Species Mus Musculus Research Articles

Small terrestrial mammals of Albania: distribution and diversity (Mammalia, Eulipotyphla, Rodentia).

In this paper new records are reported for 23 species of small terrestrial mammals (STM) of Albania collected during the field work campaigns organised in the framework of the project “Strengthening capacity in National Nature Protection – preparation for Natura 2000 network” (NaturAL) in Albania during the summer and autumn of 2016 and 2017 Data on small mammals were primarily collected through Sherman live-trapping campaigns in six high priority protected areas of Albania: Korab-Koritnik, Bredhi i Hotovës, Tomorri, Llogara-Karaburun, Divjakë-Karavasta, Liqeni i Shkodrës (Skadar lake), Lëpushë-Vermosh. Other data were obtained by analysis of owl pellets or by direct observation of individuals (dead or alive) in the field. For 21 species Erinaceus roumanicus, Neomys anomalus, Crocidura suaveolens, Crocidura leucodon, Suncus etruscus, Talpa stankovici/caeca, Myocastor coypus, Sciurus vulgaris, Glis glis, Dryomys nitedula, Muscardinus avellanarius, Microtus levis/arvalis, Microtus subterraneus, Microtus thomasi, Microtus felteni, Myodes glareolus, Apodemus sylvaticus, Apodemus flavicollis, Apodemus epimelas, Mus musculus, and Mus macedonicus additional records are provide and their distributions reviewed, while the presence of two new species of shrews (Sorex araneus and Sorex minutus) for Albania is reported for the first time. A comprehensive review of the published and unpublished distribution records of STM species of the country is made, together with an updated checklist and distribution maps of the species.

Nematodes of rodents of Armenia

This review summarizes known data on the species composition of nematodes in 24 species of rodents inhabiting the territory of Armenia (South of Lesser Caucasus). The studied rodents include members of some cosmopolitan species (Mus musculus, Rattus norvegicus, Rattus rattus), as well as endemic and narrow-areal species (Meriones vinogradovi, Spermophilus xanthoprymnus, Microtus schidlovskii, Mesocricetus brandti, Sciurus anomalus). The taxonomical identity of the nematode species reported by previous authors is discussed with regard to present knowledge about helminth fauna of rodents. Our review concludes that 34 nematode species are present in rodents in Armenia, five of which are identified for the first time in rodents from the territory of Armenia, and three of which (Trichinella spiralis, Trichostrongylus colubriformis, Trichostrongylus skrjabini) are able to parasitize humans.

Biological Concerns on the Selection of Animal Models for Teratogenic Testing.

During pregnancy fetus can be exposed to a variety of chemicals which may induce abortion and malformations. Due to the amounts of new substances coming into the market every year, a high demand for a rapid, reliable, and cost-effective method to detect potential toxicity is necessary. Different species have been used as animal models for teratogen screening, most of them sharing similar development processes with humans. However, the application of embryology knowledge to teratology is hampered by the complexity of the reproduction processes.The present chapter outlines the essential development periods in different models, and highlights the similarities and differences between species, advantages and disadvantages of each group, and specific sensitivities for teratogenic tests. These models can be organized into the following categories: (1) invertebrate species such Caenorhabditis elegans and Drosophila melanogaster, whichhave become ideal for screening simple mechanisms in the early periods of reproductive cycle, allowing for rapid results and minor ethical concerns; (2) vertebrate nonmammalian species such Xenopus laevis and Danio rerio, important models to assess teratogenic potential in later development with fewer ethical requirements; and (3) the mammalian species Mus musculus, Rattus norvegicus, and Oryctolagus cuniculus, phylogenetically more close to humans, essential to assess complex specialized processes, that occur later in development.Rules for development toxicology tests require the use of mammalian species. However, ethical concerns and costs limit their use in large-scale screening. By contrast, invertebrate and vertebrate nonmammalian species are increasing as alternative animal models, as these organisms combine less ethical requirements, low costs and culture conditions compatible with large-scale screening. In contrast to the in vitro techniques, their main advantage is to allow for high-throughput screening in a whole-animal context, not dependent on the prior identification of a target. In this chapter, the biological development of the animals most used in teratogenic tests is adressed with the aims of maximizing human translation, reducing the number of animals used, and the time to market for new drugs.

