Maternal Wnt/STOP signaling promotes cell division during early Xenopus embryogenesis.

During Xenopus development, Wnt signaling is thought to function first after midblastula transition to regulate axial patterning via β-catenin-mediated transcription. Here, we report that Wnt/glycogen synthase kinase 3 (GSK3) signaling functions posttranscriptionally already in mature oocytes via Wnt/stabilization of proteins (STOP) signaling. Wnt signaling is induced in oocytes after their entry into meiotic metaphase II and declines again upon exit into interphase.

Ing1 functions in DNA demethylation by directing Gadd45a to H3K4me3.

Active DNA demethylation regulates epigenetic gene activation in numerous processes, but how the target site specificity of DNA demethylation is determined and what factors are involved are still poorly understood. Here we show that the tumor suppressor inhibitor of growth protein 1 (Ing1) is required for targeting active DNA demethylation. Ing1 functions by recruiting the regulator of DNA demethylation growth arrest and DNA damage protein 45a (Gadd45a) to histone H3 trimethylated at Lys 4 (H3K4me3).

Gemcitabine functions epigenetically by inhibiting repair mediated DNA demethylation.

Gemcitabine is a cytotoxic cytidine analog, which is widely used in anti-cancer therapy. One mechanism by which gemcitabine acts is by inhibiting nucleotide excision repair (NER). Recently NER was implicated in Gadd45 mediated DNA demethylation and epigenetic gene activation.

Gadd45a promotes epigenetic gene activation by repair-mediated DNA demethylation.

DNA methylation is an epigenetic modification that is essential for gene silencing and genome stability in many organisms. Although methyltransferases that promote DNA methylation are well characterized, the molecular mechanism underlying active DNA demethylation is poorly understood and controversial. Here we show that Gadd45a (growth arrest and DNA-damage-inducible protein 45 alpha), a nuclear protein involved in maintenance of genomic stability, DNA repair and suppression of cell growth, has a key role in active DNA demethylation.

One step cloning of defined DNA fragments from large genomic clones.

Recently, the nucleotide sequences of entire genomes became available. This information combined with older sequencing data discloses the exact chromosomal location of millions of nucleotide markers stored in the databases at NCBI, EMBO or DDBJ. Despite having resolved the intron/exon structures of all described genes within these genomes with a stroke of a pen, the sequencing data opens up other interesting possibilities.

Antagonism between C/EBPbeta and FOG in eosinophil lineage commitment of multipotent hematopoietic progenitors.

The commitment of multipotent cells to particular developmental pathways requires specific changes in their transcription factor complement to generate the patterns of gene expression characteristic of specialized cell types. We have studied the role of the GATA cofactor Friend of GATA (FOG) in the differentiation of avian multipotent hematopoietic progenitors. We found that multipotent cells express high levels of FOG mRNA, which were rapidly down-regulated upon their C/EBPbeta-mediated commitment to the eosinophil lineage.

Distinct C/EBP functions are required for eosinophil lineage commitment and maturation.

Hematopoietic differentiation involves the commitment of multipotent progenitors to a given lineage, followed by the maturation of the committed cells. To study the transcriptional events controlling these processes, we have investigated the role of C/EBP proteins in lineage choice of multipotent hematopoietic progenitors (MEPs) transformed by the E26 virus. We found that forced expression of either the alpha or beta isoforms of C/EBP in MEPs induced eosinophil differentiation and that in addition, C/EBPbeta could induce myeloid differentiation.

Regulation of eosinophil-specific gene expression by a C/EBP-Ets complex and GATA-1.

The EOS47 antigen is an early and specific marker of eosinophil differentiation in the chicken haematopoietic system. To elucidate the transciptional events controlling commitment to the eosinophil lineage, we studied the regulation of the eosinophil-specific EOS47 promoter. This promoter is TATA-less, and binds trancription factors of the Ets, C/EBP, GATA and Myb families.

Influence of the v-Myb transactivation domain on the oncoprotein's transformation specificity.

The v-myb-containing viruses AMV and E26 induce the proliferation of myelomonocytic cells. The E26 Myb protein, by virtue of its fusion to Ets, is also able to transform multipotent haematopoietic cells (MEPs). We have examined the biological effects of substituting the v-Myb transactivation domain with the strong acidic activator domain from the C-terminus of the HSV-1 VP16 protein.

Proposed structure for the DNA-binding domain of the Myb oncoprotein based on model building and mutational analysis.

Myb-related proteins from plants to humans are characterized by a DNA-binding domain which contains two to three imperfect repeats of approximately 50 amino acids each. Based on the evolutionary conservation of specific residues, secondary structural predictions suggest an arrangement of alpha helices homologous to that seen in the homeodomains, members of the helix-turn-helix family of DNA-binding proteins. We have used molecular modelling in conjunction with site-directed mutagenesis to test the feasibility of this structure.

Monoclonal antibodies to novel erythroid differentiation antigens reveal specific effects of oncogenes on the leukaemic cell phenotype.

A panel of new monoclonal antibodies to antigens on the surface of chick erythroid progenitor cells is described. These are characterised with respect to their binding to different classes of normal haemopoietic cells of both the erythroid and myeloid lineages. Using these antibodies, we have examined the phenotype of avian leukaemic cells transformed by retroviruses carrying defined oncogenes.

Chicken hematopoietic cells transformed by seven strains of defective avian leukemia viruses display three distinct phenotypes of differentiation.

Chicken hematopoietic cells transformed in vitro and in vivo by seven strains of replication-defective avian leukemia viruses were assayed for the expression of six erythroid and five myeloid differentiation parameters, including differentiation-specific surface antigens as detected by newly developed antisera. The transformed cells were found to display three distinct phenotypes of differentiation. First, cells transformed by AEV resemble erythroblasts.

[Toxaemia of pregnancy and the optic fundus (author's transl)].

Toxaemia of pregnancy in its various forms is the most dangerous complication of pregnancy. It threatens the life of the mother in up to 30 percent of cases, and of the infant in up to 50 percent of cases. The task of systematic medical examination and advice during pregnancy is the earliest possible diagnosis and treatment of symptoms of toxaemia.