15 research outputs found
The role ofthe transcription factor GATA-6 in mouse embryonic development
Different members of the GAT A family of transcription factors have
been studied extensively in our lab. The role of GAT A-I in the differentiation
of erythroid blood cells and of GATA-3 during T-lymphocyte development are
two typical examples. GATA-6 is the most recently characterized member of
the family. Based on its expression pattern during mouse embryonic
developmentfor a role for GATA-6 in cardiogenesis had been speculated.
To investigate what role GATA-6 may play during embryogenesis we
used targeted inactivation of the gene in Embryonic Stem (ES) cells (chapter
2). Unexpectedly, homozygote mutant embryos die just after implantation at
embryonic day 5.5. Generation of chimeric embryos in which the GATA-6
mutant cell population was confmed in either the embryo or to the
extraembryonic tissues revealed that the primary defect in GATA-6 null
embryos lies in an extraembryonic cell lineage. Further in vivo and in vitro
analysis of the mutant embryos suggested that the affected lineage is the
visceral yolk sac endoderm, a derivative of the primitive endoderm.
Cardiogenesis could not be directly studied since mutant embryos die
well before heart development starts (embryonic day 8.5). However, in
chimeric embryos, GATA-6 -/- ES cells give rise to cardiomyocytes in
apparently normal hearts, possibly due to redundant functions with the coexpressed
GATA-4 and -5. In contrast, GATA-6 is the only member of the
family that is expressed in the lung endoderm. Following on a published
observation showing no contribution of GATA-6 null ES cells to the lung
epithelium, we decided to generate more highly chimeric embryos to analyze
the development of the lung, which is a derivative of another endoderm
lineage, the definitive endoderm (chapter 3). Surprisingly, we found that lung
endoderm can be formed from GATA-6 mutant cells. However, this mutant
endoderm has subsequent morphogenetic and differentiation defects.
The importance of GATA-6 protein levels during lung development
was confirmed by a different approach. The gene was overexpressed in
transgenic mice with a pulmonary epithelium specific promoter (chapter 4).
High levels of the protein resulted in branching defects and more interestingly
in a block oflung endoderm differentiation to distal alveolar epithelium
The transcription factor GATA6 is essential for early extraembryonic development
The gene coding for the murine transcription factor GATA6 was inactivated
by insertion of a beta-galactosidase marker gene. The analysis of
heterozygote GATA6/lacZ mice shows two inductions of GATA6 expression
early in development. It is first expressed at the blastocyst stage in
part of the inner mass and in the trophectoderm. The second wave of
expression is in parietal endoderm (Reichert's membrane) and the mesoderm
and endoderm that form the heart and gut. Inactivation leads to a
lethality shortly after implantation (5.5 days postcoitum). Chimeric
experiments show this to be caused by an indirect effect on the epiblast
due to a defect in an extraembryonic tissue
The transcription factor GATA6 is essential for branching morphogenesis and epithelial cell differentiation during fetal pulmonary development
Recent loss-of-function studies in mice show that the transcription factor GATA6 is important for visceral endoderm differentiation. It is also expressed in early bronchial epithelium and the observation that this tissue does not receive any contribution from Gata6 double mutant embryonic stem (ES) cells in chimeric mice suggests that GATA6 may play a crucial role in lung development. The aim of this study was to determine the role of GATA6 in fetal pulmonary development. We show that Gata6 mRNA is expressed predominantly in the developing pulmonary endoderm and epithelium, but at E15.5 also in the pulmonary mesenchyme. Blocking or depleting GATA6 function results in diminished branching morphogenesis both in vitro and in vivo. TTF1 expression is unaltered in chimeric lungs whereas SPC and CC10 expression are attenuated in abnormally branched areas of chimeric lungs. Chimeras generated in a ROSA26 background show that endodermal cells in these abnormally branched areas are derived from Gata6 mutant ES cells, implicating that the defect is intrinsic to the endoderm. Taken together, these data demonstrate that GATA6 is not essential for endoderm specification, but is required for normal branching morphogenesis and late epithelial cell differentiation
Transcription and Chromatin Organization of a Housekeeping Gene Cluster Containing an Integrated β-Globin Locus Control Region
The activity of locus control regions (LCR) has been correlated with chromatin decondensation, spreading of active chromatin marks, locus repositioning away from its chromosome territory (CT), increased association with transcription factories, and long-range interactions via chromatin looping. To investigate the relative importance of these events in the regulation of gene expression, we targeted the human β-globin LCR in two opposite orientations to a gene-dense region in the mouse genome containing mostly housekeeping genes. We found that each oppositely oriented LCR influenced gene expression on both sides of the integration site and over a maximum distance of 150 kilobases. A subset of genes was transcriptionally enhanced, some of which in an LCR orientation-dependent manner. The locus resides mostly at the edge of its CT and integration of the LCR in either orientation caused a more frequent positioning of the locus away from its CT. Locus association with transcription factories increased moderately, both for loci at the edge and outside of the CT. These results show that nuclear repositioning is not sufficient to increase transcription of any given gene in this region. We identified long-range interactions between the LCR and two upregulated genes and propose that LCR-gene contacts via chromatin looping determine which genes are transcriptionally enhanced
The mammalian gene function resource: The International Knockout Mouse Consortium
In 2007, the International Knockout Mouse Consortium (IKMC) made the ambitious promise to generate mutations in virtually every protein-coding gene of the mouse genome in a concerted worldwide action. Now, 5 years later, the IKMC members have developed highthroughput gene trapping and, in particular, gene-targeting pipelines and generated more than 17,400 mutant murine embryonic stem (ES) cell clones and more than 1,700 mutant mouse strains, most of them conditional. A common IKMC web portal (www.knockoutmouse.org) has been established, allowing easy access to this unparalleled biological resource. The IKMC materials considerably enhance functional gene annotation of the mammalian genome and will have a major impact on future biomedical research
The mammalian gene function resource: the International Knockout Mouse Consortium.
In 2007, the International Knockout Mouse Consortium (IKMC) made the ambitious promise to generate mutations in virtually every protein-coding gene of the mouse genome in a concerted worldwide action. Now, 5 years later, the IKMC members have developed high-throughput gene trapping and, in particular, gene-targeting pipelines and generated more than 17,400 mutant murine embryonic stem (ES) cell clones and more than 1,700 mutant mouse strains, most of them conditional. A common IKMC web portal (www.knockoutmouse.org) has been established, allowing easy access to this unparalleled biological resource. The IKMC materials considerably enhance functional gene annotation of the mammalian genome and will have a major impact on future biomedical research