The allergen Mus m 1.0102: Dissecting the relationship between molecular conformation and allergenic potency

BackgroundThe species Mus musculus experiences an obligate proteinuria: predominant are the Major Urinary Proteins (MUPs), that, collectively known as the major mouse allergen Mus m 1, are among the most important aeroallergens for mouse allergic patients. The production of a soluble and stable hypoallergenic form of Mus m 1 is essential for the development of immunotherapeutic protocols to treat allergic symptoms. MethodsWe introduced the substitution C138S in recombinant Mus m 1.0102, an allergenic isoform of Mus m 1. Solubility, conformation, stability and ability to refold after chemical denaturation were investigated with dynamic light scattering, circular dichroism, fluorescence and NMR spectroscopy. An in vitro degranulation assay was used to evaluate the protein allergenic potential, and compare it with Mus m 1.0102 and with an hypoallergenic variant bearing the substitution Y120A. ResultsMus m 1.0102-C138S retains a native-like fold revealing, however, local conformational alterations that influence some of its physical and allergenic properties: it is monodispersed, thermostable up to 56°C, able to reversibly unfold and it exhibits an enhanced allergenicity. ConclusionsThe unique free thiol group affects the solution structural stability of the native protein. Because the mutant C138S does not aggregate over time it is a good lead protein to develop diagnostic and therapeutic applications. General significanceWe elucidated the relationship between unfolding reversibility and sulphydryl reactivity. We ascribed the enhanced allergenicity of the mutant C138S to an increased accessibility of its allergenic determinants, an enticing feature to further investigate the structural elements of the allergen-IgE interface.

The effect of aluminum chloride and acetic acid in some blood picture of male rats

The current study was conducted to investigate the poisonous effects of Aluminum Chlorid dissolved in water alone and its effects of dissolved in acetic acid 25% in blood variables for male rats of Mus musculus . fifteen rats of the species Mus musculus ages (3-4) weeks and weights of (100±150gm) were used in this study. The study included tow experiments, (25) rat used for each experiment, which included (5) groups with (5) rat each. The first group of each experiment groups was considered the control group ,while the remaining four groups were considered as treatment groups. The first group were treated with (70 mg/kg of bodyweight) of Aluminum Chloride for different intervals (2, 5, 10, and 20 days); the second group given (70 mg/kg bodyweight) of Aluminum Chloride dissolved in acetic acid 25%. the blood variables for all rats were calculated after the different injection intervals was finished and dissected and blood was taken directly from the heart and put in experimental tube containing anticoagulant EDTA , The results showed low corporate rate of red blood cells ( RBC) and other blood variables and high moral in the rate of white blood cells ( WBC) compared to the control group, these changes were gradual as the dosage period.

Efecto del consumo del extracto de haba (Vicia faba L.) en el aumento de leucocitos, en ratones

Hemos leído con interés el artículo publicado por Amaro, donde se demuestra que existe un incremento de los leucocitos al administrar la betarraga en ratones albino de la especie Mus musculus de la cepa Balb/c (1). Queremos compartir los resultados de un estudio en el que se utilizó la haba (Vicia faba L.), un vegetal que cumple el rol en la alimentación del poblador rural y urbano por su aporte en proteínas, característico de toda leguminosa, y por su contribución en carbohidratos, minerales y vitaminas. La importancia de esta especie alimenticia se acrecienta porque también participa con los subproductos de la cosecha en la alimentación del ganado vacuno, ovino, porcino y de cuyes, así como mejorador de la fertilidad del suelo, aumentando los rendimientos de otros cultivos que le suceden en la rotación (2).

Role of Green Tea in Reducing Epidermal Thickness upon Ultraviolet Light-B Injury in BALB/c Mice

The main environmental source for skin damage is ultraviolet (UV) radiation. Many adverse effects have been recognized as the result of prolonged cutaneous exposure to solar ultraviolet radiation, such as erythema, edema, apoptosis, hyperplastic responses, photo-aging, and skin cancer development. Green tea provides photo-protection against UV radiation through many mechanisms including anti-inflammatory, immunomodulatory, and antioxidant properties. The aim of this study was to evaluate the effect of green tea in reducing epidermal thickness on mouse’s skin exposed to UVB irradiation. Thirty mice (Mus musculusspecies, BALB/c strain) underwent this study and were divided into 3 groups: control group (n=10mice), without UVB exposure and green tea administration; exposure group (n=10mice), which were exposed to UVB light only; and treatment group (n=10mice), which were exposed to UVB light and treated with 1 mL of green tea through oral gavage. Mice from both groups (exposure and treatment) were subjected to UVB irradiation 4 days/week (20 minutes/day, 4 weeks). It concluded that oral administration of green tea was provided photo-protection against UVB induced hyperplasia; therefore, it can be regarded as a natural alternative for photo-protection.

