Inference of selective forces on house mouse genomes during secondary contact in East Asia.

The house mouse (Mus musculus), which is commensal to humans, has spread globally via human activities, leading to secondary contact between genetically divergent subspecies. This pattern of genetic admixture can provide insights into the selective forces at play in this well-studied model organism. Our analysis of 163 house mouse genomes, with a particular focus on East Asia, revealed substantial admixture between the subspecies castaneus and musculus, particularly in Japan and southern China. We revealed, despite the different level of autosomal admixture among regions, that all Y Chromosomes in the East Asian samples belonged to the musculus-type haplogroup, potentially explained by genomic conflict under sex-ratio distortion owing to varying copy numbers of ampliconic genes on sex chromosomes, Slx and Sly Our computer simulations, designed to replicate the observed scenario, show that the preferential fixation of musculus-type Y Chromosomes can be achieved with a slight increase in the male-to-female birth ratio. We also investigated the influence of selection on the posthybridization of the subspecies castaneus and musculus in Japan. Even though the genetic background of most Japanese samples closely resembles the subspecies musculus, certain genomic regions overrepresented the castaneus-like genetic components, particularly in immune-related genes. Furthermore, a large genomic block (∼2 Mbp) containing a vomeronasal/olfactory receptor gene cluster predominantly harbored castaneus-type haplotypes in the Japanese samples, highlighting the crucial role of olfaction-based recognition in shaping hybrid genomes.

Genealogical characterization of regional populations and dorsal coat color variation in the house mouse Mus musculus from Asia based on haplotype structure analysis of a gene-rich region harboring Mc1r.

We analyzed 196 haplotype sequences from a gene-rich region (250 kb) that includes Mc1r, a gene involved in coat color regulation, to gain insight into the evolution of coat color variation in subspecies of the house mouse Mus musculus. Phylogenetic networks revealed haplotype groups from the major subspecies of M. m. castaneus (CAS), M. m. domesticus (DOM), and M. m. musculus (MUS). Using haplotype sequences assigned to each of CAS and MUS through phylogenetic analysis, we proposed migration routes associated with prehistoric humans from west to east across Eurasia. Comparing nucleotide diversity among subspecies-specific haplotypes in different geographic areas showed a marked reduction during migration, particularly in MUS-derived haplotypes from Korea and Japan, suggesting intensive population bottlenecks during migration. We found that a C>T polymorphism at site 302 (c.302C>T) in the Mc1r coding region correlated with a darkening of dorsal fur color in both CAS and MUS. However, C/C homozygous mice in MUS showed marked variation in lightness, indicating the possibility of another genetic determinant that affects the lightness of dorsal fur color. Detailed sequence comparisons of haplotypes revealed that short fragments assigned to DOM were embedded in CAS-assigned fragments, indicating ancient introgression between subspecies. The estimated age of c.302C>T also supports the hypothesis that genetic interaction between subspecies occurred in ancient times. This suggests that the genome of M. musculus evolved through gene flow between subspecies over an extended period before the movement of the species in conjunction with prehistoric humans.

Two Loci Contribute to Age-Related Hearing Loss Resistance in the Japanese Wild-Derived Inbred MSM/Ms Mice.

An MSM/Ms strain was established using Japanese wild mice, which exhibit resistance to several phenotypes associated with aging, such as obesity, inflammation, and tumorigenesis, compared to common inbred mouse strains. MSM/Ms strain is resistant to age-related hearing loss, and their auditory abilities are sustained for long durations. The age-related hearing loss 3 (ahl3) locus contributes to age-related hearing in MSM/Ms strain. We generated ahl3 congenic strains by transferring a genomic region on chromosome 17 from MSM/Ms mice into C57BL/6J mice. Although C57BL/6J mice develop age-related hearing loss because of the ahl allele of the cadherin 23 gene, the development of middle- to high-frequency hearing loss was significantly delayed in an ahl3 congenic strain. Moreover, the novel age-related hearing loss 10 (ahl10) locus associated with age-related hearing resistance in MSM/Ms strain was mapped to chromosome 12. Although the resistance effects in ahl10 congenic strain were slightly weaker than those in ahl3 congenic strain, slow progression of age-related hearing loss was confirmed in ahl10 congenic strain despite harboring the ahl allele of cadherin 23. These results suggest that causative genes and polymorphisms of the ahl3 and ahl10 loci are important targets for the prevention and treatment of age-related hearing loss.

