Effects of catechins and caffeine on the development of atherosclerosis in mice.

Atherosclerosis is one of the diseases related to metabolic syndrome which is caused by obesity. Previous reports have shown that green tea and its components have anti-obesity effect. We examined whether catechins and caffeine can prevent the development of atherosclerosis by oral administration, singly or in combination to the atherosclerosis model mice. Results demonstrated that the number of atherosclerotic regions in the aorta was significantly reduced by the combined treatment, and the atherosclerotic area was also improved. Serum HDL-C increased by caffeine single treatment, but no effect on the TG and TC by any treatments. Moreover, ECG illuviated to atheromatous lesions in aorta and the illuviation was enhanced by caffeine. The mRNA expression levels of LOX-1 and TNF-α showed a tendency to suppress by the combined treatment. These results indicated that the combined administration of catechins and caffeine has the inhibitory effect on the development of atherosclerosis in mice.

Characteristics of scratching behavior in ADJM mice (atopic dermatitis from Japanese mice).

In order to elucidate the characteristics of scratching behavior in atopic dermatitis from Japanese mice (ADJM) mice, the effects of some antagonists of pruritogens on this behavior were studied. Both male and female ADJM mice showed frequent scratching behavior around the face, abdomen and back. The number of scratching behavior around the face was greater than on the abdomen and back, and scratching behavior in female mice was significantly more frequent than in male mice. Histamine H1 antagonist, chlorpheniramine, p.o., inhibited this behavior potently and dose-dependently. Histamine H1 antagonist with serotonin 5-TH(5-hydroxytryptamine)2 antagonist, cyproheptadine, also inhibited this behavior. However, NK1 antagonist, aprepitant, p.o., had no significant inhibitory effect even at a dose of 100 mg/kg, p.o., Mu antagonist, naloxone, and kappa agonist, nalfurafine, significantly inhibited this behavior at doses of 0.3 mg/kg, s.c., and 0.01 mg/kg, p.o., respectively. Histamine contents in the skin of ADJM mice were significantly higher than in BALB/c mice. These results strongly indicate that scratching behavior in ADJM mice is related with histamine H1, opioid mu and opioid kappa receptors.

An atopic dermatitis-like skin disease with hyper-IgE-emia develops in mice carrying a spontaneous recessive point mutation in the Traf3ip2 (Act1/CIKS) gene.

Spontaneous mutant mice that showed high levels of serum IgE and an atopic dermatitis (AD)-like skin disease were found in a colony of the KOR inbred strain that was derived from Japanese wild mice. No segregation was observed between hyper-IgE-emia and dermatitis in (BALB/c x KOR mutant) N(2) mice, suggesting that the mutation can be attributed to a single recessive locus, which we designated adjm (atopic dermatitis from Japanese mice). All four adjm congenic strains in different genetic backgrounds showed both hyper-IgE-emia and dermatitis, although the disease severity varied among strains. Linkage analysis using (BALB/c x KOR-adjm/adjm) N(2) mice restricted the potential adjm locus to the 940 kb between D10Stm216 and D10Stm238 on chromosome 10. Sequence analysis of genes located in this region revealed that the gene AI429613, which encodes the mouse homologue of the human TNFR-associated factor 3-interacting protein 2 (TRAF3IP2) protein (formerly known as NF-kappaB activator 1/connection to IkappaB kinase and stress-activated protein kinase/Jun kinase), carried a single point mutation leading to the substitution of a stop codon for glutamine at amino acid position 214. TRAF3IP2 has been shown to function as an adaptor protein in signaling pathways mediated by the TNFR superfamily members CD40 and B cell-activating factor in epithelial cells and B cells as well as in the IL-17-mediated signaling pathway. Our results suggest that malfunction of the TRAF3IP2 protein causes hyper-IgE-emia through the CD40- and B cell-activating factor-mediated pathway in B cells and causes skin inflammation through the IL-17-mediated pathway. This study demonstrates that the TRAF3IP2 protein plays an important role in AD and suggests the protein as a therapeutic target to treat AD.

Aryl hydrocarbon receptor suppresses intestinal carcinogenesis in ApcMin/+ mice with natural ligands.

