• The Korean Journal of Zoology
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• v.13 no.1
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• pp.21-25
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• 1970

The present paper deals with the results of the experiments, in which the resistibility to NaCl in whole develomental stages is examined by the emergence rate and the effects of NaCl on the SD action in Drosophila melanogaster. The four SD strains and one mutant strain(cn bw)are used and NaCl media are prepared y adding NaCl at a concentration of 1.0M, 0.7M, 0.5M, 0.3M, 0.1M, and 0.0M to the standard media for the present investigations. The results are given below. 1. The emergence rate (resistibility to NaCl) is not significantly different among strains but strikingly different among concentrations of NaCl. 2. The emergence rate decreases as the concentration of NaCl increases; the four SD strains are considerably resistible to the NaCl from a concentration of 0.0M to 0.3M but are susceptible from 0.5M or higher concentrations of NaCl. 3. No eggs are hatched from the culture media containing a concentration of 1.0M NaCl. This suggests that the SD strains are not resistible to NaCl at a concentrations of 1.0M or higher. 4. The difference in k values is not signficant among strains and also among concentrations of NaCl. Thus the SD action is not affected as far as once emerged from the culture media whether containing NaCl or not.

• Korean Journal of Plant Tissue Culture
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• v.24 no.1
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• pp.1-35
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• 1997

Fertilized egg, by successive cell divisions, differentiates into different tissues and organs with various structures and functions. Different cells and tissues contain different proteins, products of selective gene expression. Not all the genes in any genomes are equally active, temporal and spatial gene expression being the general rule. Present paper attempts to review the tanscriptional mechanisms or the initiations of transcription from several angles. In some of the organisms the genes in the process of transcription or the genes in the inactive state can be seen under the light microscope. Some bands of Drosophila polytene chromosomes may exhibit a swollen or puff appearance under certain conditions. A puff, unfolded or decondensed form of chromomere, represents sets of intense transcriptional activity or RNA synthesis. The heterochromatic X chromosome whose genes remain inactive in the female mammals can be visualized as a dark staining structure called Barr body, Configuration of chromatin differs between transcribed and nontranscribed chromatin. Modification to the chromatin facilitates RNA synthesis. The movement of large polymerase molecule along the DNA would probably be facilitated if some modifications of the chromatin configuration is effected. Methylation of cytosines in CG sequences is associated with inactive genes. Methylation can play a role in determination of mammalian cells during embryogenesis. Demethylation is necessary for the gene to be expressed during development A histone modification that is also known to be correlated with transcriptional capacity of chromatin is acetylation of the lysine residues of the core histones. Chromatin containing a high level of histone acetylation is very sensitive to DNase 1. For the transcription to occur TBP must first bind to the TATA box. Another TF, TF IIB, then binds to the promoter-TBP complex, facilitating the access of RNA polymerase to the transcription initiation site. As recently as eight years ago researchers assumed that histones were irrelevant to the regulation of gene expression. Histones combine with the DNA to form nucleosome of the chromatin. Histones are vital participant in gene regulation. Histone and basal factors compete for access to TATA box. When DNA is exposed to basal factors before histones are introduced, the basal factors assemble on TATA boxes preventing the access of histones, allowing transcription to occur, for transcription to begin, activator protein at the upstream activation sequence or enhancer must interact with the tail of histone H4 at TATA box and cause the histone role particle to dissociate from the TATA box leading to partial breakup of the histone core particle and allowing the basal factors to bind to the TATA box. New concept of genomic flux in contrast to the old concept of static genome has been developed based on the powerful new molecular techniques. Genomic changes such as repetitive DNAs and transposable elements, it is assumed but not yet proved, may affect some of the developmental patterns that characterize particular cells, tissues, organs, and organisms. In the last decade or so remarkable achievement have been made in the researches of the structures and functions of TFs and the specific target sequences located in promoters or enhancers where these TFs bind. TFs have independent domains that bind DNA and that activate transcription. DNA binding domain of TFs serves to bring the protein into the right location. There are many types of DNA binding domains. Common types of motifs can be found that are responsible for binding to DNA. The motifs are usually quite short and comprise only a small part of the protein structure. Steroid receptors have domains for hormone binding, DNA binding, and activating transcription. The zinc finger motif comprises a DNA binding domain. Leucine zipper consist of a stretch of amino acids with a leucine residue in every seventh position Two proteins form a dimer because they interact by means of leucine zippers on similar α-helical domain. This positions their DNA binding basic domains for interaction with the two halves of a DNA sequence with dyad symmetry of TGACTCA, ACTGAGT.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.1
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• pp.171-180
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• 2003

