The breadth of genetic and phenotypic variation among inbred strains is often underappreciated because assessments include only a limited number of strains. Evaluation of a larger collection of inbred strains provides not only a greater understanding of this variation but collectively mimics much of the variation observed in human populations. We used a high-throughput phenotyping protocol to measure females and males of 43 inbred strains for body composition (weight, fat, lean tissue mass, and bone mineral density), plasma triglycerides, high-density lipoprotein and total cholesterol, glucose, insulin, and leptin levels while mice consumed a high-fat, high-cholesterol diet. Mice were fed a chow diet until they were 6-8 wk old and then fed the high-fat diet for an additional 18 wk. As expected, broad phenotypic diversity was observed among these strains. Significant variation between the sexes was also observed for most traits measured. Additionally, the response to the high-fat diet differed considerably among many strains. By the testing of such a large set of inbred strains for many traits, multiple phenotypes can be considered simultaneously and thereby aid in the selection of certain inbred strains as models for complex human diseases. These data are publicly available in the web-accessible Mouse Phenome Database (http://www.jax.org/phenome), an effort established to promote systematic characterization of biochemical and behavioral phenotypes of commonly used and genetically diverse inbred mouse strains. Data generated by this effort builds on the value of inbred mouse strains as a powerful tool for biomedical research.

The Mouse Phenome Project is an international effort to systematically gather phenotypic data for a defined set of inbred mouse strains. For such large-scale projects the development of high-throughput screening protocols that allow multiple tests to be performed on a single mouse is essential. Here we report hematologic and coagulation data for more than 30 inbred strains. Complete blood counts were performed using an Advia 120 analyzer. For coagulation testing, we successfully adapted the Dade Behring BCS automated coagulation analyzer for use in mice by lowering sample and reagent volume requirements. Seven automated assay procedures were developed. Small sample volume requirements make it possible to perform multiple tests on a single animal without euthanasia, while reductions in reagent volume requirements reduce costs. The data show that considerable variation in many basic hematological and coagulation parameters exists among the inbred strains. These data, freely available on the World Wide Web, allow investigators to knowledgeably select the most appropriate strain(s) to meet their individual study designs and goals.

In an effort to discover new mouse models of cardiovascular disease using N-ethyl-N-nitrosourea (ENU) mutagenesis followed by high-throughput phenotyping, we have identified a new mouse mutation, C699Y, in the LDL receptor (Ldlr), named wicked high cholesterol (WHC). When WHC was compared with the widely used Ldlr knockout (KO) mouse, notable phenotypic differences between strains were observed, such as accelerated atherosclerotic lesion formation and reduced hepatosteatosis in the ENU mutant after a short exposure to an atherogenic diet. This lossof-function mouse model carries a single base mutation in the Ldlr gene on an otherwise pure C57BL/6J (B6) genetic background, making it a useful new tool for understanding the pathophysiology of atherosclerosis and for evaluating additional genetic modifiers regulating hyperlipidemia and atherogenesis. Further investigation of genomic differences between the ENU mutant and KO strains may reveal previously unappreciated sequence functionality. The incidence and progression of atherosclerosis remains a challenge for public health intervention and medical research strategies. Mouse models have been of great utility in meeting this challenge and have enabled systematic evaluation of genetic and environmental influences on the pathogenesis of this disease. Lipoproteins and their receptors play crucial roles in cholesterol homeostasis and, when functionally impaired, can accelerate atherogenesis. Mice with targeted mutations resulting in loss of function and those engineered for overexpression of apolipoproteins, their receptors, and key enzymes in lipid metabolism have been used extensively to investigate the complex etiology of atherosclerosis and to develop effective approaches to treatment (1-6). In addition to genetically engineered mouse models, chemical mutagenesis using N-ethyl-N-nitrosourea (ENU), which causes primarily single-nucleotide mutations, has produced numerous new mouse models for studying human disease. Many of these mutants carry a novel functional mutation in a known gene (7-11). For known genes, having multiple models with a variety of unique mutations allows a survey of phenotypic differences and functional annotation of genes and their products. Causative mutations in numerous ENU mutants identified from large-scale mutagenesis programs worldwide, collectively representing a broad spectrum of disease-related phenotypes, have yet to be identified, and still hold promise of revealing novel genes.Here we describe the identification and initial characterization of a new mouse model of high cholesterol and atherosclerosis generated using ENU mutagenesis and high-throughput phenotyping. Candidate gene sequencing identified a point mutation in the LDL receptor (Ldlr) gene. Comparison of this mutant with the well-characterized Ldlr knockout (KO) mouse model reveals certain phenotypic differences and supports it as a new tool for the study of familial hypercholesterolemia (FH) and atherosclerosis. METHODS Mice and husbandryNonmutagenized C57BL/6J (B...

Identifying the genes and gene products relevant to physiological systems and creating opportunities to elucidate their function are essential first steps in understanding the pathophysiology of disease. To dissect the genetic variation underlying hematopoietic, cardiovascular, lung, and sleep dysfunction, we established a Center for Mouse Models of Heart, Lung, Blood and Sleep (HLBS) Disorders at The Jackson Laboratory as part of the NHLBI Program for Genomic Applications (PGA). The major goal of the JAX PGA is to enable researchers to link both single-gene mutations and quantitative trait loci (QTL) to gene function and disease. To achieve this goal, we are generating new mutations in mice by chemical (ENU) mutagenesis, and characterizing the common inbred mouse strains to detect existing genetic variation. Here, we report an extensive body of hematologically relevant strain characterization data and the establishment of new animal models. All strain characterization data is deposited into the Mouse Phenome Database (MPD, http://www.jax.org/phenome), also accessible via the JAX PGA website (http://pga.jax.org). Data for up to 48 inbred strains are currently available and include complete blood counts and coagulation profiles (PT, aPTT, fibrinogen). These data allow investigators to identify the most appropriate strains for (a) physiological testing; (b) drug development; (c) progenitors in QTL crosses; (d) sensitized mutagenesis screens; and (e) direct hypothesis testing. For example, to maximize the potential for successful QTL identification, parental strains that differ substantially in the phenotype of interest, at least 2 standard deviations (SD), should be selected. We used our strain survey data to select parental strains for identification of QTL for baseline WBC count, an important risk factor for sickle cell disease severity. The strains C57BLKS/J and SM/J have WBC counts of 12.6 ± 1.6 and 3.3 ± 0.8 x 103/μL, respectively, a difference much greater the 2 SD, indicating a high statistical power. We identified a highly significant QTL (LOD = 7) on chromosome 1 in an initial genome wide scan of 279 F2 animals. Moreover, the availability of extensive phenotypic data across the inbred strains in conjunction with the availability of saturated sslp and SNP maps has allowed us to identify QTL in silico. As an example of the utility of the MPD in hypothesis testing, a modifier gene associated with decreased VWF levels is present in 5 of the 6 MPD strains showing the highest aPTT levels (see abstract by Johnsen et al). In total, 44 different phenotypic projects, each consisting of large datasets, can be freely accessed through the MPD. The JAX PGA mutagenesis effort in C57BL/6J mice has likewise yielded valuable resources. Nearly 100 new mutant strains are in various stages of development, including strains with phenotypes of interest to the hematology community (e. g., anemia, thrombocytopenia, leukopenia, leukocytosis). These animal models and all other JAX PGA resources (protocols, software, QTL locations) are freely available to the scientific community.