory symptom development. METHODS: A prospective study of laboratory workers at The Jackson Laboratories was conducted. Allergy skin testing was performed and population demographic and clinical information was obtained at baseline. Personal exposure assessments for airborne endotoxin and surveys of self-reported symptoms were performed every 6 months. Cox proportional hazards models were used to examine the relationship between endotoxin exposure and development of mouse-associated symptoms and multivariate regression was used to test for interaction. RESULTS: Overall, 16 (9%) of 174 worker-participants developed mouse-associated rhinoconjunctivitis symptoms by 24 months and 8 (5%) developed mouse-associated lower respiratory symptoms by 24 months. Among workers with endotoxin exposure above the median (≥2.4 EU m-3), 5 (6% of 80) atopics reported mouse-associated rhinoconjunctivitis symptoms at 24 months as compared to 3 (3% of 94) non-atopics. Among workers below the median endotoxin exposure (<2.4 EU m-3), 1 (1% of 80) atopic reported mouse-associated rhinoconjunctivitis symptoms at 24 months as compared to 7 (7% of 94) non-atopics. For the combination of symptoms, the adjusted hazard ratio was 6.8 (95% confidence interval: 0.7-67.2) for atopics and 0.07 (95% confidence interval: 0.01-0.5) for non-atopics. CONCLUSION: In this occupational cohort, atopic workers may be more susceptible to, and non-atopic workers protected from, endotoxin-associated upper and lower respiratory symptoms.

Effects of Varied Housing Density on a Hybrid Mouse Strain Followed for 20 Months.

To evaluate the effect of increased housing density in a hybrid mouse strain, we evaluated a panel of physiological and behavioral traits in animals that were housed in groups of 3, 5, 8, or 12, using cages that provide 78.1 in2 of floor space. Such groupings resulted in cage densities that ranged from half to almost twice the density recommended by the Guide for the Care and Use of Laboratory Animals. While previous studies have investigated physiological effects of increased housing density using inbred mouse strains, including C57BL/6J and 129S1/SvImJ, this study tested an F1 hybrid population of C57BL/6J x 129S1/SvImJ for changes resulting from either decreased or increased housing density. Mice were followed until they were 20 months old, a substantially longer duration than has been used in previous density studies. We evaluated mortality, growth, home cage behavior, blood pressure, body composition, clinical plasma chemistries, immune function, and organ weights (heart, kidney, adrenal glands, and testes) as endpoints of chronic stress that may arise from sub-optimal housing conditions. Few statistically different parameters were observed in this study, none of which describe chronic stress and all within normal physiological ranges for research mice, suggesting that this hybrid strain was not adversely affected by housing at twice the density currently recommended.

Accessing Data Resources in the Mouse Phenome Database for Genetic Analysis of Murine Life Span and Health Span.

Understanding the source of genetic variation in aging and using this variation to define the molecular mechanisms of healthy aging require deep and broad quantification of a host of physiological, morphological, and behavioral endpoints. The murine model is a powerful system in which to understand the relations across age-related phenotypes and to identify research models with variation in life span and health span. The Jackson Laboratory Nathan Shock Center of Excellence in the Basic Biology of Aging has performed broad characterization of aging in genetically diverse laboratory mice and has placed these data, along with data from several other major aging initiatives, into the interactive Mouse Phenome Database. The data may be accessed and analyzed by researchers interested in finding mouse models for specific aging processes, age-related health and disease states, and for genetic analysis of aging variation and trait covariation. We expect that by placing these data in the hands of the aging community that there will be (a) accelerated genetic analyses of aging processes, (b) discovery of genetic loci regulating life span, (c) identification of compelling correlations between life span and susceptibility for age-related disorders, and (d) discovery of concordant genomic loci influencing life span and aging phenotypes between mouse and humans.

Integrative Mouse and Human Studies Implicate ANGPT1 and ZBTB7C as Susceptibility Genes to Ischemic Injury.