Insights into Mus musculus Population Structure across Eurasia Revealed by Whole-Genome Analysis.

For more than 100 years, house mice (Mus musculus) have been used as a key animal model in biomedical research. House mice are genetically diverse, yet their genetic background at the global level has not been fully understood. Previous studies have suggested that they originated in South Asia and diverged into three major subspecies, almost simultaneously, approximately 110,000-500,000 years ago; however, they have spread across the world with the migration of modern humans in prehistoric and historic times (∼10,000 years ago to the present day) and have undergone secondary contact, which has complicated the genetic landscape of wild house mice. In this study, we sequenced the whole-genome sequences of 98 wild house mice collected from Eurasia, particularly East Asia, Southeast Asia, and South Asia. Although wild house mice were found to consist of three major genetic groups corresponding to the three major subspecies, individuals representing admixtures between subspecies were more prevalent in East Asia than has been previously recognized. Furthermore, several samples exhibited an incongruent pattern of genealogies between mitochondrial and autosomal genomes. Using samples that likely retained the original genetic components of subspecies with the least admixture, we estimated the pattern and timing of divergence among the subspecies. The estimated divergence time of the three subspecies was 187,000-226,000 years ago. These results will help us to understand the genetic diversity of wild mice on a global scale, and the findings will be particularly useful in future biomedical and evolutionary studies involving laboratory mice established from such wild mice.

Phylogeographic study using nuclear genome sequences of Asip to infer the origins of ventral fur color variation in the house mouse Mus musculus.

While the house mouse (Mus musculus), widely distributed in Eurasia, is known to have substantial coat color variation between and within local populations, in both primary and secondary distribution areas, including the Japanese archipelago, the evolutionary history of the color variation is poorly understood. To address the ventral fur color variation, we quantified the lightness of museum skin specimens, and found that the southern subspecies, M. m. castaneus (CAS), has high and low lightness in dry and rainy geographic regions, respectively. The northern subspecies, M. m. musculus (MUS), has low and high levels of lightness in the high and middle latitudes of northern Eurasia, respectively. We examined sequence variation of the agouti signaling protein gene (Asip), which is known to be responsible for the ventral fur color. We performed phylogenetic analyses with 196 haplotype sequences of Asip (~180 kb) generated by phasing the whole-genome data of 98 wild mice reported previously. Network and phylogenetic tree construction revealed clustering of haplotypes representing the two subspecies, MUS and CAS. A number of subclusters with geographic affinities appeared within the subspecies clusters, in which the essential results were consistent with those reconstructed with whole mitochondrial genome data, indicating that the phased haplotype genome sequences of the nuclear genome can be a useful tool for tracing the dispersal of geographical lineages. The results of phylogeographic analysis showed that CAS mice with darker ventral fur possessed similar Asip haplotypes across the geographic distribution, suggesting that these haplotypes are major causes of the historical introduction of Asip haplotypes for darker ventral fur in mice from northern India to the peripheral areas, including the Japanese archipelago. Similarly, MUS in East Asia, which has a white abdomen, formed an Asip haplogroup with that from northern Iran, also with a white abdomen.

MoG+: a database of genomic variations across three mouse subspecies for biomedical research.

Laboratory mouse strains have mosaic genomes derived from at least three major subspecies that are distributed in Eurasia. Here, we describe genomic variations in ten inbred strains: Mus musculus musculus-derived BLG2/Ms, NJL/Ms, CHD/Ms, SWN/Ms, and KJR/Ms; M. m. domesticus-derived PGN2/Ms and BFM/Ms; M. m. castaneus-derived HMI/Ms; and JF1/Ms and MSM/Ms, which were derived from a hybrid between M. m. musculus and M. m. castaneus. These strains were established by Prof. Moriwaki in the 1980s and are collectively named the "Mishima Battery". These strains show large phenotypic variations in body size and in many physiological traits. We resequenced the genomes of the Mishima Battery strains and performed a comparative genomic analysis with dbSNP data. More than 81 million nucleotide coordinates were identified as variant sites due to the large genetic distances among the mouse subspecies; 8,062,070 new SNP sites were detected in this study, and these may underlie the large phenotypic diversity observed in the Mishima Battery. The new information was collected in a reconstructed genome database, termed MoG+ that includes new application software and viewers. MoG+ intuitively visualizes nucleotide variants in genes and intergenic regions, and amino acid substitutions across the three mouse subspecies. We report statistical data from the resequencing and comparative genomic analyses and newly collected phenotype data of the Mishima Battery, and provide a brief description of the functions of MoG+, which provides a searchable and unique data resource of the numerous genomic variations across the three mouse subspecies. The data in MoG+ will be invaluable for research into phenotype-genotype links in diverse mouse strains.

