Biomedical subjects

P Gruss

Publications and source records attributed to P Gruss.

At least 91 records · Page 5Linked to original sources

PubMed1998

Pax6 controls radial glia differentiation in the cerebral cortex.

Radial glia cells perform a dual function in the developing nervous system as precursor cells and guides for migrating neurons. We show here that during forebrain neurogenesis, the transcription factor Pax6 is specifically localized in radial glia cells of the cortex but not of the basal telencephalon. In Pax6-deficient mice, cortical radial glia cells were altered in their morphology, number, tenascin-C (TN-C) expression, and cell cycle. We show that some of these alterations are cell-autonomous, whereas others were rescued by coculturing with wild-type cortical cells. Our results suggest that Pax6 plays an essential role in the differentiation of cortical radial glia. Thus, despite their widespread distribution, radial glia cells are regionally specified in the developing CNS.

Animals↗

PubMed1998

Molecular regulators involved in vertebrate eye development.

Development of the eye can be subdivided into three phases. The first phase is the formation of the major structures of the eye by the processes of induction and regional specification. The second is the maturation of these structures to form the functional eye, and the third phase is the formation of neuronal connections between retina and the optic tectum. These processes are tightly regulated by signalling cascades that direct axonal outgrowth, cellular proliferation and differentiation. Some members of these signalling cascades have been identified in recent studies. These include secreted factors which transmit signals extracellularly, and receptors and transcription factors which are members of intracellular signalling pathways that respond to extracellular signals. This review summarizes the recent research that has implicated these factors in playing a role in eye development on the basis of functional or expression criteria.

Animals↗

PubMed1998

Pax3 and Pax7 are expressed in commissural neurons and restrict ventral neuronal identity in the spinal cord.

Pax3 and Pax7 are transcription factors sharing high sequence identity and overlapping patterns of expression in particular in the dorsal spinal cord. Analysis of Pax3 and Pax7 double mutant mice demonstrates that both genes share redundant functions to restrict ventral neuronal identity in the spinal cord. In their absence, the En1 expression domain is expanded dorsally but that of Evx1 is not affected. In addition, Pax3 and Pax7 are expressed in commissural neurons and double mutant embryos exhibit highly reduced ventral commissure. Our findings reveal two distinct regulatory pathways for spinal cord neurogenesis, only one of which is dependent on Pax3/7 and 6.

Animals↗

PubMed1998

Pax 4 and 6 regulate gastrointestinal endocrine cell development.

The mechanisms behind the cell-specific and compartmentalized expression of gut and pancreatic hormones is largely unknown. We hereby report that deletion of the Pax 4 gene virtually eliminates duodenal and jejunal hormone-secreting cells, as well as serotonin and somatostatin cells of the distal stomach, while deletion of the Pax 6 gene eliminates duodenal GIP cells as well as gastrin and somatostatin cells of the distal stomach. Thus, together, these two genes regulate the differentiation of all proximal gastrointestinal endocrine cells and reflect common pathways for pancreatic and gastrointestinal endocrine cell differentiation.

Animals↗

PubMed1998

Follicular cells of the thyroid gland require Pax8 gene function.

The thyroid gland develops from two distinct embryonic lineages: follicular cells (which produce thyroxine) and parafollicular C-cells (which produce calcitonin) are of endodermal and neural crest origin, respectively. Little is known about the molecular mechanisms governing the generation of these different cell types. Mice lacking the transcription factor Ttf1 lack both cell types and thus are unable to develop a thyroid gland. By analysis of Pax8-/- mice, we demonstrate that Pax8 is required for the formation of the follicular cells in the thyroid. We present evidence that Pax8 is necessary for providing cues for the differentiation of competent endoderm primordia into thyroxin-producing follicular cells.

Animals↗

PubMed1998

Vax1 is a novel homeobox-containing gene expressed in the developing anterior ventral forebrain.