A High-Resolution Comparative Chromosome Map of Cricetus cricetus and Peromyscus eremicus Reveals the Involvement of Constitutive Heterochromatin in Breakpoint Regions

Compared to humans and other mammals, rodent genomes, specifically Muroidea species, underwent intense chromosome reshuffling in which many complex structural rearrangements occurred. This fact makes them preferential animal models for studying the process of karyotype evolution. Here, we present the first combined chromosome comparative maps between 2 Cricetidae species, Cricetus cricetus and Peromyscus eremicus, and the index species Mus musculus and Rattus norvegicus. Comparative chromosome painting was done using mouse and rat paint probes together with in silico analysis from the Ensembl genome browser database. Hereby, evolutionary events (inter- and intrachromosomal rearrangements) that occurred in C. cricetus and P. eremicus since the putative ancestral Muroidea genome could be inferred, and evolutionary breakpoint regions could be detected. A colocalization of constitutive heterochromatin and evolutionary breakpoint regions in each genome was observed. Our results suggest the involvement of constitutive heterochromatin in karyotype restructuring of these species, despite the different levels of conservation of the C. cricetus (derivative) and P. eremicus (conserved) genomes.

Acute genotoxicity analysis in vivo of the aqueous extract of Maytenus guyanensis Amazonian chichuá

The species Maytenus guyanensis Klotzsch ex Reissek, Celastraceae, present a wide variety of possible pharmacological activities and its roots and stems are used by popular medicine in the western Amazon rainforest. Few studies have demonstrated the genotoxic safety of the popular use of this species, and owing to this, the present study aimed to perform an analysis of the acute genotoxicity in vivo of the aqueous extract of M. guyanensis. Male and female mice from Mus musculus species, of weights ranging from 20 to 40g, organized in eight groups with different treatments were used. The aqueous extracts of the bark of M. guyanensis were administered orally by gavage with 0.1ml of the test substance per 10g of the animal, followed by performance of comet assay in peripheral blood, PCE/NCE correlation and occurrence of micronuclei in the bone marrow. It was found that the aqueous extract of M. guyanensis, with ten times higher concentration than those used in ethnopharmacology, did not present genotoxic effect and, moreover, it has antigenotoxic action in mice treated acutely. Further studies regarding bioaccumulation and chronic effects of this species are suggested, in order to improve the understanding of its mechanism of action, ensuring the efficacy and safety of its utilization and developing phytotherapics and drugs.

Differences in embryo quality are associated with differences in oocyte composition: a proteomic study in inbred mice.

Current models of early mouse development assign roles to stochastic processes and epigenetic regulation, which are considered to be as influential as the genetic differences that exist between strains of the species Mus musculus. The aim of this study was to test whether mouse oocytes vary from each other in the abundance of gene products that could influence, prime, or even predetermine developmental trajectories and features of derivative embryos. Using the paradigm of inbred mouse strains, we quantified 2010 protein groups (SILAC LC-MS/MS) and 15205 transcripts (RNA deep sequencing) present simultaneously in oocytes of four strains tested (129/Sv, C57Bl/6J, C3H/HeN, DBA/2J). Oocytes differed according to donor strain in the abundance of catalytic and regulatory proteins, as confirmed for a subset (bromodomain adjacent to zinc finger domain, 1B [BAZ1B], heme oxygenase 1 [HMOX1], estrogen related receptor, beta [ESRRB]) via immunofluorescence in situ. Given a Pearson's r correlation coefficient of 0.18-0.20, the abundance of oocytic proteins could not be predicted from that of cognate mRNAs. Our results document that a prerequisite to generate embryo diversity, namely the different abundances of maternal proteins in oocytes, can be studied in the model of inbred mouse strains. Thus, we highlight the importance of proteomic quantifications in modern embryology. All MS data have been deposited in the ProteomeXchange with identifier PXD001059 (http://proteomecentral.proteomexchange.org/dataset/PXD001059).