Establishment and application of information resource of mutant mice in RIKEN BioResource Research Center.

Online databases are crucial infrastructures to facilitate the wide effective and efficient use of mouse mutant resources in life sciences. The number and types of mouse resources have been rapidly growing due to the development of genetic modification technology with associated information of genomic sequence and phenotypes. Therefore, data integration technologies to improve the findability, accessibility, interoperability, and reusability of mouse strain data becomes essential for mouse strain repositories. In 2020, the RIKEN BioResource Research Center released an integrated database of bioresources including, experimental mouse strains, Arabidopsis thaliana as a laboratory plant, cell lines, microorganisms, and genetic materials using Resource Description Framework-related technologies. The integrated database shows multiple advanced features for the dissemination of bioresource information. The current version of our online catalog of mouse strains which functions as a part of the integrated database of bioresources is available from search bars on the page of the Center ( https://brc.riken.jp ) and the Experimental Animal Division ( https://mus.brc.riken.jp/ ) websites. The BioResource Research Center also released a genomic variation database of mouse strains established in Japan and Western Europe, MoG+ ( https://molossinus.brc.riken.jp/mogplus/ ), and a database for phenotype-phenotype associations across the mouse phenome using data from the International Mouse Phenotyping Platform. In this review, we describe features of current version of databases related to mouse strain resources in RIKEN BioResource Research Center and discuss future views.

House mouse Mus musculus dispersal in East Eurasia inferred from 98 newly determined complete mitochondrial genome sequences.

The Eurasian house mouse Mus musculus is useful for tracing prehistorical human movement related to the spread of farming. We determined whole mitochondrial DNA (mtDNA) sequences (ca. 16,000 bp) of 98 wild-derived individuals of two subspecies, M. m. musculus (MUS) and M. m. castaneus (CAS). We revealed directional dispersals reaching as far as the Japanese Archipelago from their homelands. Our phylogenetic analysis indicated that the eastward movement of MUS was characterised by five step-wise regional extension events: (1) broad spatial expansion into eastern Europe and the western part of western China, (2) dispersal to the eastern part of western China, (3) dispersal to northern China, (4) dispersal to the Korean Peninsula and (5) colonisation and expansion in the Japanese Archipelago. These events were estimated to have occurred during the last 2000-18,000 years. The dispersal of CAS was characterised by three events: initial divergences (ca. 7000-9000 years ago) of haplogroups in northernmost China and the eastern coast of India, followed by two population expansion events that likely originated from the Yangtze River basin to broad areas of South and Southeast Asia, including Sri Lanka, Bangladesh and Indonesia (ca. 4000-6000 years ago) and to Yunnan, southern China and the Japanese Archipelago (ca. 2000-3500). This study provides a solid framework for the spatiotemporal movement of the human-associated organisms in Holocene Eastern Eurasia using whole mtDNA sequences, reliable evolutionary rates and accurate branching patterns. The information obtained here contributes to the analysis of a variety of animals and plants associated with prehistoric human migration.

Monoallelic, antisense and total RNA transcription in an in vitro neural differentiation system based on F1 hybrid mice.

We developed an in vitro system to differentiate embryonic stem cells (ESCs) derived from reciprocally crossed F1 hybrid mice into neurons, and used it to investigate poly(A)+ and total RNA transcription at different stages of cell differentiation. By comparing expression profiles of transcripts assembled from 20 RNA sequencing datasets [2 alleles×(2 cell lines×4 time-points+2 mouse brains)], the relative influence of strain, cell and parent specificities to overall expression could be assessed. Divergent expression profiles of ESCs converged tightly at neural progenitor stage. Patterns of temporal variation of monoallelically expressed transcripts and antisense transcripts were quantified. Comparison of sense and antisense transcript pairs within the poly(A)+ sample, within the total RNA sample, and across poly(A)+ and total RNA samples revealed distinct rates of pairs showing anti-correlated expression variation. Unique patterns of sharing of poly(A)+ and poly(A)- transcription were identified in distinct RNA species. Regulation and functionality of monoallelic expression, antisense transcripts and poly(A)- transcription remain elusive. We demonstrated the effectiveness of our approach to capture these transcriptional activities, and provided new resources to elucidate the mammalian developmental transcriptome.

