Combinatorial effects of Flk1 and Tal1 on vascular and hematopoietic development in the mouse.

Mouse embryos mutant for the VEGF receptor, VEGFR2, Flk-1, or Kdr, fail to form both endothelial and hematopoietic cells, suggesting a possible role in a common progenitor to both lineages. The transcription factor Tal1 (Scl), is not expressed in Flk1(-/-) embryos, consistent with a downstream role in the Flk1 pathway. We tested whether expression of Tal1 under the Flk1 promoter was sufficient to rescue the loss of endothelial and hematopoietic cells in Flk1 mutants.

Gene expression profiling of embryo-derived stem cells reveals candidate genes associated with pluripotency and lineage specificity.

Large-scale gene expression profiling was performed on embryo-derived stem cell lines to identify molecular signatures of pluripotency and lineage specificity. Analysis of pluripotent embryonic stem (ES) cells, extraembryonic-restricted trophoblast stem (TS) cells, and terminally-differentiated mouse embryo fibroblast (MEF) cells identified expression profiles unique to each cell type, as well as genes common only to ES and TS cells. Whereas most of the MEF-specific genes had been characterized previously, the majority (67%) of the ES-specific genes were novel and did not include known differentiated cell markers.

Signaling pathways in vascular development.

The vasculature is one of the most important and complex organs in the mammalian body. The first functional organ to form during embryonic development, the intricately branched network of endothelial and supporting periendothelial cells is essential for the transportation of oxygen and nutrients to and the removal of waste products from the tissues. Serious disruptions in the formation of the vascular network are lethal early in post-implantation development, while the maintenance of vessel integrity and the control of vessel physiology and hemodynamics have important consequences throughout embryonic and adult life.

Molecular profiling of non-small cell lung cancer and correlation with disease-free survival.

Recent studies have suggested that information from gene expression profiles could be used to develop molecular classifications of cancer. We hypothesized that expression levels of specific genes in operative specimens could be correlated to recurrence risk in non-small cell lung cancer (NSCLC). We performed expression profiling using 19.

Hyperphenylalaninemia and impaired glucose tolerance in mice lacking the bifunctional DCoH gene.

The bifunctional protein DCoH (Dimerizing Cofactor for HNF1) acts as an enzyme in intermediary metabolism and as a binding partner of the HNF1 family of transcriptional activators. HNF1 proteins direct the expression of a variety of genes in the liver, kidney, pancreas, and gut and are critical to the regulation of glucose homeostasis. Mutations of the HNF1alpha gene underlie maturity onset diabetes of the young (MODY3) in humans.

Stem cells from the Mammalian blastocyst.

Early differentiation of the mammalian embryo leads to the development of two distinct lineages-the inner cell mass (ICM) and the trophectoderm. Cells of the ICM are pluripotent and give rise to all tissues of the fetus, while trophectoderm cells are restricted in their potential to the trophoblast cell layers of the placenta. In the mouse, apparently immortal stem cell lines can be obtained from both cell types.

FGF signaling regulates mesoderm cell fate specification and morphogenetic movement at the primitive streak.

Although FGF signaling plays an integral role in the migration and patterning of mesoderm at gastrulation, the mechanism and downstream targets of FGF activity have remained elusive. Here, we demonstrate that FGFR1 orchestrates the epithelial to mesenchymal transition and morphogenesis of mesoderm at the primitive streak by controlling Snail and E-cadherin expression. Furthermore, we show that FGFR1 functions in mesoderm cell fate specification by positively regulating Brachyury and Tbx6 expression.

Mouse-based phenogenomics for modelling human disease.

The powerful and wide-ranging genetic tools available in the laboratory mouse make it the major experimental model for studying mammalian gene function in vivo and modelling human disease traits. Large-scale random mutagenesis approaches, either gene-driven or phenotype-driven, promise to identify new clinically relevant phenotypes and their associated genes. Development of appropriate tools for assessing clinical phenotypes in mice is a crucial component of these endeavours, as is the establishment of the infrastructure for archiving and distribution of the growing mutant resource to the community.

Liver organogenesis promoted by endothelial cells prior to vascular function.

The embryonic role of endothelial cells and nascent vessels in promoting organogenesis, prior to vascular function, is unclear. We find that early endothelial cells in mouse embryos surround newly specified hepatic endoderm and delimit the mesenchymal domain into which the liver bud grows. In flk-1 mutant embryos, which lack endothelial cells, hepatic specification occurs, but liver morphogenesis fails prior to mesenchyme invasion.

Mining mouse microarray data.

Microarrays of mouse genes are now available from several sources, and they have so far given new insights into gene expression in embryonic development, regions of the brain and during apoptosis. Microarray data posted on the internet can be reanalyzed to study a range of questions.

Placental development: lessons from mouse mutants.

The placenta is the first organ to form during mammalian embryogenesis. Problems in its formation and function underlie many aspects of early pregnancy loss and pregnancy complications in humans. Because the placenta is critical for survival, it is very sensitive to genetic disruption, as reflected by the ever-increasing list of targeted mouse mutations that cause placental defects.

Chimaeras and mosaics for dissecting complex mutant phenotypes.