Intestinal cancer is one of the most common human cancers. Aberrant activation of the canonical Wnt signaling cascade, for example, caused by adenomatous polyposis coli (APC) gene mutations, leads to increased stabilization and accumulation of beta-catenin, resulting in initiation of intestinal carcinogenesis. The aryl hydrocarbon receptor (AhR) has dual roles in regulating intracellular protein levels both as a ligand-activated transcription factor and as a ligand-dependent E3 ubiquitin ligase. Here, we show that the AhR E3 ubiquitin ligase has a role in suppression of intestinal carcinogenesis by a previously undescribed ligand-dependent beta-catenin degradation pathway that is independent of and parallel to the APC system. This function of AhR is activated by both xenobiotics and natural AhR ligands, such as indole derivatives that are converted from dietary tryptophan and glucosinolates by intestinal microbes, and suppresses intestinal tumor development in Apc(Min/+) mice. These findings suggest that chemoprevention with naturally-occurring and chemically-designed AhR ligands can be used to successfully prevent intestinal cancers.

An insertion mutation in the Apoe gene associated with spontaneous hyperlipidemia in mice.

Introduction: Spontaneously hyperlipidemic (SHL) mice, a mouse strain derived from an inbred strain of Japanese wild (original)-type mice (KOR; Mus musculus molossinus), show high plasma cholesterol concentrations with disruption of the apolipoprotein E (Apoe) gene. However, the details of the Apoe gene of SHL mice have yet to be described. Material and methods: The DNA sequence of the Apoe gene of SHL mice was compared to that of control KOR mice in genomic DNA and cDNA analyses. Results: In the DNA analysis, a 4700-bp fragment was found to be inserted into exon 4 of the Apoe gene of SHL mice. The insertion contained two 365-bp repeats at each terminal and was flanked by a 6-bp target duplication at each side. The inserted fragment produced a frameshift of an early stop codon, resulting in a protein product that consisted of 87 amino acids in SHL mice compared to 311 amino acids in control KOR mice. Conclusions: These findings provide useful information about the molecular basis of SHL mice and related lipid disorders.

Adventitial mast cells contribute to pathogenesis in the progression of abdominal aortic aneurysm.

Abdominal aortic aneurysm (AAA) is histologically characterized by medial degeneration and various degrees of chronic adventitial inflammation, although the mechanisms for progression of aneurysm are poorly understood. In the present study, we carried out histological study of AAA tissues of patients, and interventional animal and cell culture experiments to investigate a role of mast cells in the pathogenesis of AAA. The number of mast cells was found to increase in the outer media or adventitia of human AAA, showing a positive correlation between the cell number and the AAA diameter. Aneurysmal dilatation of the aorta was seen in the control (+/+) rats following periaortic application of calcium chloride (CaCl2) treatment but not in the mast cell-deficient mutant Ws/Ws rats. The AAA formation was accompanied by accumulation of mast cells, T lymphocytes and by activated matrix metalloproteinase 9, reduced elastin levels and augmented angiogenesis in the aortic tissue, but these changes were much less in the Ws/Ws rats than in the controls. Similarly, mast cells were accumulated and activated at the adventitia of aneurysmal aorta in the apolipoprotein E-deficient mice. The pharmacological intervention with the tranilast, an inhibitor of mast cell degranulation, attenuated AAA development in these rodent models. In the cell culture experiment, a mast cell directly augmented matrix metalloproteinase 9 activity produced by the monocyte/macrophage. Collectively, these data suggest that adventitial mast cells play a critical role in the progression of AAA.

Quantitative trait loci determining weight reduction of testes and pituitary by diethylstilbesterol in LEXF and FXLE recombinant inbred strain rats.

Increasing exposure to environmental endocrine disruptor, xeno-estrogen, is a serious hazard to male reproductive activity. To explore possible genetic control in susceptibility to xeno-estrogen, the weight reduction of testes induced by the continuous administration of a synthetic estrogen, diethylstilbesterol, were investigated by quantitative trait analysis in LEXF and FXLE recombinant inbred strain rats, consisting of 21 independent strains, 9 of their substrains, parental F344/Stm and LE/Stm strains, and (F344 x LE)F1. For the weight of testes, one highly significant quantitative trait locus (QTL) and one significant QTL were mapped on chromosomes 7 and 1, respectively. The QTL on chromosome 7 is closely associated with c-myc. Pituitary weight and serum prolactin were also variable among recombinant inbred strains, but no QTL was detected for them in this study.

Androgen-dependent hereditary mouse keratoconus: linkage to an MHC region.

