Approaches to Investigating Complex Genetic Traits in a Large-Scale Inbred Mouse Aging Study.

Inbred mice are a unique model system for studying aging because of the genetic homogeneity within inbred strains, the short life span of mice relative to humans, and the rich array of analytic tools that are available. A large-scale aging study was conducted on 28 inbred strains representing great genetic diversity to determine, via histopathology, the type and diversity of spontaneous diseases that aging mice develop. A total of 20 885 different diagnoses were made, with an average of 12 diagnoses per mouse in the study. Eighteen inbred strains have had their genomes sequenced, and many others have been partially sequenced to provide large repositories of data on genetic variation among the strains. This vast amount of genomic information can be utilized in genome-wide association studies to find candidate genes that are involved in the pathogenesis of spontaneous diseases. As an illustration, this article presents a genome-wide association study of the genetic associations of age-related intestinal amyloidosis, which implicated 3 candidate genes: translocating chain-associated membrane protein 1 (Tram1); splicing factor 3b, subunit 5 (Sf3b5); and syntaxin 11 (Stx11). Representative photomicrographs are available on the Mouse Tumor Biology Database and Pathbase to serve as a reference when evaluating inbred mice used in other genetic or experimental studies to rule out strain background lesions. Many of the age-related mouse diseases are similar, if not identical, to human diseases; therefore, the genetic discoveries have direct translational benefit.

Phenotypic characterization of the KK/HlJ inbred mouse strain.

Detailed histopathological diagnoses of inbred mouse strains are important for interpreting research results and defining novel models of human diseases. The aim of this study was to histologically detect lesions affecting the KK/HlJ inbred strain. Mice were examined at 6, 12, and 20 months of age and near natural death (ie, moribund mice). Histopathological lesions were quantified by percentage of affected mice per age group and sex. Predominant lesions were mineralization, hyperplasia, and fibro-osseous lesions. Mineralization was most frequently found in the connective tissue dermal sheath of vibrissae, the heart, and the lung. Mineralization was also found in many other organs but to a lesser degree. Hyperplasia was found most commonly in the pancreatic islets, and fibro-osseous lesions were observed in several bones. The percentage of lesions increased with age until 20 months. This study shows that KK/HlJ mice demonstrate systemic aberrant mineralization, with greatest frequency in aged mice. The detailed information about histopathological lesions in the inbred strain KK/HlJ can help investigators to choose the right model and correctly interpret the experimental results.

Primary neoplasms of bones in mice: retrospective study and review of literature.

To compare and summarize the mechanisms, frequencies of occurrence, and classification schemes of spontaneous, experimental, and genetically engineered mouse skeletal neoplasms, the literature was reviewed, and archived case material at The Jackson Laboratory was examined. The frequency of occurrence of spontaneous bone neoplasms was less than 1% for most strains, with the exceptions of osteomas in CF-1 (5.5% and 10% in two studies) and OF-1 outbred strains (35%), and osteosarcomas in NOD/ShiLtJ (11.5%) and NOD-derived (7.1%) mice. The frequency was 100% for osteochondromas induced by conditional inactivation of exostoses (multiple) 1 (Ext1) in chondrocytes, osteosarcomas induced by tibial intramedullary inoculation of Moloney murine sarcoma virus, and osteosarcomas induced by conditional inactivation of Trp53-with or without inactivation of Rb1-in osteoblast precursors. Spontaneous osteogenic neoplasms were more frequent than spontaneous cartilaginous and vascular types. Malignant neoplasms were more frequent than benign ones. The age of occurrence for spontaneous neoplasms ranged from 37 to 720 days (M = 316.35) for benign neoplasms and 35 to 990 (M = 299.28) days for malignant. In genetically engineered mice, the average age of occurrence ranged from 28 to 70 days for benign and from 35 to 690 days for malignant. Histologically, nonosteogenic neoplasms were similar across strains and mutant stocks; osteogenic neoplasms exhibited greater diversity. This comparison and summarization of mouse bone neoplasms provides valuable information for the selection of strains to create, compare, and validate models of bone neoplasms.