Multiple Conserved Elements Structuring Inverted Repeats in the Mammalian Coat Color-Related Gene Asip.

In the agouti signaling gene protein (Asip) of the house mouse (Mus musculus), inverted repeat (IR) arrays are known to exist in a non-coding region adjacent to the ventral-specific promoter region and the accompanying two exons (exons 1A and 1A'), which are around 100 kb upstream from the amino acid coding regions of exons 2, 3, and 4. To determine the gene structure of mammalian Asip and to elucidate trends in its evolution, non-coding sequences of six rodent (mouse, rat, Chinese hamster, squirrel, guinea pig, and naked mole rat) and three non-rodent (rabbit, human, and cow) species were retrieved from databases and compared. Our homology search analyses revealed the presence of three to five highly conserved non-coding elements (CNE). These CNEs were found to form IRs in rodents and lagomorphs. Combinations of IRs were further shown to build symmetric, long IR arrays. Intra- and inter-specific comparisons of the sequences of three universal CNEs showed homogeneity between CNE pairs within species. This implies that certain evolutionary constraints maintained the IR structure in the rodent and rabbit species.

High-Resolution Maps of Mouse Reference Populations.

Genetic reference panels are widely used to map complex, quantitative traits in model organisms. We have generated new high-resolution genetic maps of 259 mouse inbred strains from recombinant inbred strain panels (C57BL/6J × DBA/2J, ILS/IbgTejJ × ISS/IbgTejJ, and C57BL/6J × A/J) and chromosome substitution strain panels (C57BL/6J-Chr#, C57BL/6J-Chr#, and C57BL/6J-Chr#). We genotyped all samples using the Affymetrix Mouse Diversity Array with an average intermarker spacing of 4.3 kb. The new genetic maps provide increased precision in the localization of recombination breakpoints compared to the previous maps. Although the strains were presumed to be fully inbred, we found residual heterozygosity in 40% of individual mice from five of the six panels. We also identified de novo deletions and duplications, in homozygous or heterozygous state, ranging in size from 21 kb to 8.4 Mb. Almost two-thirds (46 out of 76) of these deletions overlap exons of protein coding genes and may have phenotypic consequences. Twenty-nine putative gene conversions were identified in the chromosome substitution strains. We find that gene conversions are more likely to occur in regions where the homologous chromosomes are more similar. The raw genotyping data and genetic maps of these strain panels are available at http://churchill-lab.jax.org/website/MDA.

Heterozygous mutation of Ush1g/Sans in mice causes early-onset progressive hearing loss, which is recovered by reconstituting the strain-specific mutation in Cdh23.

Most clinical reports have suggested that patients with congenital profound hearing loss have recessive mutations in deafness genes, whereas dominant alleles are associated with progressive hearing loss (PHL). Jackson shaker (Ush1gjs) is a mouse model of recessive deafness that exhibits congenital profound deafness caused by the homozygous mutation of Ush1g/Sans on chromosome 11. We found that C57BL/6J-Ush1gjs/+ heterozygous mice exhibited early-onset PHL (ePHL) accompanied by progressive degeneration of stereocilia in the cochlear outer hair cells. Interestingly, ePHL did not develop in mutant mice with the C3H/HeN background, thus suggesting that other genetic factors are required for ePHL development. Therefore, we performed classical genetic analyses and found that the occurrence of ePHL in Ush1gjs/+ mice was associated with an interval in chromosome 10 that contains the cadherin 23 gene (Cdh23), which is also responsible for human deafness. To confirm this mutation effect, we generated C57BL/6J-Ush1gjs/+, Cdh23c.753A/G double-heterozygous mice by using the CRISPR/Cas9-mediated Cdh23c.753A>G knock-in method. The Cdh23c.753A/G mice harbored a one-base substitution (A for G), and the homozygous A allele caused moderate hearing loss with aging. Analyses revealed the complete recovery of ePHL and stereocilia degeneration in C57BL/6J-Ush1gjs/+ mice. These results clearly show that the development of ePHL requires at least two mutant alleles of the Ush1g and Cdh23 genes. Our results also suggest that because the SANS and CDH23 proteins form a complex in the stereocilia, the interaction between these proteins may play key roles in the maintenance of stereocilia and the prevention of ePHL.