PURPOSE: To better understand the pathogenesis of hereditary keratoconus, an inbred line of spontaneous mutant mice with keratoconus-affected corneas (SKC mice) was established and studied with a multidisciplinary approach. METHODS: Using a mutant mouse with corneas having a keratoconical appearance as the progenitor, an inbred line of SKC mouse was established by repeated sibling mating. Morphology, cell growth, apoptosis and protein expression of SKC mouse corneas were examined. Castration of males and androgen treatment for females were conducted to determine any androgen dependency of the phenotype. Linkage analysis was conducted to reveal the responsible or predisposing gene of SKC mouse keratoconus. RESULTS: Corneas of the SKC mouse resemble those of human eyes with keratoconus. Both are conical and show similar corneal changes, including apoptosis of keratocytes and increased expression of c-fos protein. The SKC mouse phenotype was transmitted in an autosomal recessive manner, although it was observed almost exclusively in males. Intriguingly, female mice showed the phenotype when injected with testosterone, whereas male incidence of the phenotype diminished drastically when mice were castrated. Linkage analysis localized a predisposition locus to an MHC region on mouse chromosome 17, which includes a locus for the gene for sex-limited protein (Slp). CONCLUSIONS: SKC mouse keratoconus is a potential model for a subset of human keratoconus, which is a disease entity with heterogeneous pathogeneses. Alternatively, SKC mouse keratoconus could be a model for other human or mouse-specific keratopathies.

Annulus of collagen fibrils in mouse cornea and structural matrix alterations in a murine-specific keratopathy.

PURPOSE: Mouse corneas were investigated to see whether a limbal annulus of corneal collagen exists as in humans. Mice with corneas predisposed to topographical changes (the SKC strain) were also examined, to establish the size and spacing of stromal collagen fibrils and the integrity of the annulus. METHODS: X-ray diffraction was used to measure collagen fibril spacing and diameter in normal (the BALB/c strain; four male, two female) and SKC (six male and six female) corneas and to identify the degree of preferred collagen orientation at 200- microm intervals across two BALB/c and four SKC corneas. RESULTS: The average collagen fibril diameter measured 35.5 nm in 3-month-old BALB/c corneas, and 36.9 nm and 37.0 nm, respectively, in corneas of age-matched male and female SKC mice. In male and female SKC corneas, average collagen interfibrillar Bragg spacing was significantly higher (64.5 and 59.9 nm, respectively) than in corneas of BALB/c mice (49.7 nm). Circumferentially aligned collagen, indicative of a limbal annulus of fibrillar collagen 2.2 mm in diameter, was identified in mouse cornea. On occasion, this was disturbed in the SKC phenotype. CONCLUSIONS: Collagen fibrils are marginally larger in the corneas of SKC mice than in the corneas of BALB/c mice and are considerably more widely spaced. An annulus of fibrillar collagen probably exists near the limbus of the normal mouse cornea that may help promote biomechanical stability and maintain corneal shape. A loss of structural integrity in the annulus of some SKC mice may predispose the corneas to biomechanical instability and shape changes.

Effect of n-3 fatty acids on serum lipid levels and hepatic fatty acid metabolism in BALB/c.KOR-Apoeshl mice deficient in apolipoprotein E expression.

N-3 fatty acids exert a potent serum lipid-lowering effect in rodents mainly by affecting hepatic fatty acid oxidation and synthesis. However, it has been observed that fish oil and docosahexaenoic acid ethyl ester do not lower serum lipid levels in apolipoprotein E (apoE)-knockout (Apoetm1Unc) mice generated by gene targeting. To test the hypothesis that apoE expression is required for n-3 fatty acid-dependent regulation of serum lipid levels and hepatic fatty acid metabolism, we examined the effect of fish oil and n-3 fatty acid ethyl esters on the activity and gene expression of hepatic enzymes involved in fatty acid oxidation and synthesis using an alternative apoE-deficient mouse model with the BALB/c genetic background (BALB/c.KOR-Apoeshl). ApoE-deficient mice were fed diets containing 9.4% palm oil, fish oil, or 5.4% palm oil and 1% EPA plus 3% DHA ethyl esters for 15 days. In contrast to the reported data on apoE-knockout mice, fish oil and n-3 fatty acid ethyl esters greatly decreased serum triacylglycerol, cholesterol, and phospholipid levels in the Apoeshl mice. The decreases were greater with fish oil than with ethyl esters. The alterations by dietary n-3 fatty acids of serum lipid levels were accompanied by parallel changes in the activity and mRNA levels of enzymes involved in hepatic fatty acid oxidation and synthesis. The reason for the discrepancy between the results of the current study and previous studies is unknown. However, our study at least indicates that a lack of apoE expression does not necessarily accompany deficits in the n-3 fatty acid-dependent regulation of serum lipid levels and hepatic fatty acid metabolism.