BACKGROUND AND PURPOSE: The extent of ischemic injury in response to cerebral ischemia is known to be affected by native vasculature. However, the nonvascular and dynamic vascular responses and their genetic basis are not well understood. METHODS: We performed a genome-wide association study in 235 mice from 33 inbred strains using the middle cerebral artery occlusion model. Population structure and genetic relatedness were accounted for using the efficient mixed-model association method. Human orthologs to the genes associated with the significant and suggestive single-nucleotide polymorphisms from the mouse strain survey were examined in patients with M1 occlusions admitted with signs and symptoms of acute ischemic stroke. RESULTS: We identified 4 genome-wide significant and suggestive single-nucleotide polymorphisms to be associated with infarct volume in mice (rs3694965, P=2.17×10(-7); rs31924033, P=5.61×10(-6); rs32249495, P=2.08×10(-7); and rs3677406, P=9.56×10(-6)). rs32249495, which corresponds to angiopoietin-1 (ANGPT1), was also significant in the recessive model in humans, whereas rs1944577, which corresponds to ZBTB7C, was nominally significant in both the additive and dominant genetic models in humans. ZBTB7C was shown to be upregulated in endothelial cells using both in vitro and in vivo models of ischemia. CONCLUSIONS: Genetic variations of ANGPT1 and ZBTB7C are associated with increased infarct size in both mice and humans. ZBTB7C may modulate the ischemic response via neuronal apoptosis and dynamic collateralization and, in addition to ANGPT1, may serve as potential novel targets for treatments of cerebral ischemia.

Genetic Regulation of Female Sexual Maturation and Longevity Through Circulating IGF1.

We previously reported that insulin-like growth factor 1 (IGF1) was involved in coregulating female sexual maturation and longevity. To understand the underlying genetic mechanisms, based on the strain survey assays of development and aging traits, we crossed two mouse strains, KK/HIJ and PL/J, and produced 307 female F2 mice. We observed the age of vaginal patency (AVP) and the life span of these females. We also measured circulating IGF1 level at 7, 16, 24, 52, and 76 weeks. IGF1 level at 7 weeks significantly correlated with AVP. IGF1 levels at ages of 52 and 76 weeks negatively correlated with longevity (p ≤ .05). A gene mapping study found 22, 4 ,and 3 quantitative trait loci for IGF1, AVP, and life span, respectively. Importantly, the colocalization of IGF1, AVP, and life span quantitative trait loci in the distal region of chromosome 2 suggests this locus carries gene(s) that could regulate IGF1, AVP, and life span. In this region, proprotein convertase subtilisin/kexin type 2 has been found to be associated with female sexual maturation in a human genome-wide association study. We verified the roles of proprotein convertase subtilisin/kexin type 2 in regulating IGF1 and AVP by showing that depletion of proprotein convertase subtilisin/kexin type 2 significantly reduced IGF1 and delayed AVP in mice, suggesting that it also might be involved in the regulation of aging.

Effects of housing density in five inbred strains of mice.

To evaluate the effect of increased mouse density in a cage, mice were housed at the density recommended by the 1996 Guide for the Care and Use of Laboratory Animals and at densities that were approximately 2, 2.6, and 3 times greater. Five strains of mice (129S1/SvImJ, A/J, BALB/cByJ, C57BL/6J, and DBA/2J) were evaluated throughout 3- and 8-month timeframes for health and well-being, including mortality, cardiac measures, plasma cholesterol, body weight, bone mineral density, organ weights, hematology, behavioral observations, and open field and light-dark tests. For 22 of the 27 traits measured, increased housing density had no significant effect. Kidney weight, adrenal weight, and heart rate decreased as mice were housed more densely, and some of the decreases were statistically significant. Reduced kidney weight, adrenal weight, and heart rate are not considered to be negative outcomes and may even indicate reduced stress. However, all measurements of these three traits were within normal physiological ranges. Percent fat increased slightly in strains 129S1/SvImJ, A/J, and DBA/2J, but did not increase in strains BALB/cByJ, and C57BL/6J. These results indicate that mice can be housed at higher densities than those currently recommended.

The effect of culling on health and physiology of mouse litters.