The Mouse Tumor Biology Database (MTB): a central electronic resource for locating and integrating mouse tumor pathology data.

The Mouse Tumor Biology Database (MTB) is designed to provide an electronic data storage, search, and analysis system for information on mouse models of human cancer. The MTB includes data on tumor frequency and latency, strain, germ line, and somatic genetics, pathologic notations, and photomicrographs. The MTB collects data from the primary literature, other public databases, and direct submissions from the scientific community. The MTB is a community resource that provides integrated access to mouse tumor data from different scientific research areas and facilitates integration of molecular, genetic, and pathologic data. Current status of MTB, search capabilities, data types, and future enhancements are described in this article.

Novel laboratory mouse papillomavirus (MusPV) infection.

Most papillomaviruses (PVs) are oncogenic. There are at least 100 different human PVs and 65 nonhuman vertebrate hosts, including wild rodents, which have species-specific PV infections. Florid papillomatosis arose in a colony of NMRI-Foxn1(nu)/Foxn1(nu) (nude) mice at the Advanced Centre for Treatment Research and Education in Cancer in India. Lesions appeared at the mucocutaneous junctions of the nose and mouth. Histologically, lesions were classical papillomas with epidermal hyperplasia on thin fibrovascular stalks in a verrucous pattern. Koilocytotic cells were observed in the stratum granulosum of the papillomatous lesions. Immunohistochemically, these abnormal cells were positive for PV group-specific antigens. With transmission electron microscopy, virus particles were observed in crystalline intranuclear inclusions within keratinocytes. The presence of a mouse PV, designated MusPV, was confirmed by amplification of PV DNA with degenerative primers specific for PVs. This report is the first of a PV and its related disease in laboratory mice.

Primary follicular dystrophy with scarring dermatitis in C57BL/6 mouse substrains resembles central centrifugal cicatricial alopecia in humans.

A number of C57BL/6 (B6) substrains are commonly used by scientists for basic biomedical research. One of several B6 strain-specific background diseases is focal alopecia that may resolve or progress to severe, ulcerative dermatitis. Clinical and progressive histologic changes of skin disease commonly observed in C57BL/6J and preliminary studies in other closely related substrains are presented. Lesions develop due to a primary follicular dystrophy with rupture of severely affected follicles leading to formation of secondary foreign body granulomas (trichogranulomas) in affected B6 substrains of mice. Histologically, these changes resemble the human disease called central centrifugal cicatrical alopecia (CCCA). Four B6 substrains tested have a polymorphism in alcohol dehydrogenase 4 (Adh4) that reduces its activity and potentially affects removal of excess retinol. Using immunohistochemistry, differential expression of epithelial retinol dehydrogenase (DHRS9) was detected, which may partially explain anecdotal reports of frequency differences between B6 substrains. The combination of these 2 defects has the potential to make high dietary vitamin A levels toxic in some B6 substrains while not affecting most other commonly used inbred strains.

Expression of terminal differentiation proteins defines stages of mouse mammary gland development.

Immunohistochemical analysis using paraffin-embedded specimens is the method of choice to evaluate protein expression at a cellular level while preserving tissue architecture in normal and neoplastic tissues. Current knowledge of the expression of terminal differentiation markers in the mouse mammary gland relies on the evaluation of frozen tissues by use of immunofluorescence. We assessed changes in patterns of expression of terminal differentiation markers throughout the development of the mouse mammary gland in paraffin-embedded tissues. The expression of alpha-smooth muscle actin (SMA) and keratins (K) 5, 8/18, and 14 was influenced by the development stage of the mammary gland. Expression of K5 and SMA was restricted to basal cells. Keratin 14 was consistently expressed by mammary basal cells, and was detected in scattered luminal cells from 13.5 days after conception through puberty. Labeling for K8/18 of luminal cells was heterogeneous at all times. Heterogeneous expression patterns in luminal cells suggest this layer has cells with a variety of biological functions. The absence of K6 expression at any stage of the development of the mammary gland was confirmed by use of reverse transcriptase-polymerase chain reaction analysis, which indicates that this intermediate filament is not a marker of the mammary gland stem cell. Finally, consistent with results of earlier studies, keratins 1, 10, 13, and 15, and filaggrin, involucrin, and loricrin were not detected at any stage of mammary gland development.