High-incidence spontaneous tumors in JF1/Ms mice: relevance of hypomorphic germline mutation and subsequent promoter methylation of Ednrb.

PURPOSE: JF1/Ms mice, an inbred strain derived from Japanese wild mice, carry a germline hypomorphic mutation in the endothelin receptor type B gene (Ednrb). We observed that the JF1/Ms mice develop various spontaneous tumors at a high incidence late in life. The aim of this study was to elucidate the mechanism responsible for spontaneous tumors in these mice. Possible relevance of milk-borne mammary tumor virus and gene alterations in Ednrb to tumorigenesis was explored. METHODS: Expression and methylation status of Ednrb were quantitatively analyzed in normal and cancer tissues of mammary gland, liver, submandibular gland as well as in a cultured cell line, MW1, established from a submandibular gland adenocarcinoma. The biological effects of EDNRB were examined in the MW1 cells transfected with wild-type Ednrb. RESULTS: Transcripts of Ednrb were barely detectable, and the promoter region of Ednrb was hypermethylated in tumor tissues and the MW1 cells. In contrast, normal counterpart tissues showed positive expression of Ednrb transcripts and had unmethylated promoter regions. Treatment of the MW1 cells with 5-Aza-dC restored transcription of Ednrb to normal levels. Transfection of the MW1 cells with Ednrb1 (MW1-Ednrb1) resulted in lower growth rates and morphological changes compared with the mock-transfected MW1 cells (MW1-mock1). Furthermore, the MW1-Ednrb1 cells transplanted in syngeneic mice showed a lower proliferation rate than the MW1-mock1 cells. CONCLUSIONS: Germline mutation and subsequent promoter methylation of Ednrb may be relevant to cancer susceptibility in the JF1/Ms mice. These data indicate that Ednrb acts as a tumor suppressor, as reported in human prostate, bladder, and clear cell renal carcinomas.

Familial clustering of mice consistent to known pedigrees enabled by the genome profiling (GP) method.

Familial clustering without any prerequisite knowledge becomes often necessary in Behavioral Science, and forensic studies in case of great disasters like Tsunami and earthquake requiring body-identification without any usable information. However, there has been no well-established method for this purpose although conventional ones such as short tandem repeats (STR) and single nucleotide polymorphism (SNP), which might be applied with toil and moil to some extent. In this situation, we could find that the universal genome distance-measuring method genome profiling (GP), which is made up of three elemental techniques; random PCR, micro-temperature gradient gel electrophoresis (µTGGE), and computer processing for normalization, can do this purpose with ease when applied to mouse families. We also confirmed that the sequencing approach based on the ccgf (commonly conserved genetic fragment appearing in the genome profile) was not completely discriminative in this case. This is the first demonstration that the familial clustering can be attained without a priori sequence information to the level of discriminating strains and sibling relationships. This method can complement the conventional approaches in preliminary familial clustering.

Expression of truncated PITX3 in the developing lens leads to microphthalmia and aphakia in mice.

Microphthalmia is a severe ocular disorder, and this condition is typically caused by mutations in transcription factors that are involved in eye development. Mice carrying mutations in these transcription factors would be useful tools for defining the mechanisms underlying developmental eye disorders. We discovered a new spontaneous recessive microphthalmos mouse mutant in the Japanese wild-derived inbred strain KOR1/Stm. The homozygous mutant mice were histologically characterized as microphthalmic by the absence of crystallin in the lens, a condition referred to as aphakia. By positional cloning, we identified the nonsense mutation c.444C>A outside the genomic region that encodes the homeodomain of the paired-like homeodomain transcription factor 3 gene (Pitx3) as the mutation responsible for the microphthalmia and aphakia. We examined Pitx3 mRNA expression of mutant mice during embryonic stages using RT-PCR and found that the expression levels are higher than in wild-type mice. Pitx3 over-expression in the lens during developmental stages was also confirmed at the protein level in the microphthalmos mutants via immunohistochemical analyses. Although lens fiber differentiation was not observed in the mutants, strong PITX3 protein signals were observed in the lens vesicles of the mutant lens. Thus, we speculated that abnormal PITX3, which lacks the C-terminus (including the OAR domain) as a result of the nonsense mutation, is expressed in mutant lenses. We showed that the expression of the downstream genes Foxe3, Prox1, and Mip was altered because of the Pitx3 mutation, with large reductions in the lens vesicles in the mutants. Similar profiles were observed by immunohistochemical analysis of these proteins. The expression profiles of crystallins were also altered in the mutants. Therefore, we speculated that the microphthalmos/aphakia in this mutant is caused by the expression of truncated PITX3, resulting in the abnormal expression of downstream targets and lens fiber proteins.