Large mouse litters are often culled based on the premise of better survival and growth for the remaining pups. To test whether the culling of litters does provide the benefits of improved survival and growth, mortality and growth were measured in 468 litters of C57BL/6J × 129S1/SvImJ F1 hybrid mice that were unculled or culled to four or six pups per litter. In addition, a limited number of weanlings were evaluated until three months of age for growth, health and physiological measurements. Most measurements did not differ among the cull groups. These included mortality, organ weights (adrenals, kidneys and testes), bone mineral density, percent fat, 12 of the 17 blood parameters, and three of the seven electrocardiographic (EKG) parameters. Several parameters, including five of the 17 blood parameters and four of the seven EKG parameters, showed statistical differences, but all values were physiologically normal. Unculled weanlings showed a reduced weight of 4%, but this weight difference disappeared by three months. These results suggest that mice in culled litters do not demonstrate improved health compared with those in unculled litters.

Modeling hepatic osteodystrophy in Abcb4 deficient mice.

Hepatic osteodystrophy (HOD) denotes the alterations in bone morphology and metabolism frequently observed in patients with chronic liver diseases, in particular in case of cholestatic conditions. The molecular mechanisms underlying HOD are only partially understood. In the present study, we characterized the bone phenotypes of the ATP-binding cassette transporter B4 knockout mouse (Abcb4(-/-)), a well-established mouse model of chronic cholestatic liver disease, with the aim of identifying and characterizing a mouse model for HOD. Furthermore, we investigated the influence of vitamin D on bone quality in this model. The bone morphology analyses revealed reduced bone mineral contents as well as changes in trabecular bone architecture and decreased cortical bone densities in Abcb4(-/-) mice with severe liver fibrosis. We observed dysregulation of genes involved in bone remodeling (osteoprotegerin, osteocalcin, osteopontin) and vitamin D metabolism (7-dehydrocholesterol reductase, Gc-globulin, Cyp2r1, Cyp27a1) as well as alterations in calcium and vitamin D homeostasis. In addition, serum RANKL and TGF-ß levels were increased in Abcb4(-/-) mice. Vitamin D dietary intervention did not restore the bone phenotypes of Abcb4(-/-) animals. We conclude that the Abcb4(-/-) mouse provides an experimental framework and a preclinical model to gain further insights into the molecular pathobiology of HOD and to study the systemic effects of therapeutic interventions.

Recalculation of 23 mouse HDL QTL datasets improves accuracy and allows for better candidate gene analysis.

In the past 15 years, the quantitative trait locus (QTL) mapping approach has been applied to crosses between different inbred mouse strains to identify genetic loci associated with plasma HDL cholesterol levels. Although successful, a disadvantage of this method is low mapping resolution, as often several hundred candidate genes fall within the confidence interval for each locus. Methods have been developed to narrow these loci by combining the data from the different crosses, but they rely on the accurate mapping of the QTL and the treatment of the data in a consistent manner. We collected 23 raw datasets used for the mapping of previously published HDL QTL and reanalyzed the data from each cross using a consistent method and the latest mouse genetic map. By utilizing this approach, we identified novel QTL and QTL that were mapped to the wrong part of chromosomes. Our new HDL QTL map allows for reliable combining of QTL data and candidate gene analysis, which we demonstrate by identifying Grin3a and Etv6, as candidate genes for QTL on chromosomes 4 and 6, respectively. In addition, we were able to narrow a QTL on Chr 19 to five candidates.

Early gene expression differences in inbred mouse strains with susceptibility to pulmonary adenomas.

