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Biomedical subjects

H Eggert

Publications and source records attributed to H Eggert.

At least 19 recordsLinked to original sources
PubMed2001

The murine Wilms tumor suppressor gene (wt1) locus.

The Wilms tumor suppressor gene WT1 plays a crucial role in the etiology of various human diseases as well as in the development of specific organs including the kidneys, gonads and the spleen. At present the human as well as the Fugu wt1 locus have been characterized. We have used a PAC clone to analyze the murine wt1 locus and report here the structure of the wt1 gene as well as a characterization of the nine wt1 introns regarding their size and sequence at the exon/intron and intron/exon boundaries. In addition we provide a restriction map of the murine wt1 locus which should prove useful for the cloning of various constructs designed for the generation of mouse models. Prompted by the existence of a WT1 antisense transcript in humans we also examined strand-specific transcription at the murine wt1 locus. Our analysis suggests that there is no detectable antisense transcription of sequences within or immediately downstream of wt1 exon 1. We find, however, evidence for a divergent transcript which encompasses sequences at and around minor transcriptional initiation sites of wt1 and which is transcribed in the opposite direction. Despite the very high degree of similarity between the human and the murine wt1 sequence and expression as well as the presence of divergent transcripts in both cases, the existence of antisense transcription does not seem to be conserved between the two species.

Amino Acid Sequence↗
PubMed2001

Effects of the heterogeneous nuclear ribonucleoprotein U (hnRNP U/SAF-A) on glucocorticoid-dependent transcription in vivo.

The glucocorticoid receptor (GR) is a ligand dependent transcription factor, which regulates the transcription of multiple hormone-dependent genes. The transcriptional regulation by GR takes place by interaction of GR with the basal transcription machinery and by recruiting glucocorticoid receptor interacting proteins (GRIPs). Previously we identified hnRNP U/SAF-A as a factor interfering with GR-dependent transcription by repressing glucocorticoid induced activation. To gain insight into the mechanisms that govern this interference, we have now investigated the transcription of GR-dependent reporter genes in Ltk(-) cells transiently transfected with a variety of hnRNP U constructs. We demonstrate that a hnRNP U construct lacking the GR-binding domain acts as a dominant negative factor that now enhances GR-driven transcription. In addition, hnRNP U repression of glucocorticoid induced transcription was found to be dependent on the amount of cotransfected GR, where a high amount of GR leads to ligand-inducible repression of GR-dependent reporter gene activity by hnRNP U, whereas low amounts of GR showed nearly no effect. The relative concentrations of GR, hnRNP U and DNA-binding sites for GR are important for the effect of hnRNP U on transcription, suggesting a model where hnRNP-U acts as a storage site for intranuclear GR.

Binding Sites↗
PubMed2000

Distinct proteins interacting with the glucocorticoid receptor.

The glucocorticoid receptor (GR) is a hormone-dependent transcription factor that modulates gene transcription by binding to its response element, interacting with other transcription factors, contacting the basal transcription machinery and by interacting with several intermediary proteins, such as coactivators. Here we discuss the most prominent examples for interacting transcription factors, interacting proteins that belong to the basal transcription apparatus and intermediary factors. Furthermore, we describe a new class of GR-interacting proteins (GRIPs) which have been identified by a blotting technique, using a radioactively labeled GR/GRE complex as a probe to identify proteins that interact with the activated GR. Two of these GRIPs, termed GRIP170 and GRIP 120, which were identified by biochemical purification and microsequencing and have turned out to play a role in modulating GR-mediated transcription, are discussed in detail.

Animals↗
PubMed1998

Molecular screening for P-element insertions in a large genomic region of Drosophila melanogaster using polymerase chain reaction mediated by the vectorette.

As an alternative to existing methods for the detection of new insertions during a transposon mutagenesis, we adapted the method of vectorette ligation to genomic restriction fragments followed by PCR to obtain genomic sequences flanking the transposon. By combining flies containing a defined genomic transposon with an excess of flies containing unrelated insertion sites, we demonstrate the specificity and sensitivity of the procedure in the detection of integration events. This method was applied in a transposon-tagging screen for BJ1, the Drosophila homolog of the vertebrate gene Regulator of Chromosome Condensation (RCCI). Genetic mobilization of a single genomic P element was used to generate preferentially new local insertions from which integrations into a genomic region surrounding the BJ1 gene were screened. Flies harboring new insertions were phenotypically selected on the basis of the zeste1-dependent transvection of white. We detected a single transposition to a 13-kb region close to the BJ1 gene among 6650 progeny that were analyzed. Southern analysis of the homozygous line confirmed the integration 3 kb downstream of BJ1.

