Biomedical subjects

Jesse Mager

Publications and source records attributed to Jesse Mager.

5 recordsLinked to original sources

PubMed2006

Identification of candidate maternal-effect genes through comparison of multiple microarray data sets.

Transcriptional profiling by microarray hybridization has become a standard method to analyze global gene expression and has resulted in the availability of enormous amounts of experimental data. Given the number of different microarray platforms currently in use, it is critical to determine how reproducible results are from one platform to another. Additional variability may also arise from tissue collection and protocol differences among laboratories. In an effort to identify genes whose maternal mRNA pools are critical during preimplantation development, we compared published results of three independent studies of the mouse preimplantation embryo transcriptome, each performed in a different laboratory using different microarray platforms. We searched the combined data set for genes whose expression patterns were consistent among the three experiments. Querying for presence or absence at single developmental windows indicates that between 52% and 60% of genes are in agreement among the three experiments. Searching for expression patterns across three developmental windows (oocyte + 1-cell, 2- through 8-cell, and blastocyst stage) revealed approximately 33% agreement among the three experiments, although the majority of these genes were either always present or always absent. Using this approach, we identified 51 genes with a predicted expression pattern of maternal RNA only (not present during 2-cell through 8-cell or at the blastocyst stage). RT-PCR validation indicates 37 (72%) of these candidates have the microarray-predicted expression pattern and represent candidate maternal-effect genes. Based on our analysis, we conclude that data mining microarray experiments in this way greatly enhances candidate gene expression pattern accuracy.

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PubMed2005

Strategies for dissecting epigenetic mechanisms in the mouse.

Epigenetics generally refers to heritable changes in gene expression that are independent of nucleotide sequence. With complete genome sequences in hand, understanding the epigenetic control of genomes is the next step towards comprehending how the same DNA sequence gives rise to different cells, lineages and organs. Epigenetics also contributes to individual variation in normal biology and in disease states. The mouse provides a unique opportunity to understand how epigenetic differences contribute to both development and disease in a tractable mammalian system. Here we discuss current approaches and protocols used to study epigenetics in the mouse, including loss-of-function studies, mutagenesis screens, somatic cell nuclear transfer, genomics and proteomics.

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PubMed2003

Dynamic morphogenetic events characterize the mouse visceral endoderm.

Several lines of evidence suggest that the extraembryonic endoderm of vertebrate embryos plays an important role in the development of rostral neural structures. In mice, neural inductive signals are thought to reside in an area of visceral endoderm that expresses the Hex gene. Here, we have conducted a morphological and lineage analysis of visceral endoderm cells spanning pre- and postprimitive streak stages. Our results show that Hex-expressing cells have a tall, columnar epithelial morphology, which distinguishes them from other visceral endoderm cells. This region of visceral endoderm thickening (VET) is found overlying first the distal and then one side of the epiblast at stages between 5.5 and 5.75 days post coitum (d.p.c.). In addition, we show that the epiblast has an anteroposterior-compressed appearance that is aligned with the position of the VET. Intracellular labeling of VET/Hex-expressing cells reveals an anterior and anterolateral shift from their distal epiblast position. VET/Hex-expressing cells are first localized to the anterior side of the epiblast by 5.75 d.p.c. and form a crescent on the anterior half of the embryo at the onset of gastrulation. Subsequently, VET descendants are distributed along the embryonic/extraembryonic boundary by headfold stages at 7.5 d.p.c. The morphological characteristics and position of VET/Hex-expressing cells distinguishes the future anteroposterior axis of the embryo and provide landmarks to stage mouse embryos at preprimitive streak stages. Moreover, the morphological characteristics of pregastrulation mouse embryos together with the stereotyped shift in the position of visceral endoderm cells reveal similarities among amniote embryos that suggest an evolutionary conservation of the mechanisms that pattern the rostral neurectoderm at pregastrula stages.

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PubMed2003

Genome imprinting regulated by the mouse Polycomb group protein Eed.

Epigenetic regulation is essential for temporal, tissue-specific and parent-of-origin-dependent gene expression. It has recently been found that the mouse Polycomb group (PcG) gene Eed (embryonic ectoderm development) acts to maintain repression of the imprinted X chromosome. Here, we investigated whether Eed is also required for regulation of autosomal imprinted loci. Expression analyses showed that transcripts from the silent alleles of a subset of paternally repressed genes were present in Eed(-/-) embryos. Parent-of-origin methylation was preserved in these embryos, but we observed changes in the methylation status of specific CpGs in differentially methylated regions (DMRs) at affected but not at unaffected loci. These data identify Eed as a member of a new class of trans-acting factors that regulate parent-of-origin expression at imprinted loci.

Alleles↗

PubMed2002

The mouse PcG gene eed is required for Hox gene repression and extraembryonic development.

The Polycomb group (PcG) of genes was first identified in Drosophila as maintenance factors for long-term transcriptional repression of homeotic genes. In mice, the PcG protein Eed (Embryonic ectoderm development) is present in a distinct complex that interacts with histone deacetylase (HDAC) and the PcG member Ezh2 (Enhancer of zeste homolog 2), but not in the larger Polycomb repressive complex 1 (PRC1) formed by several other PcG proteins. eednull mutants manifest a distinct early gastrulation defect that occurs prior to homeotic gene expression. To determine whether Eed is also required for regulating homeotic genes, a later acting eedhypomorph mutation was analyzed. The anterior expression boundaries of several Hox genes were shifted rostrally by one segment, indicating that Eed is required for stable repression of homeotic genes. Furthermore, although the eednull/hypomorph compound heterozygotes die during mid-gestation stage, they did not show a more severe derepression of Hox genes than the eedhypomorph/hypomorph homozygotes. A detailed analysis of the mid-gestation lethality associated with the eednull/hypomorph compound heterozygotes revealed a novel function for eed in the development of secondary trophoblast giant cells during murine placenta formation. Tetraploid rescue experiments demonstrated that the defect is cell autonomous in the extraembryonic lineage. Mash2, a paternally imprinted gene important for trophoblast development, was ectopically expressed in the eed mutants. However, genetic crosses with a Mash2 null allele suggested that Eed was not required to maintain Mash2 imprinting, but could be required in a lineage specific fashion to suppress Mash2 expression.

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