Drosophila damaged DNA binding protein 1 contributes to genome stability in somatic cells

The damaged DNA-binding protein (DDB) complex consists of a heterodimer of p127 (DDB1) and p48 (DDB2) subunits and is believed to have a role in nucleotide excision repair (NER). We used the GAL4-UAS targeted expression system to knock down DDB1 in wing imaginal discs of Drosophila. The knock-down was achieved in transgenic flies using over-expression of inverted repeat RNA of the D-DDB1 gene [UAS-D-DDB1(650)-dsRNA]. As a consequence of RNA interference (RNAi), the fly had a shrunken wing phenotype. The wing spot test showed induced genome instability in transgenic flies with RNAi knock-down of D-DDB1 in wing imaginal discs. When Drosophila larvae with RNAi knock-down of D-DDB1 in wing imaginal discs were treated with the chemical mutagen methyl methanesulfonate (MMS), the frequency of flies with a severely shrunken wing phenotype increased compared to non-treated transgenic flies. These results suggested that DDB1 plays a role in the response to DNA damaged with MMS and in genome stability in Drosophila somatic cells.     

Characterization of a counterpart to Mammalian ornithine decarboxylase antizyme in prokaryotes

The degradation of mammalian ornithine decarboxylase (ODC) (EC 4.1.1.17) by 26 S proteasome, is accelerated by the ODC antizyme (AZ), a trigger protein involved in the specific degradation of eukaryotic ODC. In prokaryotes, AZ has not been found. Previously, we found that in Selenomonas ruminantium, a strictly anaerobic and Gram-negative bacterium, a drastic degradation of lysine decarboxylase (LDC; EC 4.1.1.18), which has decarboxylase activities toward both L-lysine and L-ornithine with similar K(m) values, occurs upon entry into the stationary phase of cell growth by protease together with a protein of 22 kDa (P22). Here, we show that P22 is a direct counterpart of eukaryotic AZ by the following evidence. (i) P22 synthesis is induced by putrescine but not cadaverine. (ii) P22 enhances the degradation of both mouse ODC and S. ruminantium LDC by a 26 S proteasome. (iii) S. ruminantium LDC degradation is also enhanced by mouse AZ replacing P22 in a cell-free extract from S. ruminantium. (iv) Both P22 and mouse AZ bind to S. ruminantium LDC but not to the LDC mutated in its binding site for P22 and AZ. In this report, we also show that P22 is a ribosomal protein of S. ruminantium.     

Effects of storage temperature on the contents of sugars and free amino acids in tubers from different potato cultivars and acrylamide in chips

To clarify the effects of storage temperature on potato components and acrylamide in chips, tubers from five cultivars were stored at various temperatures (2, 6, 8, 10, and 18 degrees C) for 18 weeks, and the contents of sugars, free amino acids in tubers, and acrylamide in chips after frying were analyzed. At temperatures lower than 8 degrees C, the contents of reducing sugars increased markedly in all cultivars, with similar increases in the acrylamide level and dark brown chip color. Free amino acids showed little change at the storage temperatures tested and varied within certain ranges characteristic of each cultivar. The contents of reducing sugars correlated well with the acrylamide level when the fructose/asparagine molar ratio in the tubers was <2. When the fructose/asparagine ratio was >2 by low-temperature storage, the asparagine content, rather than the reducing sugar content, was found to be the limiting factor for acrylamide formation.     

Modulation by the steroid/thyroid hormone superfamily of TGF-beta-stimulated VEGF release from vascular smooth muscle cells