Restoration of hair growth in mice with an alopecia areata-like disease using topical anthralin.

Anthralin is a widely used topical anti-psoriatic drug that may have an immunomodulating effect on alopecia areata (AA) as it does in psoriasis. The aims of the present study were to investigate the effects of anthralin on hair growth in balding C3H/HeJ mice affected by an AA-like disease and to study the underlying mechanisms. Affected C3H/HeJ mice were treated daily for 10 weeks on half of the dorsal skin with 0.2% anthralin and the contra-lateral side was treated with the vehicle ointment. The percentage of surface hair coverage and hair density was graded weekly for both sides and hair growth indices were calculated using these two variables. Hair regrowth was observed in 9/14 mice on the treated sides. Four mice displayed near complete replacement of normal density and length hairs. All the vehicle-treated sides showed either no change or continued hair loss. An RNase protection assay (RPA) showed that expression of tumor necrosis factor-alpha (TNF-alpha) and -beta were inhibited by anthralin upon successful treatment. It appears that anthralin may be an effective therapy for C3H/HeJ mice with AA and certain cytokines may be involved in the therapeutic effects of anthralin on restoring hair regrowth in AA-affected C3H/HeJ mice.

Alopecia areata in C3H/HeJ mice involves leukocyte-mediated root sheath disruption in advance of overt hair loss.

Alopecia areata (AA) can be induced in C3H/HeJ mice by grafting full-thickness AA-affected skin. An 8- to 12-week delay between surgery and overt hair loss onset provides an opportunity to examine disease pathogenesis. Normal haired C3H/HeJ mice were sham-grafted or grafted with AA-affected skin. Mice were euthanatized 2, 4, 6, 8, 10, and 12 weeks after surgery along with chronic AA-affected mice as a positive control. Until 6 weeks after grafting, inflammation was only evident around anagen-stage hair follicles in host skin adjacent to but not distant from the AA-affected graft. From 8 weeks on, AA-grafted but not sham-grafted mice exhibited a diffuse dermal inflammation at distant sites that progressively focused on anagen-stage hair follicles at 10 and 12 weeks. Perifollicular inflammation was primarily composed of CD4+ and CD8+ cells associated with follicular epithelium intercellular adhesion molecule -1 expression. Only CD8+ cells penetrated intrafollicularly by 12 weeks after surgery, although both CD4+ and CD8+ intrafollicular cells were observed in chronic AA-affected mice. Under electron microscopy, intrafollicular lymphocyte and macrophage infiltration associated with hair follicle dystrophy was prominent 10 weeks after surgery, primarily within the differentiating outer and inner root sheaths. This study shows that focal follicular inflammation develops some time in advance of overt hair loss and focuses on the differentiating root sheaths in C3H/HeJ mice. The severity of inflammation and the degree of hair follicle dystrophy induced by the infiltrate appear to reach a threshold level before overt hair loss occurs.

Dietary soy oil content and soy-derived phytoestrogen genistein increase resistance to alopecia areata onset in C3H/HeJ mice.