Back at the first half of the 1980s, there was no mammalian experimental embryology in Hungary. One of us, AN, took up the challenge of establishing a small group in the field. In the absence of local information, AN and his former colleague, Andras Paldi (AP), used their tourist passport to visit several laboratories in Western Europe and collect information and advice.

FoxH1 (Fast) functions to specify the anterior primitive streak in the mouse.

The node and the anterior visceral endoderm (AVE) are important organizing centers that pattern the mouse embryo by establishing the anterior-posterior (A-P), dorsal-ventral (D-V), and left-right (L-R) axes. Activin/nodal signaling through the Smad2 pathway has been implicated in AVE formation and in morphogenesis of the primitive streak, the anterior end of which gives rise to the node. The forkhead DNA-binding protein, FoxH1 (or Fast), functions as a Smad DNA-binding partner to regulate transcription in response to activin signaling.

Vascular patterning defects associated with expression of activated Notch4 in embryonic endothelium.

Notch proteins function as receptors for membrane-bound ligands (Jagged and Delta-like) to regulate cell-fate determination. We have investigated the role of Notch signaling in embryonic endothelium of the mouse by expressing an activated form of the Notch4 protein in vasculature under the regulation of the Flk1 (VEGFR) locus. Expression of activated Notch4 results in a growth and developmental delay and embryonic lethality at about 10 days postcoitum.

Direct neural fate specification from embryonic stem cells: a primitive mammalian neural stem cell stage acquired through a default mechanism.

Little is known about how neural stem cells are formed initially during development. We investigated whether a default mechanism of neural specification could regulate acquisition of neural stem cell identity directly from embryonic stem (ES) cells. ES cells cultured in defined, low-density conditions readily acquire a neural identity.

Diethylstilbestrol regulates trophoblast stem cell differentiation as a ligand of orphan nuclear receptor ERR beta.

The orphan nuclear receptor ERR beta is expressed in undifferentiated trophoblast stem cell lines and extraembryonic ectoderm, and genetic ablation of ERR beta results in abnormal trophoblast proliferation and precocious differentiation toward the giant cell lineage. Here, we show that the synthetic estrogen diethylstilbestrol (DES) promotes coactivator release from ERR beta and inhibits its transcriptional activity. Strikingly, treatment of trophoblast stem cells with DES led to their differentiation toward the polyploid giant cell lineage.

Otx2 and HNF3beta genetically interact in anterior patterning.

Patterning the developing nervous system in the mouse has been proposed to depend on two separate sources of signals, the anterior visceral endoderm (AVE) and the node or organizer. Mutation of the winged-helix gene HNF3beta leads to loss of the node and its derivatives, while mutation of the homeobox gene Otx2 results in loss of head structures, apparently at least partially because of defects in the AVE. To investigate the potential genetic interactions between the two signaling centers, we crossed Otx2+/- and HNF3beta+/- mice and found that very few Otx2+/-;HNF3beta+/- double heterozygous mutants survived to weaning.

The retinoic acid-inactivating enzyme CYP26 is essential for establishing an uneven distribution of retinoic acid along the anterio-posterior axis within the mouse embryo.

Retinoic acid (RA), a derivative of vitamin A, plays a pivotal role in vertebrate development. The level of RA may be determined by the balance between its synthesis and degradation. We have examined the role of CYP26, a P450 enzyme that may degrade RA, by generating mutant mice that lack CYP26.

Role of N-myc in the developing mouse kidney.

N-myc is a transcription factor expressed in the developing metanephric kidney and other organs. In mice, complete disruption of the N-myc gene results in fetal death on the first day of renal organogenesis. In addition to the null N-myc allele, others have generated a hypomorphic N-myc allele.

Rom-1 is required for rod photoreceptor viability and the regulation of disk morphogenesis.

The homologous membrane proteins Rom-1 and peripherin-2 are localized to the disk rims of photoreceptor outer segments (OSs), where they associate as tetramers and larger oligomers. Disk rims are thought to be critical for disk morphogenesis, OS renewal and the maintenance of OS structure, but the molecules which regulate these processes are unknown. Although peripherin-2 is known to be required for OS formation (because Prph2-/- mice do not form OSs; ref.

The SH2 tyrosine phosphatase shp2 is required for mammalian limb development.

The tyrosine phosphatase Shp2 is recruited into tyrosine-kinase signalling pathways through binding of its two amino-terminal SH2 domains to specific phosphotyrosine motifs, concurrent with its re-localization and stimulation of phosphatase activity. Shp2 can potentiate signalling through the MAP-kinase pathway and is required during early mouse development for gastrulation. Chimaeric analysis can identify, by study of phenotypically normal embryos, tissues that tolerate mutant cells (and therefore do not require the mutated gene) or lack mutant cells (and presumably require the mutated gene during their developmental history).

The organizer factors Chordin and Noggin are required for mouse forebrain development.

In mice, there is evidence suggesting that the development of head and trunk structures is organized by distinctly separated cell populations. The head organizer is located in the anterior visceral endoderm (AVE) and the trunk organizer in the node and anterior primitive streak. In amphibians, Spemann's organizer, which is homologous to the node, partially overlaps with anterior endoderm cells expressing homologues of the AVE markers cerberus, Hex and Hesx1.