Lung cancer is the most common cause of cancer-related deaths in both men and women, and effective preventatives are rare due to the difficulty of early detection. Specific gene expression signatures have been identified in individuals that already developed lung cancer. To identify if gene expression differences could be detected in individuals before the onset of the disease, we obtained lung tissues for microarray analysis from young, healthy mice of 9 inbred strains with known differences in their susceptibility to spontaneous pulmonary adenomas when aged. We found that the most common differentially expressed genes among all possible 36 strain comparisons showed significant associations with cancer- and inflammation-related processes. Significant expression differences between susceptible and resistant strains were detected for Aldh3a1, Cxcr1 and 7, Dpt, and Nptx1-genes with known cancer-related functions, and Cd209, Cxcr1 and 7, and Plag2g1b-genes with known inflammatory-related functions. Whereas Aldh3a1, Cd209, Dpt, and Pla2g1b had increased expression, Cxcr1 and 7, and Nptx1 had decreased expression in strains susceptible to pulmonary adenomas. Thus, our study shows that expression differences between susceptible and resistant strains can be detected in young and healthy mice without manifestation of pulmonary adenomas and, thus, may provide an opportunity of early detection. Finally, the identified genes have previously been reported for human non-small cell lung cancer suggesting that molecular pathways may be shared between these two cancer types.

A major X-linked locus affects kidney function in mice.

Chronic kidney disease is a common disease with increasing prevalence in the western population. One common reason for chronic kidney failure is diabetic nephropathy. Diabetic nephropathy and hyperglycemia are characteristics of the mouse inbred strain KK/HlJ, which is predominantly used as a model for metabolic syndrome due to its inherited glucose intolerance and insulin resistance. We used KK/HlJ, an albuminuria-sensitive strain, and C57BL/6J, an albuminuria-resistant strain, to perform a quantitative trait locus (QTL) cross to identify the genetic basis for chronic kidney failure. Albumin-creatinine ratio (ACR) was measured in 130 F2 male offspring. One significant QTL was identified on chromosome (Chr) X and four suggestive QTL were found on Chrs 6, 7, 12, and 13. Narrowing of the QTL region was focused on the X-linked QTL and performed by incorporating genotype and expression analyses for genes located in the region. From the 485 genes identified in the X-linked QTL region, a few candidate genes were identified using a combination of bioinformatic evidence based on genomic comparison of the parental strains and known function in urine homeostasis. Finally, this study demonstrates the significance of the X chromosome in the genetic determination of albuminuria.

Genetic analysis of albuminuria in collaborative cross and multiple mouse intercross populations.

Albuminuria is an important marker of nephropathy that increases the risk of progressive renal and chronic cardiovascular diseases. The genetic basis of kidney disease is well-established in humans and rodent models, but the causal genes remain to be identified. We applied several genetic strategies to map and refine genetic loci affecting albuminuria in mice and translated the findings to human kidney disease. First, we measured albuminuria in mice from 33 inbred strains, used the data for haplotype association mapping (HAM), and detected 10 genomic regions associated with albuminuria. Second, we performed eight F(2) intercrosses between genetically diverse strains to identify six loci underlying albuminuria, each of which was concordant to kidney disease loci in humans. Third, we used the Oak Ridge National Laboratory incipient Collaborative Cross subpopulation to detect an additional novel quantitative trait loci (QTL) underlying albuminuria. We also performed a ninth intercross, between genetically similar strains, that substantially narrowed an albuminuria QTL on Chromosome 17 to a region containing four known genes. Finally, we measured renal gene expression in inbred mice to detect pathways highly correlated with albuminuria. Expression analysis also identified Glcci1, a gene known to affect podocyte structure and function in zebrafish, as a strong candidate gene for the albuminuria QTL on Chromosome 6. Overall, these findings greatly enhance our understanding of the genetic basis of albuminuria in mice and may guide future studies into the genetic basis of kidney disease in humans.

Differences in health status affect susceptibility and mapping of genetic loci for atherosclerosis (fatty streak) in inbred mice.