Alopecia areata (AA) is a complex, multi-factorial disease where genes and the environment may affect susceptibility and severity. Diet is an environmental factor with the potential to influence disease susceptibility. We considered dietary soy (soya) oil content and the soy-derived phytoestrogen genistein as potential modifying agents for C3H/HeJ mouse AA. Normal haired C3H/HeJ mice were grafted with skin from spontaneous AA affected mice, a method previously shown to induce AA. Grafted mice were given one of three diets containing 1%, 5% or 20% soy oil and observed for AA development. In a separate study, mice on a 1% soy oil diet were injected with 1 mg of genistein three times per week for 10 weeks or received the vehicle as a control. Of mice on 1%, 5%, and 20% soy oil diets, 43 of 50 mice (86%), 11 of 28 mice (39%), and 2 of 11 mice (18%) developed AA, respectively. Four of 10 mice injected with genistein and 9 of 10 controls developed AA. Mice with AA had hair follicle inflammation consistent with observations for spontaneous mouse AA, but no significant association was observed between the extent of hair loss and diet or genistein injection. Mice that failed to develop AA typically experience white hair regrowth from their skin grafts associated with a moderate macrophage and dendritic cell infiltration. Soy oil and derivatives have previously been reported to modify inflammatory conditions. Hypothetically, soy oil compounds may act on C3H/HeJ mice through modulating estrogen-dependent mechanisms and/or inflammatory activity to modify AA susceptibility.

Melanocyte and gonad activity as potential severity modifying factors in C3H/HeJ mouse alopecia areata.

Circumstantial evidence has previously suggested gonad derived steroid hormones and melanogenesis related antigens may modify human alopecia areata (AA). AA-like hair loss can be induced in C3H/HeJ mice after skin allografts from spontaneous AA-affected mice. This inducible model was used to evaluate hormones and hair follicle melanocyte presence as disease-severity modifiers. Ten females and 9 males were gonadectomized and received AA-affected allografts. All gonadectomized mice had 2-4 weeks delay in AA onset relative to non-gonadectomized controls. Two females and 4 males failed to develop any AA by 25 weeks after grafting. The experiment was repeated with gonadectomized female and male mice plus non-gonadectomized mice subcutaneously implanted with silastic capsules containing 80 microg 17beta estradiol or 10 mg 5alpha dihydrotestosterone, respectively. Five of 11 ovariectomized and 9 of 11 non-ovariectomized, estradiol supplemented females developed AA with extremely rapid progression. Three of 8 castrated, but none of 11 non-castrated, dihydrotestosterone-supplemented males expressed AA. In a separate study, 14 mice were freeze-branded, producing white hair on the dorsal lumbar region, and later received full-thickness allografts. Thirteen mice developed patchy pigmented and non-pigmented hair loss. One mouse developed diffuse, pigmented hair loss, but with white hair survival persisting 25 weeks after grafting. The results suggest that gonadal steroid hormones can modulate C3H/HeJ mouse AA where estradiol promoted rapid progression of AA while dihydrotestosterone increased resistance to AA onset. In general, both pigmented and non-pigmented C3H/HeJ mouse hair is susceptible to AA. Murine AA susceptibility and severity clearly involves an interplay between genetic and epigenetic factors.

The nude mouse skin phenotype: the role of Foxn1 in hair follicle development and cycling.

The original nude mouse mutation has proven to be an incredibly valuable biomedical tool since its discovery in 1966. Initially its value was as a tool to study the immune system. The immunodeficiency in this mutant mouse made nude mice valuable as hosts for xenografts, primarily for cancer research. More recently, the most obvious clinical feature of this mutant mouse, lack of hair, has been capitalized on to define the role of Foxn1 in normal and pathological skin and hair follicle physiology.

Human papillomavirus and skin cancer.

Human papillomavirus (HPV) appears to be the most ubiquitous of the human viruses. Over 100 HPV types have been identified. A minority of HPV cause cutaneous warts and mucosal condylomata. The HPV that cause mucosal condylomata put the patient at various degrees of risk for developing cancers, particularly cervical cancer. The majority of HPV infect the skin of normal and immunocompromised individuals. In normal people, most of these HPV appear to establish a latent infection of the skin, most likely as normal flora residing in hair follicles; however, in patients with various systemic and localized depressions of cell-mediated immunity, some HPV infections appear to be involved in the development of nonmelanotic skin cancer and its precursor lesions in skin, usually in sunlight-exposed areas. Circumstantial evidence suggests that these HPV may have a role in promoting proliferative lesions of the skin, although their sites of active infection and mode of transmission to susceptible individuals remain unknown.

