Isopentenyl-diphosphate isomerase is essential for viability of Caenorhabditis elegans

Identification and functional analysis of isopentenyl pyrophosphate isomerase genes in the whiteflies Bemisia tabaci (Hemiptera: Aleyrodidae)

The juvenile hormone (JH) plays a vital role in the regulation of a number of physiological processes, including development, reproduction, and ovarian maturation. Isopentenyl pyrophosphate isomerase (IPPI) is a key enzyme in the biosynthetic pathway of JH. In this study, we identified an isopentenyl pyrophosphate isomerase protein from Bemisia tabaci and named it BtabIPPI. The open reading frame (ORF) of BtabIPPI is 768 bp and encodes a protein of 255 amino acids that contains a conserved domain of the Nudix family. The temporal and spatial expression profiles showed that BtabIPPI was highly expressed in the female adults.RNA interference (RNAi)-mediated silencing of BtabIPPI reduced JH titers and the relative expression of vitellogenin receptor (VgR) and JH signaling pathway genes, resulting in a dramatic reduction in fecundity and hatchability. These results indicate that the BtabIPPI gene plays an important role in the female fecundity of B. tabaci. This study will broaden our understanding of the function of IPPI in regulating insect reproduction and provide a theoretical basis for targeting IPPI for pest control in the future.

A Caenorhabditis elegans Genome-Scale Metabolic Network Model

Caenorhabditis elegans is a powerful model to study metabolism and how it relates to nutrition, gene expression, and life history traits. However, while numerous experimental techniques that enable perturbation of its diet and gene function are available, a high-quality metabolic network model has been lacking. Here, we reconstruct an initial version of the C. elegans metabolic network. This network model contains 1,273 genes, 623 enzymes, and 1,985 metabolic reactions and is referred to as iCEL1273. Using flux balance analysis, we show that iCEL1273 is capable of representing the conversion of bacterial biomass into C. elegans biomass during growth and enables the predictions of gene essentiality and other phenotypes. In addition, we demonstrate that gene expression data can be integrated with the model by comparing metabolic rewiring in dauer animals versus growing larvae. iCEL1273 is available at a dedicated website (wormflux.umassmed.edu) and will enable the unraveling of the mechanisms by which different macro- and micronutrients contribute to the animal's physiology.

Cardioprotective Effects of Quercetin in Cardiomyocyte under Ischemia/Reperfusion Injury

Quercetin, a polyphenolic compound existing in many vegetables, fruits, has antiinflammatory, antiproliferation, and antioxidant effect on mammalian cells. Quercetin was evaluated for protecting cardiomyocytes from ischemia/reperfusion injury, but its protective mechanism remains unclear in the current study. The cardioprotective effects of quercetin are achieved by reducing the activity of Src kinase, signal transducer and activator of transcription 3 (STAT3), caspase 9, Bax, intracellular reactive oxygen species production, and inflammatory factor and inducible MnSOD expression. Fluorescence two-dimensional differential gel electrophoresis (2D-DIGE) and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) can reveal the differentially expressed proteins of H9C2 cells treated with H₂O₂ or quercetin. Although 17 identified proteins were altered in H₂O₂-induced cells, these proteins such as alpha-soluble NSF attachment protein (α-SNAP), Ena/VASP-like protein (Evl), and isopentenyl-diphosphate delta-isomerase 1 (Idi-1) were reverted by pretreatment with quercetin, which correlates with kinase activation, DNA repair, lipid, and protein metabolism. Quercetin dephosphorylates Src kinase in H₂O₂-induced H9C2 cells and likely blocks the H₂O₂-induced inflammatory response through STAT3 kinase modulation. This probably contributes to prevent ischemia/reperfusion injury in cardiomyocytes.