The uncharacterized gene 1700093K21Rik and flanking regions are correlated with reproductive isolation in the house mouse, Mus musculus

Reproductive barriers exist between the house mouse subspecies, Mus musculus musculus and M. m. domesticus, members of the Mus musculus species complex, primarily as a result of hybrid male infertility, and a hybrid zone exists where their ranges intersect in Europe. Using single nucleotide polymorphisms (SNPs) diagnostic for the two taxa, the extent of introgression across the genome was previously compared in these hybrid populations. Sixty-nine of 1316 autosomal SNPs exhibited reduced introgression in two hybrid zone transects suggesting maladaptive interactions among certain loci. One of these markers is within a region on chromosome 11 that, in other studies, has been associated with hybrid male sterility of these subspecies. We assessed sequence variation in a 20Mb region on chromosome 11 flanking this marker, and observed its inclusion within a roughly 150kb stretch of DNA showing elevated sequence differentiation between the two subspecies. Four genes are associated with this genomic subregion, with two entirely encompassed. One of the two genes, the uncharacterized 1700093K21Rik gene, displays distinguishing features consistent with a potential role in reproductive isolation between these subspecies. Along with its expression specifically within spermatogenic cells, we present various sequence analyses that demonstrate a high rate of molecular evolution of this gene, as well as identify a subspecies amino acid variant resulting in a structural difference. Taken together, the data suggest a role for this gene in reproductive isolation.

Increased seroprevalence of lymphocytic choriomeningitis virus infection in mice sampled in illegal waste sites

Lymphocytic choriomeningitis virus (LCMV), the prototypic member of the Arenaviridae family, was isolated from a fatal case of aseptic meningitis during the St. Louis encephalitis epidemic in 1933. Although it was among the first isolated human pathogenic viruses, LCMV remained less attractive through years due to its lack of clinical importance even though it is an important teratogen causing a severe and permanent brain injury in newborns. Recently, this old neglected virus found a new niche in immunosuppressed solid organs recipients. The natural host and reservoir of LCMV is a common house mouse, Mus musculus. Zoonotic transmission of LCMV to humans occurs worldwide by direct route with mice secretions. LCMV has been also isolated from several arthropods including fleas, Culicoides flies, Aedes mosquitoes and ticks, but it is believed that arthropods play a minor role in LCMV transmission. However, in habitats where mice and arthropod vectors are abundant, a vector transmission of LCMV could be important. The illegal waste sites present optimal conditions for spread of rodents, common house mice and rats in particular. Therefore, we tested 83 samples of Mus or Apodemus species sampled on illegal waste sites in Slovenia and Croatia. LCMV infection was determined with IFA and RT-PCR techniques. IFA slides and positive controls were kindly provided by Remi Charrel. The presence of IgG against LCMV was detected in 47% and 16% sera samples of Mus musculus and Apodemus species, respectively. Total RNA was extracted from spleen using RTP Pathogen Kit (Invitek-Stratec) and tested with nested RT-PCR specific for amplification of LCMV genome. Amplicons are in process of sequencing to obtain the nucleotide sequence and confirm the presence of LCMV. Since the seroprevalence studies in Europe revealed up to 17% prevalence of LCMV infection in mice and voles sampled in natural host habitat, we concluded that illegal waste sites accelerate the spread of rodent-borne pathogenic LCMV.

Evaluation of effectiveness of some mitochondrial genes in biosystematics and phylogeographic studies of house mouse (Mus musculus ) subspecies

The identification of the efficiency of some mtDNA genes of Mus musculus species complex (house mouse) for biosystematics research was studied in this approach. Recent studies have made use of different mitochondrial genes including NADH dehydrogenase genes, cytochrome b gene, cytochrome oxidase genes, D-loop region and whole mtDNA genome to study the house mouse species. Usage of each of these genome regions has its own advantages and disadvantages. Identification of appropriate genomic regions is very important for molecular biosystematic research. We have shown here that NADH dehydrogenase and Cytochrome oxidase genes (particularly COX2) are especially useful in biosystematics studies and subspecies identification,whereas D-loop region is the best candidate for biogeographic and phylogeographic studiesof subspecies of this species efficiency-wise as well as economically. These candidates areintroduced considering that the first two gene complexes are highly conserved whereas the latteris well receptive to gaining and preserving the mutations through time.