OBJECTIVE: We observed differences in atherosclerosis susceptibility in mouse inbred strains over the years as the health status of our animal rooms increased. Therefore, we investigated the effect of animal room health status on atherosclerosis susceptibility in different strains. As these data can also be used for genome-wide association mapping, we performed a mapping study and compared our results with previously found quantitative trait loci for atherosclerosis in mouse and humans. METHODS AND RESULTS: Males and females from 48 inbred strains were housed in 2 animal rooms with different health status and given an atherogenic diet. We compared atherosclerosis susceptibility between animal rooms and between sexes and found that susceptibility is dependent on both health status and sex. Subsequently, the data were used for associations with loci on the mouse genome using 63 222 single nucleotide polymorphism. Three loci in males and 4 loci in females were identified using the data from the low-health status room. No significant associations were identified using the data from the high-health status room. CONCLUSIONS: Health status influences susceptibility to atherosclerosis and suggests that microbiological pressure plays an important role in the development of atherosclerosis in many strains. As we were only able to map susceptibility loci using the data from the lower health status room, we argue that susceptibility under these conditions is determined by a few key loci, whereas in the higher health status room different mechanisms might play a role in the differences in atherosclerosis susceptibility between strains and we did not have enough power to map the loci that are involved.

Genetic coregulation of age of female sexual maturation and lifespan through circulating IGF1 among inbred mouse strains.

We previously reported that mouse strains with lower circulating insulin-like growth factor 1 (IGF1) level at 6 mo have significantly extended longevity. Here we report that strains with lower IGF1 have significantly delayed age of female sexual maturation, measured by vaginal patency (VP). Among strains with normal lifespans (mean lifespan >600 d), delayed age of VP associated with greater longevity (P = 0.015), suggesting a genetically regulated tradeoff at least partly mediated by IGF1. Supporting this hypothesis, C57BL/6J females had 9% lower IGF1, 6% delayed age of VP, and 24% extended lifespan compared with C57BL/6J.C3H/HeJ-Igf1, which carries a C3H/HeJ allele on chromosome (Chr) 10 that increases IGF1. To identify genetic loci/genes that regulate female sexual maturation, including loci that mediate lifespan tradeoffs, we performed haplotype association mapping for age of VP and identified significant loci on Chrs 4 (Vpq1) and 16 (Vpq2 and 3). At each locus, wild-derived strains share a unique haplotype that associates with delayed VP. Substitution of Chr 16 of C57BL/6J with Chr 16 from a wild-derived strain significantly reduced IGF1 and delayed VP. Strains with a wild-derived allele at Vpq3 have significantly extended longevity compared with strains with other alleles. Bioinformatic analysis identified Nrip1 at Vpq3 as a candidate gene. Nrip1(-/-) females have significantly reduced IGF1 and delayed age of VP compared with Nrip1(+/+) females. We conclude that IGF1 may coregulate female sexual maturation and longevity; wild-derived strains carry specific alleles that delay sexual maturation; and Nrip1 is involved in regulating sexual maturation and may affect longevity by regulating IGF1 level.

Using bioinformatics and systems genetics to dissect HDL-cholesterol genetics in an MRL/MpJ x SM/J intercross.

A higher incidence of coronary artery disease is associated with a lower level of HDL-cholesterol. We searched for genetic loci influencing HDL-cholesterol in F2 mice from a cross between MRL/MpJ and SM/J mice. Quantitative trait loci (QTL) mapping revealed one significant HDL QTL (Apoa2 locus), four suggestive QTL on chromosomes 10, 11, 13, and 18 and four additional QTL on chromosomes 1 proximal, 3, 4, and 7 after adjusting HDL for the strong Apoa2 locus. A novel nonsynonymous polymorphism supports Lipg as the QTL gene for the chromosome 18 QTL, and a difference in Abca1 expression in liver tissue supports it as the QTL gene for the chromosome 4 QTL. Using weighted gene co-expression network analysis, we identified a module that after adjustment for Apoa2, correlated with HDL, was genetically determined by a QTL on chromosome 11, and overlapped with the HDL QTL. A combination of bioinformatics tools and systems genetics helped identify several candidate genes for both the chromosome 11 HDL and module QTL based on differential expression between the parental strains, cis regulation of expression, and causality modeling. We conclude that integrating systems genetics to a more-traditional genetics approach improves the power of complex trait gene identification.

Genetic variation in TRPS1 may regulate hip geometry as well as bone mineral density.