Animals↗
PubMed1995

Dynamic changes in gene expression during in vitro differentiation of mouse embryonic stem cells.

The expression pattern of protein tyrosine kinases (PTK) and phosphatases (PTP) was determined during the first eight days of in vitro differentiation of mouse embryonic stem (ES) cells. DNA fingerprinting of catalytic domains amplified from cDNA revealed dynamic changes in expression of previously described genes. A novel PTP is expressed in undifferentiated ES cells, and is down-regulated during in vitro differentiation.

Animals↗
PubMed1994

Gene inactivation in Drosophila mediated by the Polycomb gene product or by position-effect variegation does not involve major changes in the accessibility of the chromatin fibre.

In Drosophila position effect variegation and Polycomb-dependent regulation of homeotic gene expression are phenomena in which genes are inactivated in a clonally inherited manner. In both processes inactivation involves proteins that interact with the chromosome at or close to the position of inactivated genes. Two models have been proposed to explain this form of genetic silencing. In one, cooperative concatamerisation of a large multisubunit protein complex packages the chromatin fibre into a higher order structure, which is inaccessible for the transcription apparatus. In the second, the chromatin fibre is left unaltered but the region to be silenced is assigned to a compartment within the nucleus to which not all transcription factors have access. To distinguish between these types of model we have used the ligation-mediated PCR procedure to quantitate the accessibility of restriction sites in the chromatin fibre in both the active and inactivated forms. By making use of appropriate mutations and tissues we show that the inactivation of genes by Polycomb or by position effect variegation is not accompanied by a substantial change in the accessibility of the fibre. These results favour models in which the inactivation is achieved by sequestration of the silenced region in a particular nuclear compartment rather than by a chromatin packaging model.

Animals↗
PubMed1992

The elusive nuclear matrix.

The structure of the interphase nucleus is a major area of current interest in cell biology. It is thought likely that the nucleus is organised around some form of structural matrix and that this matrix will play a role in processes as diverse as chromosome replication and the integration of gene expression. However, the structure of the matrix within the nucleus has remained elusive, largely because attempts to define it have been dogged by technical problems arising from the great complexity of this organelle. This situation is now being changed by the application of in situ analysis and of molecular genetic methodologies which are opening up this hitherto intractable field.

Animals↗
PubMed1991

An ectopic copy of the Drosophila ftz associated SAR neither reorganizes local chromatin structure nor hinders elution of a chromatin fragment from isolated nuclei.

In vitro assays using detergent extracted nuclei allow the operational definition of SARs--specific sequences in the chromosome which are thought to interact with a structural matrix or scaffold. This interaction results in the formation of large stable protein-DNA complexes. We have used P-element transformation to introduce a characterized SAR into the Drosophila genome. The standard assay, which uses detergent extracted nuclei, shows that the ectopic SAR is indeed bound to the scaffold. However, in unextracted nuclei, a chromatin fragment containing the SAR sequence is eluted from the nucleus as readily as a fragment which lacks an SAR. Furthermore, an analysis of the accessibility of the neighbouring chromosomal restriction sites in unextracted nuclei indicates that the introduction of this ectopic SAR does not influence the local structure of chromatin. We conclude that the ectopic SAR site is not attached to a nuclear scaffold or matrix in vivo.

Animals↗
PubMed1990

Restriction enzymes have limited access to DNA sequences in Drosophila chromosomes.

Sequence specific DNA binding proteins in eukaryotic cells must efficiently locate their binding sites in chromosomes. Restriction enzymes provide a simple model system with which to investigate the factors which influence this process. We have used P element mediated transformation to introduce a DNA fragment containing a set of characterized restriction sites into the Drosophila germline. Embryonic nuclei prepared from these transgenic animals were treated with restriction enzymes to probe the accessibility of the target restriction sites. The results show that the insert is within an accessible region of the chromosome and that restriction sites within the inserted sequence can be cut. However, the rate of cutting is biphasic. At each restriction site, a fraction of the chromosomes is cut rapidly after which the remainder is refractory. Similar levels of incomplete cutting are obtained when the same P element construct is examined at a different chromosomal location, when different sequence elements are introduced into the P element vector or when the experiment is carried out on nuclei from different embryonic stages. These results are discussed in terms of how sequence specific DNA binding proteins may locate their genomic targets in vivo.

