Peromyscus as a Mammalian Epigenetic Model

Deer mice (Peromyscus) offer an opportunity for studying the effects of natural genetic/epigenetic variation with several advantages over other mammalian models. These advantages include the ability to study natural genetic variation and behaviors not present in other models. Moreover, their life histories in diverse habitats are well studied. Peromyscus resources include genome sequencing in progress, a nascent genetic map, and >90,000 ESTs. Here we review epigenetic studies and relevant areas of research involving Peromyscus models. These include differences in epigenetic control between species and substance effects on behavior. We also present new data on the epigenetic effects of diet on coat-color using a Peromyscus model of agouti overexpression. We suggest that in terms of tying natural genetic variants with environmental effects in producing specific epigenetic effects, Peromyscus models have a great potential

Comparative genome mapping of the deer mouse (Peromyscus maniculatus) reveals greater similarity to rat (Rattus norvegicus) than to the lab mouse (Mus musculus)

<p>Abstract</p> <p>Background</p> <p>Deer mice (<it>Peromyscus maniculatus</it>) and congeneric species are the most common North American mammals. They represent an emerging system for the genetic analyses of the physiological and behavioral bases of habitat adaptation. Phylogenetic evidence suggests a much more ancient divergence of <it>Peromyscus </it>from laboratory mice (<it>Mus</it>) and rats (<it>Rattus</it>) than that separating latter two. Nevertheless, early karyotypic analyses of the three groups suggest <it>Peromyscus </it>to be exhibit greater similarities with <it>Rattus </it>than with <it>Mus</it>.</p> <p>Results</p> <p>Comparative linkage mapping of an estimated 35% of the deer mouse genome was done with respect to the Rattus and Mus genomes. We particularly focused on regions that span synteny breakpoint regions between the rat and mouse genomes. The linkage analysis revealed the Peromyscus genome to have a higher degree of synteny and gene order conservation with the Rattus genome.</p> <p>Conclusion</p> <p>These data suggest that: 1. the <it>Rattus </it>and <it>Peromyscus </it>genomes more closely represent ancestral Muroid and rodent genomes than that of <it>Mus</it>. 2. the high level of genome rearrangement observed in Muroid rodents is especially pronounced in <it>Mus</it>. 3. evolution of genome organization can operate independently of more commonly assayed measures of genetic change (e.g. SNP frequency).</p

Mapping and identification of candidate loci responsible for Peromyscus hybrid overgrowth

Crosses between two recently diverged rodent species of the genus Peromyscus result in dramatic parent-of-origin effects on growth and development. P. maniculatus females crossed with P. polionotus males yield growth-retarded conceptuses, whereas the reciprocal cross results in overgrowth and lethality. These hybrid effects are particularly pronounced in the placenta. We previously detected linkage to two regions of the genome involved in the overgrowth effects. One locus, termed Peal, is a paternally expressed autosomal locus mapping to a domain whose house mouse equivalent contains several clusters of imprinted genes. The other locus, termed Mexl, maps to a gene-poor region of the X chromosome. Here we use an advanced intercross line to verify and narrow the regions of linkage and identify candidate genes for Mexl and Peal. While we have previously shown that Mexl affects both pre-and postnatal growth, we show here that Peal affects only prenatal growth. Utilizing criteria such as mutant phenotypes and allelic expression, we identify the loci encoding the homeobox protein Esx1 and the zinc-finger protein Pw1/Peg3 as candidates. Both loci exhibit expression changes in the hybrids

Patterns of Hybrid Loss of Imprinting Reveal Tissue- and Cluster-Specific Regulation

Background: Crosses between natural populations of two species of deer mice, Peromyscus maniculatus (BW), and P. polionotus (PO), produce parent-of-origin effects on growth and development. BW females mated to PO males (bw6po) produce growth-retarded but otherwise healthy offspring. In contrast, PO females mated to BW males (PO6BW) produce overgrown and severely defective offspring. The hybrid phenotypes are pronounced in the placenta and include PO6BW conceptuses which lack embryonic structures. Evidence to date links variation in control of genomic imprinting with the hybrid defects, particularly in the PO6BW offspring. Establishment of genomic imprinting is typically mediated by gametic DNA methylation at sites known as gDMRs. However, imprinted gene clusters vary in their regulation by gDMR sequences. Methodology/Principal Findings: Here we further assess imprinted gene expression and DNA methylation at different cluster types in order to discern patterns. These data reveal PO6BW misexpression at the Kcnq1ot1 and Peg3 clusters, both of which lose ICR methylation in placental tissues. In contrast, some embryonic transcripts (Peg10, Kcnq1ot1) reactivated the silenced allele with little or no loss of DNA methylation. Hybrid brains also display different patterns of imprinting perturbations. Several cluster pairs thought to use analogous regulatory mechanisms are differentially affected in the hybrids. Conclusions/Significance: These data reinforce the hypothesis that placental and somatic gene regulation differs significantly, as does that between imprinted gene clusters and between species. That such epigenetic regulatory variatio

Immunocompetent 3D Model of Human Upper Airway for Disease Modeling and In Vitro Drug Evaluation