Web-based access to mouse models of human cancers: the Mouse Tumor Biology (MTB) Database.

The Mouse Tumor Biology (MTB) Database serves as a curated, integrated resource for information about tumor genetics and pathology in genetically defined strains of mice (i.e., inbred, transgenic and targeted mutation strains). Sources of information for the database include the published scientific literature and direct data submissions by the scientific community. Researchers access MTB using Web-based query forms and can use the database to answer such questions as 'What tumors have been reported in transgenic mice created on a C57BL/6J background?', 'What tumors in mice are associated with mutations in the Trp53 gene?' and 'What pathology images are available for tumors of the mammary gland regardless of genetic background?'. MTB has been available on the Web since 1998 from the Mouse Genome Informatics web site (http://www.informatics.jax.org). We have recently implemented a number of enhancements to MTB including new query options, redesigned query forms and results pages for pathology and genetic data, and the addition of an electronic data submission and annotation tool for pathology data.

Loss of normal profilaggrin and filaggrin in flaky tail (ft/ft) mice: an animal model for the filaggrin-deficient skin disease ichthyosis vulgaris.

Flaky tail (gene symbol ft) is an autosomal recessive mutation in mice that results in a dry, flaky skin, and annular tail and paw constrictions in the neonatal period. Previous studies demonstrated that the ft mutation maps to the central region of mouse chromosome 3, in the vicinity of the epidermal differentiation complex, a gene locus that includes many nonkeratin genes expressed in epidermis. In this study we report a detailed characterization of the flaky tail mouse. Affected homozygous ft/ft mice exhibit large, disorganized scales on tail and paw skin, marked attenuation of the epidermal granular layer, mild acanthosis, and orthokeratotic hyperkeratosis. Biochemical analysis demonstrated that ft/ft mice lacked normal high molecular profilaggrin (approximately 500 kDa), and instead expressed a lower molecular weight form of profilaggrin (220 kDa) that is not proteolytically processed to profilaggrin intermediates or filaggrin. Mutant mice lacked the large, irregular F-type keratohyalin granules that contain profilaggrin, and filaggrin was absent from the cornified layers of ft/ft epidermis. The expression of epidermal keratins was unchanged, whereas the cornified envelope proteins involucrin and loricrin were increased in ft/ft epidermis. Cultured ft/ft keratinocytes also synthesized reduced amounts of profilaggrin mRNA and protein, demonstrating that the defect in profilaggrin expression is intrinsic to epidermal cells. These findings demonstrate that flaky tail mice express an abnormal profilaggrin polypeptide that does not form normal keratohyalin F-granules and is not proteolytically processed to filaggrin. We propose that the absence of filaggrin, and in particular the hygroscopic, filaggrin-derived amino acids that are thought to function in epidermal hydration, underlies the dry, scaly skin characteristic of ft/ft mice. This animal model provides a tool for understanding the role of filaggrin in normal epidermal function and may provide insight into the molecular basis of the filaggrin-deficient human skin disorder ichthyosis vulgaris. J Invest Dermatol 115:1072-1081 2000

Urinary bladder transitional cell papilloma in a shorthorn heifer.

A 12-month-old shorthorn heifer was presented for pollakiuria of 4 months' duration. Urinary bladder transitional cell papilloma was diagnosed. The heifer had no exposure to bracken fern and no papillomavirus or bacterium was demonstrated. Laser surgery was used in an attempt to debulk the mass.

Expression and immune recognition of SV40 Tag in transgenic mice that develop metastatic osteosarcomas.