NIG_MoG: a mouse genome navigator for exploring intersubspecific genetic polymorphisms.

The National Institute of Genetics Mouse Genome database (NIG_MoG; http://molossinus.lab.nig.ac.jp/msmdb/) primarily comprises the whole-genome sequence data of two inbred mouse strains, MSM/Ms and JF1/Ms. These strains were established at NIG and originated from the Japanese subspecies Mus musculus molossinus. NIG_MoG provides visualized genome polymorphism information, browsing single-nucleotide polymorphisms and short insertions and deletions in the genomes of MSM/Ms and JF1/Ms with respect to C57BL/6J (whose genome is predominantly derived from the West European subspecies M. m. domesticus). This allows users, especially wet-lab biologists, to intuitively recognize intersubspecific genome divergence in these mouse strains using visual data. The database also supports the in silico screening of bacterial artificial chromosome (BAC) clones that contain genomic DNA from MSM/Ms and the standard classical laboratory strain C57BL/6N. NIG_MoG is thus a valuable navigator for exploring mouse genome polymorphisms and BAC clones that are useful for studies of gene function and regulation based on intersubspecific genome divergence.

Influence analysis in quantitative trait loci detection.

This paper presents systematic methods for the detection of influential individuals that affect the log odds (LOD) score curve. We derive general formulas of influence functions for profile likelihoods and introduce them into two standard quantitative trait locus detection methods-the interval mapping method and single marker analysis. Besides influence analysis on specific LOD scores, we also develop influence analysis methods on the shape of the LOD score curves. A simulation-based method is proposed to assess the significance of the influence of the individuals. These methods are shown useful in the influence analysis of a real dataset of an experimental population from an F2 mouse cross. By receiver operating characteristic analysis, we confirm that the proposed methods show better performance than existing diagnostics.

Evolutionarily diverged regulation of X-chromosomal genes as a primal event in mouse reproductive isolation.

Improper gene regulation is implicated in reproductive isolation, but its genetic and molecular bases are unknown. We previously reported that a mouse inter-subspecific X chromosome substitution strain shows reproductive isolation characterized by male-specific sterility due to disruption of meiotic entry in spermatogenesis. Here, we conducted comprehensive transcriptional profiling of the testicular cells of this strain by microarray. The results clearly revealed gross misregulation of gene expression in the substituted donor X chromosome. Such misregulation occurred prior to detectable spermatogenetic impairment, suggesting that it is a primal event in reproductive isolation. The misregulation of X-linked genes showed asymmetry; more genes were disproportionally downregulated rather than upregulated. Furthermore, this misregulation subsequently resulted in perturbation of global transcriptional regulation of autosomal genes, probably by cascading deleterious effects. Remarkably, this transcriptional misregulation was substantially restored by introduction of chromosome 1 from the same donor strain as the X chromosome. This finding implies that one of regulatory genes acting in trans for X-linked target genes is located on chromosome 1. This study collectively suggests that regulatory incompatibility is a major cause of reproductive isolation in the X chromosome substitution strain.

The ancestor of extant Japanese fancy mice contributed to the mosaic genomes of classical inbred strains.

Commonly used classical inbred mouse strains have mosaic genomes with sequences from different subspecific origins. Their genomes are derived predominantly from the Western European subspecies Mus musculus domesticus, with the remaining sequences derived mostly from the Japanese subspecies Mus musculus molossinus. However, it remains unknown how this intersubspecific genome introgression occurred during the establishment of classical inbred strains. In this study, we resequenced the genomes of two M. m. molossinus-derived inbred strains, MSM/Ms and JF1/Ms. MSM/Ms originated from Japanese wild mice, and the ancestry of JF1/Ms was originally found in Europe and then transferred to Japan. We compared the characteristics of these sequences to those of the C57BL/6J reference sequence and the recent data sets from the resequencing of 17 inbred strains in the Mouse Genome Project (MGP), and the results unequivocally show that genome introgression from M. m. molossinus into M. m. domesticus provided the primary framework for the mosaic genomes of classical inbred strains. Furthermore, the genomes of C57BL/6J and other classical inbred strains have long consecutive segments with extremely high similarity (>99.998%) to the JF1/Ms strain. In the early 20th century, Japanese waltzing mice with a morphological phenotype resembling that of JF1/Ms mice were often crossed with European fancy mice for early studies of "Mendelism," which suggests that the ancestor of the extant JF1/Ms strain provided the origin of the M. m. molossinus genome in classical inbred strains and largely contributed to its intersubspecific genome diversity.