The vertebrate forebrain is formed at the rostral end of the neural plate under the regulation of local and specific signals emanating from both the endomesoderm and neuroectoderm. The development of the rostral and ventral forebrain in particular was difficult to study, mainly because no specific markers are available to date. Here, we report the identification of Vax1, a novel homeobox-containing gene identified in mouse, Xenopus and human. It is closely related to members of the Not and Emx gene families, all of which are required for the formation of structures where they are expressed. In mouse and Xenopus, Vax1 expression first occurs in the rostral neural plate, in the medial anterior neural ridge and adjacent ectoderm. Later, at midgestation in the mouse and tadpole stage in Xenopus, the expression remains confined in the derivatives of this territory which differentiate into rostromedial olfactory placode, optic nerve and disc, and anterior ventral forebrain. Together, these observations suggest that Vax1 could have an early evolutionary origin and could participate in the specification and formation of the rostral and ventral forebrain in vertebrates. Comparison of the limits of the expression territory of Vax1 with that of Dlx1, Pax6 and Emx1 indicates that the corticostriatal ridge is a complex structure with distinct identifiable genetic compartments. Besides, the study of Vax1 expression in Pax6-deficient homozygous brains indicates that its regulation is independent of Pax6, although the expression patterns of these two genes appear complementary in wild-type animals. Vax1 chromosomal location is mapped at the distal end of the mouse chromosome 19, linked with that of Emx2. These two genes may have arisen by tandem duplication. The Vax1 gene is thus an interesting new tool to study the rostral ventral forebrain patterning, morphogenesis and evolution as well as the terminal differentiation of the forebrain in mouse and Xenopus.

Amino Acid Sequence↗

PubMed1998

Differentiation of the mouse embryoid bodies grafted on the chorioallantoic membrane of the chick embryo.

In order to test the developmental potential of the mouse embryonic-stem-cell-derived embryoid bodies as chorioallantoic grafts, the embryoid bodies were transplanted to the chorioallantoic membrane (CAM) of the chick embryo. The graft implantation was achieved if the embryoid bodies were transferred to the CAM into the blood drop created by gentle laceration of a CAM blood vessel. The resulting tumors were recovered after 10 days, when they were rounded white elevations, up to 1 mm big. Histological analysis showed that they were made of groups of compacted epithelial-like cells and fibroblast-like spindle shaped cells divided by the CAM mesenchyme. The grafting caused angiogenic response of the CAM. Blood vessels converged toward the tumor and spread through the CAM mesenchyme among the groups of condensed cells. Although the embryonic bodies were able to implant to the CAM of the chick, their differentiation did not result in a wide variety of differentiated cell types or in the formation of complex structures resembling morphogenesis. Thus in comparison with in vitro differentiation of embryoid bodies on an adhesive substrate, or in vivo differentiation under the mouse kidney capsule, the differentiation potential of embryoid bodies as chorioallantoic grafts appeared restricted. However, we suggest that the accessibility of the chorioallantoic graft can be an advantage for future experiments.

Allantois↗

PubMed1997

Conserved biological function between Pax-2 and Pax-5 in midbrain and cerebellum development: evidence from targeted mutations.

The development of two major subdivisions of the vertebrate nervous system, the midbrain and the cerebellum, is controlled by signals emanating from a constriction in the neural primordium called the midbrain/hindbrain organizer (Joyner, A. L. (1996) Trends Genet. 12, 15-201). The closely related transcription factors Pax-2 and Pax-5 exhibit an overlapping expression pattern very early in the developing midbrain/hindbrain junction. Experiments carried out in fish (Krauss, S., Maden, M., Holder, N. & Wilson, S. W. (1992) Nature (London) 360, 87-89) with neutralizing antibodies against Pax-b, the orthologue of Pax-2 in mouse, placed this gene family in an regulatory cascade necessary for the development of the midbrain and the cerebellum. The targeted mutation of Pax-5 has been reported to have only slight effects in the development of structures derived from the isthmic constriction, whereas the Pax-2 null mutant mice show a background-dependent phenotype with varying penetrance. To test a possible redundant function between Pax-2 and Pax-5 we analyzed the brain phenotypes of mice expressing different dosages of both genes. Our results demonstrate a conserved biological function of both proteins in midbrain/hindbrain regionalization. Additionally, we show that one allele of Pax-2, but not Pax-5, is necessary and sufficient for midbrain and cerebellum development in C57BL/6 mice.

Animals↗

PubMed1997

Cre-mediated gene deletion in the mammary gland.

To delete genes specifically from mammary tissue using the Cre-lox system, we have established transgenic mice expressing Cre recombinase under control of the WAP gene promoter and the MMTV LTR. Cre activity in these mice was evaluated by three criteria. First, the tissue distribution of Cre mRNA was analyzed. Second, an adenovirus carrying a reporter gene was used to determine expression at the level of single cells. Third, tissue specificity of Cre activity was determined in a mouse strain carrying a reporter gene. In adult MMTV-Cre mice expression of the transgene was confined to striated ductal cells of the salivary gland and mammary epithelial cells in virgin and lactating mice. Expression of WAP-Cre was only detected in alveolar epithelial cells of mammary tissue during lactation. Analysis of transgenic mice carrying both the MMTV-Cre and the reporter transgenes revealed recombination in every tissue. In contrast, recombination mediated by Cre under control of the WAP gene promoter was largely restricted to the mammary gland but occasionally observed in the brain. These results show that transgenic mice with WAP-Cre but not MMTV-Cre can be used as a powerful tool to study gene function in development and tumorigenesis in the mammary gland.