Evolution of the ABPA Subunit of Androgen-Binding Protein Expressed in the Submaxillary Glands in New and Old World Rodent Taxa

The salivary androgen-binding proteins (ABPs) are members of the secretoglobin gene family present in mammals. Each ABP is a heterodimer assembled as an ABPA subunit encoded by an Abpa gene and linked by disulfide bridges to an ABPBG subunit encoded by an Abpbg gene. The ABP dimers are secreted into the saliva of mice and then transferred to the pelage after grooming and subsequently to the environment allowing an animal to mark territory with a biochemical signal. The putative role of the mouse salivary ABPs is that of pheromones mediating mate selection resulting in assortative mating in the Mus musculus species complex. We focused on comparing patterns of molecular evolution between the Abpa genes expressed in the submaxillary glands of species of New World and Old World muroids. We found that in both sets of rodents the Abpa genes expressed in the submaxillary glands appear to be evolving under a similar evolutionary regime, with relatively high nonsynonymous substitution rates, suggesting that ABP might play a similar biological role in both systems. Thus, ABP could be involved with mate recognition and species isolation in New World as well as Old World muroids.

Acute toxicity evaluation of Genipa americana L. (Rubiaceae)

</I>;The specie G. americana L. (Rubiaceae) is an exotic plant with edible fruit, aphrodisiac, antianaemic and useful in diseases of the spleen and liver. The objective of this study was to determine the acute toxicity of crude ethanol extract of the fruit of G. americana parameters by evaluating general toxicity. For the tests were selected Swiss albino mice of the species Mus musculus females, weighing 25–30g were divided into groups of six. The animals were kept in polypropylene cages under controlled lighting (cycle 12 hours light/dark) and temperature (25 ± 2 °C), receiving food and water ad libtum. The doses of 1000, 2000 and 3000 mg/kg administered intraperitoneally (VIP) and 1500, 3000 and 4500 mg/kg orally. The 50% lethal dose (LD50) was not determined due to lack of deaths of the animals at the doses employed, being regarded maximal for the route. Among the signs of toxicity observed highlight the stimulating effect on the CNS. The results indicate that the ethanol extract of G. americana has low acute toxicity in mice when administered by oral and intraperitoneal administration.

Antinociceptive, neurobehavioral and antioxidant effects of Eupatorium triplinerve Vahl on rats

Ethnopharmacological relevanceEupatorium triplinerve Vahl belongs to the Asteraceae family, popularly known as Japana. It is a perennial shrub native to Amazon rainforests of South America. Its leaves are used through infusions, decoctions, baths, and tea. It is largely used in Brazilian folk medicine as sedative, febrifuge, stimulant, tonic and anti-inflammatory. Aim of the studyThe present study evaluated the putative effects of Eupatorium triplinerve on the central nervous system (CNS), including locomotor and anxiety activity, depression-like behavior, and antinociception and oxidative stress. Materials and methodsTwo-month-old male Wistar rats (n=7–10 rats/group) and Swiss male and female mice of the species Mus musculus (n=7–10 per group) were administered with 100mg/kg, 200mg/kg, 400mg/kg, 600mg/kg, and 800mg/kg of hydroalcoholic extracts of Eupatorium triplinerve (HEET). The behavioral assays included open-field (OF), elevated Plus-maze (EPM), and forced swimming tests (FS). The antinociceptive activity was verified using chemical (acetic acid and formalin) and thermal (hot plate) models of nociception. The oxidative stress levels were measured in rat blood samples after behavioral assays and Trolox equivalent antioxidant capacity (TEAC), nitric oxide and malondialdehyde (MDA) levels were measured in vivo. ResultsOral pretreatment with HEET reduced the locomotion in OF test (200–800mg/kg), increased central locomotion and open arms entries in the OF and EPM tests, respectively (600–800mg/kg), and decreased the immobility time in the FS (200–800mg/kg). It also reduced the writhing number evoked by acetic acid injection (200–800mg/kg) and licking time in the first phase of the formalin test (400–800mg/kg). In the oxidative stress assays, the extract decreased TEAC, Nitric Oxide and MDA levels in response to swimming stress induced in rats. ConclusionsThese results were indicative for the first time that Eupatorium triplinerve exerted mild sedative, anxiolytic and antidepressive effects on the CNS. Antinociceptive effects not related to opioid system and antioxidant activity were also observed. These results support the ethnopharmacological use of Eupatorium triplinerve in popular medicine.

Verification of natural infection of peridomestic rodents by PCV2 on commercial swine farms

The porcine circovirus-2 (PCV2) is the main agent responsible for porcine circovirus associated diseases (PCVAD). Few studies have been done regarding PCV2 infection in other species. The purpose of this study was to investigate the occurrence of PCV2 infection in the peridomestic rodent species Mus musculus and Rattus rattus on commercial pig farms in Brazil. Immunohistochemistry assay demonstrated PCV2 in the spleen, lung and kidney. Viral DNA was detected in tissues by nested PCR assay. Partial sequences of PCV2 genomes detected in the rodents had strong identity with gene sequences of PCV2 isolates from pigs. These results show that the studied peridomestic rodent species can be naturally infected by PCV2. However, further studies are needed to confirm PCV2 transmission from rodents to pigs.