The mevalonate pathway in C. elegans

The mevalonate pathway in human is responsible for the synthesis of cholesterol and other important biomolecules such as coenzyme Q, dolichols and isoprenoids. These molecules are required in the cell for functions ranging from signaling to membrane integrity, protein prenylation and glycosylation, and energy homeostasis. The pathway consists of a main trunk followed by sub-branches that synthesize the different biomolecules. The majority of our knowledge about the mevalonate pathway is currently focused on the cholesterol synthesis branch, which is the target of the cholesterol-lowering statins; less is known about the function and regulation of the non-cholesterol-related branches. To study them, we need a biological system where it is possible to specifically modulate these metabolic branches individually or in groups. The nematode Caenorhabditis elegans (C. elegans) is a promising model to study these non-cholesterol branches since its mevalonate pathway seems very well conserved with that in human except that it has no cholesterol synthesis branch. The simple genetic makeup and tractability of C. elegans makes it relatively easy to identify and manipulate key genetic components of the mevalonate pathway, and to evaluate the consequences of tampering with their activity. This general experimental approach should lead to new insights into the physiological roles of the non-cholesterol part of the mevalonate pathway. This review will focus on the current knowledge related to the mevalonate pathway in C. elegans and its possible applications as a model organism to study the non-cholesterol functions of this pathway.

Segmental copy-number gain within the region of isopentenyl diphosphate isomerase genes in sporadic amyotrophic lateral sclerosis

AIMS

Sporadic amyotrophic lateral sclerosis (SALS) seems to be a multifactorial disease, the pathogenesis of which may involve both genetic and environmental factors. The present study aims at identifying a possible genetic change that confers risk for SALS.

METHODS

We performed whole-genome screening of a copy-number variation (CNV) using a CNV beadchip, followed by real-time quantitative polymerase chain reaction (qPCR) and region-targeted high-density oligonucleotide tiling microarray.

RESULTS

Within the 40-kb region on 10p15.3 subtelomere, which harbours two genes encoding isopentenyl diphosphate isomerase 1 (IDI1) and IDI2, we found a segmental copy-number gain in a large proportion of SALS patients. qPCR analysis demonstrated the copy-number gain in 46 out of 83 SALS patients, as compared with 10 out of 99 controls (p=4.86×10(-11), Odds Ratio 10.8); subsequent tiling microarray validated qPCR results and elucidated the fine structure of segmental gains.

CONCLUSIONS

A segmental copy-number gain in the IDI1/IDI2 gene region may play a significant role in the pathogenesis of SALS.

Visualization of C. elegans transgenic arrays by GFP

BACKGROUND

Targeting the green fluorescent protein (GFP) via the E. coli lac repressor (LacI) to a specific DNA sequence, the lac operator (lacO), allows visualization of chromosomes in yeast and mammalian cells. In principle this method of visualization could be used for genetic mosaic analysis, which requires cell-autonomous markers that can be scored easily and at single cell resolution. The C. elegans lin-3 gene encodes an epidermal growth factor family (EGF) growth factor. lin-3 is expressed in the gonadal anchor cell and acts through LET-23 (transmembrane protein tyrosine kinase and ortholog of EGF receptor) to signal the vulval precursor cells to generate vulval tissue. lin-3 is expressed in the vulval cells later, and recent evidence raises the possibility that lin-3 acts in the vulval cells as a relay signal during vulval induction. It is thus of interest to test the site of action of lin-3 by mosaic analysis.

RESULTS

We visualized transgenes in living C. elegans by targeting the green fluorescent protein (GFP) via the E. coli lac repressor (LacI) to a specific 256 sequence repeat of the lac operator (lacO) incorporated into transgenes. We engineered animals to express a nuclear-localized GFP-LacI fusion protein. C. elegans cells having a lacO transgene result in nuclear-localized bright spots (i.e., GFP-LacI bound to lacO). Cells with diffuse nuclear fluorescence correspond to unbound nuclear localized GFP-LacI. We detected chromosomes in living animals by chromosomally integrating the array of the lacO repeat sequence and visualizing the integrated transgene with GFP-LacI. This detection system can be applied to determine polyploidy as well as investigating chromosome segregation. To assess the GFP-LacI*lacO system as a marker for mosaic analysis, we conducted genetic mosaic analysis of the epidermal growth factor lin-3, expressed in the anchor cell. We establish that lin-3 acts in the anchor cell to induce vulva development, demonstrating this method's utility in detecting the presence of a transgene.

CONCLUSION

The GFP-LacI*lacO transgene detection system works in C. elegans for visualization of chromosomes and extrachromosomal transgenes. It can be used as a marker for genetic mosaic analysis. The lacO repeat sequence as an extrachromosomal array becomes a valuable technique allowing rapid, accurate determination of spontaneous loss of the array, thereby allowing high-resolution mosaic analysis. The lin-3 gene is required in the anchor cell to induce the epidermal vulval precursors cells to undergo vulval development.