We previously reported that transforming growth factor-beta (TGF-beta) stimulates the release of vascular endothelial growth factor (VEGF) from aortic smooth muscle A10 cells via activation of p38 mitogen-activated protein (MAP) kinase. In the present study, we investigated whether nuclear hormone receptor superfamily members affect TGF-beta-stimulated VEGF release from A10 cells. Retinoic acid or 1,25-dihydroxyvitamin D3 enhanced TGF-beta-induced VEGF release in a concentration-dependent manner, whereas dexamethasone or corticosterone suppressed TGF-beta-induced VEGF release. 1,25-Dihydroxyvitamin D3 and TGF-beta stimulated phosphorylation of p38 MAP kinase in an additive manner. SB203580, an inhibitor of p38 MAP kinase, decreased the VEGF release induced by TGF-beta or 1,25-dihydroxyvitamin D3. However, retinoic acid, dexamethasone, or corticosterone did not affect phosphorylation of p38 MAP kinase. These results indicate that retinoic acid, 1,25-dihydroxyvitamin D3, and glucocorticoids affect TGF-beta-stimulated VEGF release from aortic smooth muscle cells. The stimulatory effect of 1,25-dihydroxyvitamin D3 occurs, in part, via modification of TGF-beta-induced activation of p38 MAP kinase.     

Overexpression of Kruppel-like factor 7 regulates adipocytokine gene expressions in human adipocytes and inhibits glucose-induced insulin secretion in pancreatic beta-cell line

We have identified Kruppel-like factor 7 (KLF7) as a new candidate for conferring susceptibility to type 2 diabetes. To ascertain the possible involvement of KLF7 in the pathogenesis of type 2 diabetes, we examined the functional roles of KLF7 in various types of cells. In human adipocytes overexpressing KLF7, the expression of adiponectin and leptin was decreased compared with that in control cells, whereas expression of IL-6 was increased. In the insulin-secreting cell line (HIT-T15 cells), the expression and glucose-induced secretion of insulin were significantly suppressed in KLF7-overexpressed cells compared with control cells, accompanied by the reduction in the expression of glucose transporter 2, sulfonylurea receptor 1, Kir6.2, and pancreatic-duodenal homeobox factor 1. We also found that the overexpression of KLF7 resulted in the decrease of hexokinase 2 expression in smooth muscle cells, and of glucose transporter 2 expression in the HepG2 cells. These results suggest that KLF7 may contribute to the pathogenesis of type 2 diabetes through an impairment of insulin biosynthesis and secretion in pancreatic beta-cells and a reduction of insulin sensitivity in peripheral tissues. Therefore, we suggest that KLF7 plays an important role in the pathogenesis of type 2 diabetes, and may be a useful target for new drugs to aid in the prevention and treatment of this disease.     

Identification and characterization of genes induced for anthocyanin synthesis and chlorophyll degradation in regenerated torenia shoots using suppression subtractive hybridization, cDNA microarrays, and RNAi techniques

Anthocyanin synthesis and chlorophyll degradation in regenerated torenia (Torenia fournieri Linden ex Fourn.) shoots induced by osmotic stress with 7% sucrose were examined to identify the genes regulating the underlying molecular mechanism. To achieve this, suppression subtractive hybridization was performed to enrich the cDNAs of genes induced in anthocyanin-synthesizing and chlorophyll-degrading regenerated shoots. The nucleotide sequences of 1,388 random cDNAs were determined, and these were used in the preparation of cDNA microarrays for high-throughput screening. From 1,056 cDNAs analyzed in the microarrays, 116 nonredundant genes were identified, which were up regulated by 7% sucrose to induce anthocyanin synthesis and chlorophyll degradation in regenerated shoots. Of these, eight genes were selected and RNAi transformants prepared, six of which exhibited anthocyanin synthesis inhibition and/or chlorophyll degradation in their leaf discs. Notably, the RNAi transformants of the glucose 6-phosphate/phosphate translocator gene displayed inhibition both of anthocyanin synthesis and chlorophyll degradation in both leaf discs and regenerated shoots. There was also less accumulation of anthocyanin in the petals, and flowering time was shortened. The genes we identified as being up-regulated in the regenerated torenia shoots may help further elucidate the molecular mechanism underlying the induction of anthocyanin synthesis and chlorophyll degradation.     