Chromosome substitution strains: gene discovery, functional analysis, and systems studies.

Laboratory mice are valuable in biomedical research in part because of the extraordinary diversity of genetic resources that are available for studies of complex genetic traits and as models for human biology and disease. Chromosome substitution strains (CSSs) are important in this resource portfolio because of their demonstrated use for gene discovery, genetic and epigenetic studies, functional characterizations, and systems analysis. CSSs are made by replacing a single chromosome in a host strain with the corresponding chromosome from a donor strain. A complete CSS panel involves a total of 22 engineered inbred strains, one for each of the 19 autosomes, one each for the X and Y chromosomes, and one for mitochondria. A genome survey simply involves comparing each phenotype for each of the CSSs with the phenotypes of the host strain. The CSS panels that are available for laboratory mice have been used to dissect a remarkable variety of phenotypes and to characterize an impressive array of disease models. These surveys have revealed considerable phenotypic diversity even among closely related progenitor strains, evidence for strong epistasis and for heritable epigenetic changes. Perhaps most importantly, and presumably because of their unique genetic constitution, CSSs, and congenic strains derived from them, the genetic variants underlying quantitative trait loci (QTLs) are readily identified and functionally characterized. Together these studies show that CSSs are important resource for laboratory mice.

Complex quantitative traits cracked by the mouse inter-subspecific consomic strains.

Mammalian quantitative traits that are observed at the whole-body level, such as body weight and length and blood biochemical parameters, are determined by the cooperative effects of multiple genetic and epigenetic factors as well as environmental factors. This complexity has hampered the genetic analysis of quantitative traits. To overcome this difficulty, we have established a full set of consomic mouse strains, also known as chromosome substitution strains, by replacing every chromosome of the classical inbred strain C57BL/6J with its counterpart from the Japanese wild-mouse-derived inbred strain MSM/Ms. The core components of the genomes of these two strains originated from different mouse subspecies. The inter-subspecific large-genome divergence and phenotypic differences between the two strains allowed the identification of genetic determinants for many quantitative traits by comprehensive phenotype screening. For some quantitative traits, the genetic determinants could be dissected into multiple chromosomes, thereby reflecting strain differences between C57BL/6J and MSM/Ms and their simple additive effects on the background of the consomic host strain. For other quantitative traits, the measured values of some consomic strains often far exceeded the range of the two parental strains, which suggests that nonadditive genetic interactions occur among multiple genes located on the substituted MSM/Ms chromosomes and the consomic host chromosomes. Thus, the inter-subspecific consomic strains are unique tools that can be used to identify both additive and nonadditive genetic effects on quantitative complex traits.

Genetic divergence and the genetic architecture of complex traits in chromosome substitution strains of mice.

BACKGROUND: The genetic architecture of complex traits strongly influences the consequences of inherited mutations, genetic engineering, environmental and genetic perturbations, and natural and artificial selection. But because most studies are under-powered, the picture of complex traits is often incomplete. Chromosome substitution strains (CSSs) are a unique paradigm for these genome surveys because they enable statistically independent, powerful tests for the phenotypic effects of each chromosome on a uniform inbred genetic background. A previous CSS survey in mice and rats revealed many complex trait genes (QTLs), large phenotypic effects, extensive epistasis, as well as systems properties such as strongly directional phenotypic changes and genetically-determined limits on the range of phenotypic variation. However, the unusually close genetic relation between the CSS progenitor strains in that study raised questions about the impact of genetic divergence: would greater divergence between progenitor strains, with the corresponding changes in gene regulation and protein function, lead to significantly more distinctive phenotypic features, or alternatively would epistasis and systems constraints, which are pervasive in CSSs, limit the range of phenotypic variation regardless of the extent of DNA sequence variation? RESULTS: We analyzed results for an extensive survey of traits in two new panels of CSSs where the donor strains were derived from inbred strains with more distant origins and discovered a strong similarity in genetic and systems properties among the three CSS panels, regardless of divergence time. CONCLUSION: Our results argue that DNA sequence differences between host and donor strains did not substantially affect the architecture of complex traits, and suggest instead that strong epistasis buffered the phenotypic effects of genetic divergence, thereby constraining the range of phenotypic variation.

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.