Japanese wild mice: a rich resource for new disease models.

Breeding of fancy mice has been a tradition in Japan. Recent progress in animal science has shed a new light on Japanese wild-derived mice as tools for discovery of new disease models because these mice, Mus musculus molossinus, are genetically far remote from the majority of available laboratory mice. After decades of effort, five inbred strains of mice have been established from pairs of wild mice trapped in Tohoku, northeastern Japan, namely KOR1/Stm, KOR5/Stm, KOR7/Stm, AIZ/Stm, and MAE/Stm. They carried numerous mutations, leading to a variety of diseases. During the inbreeding of KOR1, the first spontaneous mutation was found in the Apoe (apolipoprotein E) gene, and the mutant was later designated as spontaneous hyperlipidemic (SHL). Thereafter, a number of other mutations were discovered among wild-derived inbred strains, including atopic dermatitis, microphthalmia, dominant white spots, sebaceous gland abnormalities, and audible song-like vocalization. Furthermore, to examine the possible effects of the genetic background for these mutant genes, sets of congenic strains were generated, in which the mutant gene was introduced into at least 3 different strains of laboratory mice, including BALB/c and C57BL/6. These congenic strains have now been established as novel disease models. These wild-derived inbred strains serve as a treasure trove for novel disease models. Most of them have been deposited in the Riken BioResource Center (BRC), and some are also available from commercial breeders.

Proatherogenic effect of interleukin-18 is exerted with high-fat diet, but not with normal diet in spontaneously hyperlipidemic mice.

AIM: It has been considered that interleukin (IL)-18, a T helper 1(Th1) type cytokine, has a promoting effect on atherosclerosis development. A previous mouse study demonstrated that short-term exogenous IL-18 promoted atherosclerosis through a Th1 type immune response; however, the serum IL-18 may have increased greatly beyond its physiological range, and the effect of increased serum IL-18 on atherosclerosis development has not been investigated under different conditions of dietary fat content. The purpose of this study was to reveal the effect of increased serum IL-18 within its physiological fluctuations on atherosclerosis development under different conditions of dietary fat content. METHODS: Spontaneously hyperlipidemic (SHL) mice were systemically supplied with IL-18 for 10 weeks by means of an in vivo gene transfer system with a high-fat diet containing 0.15% cholesterol or a normal diet. RESULTS: Serum IL-18 steadily elevated within its physiological fluctuations. An atherosclerotic lesion area in the aortic root significantly increased with a high-fat diet. Systemic cytokine balance shifted to a Th1-dominant state, and IL-12 mRNA in the arterial wall significantly increased with a high-fat diet; however, these findings were not observed with a normal diet. CONCLUSIONS: It was suggested that the proatherogenic effect of IL-18 is physiologically exerted exclusively with a high-fat diet through Th1 type immune responses, but not with a normal diet.

The new disease models from genetic polymorphisms of Japanese wild mice.

Personalized medicine offers a custom-made treatment for each patient directed by information of individual's genetic variation. Despite plenty of information about human single nucleotide polymorphisms (SNPs) and gene expression profile, predicting functions of genetic variations in humans is still a difficult task. Genetic analysis using experimental animals is possible to provide information about the functions of genetic polymorphisms over experimental invention in humans. In particular, inbred strains established from wild mice are valuable resources for analyzing functions of genetic polymorphisms. In this article, first I describe history of inbred strains derived from Japanese wild mice, Mus musuclus molossinus. Next, I discuss a mouse model for hyperlipidemia, which was isolated from a colony of Japanese wild mice. Interestingly, the hyperlipimic phenotypes are varied in congenic strains on other genetic backgrounds, reflecting phenotype variation of hyperlipidemia in human populations. Thus, further genetic analysis of Japanese wild mice can contribute to functional analysis of human genetic variation leading to personalized medicine.

Mutation of Dock5, a member of the guanine exchange factor Dock180 superfamily, in the rupture of lens cataract mouse.