Adenoviridae↗

PubMed1997

Pax6 is required for differentiation of glucagon-producing alpha-cells in mouse pancreas.

The functional unit of the endocrine pancreas is the islet of Langerhans. Islets are nested within the exocrine tissue of the pancreas and are composed of alpha-, beta-, delta- and gamma-cells. beta-Cells produce insulin and form the core of the islet, whereas alpha-, delta- and gamma-cells are arranged at the periphery of the islet and secrete glucagon, somatostatin and a pancreatic polypeptide, respectively. Little is known about the molecular and genetic factors regulating the lineage of the different endocrine cells. Pancreas development is known to be abolished in Pdx1-mutant mice and Pax4 mutants lack insulin-producing beta-cells. Here we show that the paired-box gene Pax6 is expressed during the early stages of pancreatic development and in mature endocrine cells. The pancreas of Pax6 homozygous mutant mice lack glucagon-producing cells, suggesting that Pax6 is essential for the differentiation of alpha-cells. As mice lacking Pax4 and Pax6 fail to develop any mature endocrine cells, we conclude that both Pax genes are required for endocrine fate in the pancreas.

Animals↗

PubMed1997

Evidence for the stochastic integration of gene trap vectors into the mouse germline.

A large scale insertional mutagenesis experiment was performed in embryonic stem (ES) cells by introducing two types of gene trap vectors into the genome. These cell lines carrying mutations were introduced into the mouse germline. In order to assess the feasibility of a large scale cloning of the targeted genes from these lines, we have isolated and characterized 55 trapped exons from the corresponding ES cells. Analysis of the data has revealed that vectors containing or lacking an internal ribosome entry site (IRES) can integrate into the ES cell genome stochastically. The targeted genes comprise 30% known genes, 20% expressed sequence tags (ESTs) and 50% novel or unknown genes. The known genes belong to several major classes and represent complete or partial knockouts. Using currently available methods or modifications of them, it should be feasible to do a large scale cloning of trapped genes from the mouse ES cell lines.

Animals↗

PubMed1997

The Pax4 gene is essential for differentiation of insulin-producing beta cells in the mammalian pancreas.

The mammalian pancreas contains two distinct cell populations: endocrine cells which secrete hormones into the bloodstream, and exocrine cells, which secrete enzymes into the digestive tract. The four endocrine cell types found in the adult pancreas-(alpha, beta, delta and PP-synthesize glucagon, insulin, somatostatin and pancreatic polypeptide, respectively. All of these endocrine cells arise from common multipotent precursors, which coexpress several hormones when they start to differentiate. Expression of some homeobox genes in the early developing pancreas has been reported. The Pax4 gene is expressed in the early pancreas, but is later restricted to beta cells. Inactivation of Pax4 by homologous recombination results in the absence of mature insulin- and somatostatin-producing cells (beta and delta, respectively) in the pancreas of Pax4 homozygous mutant mice, but glucagon-producing alpha cells are present in considerably higher numbers. We propose that the early expression of Pax4 in a subset of endocrine progenitors is essential for the differentiation of the beta and delta cell lineages. A default pathway would explain the elevated number of alpha cells in the absence of Pax4.

Animals↗

PubMed1997

Transgenic mouse model for studying the transcriptional activity of the p53 protein: age- and tissue-dependent changes in radiation-induced activation during embryogenesis.

The p53 tumor suppressor protein is a sequence-specific transcriptional activator of target genes. Exposure of cells to DNA damage results in accumulation of biochemically active p53, with consequent activation of p53-responsive promoters. In order to study how the transcriptional activity of the p53 protein is regulated in vivo, a transgenic mouse strain was generated. These mice harbor the p53-dependent promoter of the mdm2 gene, fused to a lacZ reporter gene. Induction of lacZ activity by DNA damage (ionizing radiation) was monitored in embryos of different p53 genotypes. The transgenic promoter was substantially activated in vivo following irradiation; activation required functional p53. The activation pattern became more restricted with increasing embryo age, as well as with the state of differentiation of a given tissue. Generally, maximal p53 activation occurred in rapidly proliferating, relatively less differentiated cells. A striking extent of haploinsufficiency was revealed-induction of promoter activity was far less efficient in mice carrying only one wild-type p53 allele. This suggests that normal levels of cellular p53 are limiting, and any further reduction already compromises the p53 response significantly. Thus, the activation potential of p53 is tightly controlled in vivo, both spatially and temporally, and an important element in this control is the presence of limiting basal levels of activatable p53.