The development of calvarial bones is tighly co-ordinated with the growth of the brain and needs of harmonious interactions between different tissues within the calvarial sutures. Premature fusion of cranial sutures, known as craniosynostosis, presumably involves disturbance of these interactions. Mutations in the homeobox-containg gene Msx2 cause human craniosynostosis syndrome. Msx genes, which are consist of Msx1, Msx2 and Msx3, are homeobox-containg transcripton factors, and were originally identified as homologue of Drosophila msh(muscle segment homeobox) gene. Msx1 and Msx2 genes, expressed mostly in overlapping patterns at multiple site of tissue interactions during vertebrate development, are associated with epithelial-mesenchymal interactions during organogenesis, targets of BMP and FGF signaling. To elucidate the function of Msx genes in the early morphogenesis of mouse cranial suture, we analyzed the expression of them by in situ hybridization during embryonic(E15-E18) stage, and did vivo experiments in E15.5 mouse using rhBMP-2, rhFGF-2 protein soaked bead. In the sagittal suture, Msx1 was expressed in the mesenchyme of suture and the dura mater, Msx2 was intensely expressed in the sutural mesenchyme and the dura mater. In the coronal suture both of Msx genes were expressed intensely in the sutural mesenchyme and expressed in the periosteum also. Msx1 had a broader expression pattern than Msx2. BMP2 beads induced expression of both Msx1 and Msx2, FGF2 beads induced expression of Msx1, but not Msx2. Taken together, these data suggest that Msx1 and Msx2 genes have important role in regulating the morphogenesis and maintenance of embryonic cranial suture. Both of Msx genes are expressed similarly but because of their upstream signaling, they function dependently or cooperatively according to change of signaling molecule.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.4
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• pp.651-658
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• 2004

Runx2 is a transcription factor in homologous with Drosophila runt gene and it is essential for bone formation during embryogenesis and a critical gene for osteoblast differentiation and osteoblast function. Runx2-haploinsufficency causes cleidocranial dysplasia (CCD). CCD is an autosomal-dominant inherited disorder characterized by hypoplastic clevicle and delayed ossification in fontanelles and wormian bones. Dental defects are possibly shown to CCD patients : multiple supernumerary teeth, irregular and compressed permanent tooth crowns, hypoplastic and hypomineralized defects in enamel and dentin, an excess of epithelial root remnants, the absence of cellular cementum, and abnormally shaped roots. In addition, delayed eruption of the secondary dentition is a constant finding. The aim of this study is to evaluate the role of Runx2 in the tooth development and eruption through analyzing the expression pattern of Runx2 by in situ hybridization during crown (late bell stage) and root formation of tooth, using postnatal day 1, 4, 7, 14 and 21 mice mandibular molar teeth. mRNA of Runx2-full length is expressed in dental follicle and surrounding tissue at postnatal day1 and 4. At postnatal day 7, it is expressed in ameloblasts of occlusal surface of enamel and bone area surrounding the tooth. In comparison with previous stage, at postnatal day 14, it is expressed in ameloblasts of proximal surface of enamel. At postnatal day 21 it's expression is observed only in bone area. mRNA of Runx2-typeII is not expressed. At postnatal day 1 and 7. At postnatal day 14 and 21, it's expression is observed in the bone area. In this study, we suggest that Runx2 have a relation of ameloblasts differentiation and an important role to tooth eruption made by dental follicle during intraosseous eruption stage. Also we can confirm that Runx2 has a role to bone formation.