In vitro immunization can elicit the expansion of diverse repertoire of B cells from peripheral blood mononuclear cells

We previously developed an in vitro immunization (IVI) protocol of human peripheral blood mononuclear cells (PBMC) for generating antigen-specific human antibodies. In order to clarify whether IVI protocolinduces antigen-specific B cell responses in PBMC, we analyzed family gene usage and sequence of the variable region gene of immunoglobulin heavy chain (VH gene) of the antibody produced from the in vitro immunized PBMC. Sequence homology analyses of VH gene demonstrated that a larger repertoire of B cells can be sensitized with mite-extract than with cholera toxin B subunit and rice allergen. Further, antigen-specific B cells were efficiently expanded by using CpG oligodeoxynucleotide as adjuvant. These results suggest that appropriate combination of sensitizing antigen and adjuvant is primarily important for expansion of antigen-specific B cells in IVI protocol.     

Evidence for activation of Amh gene expression by steroidogenic factor 1

The anti-Müllerian hormone gene (Amh) is responsible for regression in males of the Müllerian ducts. The molecular mechanism of regulation of chicken Amh expression is poorly understood. To investigate the regulation of chicken Amh expression, we have cloned Amh cDNAs from quail and duck as well as the promoter regions of the gene from chicken, quail, and duck. The expression patterns of Amh during embryonic development in these three species were found to be similar, suggesting that the regulatory mechanisms of Amh expression are conserved. The sequence of the proximal promoter of Amh contains a putative binding site for steroidogenic factor 1 (SF1), the protein product of which can up-regulate Amh in mammals. We showed here that SF1 is able to activate the chicken Amh promoter and binds to its putative SF1 binding site. These results suggest that SF1 plays a role in regulation of Amh expression in avian species.     

TGFbeta-mediated FGF signaling is crucial for regulating cranial neural crest cell proliferation during frontal bone development

The murine frontal bone derives entirely from the cranial neural crest (CNC) and consists of the calvarial (lateral) aspect that covers the frontal lobe of brain and the orbital aspect that forms the roof of bony orbit. TGFbeta and FGF signaling have important regulatory roles in postnatal calvarial development. Our previous study has demonstrated that conditional inactivation of Tgfbr2 in the neural crest results in severe defects in calvarial development, although the cellular and molecular mechanisms by which TGFbeta signaling regulates the fate of CNC cells during frontal bone development remain unknown. Here, we show that TGFbeta IIR is required for proliferation of osteoprogenitor cells in the CNC-derived frontal bone anlagen. FGF acts downstream of TGFbeta signaling in regulating CNC cell proliferation, and exogenous FGF2 rescues the cell proliferation defect in the frontal primordium of Tgfbr2 mutant. Furthermore, the CNC-derived frontal primordium requires TGFbeta IIR to undergo terminal differentiation. However, this requirement is restricted to the developing calvarial aspect of the frontal bone, whereas the orbital aspect forms despite the ablation of Tgfbr2 gene, implying a differential requirement for TGFbeta signaling during the development of various regions of the frontal bone. This study demonstrates the biological significance of TGFbeta-mediated FGF signaling cascade in regulating frontal bone development, suggests that TGFbeta functions as a morphogen in regulating the fate of the CNC-derived osteoblast and provides a model for investigating abnormal craniofacial development.     

Adaptive significance of death feigning posture as a specialized inducible defence against gape-limited predators

Death feigning is fairly common in a number of taxa, but the adaptive significance of this behaviour is still unclear and has seldom been tested. To date, all proposed hypotheses have assumed that prey manage to escape predation by sending a death-mimicking signal, although death-feigning postures are markedly different from those of dead animals. Moreover, the efficacy of this technique may largely depend on the foraging mode of the predator; death feigning seldom works with sit-and-wait predators that make the decision to attack and consume prey within a very brief time. We examined whether death feigning in the pygmy grasshopper Criotettix japonicus Haan was an inducible defence behaviour against the frog Rana nigromaculata, a sit-and-wait, gape-limited predator. The characteristic posture assumed by the grasshopper during death feigning enlarges its functional body size by stretching each of three body parts (pronotum, hind legs and lateral spines) in three different directions, thereby making it difficult for the predator to swallow the prey. Our result is the first consistent explanation for why death-mimicking animals do not always mimic the posture of dead animals.