Alleles↗

PubMed1997

An alpha-E-catenin gene trap mutation defines its function in preimplantation development.

Catenins are proteins associated with the cytoplasmic domain of cadherins, a family of transmembrane cell adhesion molecules. The cadherin-catenin adhesion system is involved in morphogenesis during development and in the maintenance of the integrity of different tissue types. Using a gene trap strategy, we have isolated a mouse mutation for the gene encoding the alpha-E-catenin. This form of the alpha-catenin appears frequently coexpressed with E-cadherin in epithelial cell types. The mutation obtained eliminates the carboxyl-terminal third of the protein but nevertheless provokes a complete loss-of-function phenotype. Homozygous mutants show disruption of the trophoblast epithelium (the first differentiated embryonic tissue), and development is consequently blocked at the blastocyst stage. This phenotype parallels the defects observed in E-cadherin mutant embryos. Our results show the requirement of the alpha-E-catenin carboxy terminus for its function and represent evidence of the role of the alpha-E-catenin in vivo, identifying this molecule as the natural partner of the E-cadherin in trophoblast epithelium.

Animals↗

PubMed1997

Germ line chimeras from female ES cells.

Murine embryonic stem cells (ES cells) are pluripotent cells that can contribute to all tissues of developing mice including the germ line when aggregated with 8-cell-stage embryos or injected into the blastocoel cavity of murine blastocysts. As well as for in vitro studies, they are used to introduce mutations into the murine genome, thereby producing new mutant mouse lines. All ES cell lines so far described that contribute to the germ line have been male. However, for many studies female ES cell lines may be essential. Female ES cells may be particularly useful for mutating genes located on the X chromosome which would otherwise be hemizygously lethal in males. We show here that female ES cells are able to form germ line chimeras and to sex convert a male host embryo.

Animals↗

PubMed1997

Paired-related murine homeobox gene expressed in the developing sclerotome, kidney, and nervous system.

We isolated a murine homeobox containing gene, Uncx4.1. The homeodomain sequence exhibits 88% identity to the unc-4 protein at the amino acid level. In situ hybridization analysis revealed that Uncx4.1 is expressed in the paraxial mesoderm, in the developing kidney, and central nervous system. The most intriguing expression domain is the somite, where it is confined to the caudal part of the newly formed somite and subsequently restricted to the caudal domain of the developing sclerotome. In the central nervous system, Uncx4.1 is detected in the developing spinal cord, hindbrain, mesencephalon, and telencephalon. The temporal and spatial expression pattern suggests that Uncx4.1 may play an important role in kidney development and in the differentiation of the sclerotome and the nervous system.

Amino Acid Sequence↗

PubMed1997

Expression of Meis2, a Knotted-related murine homeobox gene, indicates a role in the differentiation of the forebrain and the somitic mesoderm.

Knotted (Kn) genes are expressed within restricted domains of the plant meristems and play a key role in the control of plant morphogenesis. We have isolated the Kn-related gene Meis2 in mouse, which labels the lateral somitic compartment and its derivatives during early mouse embryogenesis and later becomes a marker for the dorso-ectodermal region overlying cells of the paraxial mesoderm. Meis2 is also highly expressed in specific areas of the developing central nervous system from embryonic day 9 (e9) onward. In later developmental stages, a strong expression is detectable in differentiating nuclei and regions of the forebrain, midbrain, hindbrain, and spinal cord. This temporal and spatial expression pattern suggests that Meis2 may play an important role in the cascade of induction leading to somitic differentiation as well as in brain regionalization and histogenesis.

Amino Acid Sequence↗

PubMed1997

Pax-2 in the chiasm.

Pax genes are expressed in specific patterns in the nervous system during development and in the adult. Recent findings suggest a link between the expression of Pax-2 and axonal guidance. Mice with a targeted deletion of Pax-2 are an excellent tool for studying axonal pathfinding at the molecular level, especially with respect to the optic chiasm. The date reviewed here suggest that Pax-2 regulates the expression of surface molecules involved in contact attraction and that the mutual regulation of the expression of Pax-2 and the Sonic hedgehog gene is of importance in the formation of the chiasm region.

Animals↗