Trps1 has been proposed as a candidate gene for a mouse bone mineral density (BMD) QTL on Chromosome (Chr) 15, but it remained unclear if this gene was associated with BMD in humans. We used newly available data and advanced bioinformatics techniques to confirm that Trps1 is the most likely candidate gene for the mouse QTL. In short, by combining the raw genetic mapping data from two F2 generation crosses of inbred strains of mice, we narrowed the 95% confidence interval of this QTL down to the Chr 15 region spanning from 6 to 24cM. This region contains 131 annotated genes. Using block haplotyping, all other genes except Trps1 were eliminated as candidates for this QTL. We then examined associations of 208 SNPs within 10kb of TRPS1 with BMD and hip geometry, using human genome-wide association study (GWAS) data from the GEFOS consortium. After correction for multiple testing, six TRPS1 SNPs were significantly associated with femoral neck BMD (P=0.0015-0.0019; adjusted P=0.038-0.048). We also found that three SNPs were highly associated with femoral neck width in women (rs10505257, P=8.6×10(-5), adjusted P=2.15×10(-3); rs7002384, P=5.5×10(-4), adjusted P=01.38×10(-2)). In conclusion, we demonstrated that combining association studies in humans with murine models provides an efficient strategy to identify new candidate genes for bone phenotypes.

Identification of fat4 and tsc22d1 as novel candidate genes for spontaneous pulmonary adenomas.

Genetic influences that underlie spontaneous lung oncogenesis are poorly understood. The objective of this study was to determine the genetic influences on spontaneous pulmonary adenoma frequency and severity in 28 strains of mice as part of a large-scale aging study conducted at the Jackson Aging Center (http://agingmice.jax.org/). Genome-wide association studies were conducted in these strains with both low-density (132,000) and high-density (4,000,000) panel of single-nucleotide polymorphisms (SNP). Our analysis revealed that adenomas were relatively less frequent and less severe in females than males, and that loci implicated in frequency and severity were often different between male and female mice. While some of the significant loci identified mapped to genomic locations known to be responsible for carcinogen-induced cancers (e.g., Pas1), others were unique to our study. In particular, Fat4 was influential in males and Tsc22d1 was influential in females. SNPs implicated were predicted to alter amino acid sequence and change protein function. In summary, our results suggested that genetic influences that underlie pulmonary adenoma frequency are dependent on gender, and that Fat4 and Tsc22d1 are likely candidate genes to influence formation of spontaneous pulmonary adenoma in aging male and female mice, respectively.

Both the variability and level of mouse allergen exposure influence the phenotype of the immune response in workers at a mouse facility.

BACKGROUND: The role of natural aeroallergen exposure in modulating allergen-specific immune responses is not well understood. OBJECTIVE: We sought to examine relationships between mouse allergen exposure and mouse-specific immune responses. METHODS: New employees (n = 179) at a mouse facility underwent repeated assessment of mouse allergen exposure, skin prick tests (SPTs), and measurement of mouse-specific IgG levels. Relationships between the mean level of exposure, variability of exposure (calculated as log deviation), and time to development of immunologic outcomes were examined by using Cox proportional hazards models. RESULTS: By 24 months, 32 (23%) participants had experienced a positive SPT response, and 10 (8%) had mouse-specific IgG4. The incidence of a positive SPT response increased as levels of exposure increased from low to moderate, peaking at 1.2 ng/m³, and decreased beyond this point (P = .04). The more variable the exposure was across visits, the lower the incidence of a positive SPT response (hazard ratio [HR], 0.17; 95% CI, 0.07-0.41). Variability of exposure was an independent predictor of a positive SPT response in a model that included both exposure metrics. In contrast, the incidence of mouse-specific IgG4 increased with increasing levels of mouse allergen exposure (HR, 2.9; 95% CI, 1.4-6.0), and there was evidence of a higher risk of mouse-specific IgG4 with greater variability of exposure (HR, 6.3; 95% CI, 0.4-95.2). CONCLUSION: Both the level and variability of mouse allergen exposure influence the humoral immune response, with specific patterns of exposure associated with specific immunophenotypes. Exposure variability might be a more important predictor of a positive SPT response, whereas the average exposure level might be a more important predictor of mouse-specific IgG4.