The development of more complex in vitro models for the assessment of novel drugs and chemicals is needed because of the limited biological relevance of animal models to humans as well as ethical considerations. Although some human-cell-based assays exist, they are usually 2D, consist of single cell type, and have limited cellular and functional representation of the native tissue. In this study, we have used biomimetic porous electrospun scaffolds to develop an immunocompetent 3D model of the human respiratory tract comprised of three key cell types present in upper airway epithelium. The three cell types, namely, epithelial cells (providing a physical barrier), fibroblasts (extracellular matrix production), and dendritic cells (immune sensing), were initially grown on individual scaffolds and then assembled into the 3D multicell tissue model. The epithelial layer was cultured at the air–liquid interface for up to four weeks, leading to formation of a functional barrier as evidenced by an increase in transepithelial electrical resistance (TEER) and tight junction formation. The response of epithelial cells to allergen exposure was monitored by quantifying changes in TEER readings and by assessment of cellular tight junctions using immunostaining. It was found that epithelial cells cocultured with fibroblasts formed a functional epithelial barrier at a quicker rate than single cultures of epithelial cells and that the recovery from allergen exposure was also more rapid. Also, our data show that dendritic cells within this model remain viable and responsive to external stimulation as evidenced by their migration within the 3D construct in response to allergen challenge. This model provides an easy to assemble and physiologically relevant 3D model of human airway epithelium that can be used for studies aiming at better understanding lung biology, the cross-talk between immune cells, and airborne allergens and pathogens as well as drug delivery

Retrieval of Mouse Oocytes

To date, only a few studies have reported successful manipulations of Peromyscus embryogenesis or reproductive biology. Together with the Peromyscus Genetic Stock Center (http://stkctr.biol.sc.edu), we are characterizing the salient differences needed to develop this system. A primary goal has been to optimize oocyte/early embryo retrieval

Harvesting Sperm and Artificial Insemination of Mice

Rodents of the genus Peromyscus (deer mice) are the most prevalent native North American mammals. Peromyscus species are used in a wide range of research including toxicology, epidemiology, ecology, behavioral, and genetic studies. Here they provide a useful model for demonstrations of artificial insemination

Aberrant Growth and Pattern Formation in Peromyscus Hybrid Placental Development1

Crosses between the North American deer mouse species Peromyscus maniculatus (BW) and P. polionotus (PO) produce dramatic asymmetric developmental effects. BW females mated to PO males (female bw × male po) produce viable growth-retarded offspring. In contrast, PO females mated to BW males (female PO × male BW) produce overgrown but dysmorphic conceptuses. Most female PO × male BW offspring are dead by midgestation; those surviving to later time points display numerous defects reminiscent of several diseases. The hybrid effects are particularly pronounced in the placenta. Here we examine placental morphological defects via histology and in situ hybridization as well as the relationship between growth and mortality in the female PO × male BW cross. These assays indicate altered hybrid fetal:placental ratios by the equivalent of mouse (Mus) Embryonic Day (E) 13 and disorganization and labyrinth defects in female PO × male BW placentas and confirm earlier suggestions of a severely reduced junctional zone in the female bw × male po hybrids. Further, we show that both cellular proliferation and death are abnormal in the hybrids through BrdU incorporation and TUNEL assays, respectively. Together the data indicate that the origin of the effects is prior to the equivalent of Mus E10. Finally, as the majority of these assays had not previously been performed on Peromyscus, these studies provide comparative data on wild-type placentation

Maternal methyl supplemented diets and effects on offspring health

Women seeking to become pregnant and pregnant women are currently advised to consume high amounts of folic acid and other methyl donors to prevent neural tube defects in their offspring. These diets can alter methylation patterns of several biomolecules, including nucleic acids and histone proteins. Limited animal model data suggests that developmental exposure to these maternal methyl supplemented (MS) diets leads to beneficial epimutations. However, other rodent and humans studies have yielded opposing findings with such diets leading to promiscuous epimutations that are likely associated with negative health outcomes. Conflict exists to whether these maternal diets are preventative or exacerbate the risk for ASD in children. This review will discuss the findings to date on the potential beneficial and aversive effects of maternal MS diets. We will also consider how other factors might influence the effects of MS diets. Current data suggest that there is cause for concern as maternal MS diets may lead to epimutations that underpin various diseases, including neurobehavioral disorders. Further studies are needed to explore the comprehensive effects maternal MS diets have on the offspring epigenome and subsequent overall health

Patterns of Hybrid Loss of Imprinting Reveal Tissue- and Cluster-Specific Regulation

BackgroundCrosses between natural populations of two species of deer mice, Peromyscus maniculatus (BW), and P. polionotus (PO), produce parent-of-origin effects on growth and development. BW females mated to PO males (bw×po) produce growth-retarded but otherwise healthy offspring. In contrast, PO females mated to BW males (PO×BW) produce overgrown and severely defective offspring. The hybrid phenotypes are pronounced in the placenta and include PO×BW conceptuses which lack embryonic structures. Evidence to date links variation in control of genomic imprinting with the hybrid defects, particularly in the PO×BW offspring. Establishment of genomic imprinting is typically mediated by gametic DNA methylation at sites known as gDMRs. However, imprinted gene clusters vary in their regulation by gDMR sequences.Methodology/Principal FindingsHere we further assess imprinted gene expression and DNA methylation at different cluster types in order to discern patterns. These data reveal PO×BW misexpression at the Kcnq1ot1 and Peg3 clusters, both of which lose ICR methylation in placental tissues. In contrast, some embryonic transcripts (Peg10, Kcnq1ot1) reactivated the silenced allele with little or no loss of DNA methylation. Hybrid brains also display different patterns of imprinting perturbations. Several cluster pairs thought to use analogous regulatory mechanisms are differentially affected in the hybrids.Conclusions/SignificanceThese data reinforce the hypothesis that placental and somatic gene regulation differs significantly, as does that between imprinted gene clusters and between species. That such epigenetic regulatory variation exists in recently diverged species suggests a role in reproductive isolation, and that this variation is likely to be adaptive