Rupture of lens cataract (RLC) in the mouse is a spontaneous mutation inherited by a single autosomal recessive gene mapped on chromosome 14. Fine mapping of the mutant locus revealed a nucleotide deletion of 27-bp at the end of 15th exon of Dock5 (Dedicator of cytokinesis-5), a member of the Dock gene superfamily. Since the deletion occurred in-frame, the RLC-DOCK5 protein had a deletion of 9 amino acids (a.a. 506-514) in the DHR1 (DOCK homology region-1) domain that is essential for DOCK5, a GTP-exchanger for Rac1. Although Dock5 mRNA was intensely expressed equally in mutant and wild-type lenses, DOCK5 protein was hardly detectable in the mutant lens. In contrast, expression of Dock180, another member of Dock subfamily A, was not affected in RLC. Immunohistochemically, DOCK5 was stained intensely in the cytoplasm of the anterior epithelial cells and weakly in lens fiber of the wild type lenses, but little in RLC lens. These observations suggest that the mutation may somehow destabilize DOCK5 protein. We propose to designate the mutant allele of rlc as Dock5rlc. Relevance of the signaling pathway involving DOCK5-RAC1 in maintenance of lens integrity of growing lens is discussed.

A deletion in the endothelin-B receptor gene is responsible for the Waardenburg syndrome-like phenotypes of WS4 mice.

The WS4 mouse is an animal model for human Waardenburg syndrome type 4 (WS4), showing pigmentation anomalies, deafness and megacolon, which are caused by defects of neural crest-derived cells. We have previously reported that the gene responsible for the WS4 mouse is an allele of the piebald mutations of the endothelin B receptor gene (Ednrb). In this study, we examined the genomic sequence of the Ednrb gene in WS4 mice and found a 598-bp deletion in the gene. The deleted region contains the entire region of exon 2 and the 5' part of exon 3 and is flanked by inverted repeat sequences which are suggested to trigger the deletion. We concluded that the deletion in the Ednrb gene is the causative mutation for the phenotype of WS4 mice.

A new mouse model for infantile neuroaxonal dystrophy, inad mouse, maps to mouse chromosome 1.

Infantile neuroaxonal dystrophy (INAD) is a rare autosomal recessive hereditary neurodegenerative disease of humans. So far, no responsible gene has been cloned or mapped to any chromosome. For chromosome mapping and positional cloning of the responsible gene, establishment of an animal model would be useful. Here we describe a new mouse model for INAD, named inad mouse. In this mouse, the phenotype is inherited in an autosomal recessive manner, symptoms occur in the infantile period, and the mouse dies before sexual maturity. Axonal dystrophic change appearing as spheroid bodies in central and peripheral nervous system was observed. These features more closely resembled human INAD than did those of the gad mouse, the traditional mouse model for INAD. Linkage analysis linked the inad gene to mouse Chromosome 1, with the highest LOD score (=128.6) at the D1Mit45 marker, and haplotype study localized the inad gene to a 7.5-Mb region between D1Mit84 and D1Mit25. In this linkage area some 60 genes exist: Mutation of one of these 60 genes is likely responsible for the inad mouse phenotype. Our preliminary mutation analysis in 15 genes examining the nucleotide sequence of exons of these genes did not find any sequence difference between inad mouse and C57BL/6 mouse.

Mouse models for four types of Waardenburg syndrome.

Waardenburg syndrome (WS) is an auditory-pigmentary syndrome caused by a deficiency of melanocytes and other neural crest-derived cells. Depending on a variety of symptoms associated with the auditory-pigmentary symptoms, WS is classified into four types: WS type 1 (WS1), WS2, WS3, and WS4. Six genes contributing to this syndrome--PAX3, SOX10, MITF, SLUG, EDN3 and EDNRB--have been cloned so far, all of them necessary for normal development of melanocytes. Mutant mice with coat color anomalies were helpful in identifying these genes, although the phenotypes of these mice did not necessarily perfectly match those of the four types of WS. Here we describe mice with mutations of murine homologs of WS genes and verify their suitability as models for WS with special interest in the cochlear disorder. The mice include splotch (Sp), microphthalmia (mi), Slugh-/-, WS4, JF1, lethal-spotting (ls), and Dominant megacolon (Dom). The influence of genetic background on the phenotypes of mice mutated in homologs of WS genes is also addressed. Finally, possible interactions among the six WS gene products are discussed.