Project description:The multi-lab International Life Sciences Institute (ILSI) project on the application of genomics to risk assessment offered the unique opportunity to investigate the influence of variability within and between laboratories on identifying biologically relevant gene expression changes. We assessed the gene expression profiles of mouse lymphoma L5178Y cells treated with hydroxyurea (HU) in three independent studies from two different laboratories, Sanofi-Aventis and Procter and Gamble. Cells were dosed for 4 hr and harvested immediately at the end of the treatment or after a 20-hr recovery period. Cytotoxicity and genotoxicity were evaluated by standard assays. Statistical analysis of these data revealed that, while gene expression responses to HU treatment were markedly different at 4 hr vs. 24 hr, there was otherwise a consistent pattern of dose-response across the three studies. Therefore, the studies were merged and each time point was evaluated separately. At 4 hr, we identified 173 (P lt 0.0001) dose-responsive genes with a common trend in all three studies. These were mainly associated with the cell cycle, DNA repair and DNA metabolism, and in particular, the intra-S and G2/M phase checkpoints. At 24 hr, we identified 434 dose-responsive genes common across studies. These genes were involved in lymphocyte-specific activities and the activation of apoptosis via the caspase cascade. Our results show that despite inter-laboratory variability, combining the three studies in a single statistical analysis identifies more significantly-modulated genes than in any of the individual studies, due to improved statistical sensitivity. The genes identified in our study provide information that is relevant to HU biology.
Project description:AtGenExpress: A multinational coordinated effort to uncover the transcriptome of the multicellular model organism Arabidopsis thaliana. The activity of genes and their encoded products can be regulated in several ways, but transcription is the primary level, since all other modes of regulation (RNA splicing, RNA and protein stability, etc.) are dependent on a gene being transcribed in the first place. The importance of transcriptional regulation has been underscored by the recent flood of global expression analyses, which have confirmed that transcriptional co-regulation of genes that act together is the norm, not the exception. Moreover, many studies suggest that evolutionary change is driven in large part by modifications of transcriptional programs. An essential first step toward deciphering the transcriptional code is to determine the expression pattern of all genes. With this goal in mind, an international effort to develop a gene expression atlas of Arabidopsis has been underway since fall 2003. This project, dubbed AtGenExpress, is funded by the DFG, and will provide the Arabidopsis community with access to a large set of Affymetrix microarray data. As part of this collaboration, we have generated expression data from 80 biologicaly different samples in triplicate. Seeds of Arabidopsis thaliana Wild Type (col-0) were sown on rafts in Magenta boxes containing MS-Agar-media. After 2 days in the cold room (4°C, dark) the boxes were transferred to the long day chamber. Long day conditions were 16/8 hrs light/dark, 24°C, 50% humidity and 150 µEinstein/cm2 sec light intensity. At day 11 the rafts were transferred in Magenta boxes containing MS-liquid-media. At day 16 stress treatment started at 3 hrs of light period; samples taken at 0.5, 1, 3, 6, 12, 24 h after treatment (in selected indicated cases 0.25h and 4.0h too), control samples include 0h; roots and shoots were prepared separately; all treatments and preparations were done on the same batch of seedlings in one place (Lab J.Kudla/Ulm, Germany) by coworkers from the indicated groups. Experimenter name = Holger Puchta , I-Peng Chen; Experimenter institute = AtGenExpress Experiment Overall Design: 24 samples were used in this experiment