Protection Against Toxoplasmosis in Swiss Albino Mice Immunized with Attenuated Toxoplasma Gondi

The present study aimed at investigation on developing the immune response against Toxoplasmosis in Swiss Albino mice of the species Mus musculus, BALB/c strain, which were infected, experimentally, with Toxoplasma gondii in order to render the host able to resist any infection with this disease in the future. To achieve this, Toxoplasma gondii tissue cysts, collected from placenta of aborted women, they attenuated by irradiation with two absorbed doses of X-Ray irradiation 0.4 and 0.8 KGy. Mice were injected, intraperitoneally with tissue cysts at a rate of 100 cysts/mice single or double doses. In addition, groups of mice were injected with non-irradiated tissue cysts, as a positive control groups. The criteria used in the present study was humoral immunity, represented by IgM using Enzyme-Linked Immunosorbent Assay (ELISA IgM) to demonstrate the differentiated in IgM level between mice inoculated with X-Ray irradiated tissue cysts and positive control groups, which infected with non- irradiated tissue cysts. The result shown that the immunization with X-Ray irradiated Toxoplasma gondii tissue cysts could partially protect the mice from Toxoplasma gondii infection, and produce specific IgM antibody.

Differences in hippocampal protein levels between C57Bl/6J, PWD/PhJ, and Apodemus sylvaticus are paralleled by differences in spatial memory

There is a significant strain-dependent performance in the Morris water maze (MWM), a paradigm for the evaluation of spatial memory. In contrast, information on molecular differences that may be responsible for differences in spatial memory performance is limited. The aim of the study was therefore to investigate differences in hippocampal protein levels in three groups with different performance in the MWM. C57BL/6J (inbred laboratory strain), PWD/PhJ (inbred strain derived from wild animals of Mus musculus), and Apodemus sylvaticus (AS, genus Apodemus) mice were used for the experiments. Proteins from hippocampi, obtained from a behavioral study on these animals, were extracted and run on two-dimensional gel electrophoresis. Proteins spots were quantified, and spots with significantly different levels were identified by mass spectrometry using an ion trap. A series of 49 proteins from different pathways and cascades (signaling, neuronal network, protein synthesis, secretion and degradation, and antioxidant system; intermediary, fat, and carbohydrate metabolism) were significantly different among hippocampi at the stringent statistical level of P ≤ 0.001. These findings are paralleled by differences in the spatial navigation abilities between the strains within the species Mus musculus (C57BL/6 vs. PWD/PhJ) and between the genera Mus and Apodemus. As shown previously, AS learned the task in the MWM and showed good memory retention when tested at the probe trial (day 12), whereas C57BL/6J learned the task, but failed at the probe trial at day 12 as well as PWD/PhJ that failed to learn the task and failed at the probe trial at day 12. A list of above-mentioned proteins were different between PWD/PhJ with bad and AS with good memory retention and may therefore be related to performance in the MWM and thus to spatial memory formation. The experimental approach, however, does not allow discriminating between differences in protein levels a priori and different protein levels induced by the MWM testing. © 2010 Wiley-Liss, Inc.

Clcn4-2 genomic structure differs between the X locus in Mus spretus and the autosomal locus in Mus musculus: AT motif enrichment on the X

In Mus spretus, the chloride channel 4 gene Clcn4-2 is X-linked and dosage compensated by X up-regulation and X inactivation, while in the closely related mouse species Mus musculus, Clcn4-2 has been translocated to chromosome 7. We sequenced Clcn4-2 in M. spretus and identified the breakpoints of the evolutionary translocation in the Mus lineage. Genetic and epigenetic differences were observed between the 5'ends of the autosomal and X-linked loci. Remarkably, Clcn4-2 introns have been truncated on chromosome 7 in M. musculus as compared with the X-linked loci from seven other eutherian mammals. Intron sequences specifically preserved in the X-linked loci were significantly enriched in AT-rich oligomers. Genome-wide analyses showed an overall enrichment in AT motifs unique to the eutherian X (except for genes that escape X inactivation), suggesting a role for these motifs in regulation of the X chromosome.