Mature adult mice of the C57BL/6-TgN(Amy1TAg)501Knw transgenic mouse lineage, 501, containing a liver alpha-amylase promoted-SV40 Tag hybrid gene, routinely develop SV40 Tag-induced metastatic osteosarcomas. This form of alpha-amylase was known to be expressed in the liver, salivary glands, pancreas, and fat. Cells in the normal rib adjacent to the periosteum also express alpha-amylase suggesting that transgene expression is correctly targeted to generate osteosarcomas. 501 mice express SV40 Tag in the salivary glands but do not develop abnormalities in these organs by the time of their death from SV40-induced osteosarcomas. Mice of the C57BL/6 strain make a strong and effective anti-tumor immune response to SV40 Tag immunization. However, immunization of 501 mice with SV40 Tag early in life does not alter or prevent SV40 Tag-induced osteosarcomagenesis. 501 mice mount a significantly less effective cytotoxic T-lymphocyte response following SV40 Tag immunization while 501 osteosarcoma-derived cells are fully susceptible to SV40 Tag-specific T-cell lysis. This suggests that partial tolerance, not loss of antigen presentation by tumor cells, characterizes this mouse model of endogenous bone tumor development. To determine whether the immune recognition of endogenous SV40 Tag could influence tumorigenesis, the metastatic potential and time of death from tumor was investigated in CD4-null mutant 501 mice and beta-2 microglobulin-null mutant 501 mice. The size and number of metastases in these strains and longevity of these strains varied. We suggest that components of both the innate and adaptive immune response control tumor appearance and progression.

Branchial cysts in laboratory mice.

Large solitary cysts in the superficial tissues of the ventral neck are described in five laboratory mice of two inbred strains and one outbred line. The cysts were lined by cuboidal to columnar epithelium similar to that in branchial cysts reported in other animal species but distinct from the stratified squamous epithelium with prominent lymphoid tissue typical of branchial cysts in man. These findings suggest that the lesion referred to as a branchial cyst in animals differs slightly from the lesion of the same name in man.

Notch signaling is essential for vascular morphogenesis in mice.

The Notch gene family encodes large transmembrane receptors that are components of an evolutionarily conserved intercellular signaling mechanism. To assess the role of the Notch4 gene, we generated Notch4-deficient mice by gene targeting. Embryos homozygous for this mutation developed normally, and homozygous mutant adults were viable and fertile. However, the Notch4 mutation displayed genetic interactions with a targeted mutation of the related Notch1 gene. Embryos homozygous for mutations of both the Notch4 and Notch1 genes often displayed a more severe phenotype than Notch1 homozygous mutant embryos. Both Notch1 mutant and Notch1/Notch4 double mutant embryos displayed severe defects in angiogenic vascular remodeling. Analysis of the expression patterns of genes encoding ligands for Notch family receptors indicated that only the Dll4 gene is expressed in a pattern consistent with that expected for a gene encoding a ligand for the Notch1 and Notch4 receptors in the early embryonic vasculature. These results reveal an essential role for the Notch signaling pathway in regulating embryonic vascular morphogenesis and remodeling, and indicate that whereas the Notch4 gene is not essential during embryonic development, the Notch4 and Notch1 genes have partially overlapping roles during embryogenesis in mice.

Spontaneously regressing oral papillomas induce systemic antibodies that neutralize canine oral papillomavirus.

Canine oral papillomavirus (COPV) infection of naive beagle dogs causes oral papillomas, most of which spontaneously regress. Regressor beagles do not develop new oral papillomas because of COPV type-specific, cell-mediated immunity, COPV neutralizing antibodies, or both. Formalin-fixed native and recombinant COPV vaccines that target the systemic immune system induce neutralizing antibodies that prevent development of oral papillomas. This study was designed to determine whether spontaneously regressing mucosal papillomas also targeted the systemic immune system to induce circulating, neutralizing IgG antibodies that protect against infection by COPV. To accomplish this goal, IgG was fractionated from sera collected from weanling beagles and regressor beagles and tested for conferring protection by passive immunization. Serum was tested by ELISA for antibodies against intact virions and then pooled for passive transfer to naive beagles. Preimmune sera were neither reactive by ELISA nor protective by passive transfer. On the other hand, IgG antibodies from regressor beagles were reactive by ELISA and passive transfer conferred protection against COPV challenge. Circulating IgG antibodies induced by spontaneous regression of canine oral papillomas protect beagles against intraoral infection by COPV, a model for mucosotropic HPV.