Animals↗
PubMed1990

DNA intercalating properties of tetrahydro-9-aminoacridines. Synthesis and 23Na NMR spin-lattice relaxation time measurements.

A series of 9-(arylamino)-1,2,3,4-tetrahydroacridines, including the tetrahydro m-AMSA [N-[4-(acridin-9-yl-amino)-3- methoxyphenyl]methanesulfonamide] derivative, has been synthesized. 23Na NMR spin-lattice relaxation rate (1/T1) measurements have been used to study whether these hydrogenated acridines were capable of intercalative binding to calf thymus DNA. The results have been compared to corresponding measurements for 9-aminoacridine, m-AMSA, and MgCl2. All compounds studied were capable of intercalative binding to DNA. However, it was found that the interaction was strongly influenced by substituents on the 9-arylamino group. Thus, tetrahydro m-AMSA was found to intercalate much more weakly with DNA than m-AMSA. Removal of the 3'-methoxy substituent of the 9-arylamino group resulted in intercalation in DNA that was almost as strong as that for m-AMSA.

Aminacrine↗
PubMed1989

Sodium-23 NMR spin-lattice relaxation rate studies of mono- and bis-intercalation in DNA.

23Na spin-lattice relaxation rate (1/T1 = R1) measurements have been used to study the intercalation of a series of 9-aminoacridine derivatives in DNA. The 23Na relaxation rate is strongly dependent upon the amount of intercalator added to a sodium DNA solution. The results are analyzed by a combined use of the ion condensation theory and the quadrupolar relaxation theory of polyelectrolyte solutions. This interpretation shows that the major effect in lowering the relaxation rate by intercalation is not due to the release of sodium ions but is caused by a substantial decrease in the relaxation rate Rb for the remaining bound sodium ions. Likewise, titration of NaDNA solutions with MgCl2 shows that condensation of Mg2+ on the DNA double helix reduces Rb. A good agreement between experiment and theory is found if the average lengthening following intercalation of a 9-aminoacridine moiety is assumed to be approximately 2.7 A. The distinction between mono- and bis-intercalation is clearly indicated by the results. The two bis-intercalating drugs examined are found to bis-intercalate only up to r less than or equal to 0.02. For r greater than 0.02 the drugs apparently mono-intercalate.

Aminoacridines↗
PubMed1981

Measurement of chemiluminescence in freshly drawn human blood. I. Role of granulocytes, platelets, and plasma factors in zymosan-induced chemiluminescence.

The present investigations were undertaken to find out whether chemiluminescence measurements of stimulated granulocytes can be carried out in freshly drawn blood and -- because of the ease of the method -- be introduced into routine diagnostics. Blood was drawn from the cubital vein of healthy volunteers at various times and under various conditions. Subsequently the zymosan induced and luminol amplified chemiluminescence was recorded and analyzed. It could be demonstrated that variations existed between individuals which can, however, be minimized when photon counts obtained under standard conditions were related to the number of granulocytes present in the blood samples. It could be further demonstrated that also platelets are activated by zymosan as well an that they, contribute to the total chemiluminescence by a share of about 5%. Platelet chemiluminescence can effectively be suppressed by aspirin. Opsonising factors in plasma (presumably antibodies and/or complement) play a decisive role in the intensity and kinetics of blood chemiluminescence. Measurements of zymosan induced chemiluminescence in freshly drawn unfractionated and fractionated blood seem to be especially suited to monitor and analyze deviations and defects of the cellular and humoral defence mechanisms.

Aspirin↗
PubMed1977

[Cavernous hemangiomas of the skull. Clinical, radiological and therapeutical aspects].

A series of 26 cases of hemangioma of the skull and review the literature are reported. The frontal localization was most frequent, contrary to the data of the literature suggesting the predominance of the parietal localization. The reported predominance of females has not been confirmed. In the present series the relation of males to females was 17:9. The radiological findings and treatment of hemangiomas are discussed. Direct puncture and injection of contrast medium is the best method for the visualization of the tumor. Treatment should be surgical consisting of total extirpation of the tumor with a margin of the healthy tissues. Direct extirpation is indicated only when soft-tissues are involved and there is no bone lesion. The en-bloque method is the technique of choice.

Adolescent↗