Search results for "Animal Structures"
showing 10 items of 876 documents
Regulation of the sea urchin early H2A histone gene expression depends on the modulator element and on sequences located near the 3' end
1999
Abstract Transcription of the sea urchin early histone genes occurs transiently during early cleavage, reaching the maximum at the morula stage and declining to an undetectable level at the gastrula stage. To identify the regulatory elements responsible for the timing and the levels of transcription of the H2A gene, we used promoter binding studies in nuclear extracts and microinjection of a CAT transgene driven by the early H2A promoter. We found that morula and gastrula nuclear proteins produced indistinguishable DNase I footprint patterns on the H2A promoter. Two sites of interactions, centred on the modulator/enhancer and on the CCAAT box respectively, were detected. Deletion of the mod…
The modulator is a constitutive enhancer of a developmentally regulated sea urchin histone H2A gene.
2002
Going back to the late 1970s and early 1980s, we trace the Xenopus oocyte microinjection experiments that led to the emergence of the concept of “modulator”. The finding that the modulator could transactivate transcription from far upstream and in either orientation suggested that a new genetic element, different from the classical prokaryotic promoter sequences, had been discovered. This particular enhancer transactivates transcription of the sea urchin early (α) histone H2A gene which is regulated in early sea urchin development. We summarise the data from sea urchin microinjection experiments that confirm and extend the results obtained with Xenopus oocytes. We conclude that the H2A enha…
Impairing Otp homeodomain function in oral ectoderm cells affects skeletogenesis in sea urchin embryos
2003
AbstractIn the sea urchin embryo skeletogenesis is the result of a complex series of molecular and cellular events that coordinate the morphogenetic process. Past and recent evidence strongly indicate that skeletal initiation and growth are strictly dependent on signals emanating from the oral ectodermal wall. As previously suggested, Orthopedia (Otp), a homeodomain-containing transcription factor specifically expressed in a small subset of oral ectoderm cells, might be implicated in this signalling pathway. In this study, we utilize three different strategies to address the issue of whether Otp is an upstream regulator of sketelogenesis. We describe the effects of microinjection of Otp mor…
Physiological activation of the IgH 3' enhancer in B lineage cells is not blocked by Pax-5.
1996
The mouse 3' enhancer contains a high-affinity binding site for the paired box protein Pax-5. Here, we demonstrate by genomic footprinting that the rat 3' enhancer contains a low-affinity binding site for Pax-5, which is occupied in activated splenic B cells. Thus, binding of Pax-5 to the IgH 3' enhancer appears to be evolutionarily conserved in rodents. Analysis of Pax-5 expression in primary B cells demonstrates that Pax-5 remains expressed after 4 days of lipopolysaccharide (LPS) induction, but is down-regulated in 5-day stimulated cells. Similarly, the expression of Pax-5 is down-regulated in vivo in activated large splenocytes, in contrast to small resting cells. Multimerization of the…
Protease-mediated processing of Argonaute proteins controls small RNA association
2020
SummarySmall RNA pathways defend the germlines of animals against selfish genetic elements and help to maintain genomic integrity. At the same time, their activity needs to be well-controlled to prevent silencing of ‘self’ genes. Here, we reveal a proteolytic mechanism that controls endogenous small interfering (22G) RNA activity in the Caenorhabditis elegans germline to protect genome integrity and maintain fertility. We find that WAGO-1 and WAGO-3 Argonaute (Ago) proteins are matured through proteolytic processing of their unusually proline-rich N-termini. In the absence of DPF-3, a P-granule-localized N-terminal dipeptidase orthologous to mammalian DPP8/9, processing fails, causing a cha…
Drosophila melanogaster histone H2B retropseudogene is inserted into a region rich in transposable elements.
1998
We have isolated and characterized the genomic sequence of a Drosophila melanogaster histone H2B pseudogene that is localized outside of the cluster of the replication-dependent histone genes and has all the properties of a retropseudogene. It is highly homologous to the transcribed region of the D. melanogaster histone H2B gene, but not to its flanking regions, and is surrounded by short direct repeats. The pseudogene contains several point mutations that preclude its translation. The sequence of the 3' region of this pseudogene is compatible with the hypothesis that the 3' terminal stem-loop structure of the histone H2B mRNA has served as a primer for the reverse transcription event from …
Sonic Hedgehog-Mediated Synergistic Effects Guiding Angiogenesis and Osteogenesis
2012
Sonic hedgehog (Shh) is a morphogen controlling the skeletal and vascular development in the embryo but is also reactivated during adult repair processes. Thus, this molecule holds great therapeutic potential for biotechnological and biomedical approaches aiming to enhance tissue regeneration or to replace damaged tissues. According to present knowledge, Shh signaling controls the expression of several families of growth factors involved in neovascularization and vessel maturation and acts upstream of the most prominent angiogenic growth factor, vascular endothelial growth factor. In this context, a very interesting feature of Shh is that it controls both angiogenic activity and vessel stab…
Zebrafish xenografts as a tool for in vivo studies on human cancer
2012
The zebrafish has become a powerful vertebrate model for genetic studies of embryonic development and organogenesis and increasingly for studies in cancer biology. Zebrafish facilitate the performance of reverse and forward genetic approaches, including mutagenesis and small molecule screens. Moreover, several studies report the feasibility of xenotransplanting human cells into zebrafish embryos and adult fish. This model provides a unique opportunity to monitor tumor-induced angiogenesis, invasiveness, and response to a range of treatments in vivo and in real time. Despite the high conservation of gene function between fish and humans, concern remains that potential differences in zebrafis…
Does the freshwater mussel Anodonta anatina remove the fish pathogen Flavobacterium columnare from water?
2021
AbstractGlobal decline of freshwater mussels (Unionoida) is threatening biodiversity and the essential ecosystem services that mussels provide. As filter-feeding organisms, freshwater mussels remove phytoplankton and suspended particles from the water. By filtering bacteria, freshwater mussels also decrease pathogen loads in the water. The objective of this study was to evaluate whether the common freshwater bivalve Anodonta anatina (duck mussel) could remove the bacterial fish pathogen Flavobacterium columnare from the water. Mussels reduced bacteria in both of the two experiments performed, so that the bacterial concentration at the end of the 96-h monitoring in mussel treatments was only…
Comparative study assessing effects of sonic hedgehog and VEGF in a human co-culture model for bone vascularisation strategies.
2011
The morphogen sonic hedgehog (Shh) seems to mediate adult repair processes in bone regeneration and vascularisation. In this study we investigated the effects of Shh on co-cultures consisting of human primary osteoblasts and outgrowth endothelial cells in terms of angiogenic activation and vessel maturation in comparison to the treatment with the commonly used proangiogenic factor, VEGF. Both, stimulation with VEGF or Shh, leads to an increase in the formation of microvessel-like structures compared to untreated controls. In contrast to VEGF, proangiogenic effects by Shh could already be observed after 24 h of treatment. Nevertheless, after 14 days the angiogenic activity of OEC was compara…