Current environmental monitoring programs focus primarily on legacy contaminants identified in the past as priority pollutants. Many new chemicals including so-called contaminants of emerging concern (CECs) are being widely dispersed into the environment and the development of sensitive tools that can screen endocrine responses and monitor the harmful effects of pollutants has become a priority. We developed a focused quantitative polymerase chain reaction (q-PCR) panel containing key endocrine gene targets for investigation of the effects of contaminants on transcriptional patterns in the demersal marine flatfish, hornyhead turbot (Pleuronichthys verticalis). An additional objective was to develop this tool so that it had broad applicability for monitoring endocrine disruption in other sentinel species, including California flatfish. This endocrine q-PCR panel was validated by studying transcriptional perturbations in 2 important sentinel species, hornyhead turbot and English sole (Parophrys vetulus), both sampled from sewage outfall and reference coastal waters in Southern California. In addition, the cross species utility of the endocrine q-PCR panel was examined by its application to the study of gene expression changes in laboratory male zebrafish (Danio rerio) following exposure to 17-β estradiol and 4-nonylphenol.

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In eukaryotic cells, chromatin reorganizes within promoters of active genes to allow the transcription machinery and various transcription factors to access DNA. In this model, promoter-specific transcription factors bind DNA to initiate the production of mRNA in a tightly regulated manner. In the case of the human malaria parasite, Plasmodium falciparum, specific transcription factors are apparently underrepresented with regards to the size of the genome, and mechanisms underlying transcriptional regulation are controversial. Here, we investigate the modulation of DNA accessibility by chromatin remodeling during the parasite infection cycle. We have generated genome-wide maps of nucleosome occupancy across the parasite erythrocytic cycle using two complementary assays--the formaldehyde-assisted isolation of regulatory elements to extract protein-free DNA (FAIRE) and the MNase-mediated purification of mononucleosomes to extract histone-bound DNA (MAINE), both techniques being coupled to high-throughput sequencing. We show that chromatin architecture undergoes drastic upheavals throughout the parasite's cycle, contrasting with targeted chromatin reorganization usually observed in eukaryotes. Chromatin loosens after the invasion of the red blood cell and then repacks prior to the next cycle. Changes in nucleosome occupancy within promoter regions follow this genome-wide pattern, with a few exceptions such as the var genes involved in virulence and genes expressed at early stages of the cycle. We postulate that chromatin structure and nucleosome turnover control massive transcription during the erythrocytic cycle. Our results demonstrate that the processes driving gene expression in Plasmodium challenge the classical eukaryotic model of transcriptional regulation occurring mostly at the transcription initiation level.

Department of Cell Biology and Neuroscience, University of California, Riverside, 900 University Avenue, Riverside, CA 92521, USA. Department of Computer Science and Engineering, University of California, Riverside, 900 University Avenue, Riverside, CA 92521, USA. BIOGEM, School of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA. Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA. Institute of Integrative Genomics Biology, University of California, Riverside, 900 University Avenue, Riverside, CA 92521, USA.

BackgroundEndocrine disruptors include plasticizers, pesticides, detergents, and pharmaceuticals. Turbot and other flatfish are used to characterize the presence of chemicals in the marine environment. Unfortunately, there are relatively few genes of turbot and other flatfish in GenBank, which limits the use of molecular tools such as microarrays and quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) to study disruption of endocrine responses in sentinel fish captured by regulatory agencies.ObjectivesWe fabricated a multigene cross-species microarray as a diagnostic tool to screen the effects of environmental chemicals in fish, for which there is minimal genomic information. The array included genes that are involved in the actions of adrenal and sex steroids, thyroid hormone, and xenobiotic responses. This microarray will provide a sensitive tool for screening for the presence of chemicals with adverse effects on endocrine responses in coastal fish species.MethodsWe used a custom multispecies microarray to study gene expression in wild hornyhead turbot (Pleuronichthys verticalis) collected from polluted and clean coastal waters and in laboratory male zebrafish (Danio rerio) after exposure to estradiol and 4-nonylphenol. We measured gene-specific expression in turbot liver by qRT-PCR and correlated it to microarray data.ResultsMicroarray and qRT-PCR analyses of livers from turbot collected from polluted areas revealed altered gene expression profiles compared with those from nonaffected areas.ConclusionsThe agreement between the array data and qRT-PCR analyses validates this multispecies microarray. The microarray measurement of gene expression in zebrafish, which are phylogenetically distant from turbot, indicates that this multispecies microarray will be useful for measuring endocrine responses in other fish.

Background Successful microarray experimentation requires a complex interplay between the slide chemistry, the printing pins, the nucleic acid probes and targets, and the hybridization milieu. Optimization of these parameters and a careful evaluation of emerging slide chemistries are a prerequisite to any large scale array fabrication effort. We have developed a 'microarray meter' tool which assesses the inherent variations associated with microarray measurement prior to embarking on large scale projects. Findings The microarray meter consists of nucleic acid targets (reference and dynamic range control) and probe components. Different plate designs containing identical probe material were formulated to accommodate different robotic and pin designs. We examined the variability in probe quality and quantity (as judged by the amount of DNA printed and remaining post-hybridization) using three robots equipped with capillary printing pins. Discussion The generation of microarray data with minimal variation requires consistent quality control of the (DNA microarray) manufacturing and experimental processes. Spot reproducibility is a measure primarily of the variations associated with printing. The microarray meter assesses array quality by measuring the DNA content for every feature. It provides a post-hybridization analysis of array quality by scoring probe performance using three metrics, a) a measure of variability in the signal intensities, b) a measure of the signal dynamic range and c) a measure of variability of the spot morphologies.

In adult cystic fibrosis patient populations, gram-negative bacteria, particularly Pseudomonas aeruginosa, frequently require aggressive therapy including systemic antibiotics, bronchodilators and airway clearance techniques. Aminoglycosides including tobramycin are used frequently to control these chronic airway infections. They, however, cause important nephrotoxic and ototoxic effects that can significantly alter the quality of life. We investigated the genetic predisposition to aminoglycoside ototoxicity in a typical unscreened North American cystic fibrosis population by screening for variants in mitochondrial 12S ribosomal RNA and noted several polymorphisms occurred at higher frequencies than expected and were associated with clinically significant cases of hearing loss. In the population studied, both patients possessing the 1555A>G transition exhibited profound ototoxicity after nontoxic dosing of tobramycin. We also identified new homoplasmic genetic variations in the mitochondrial 12S ribosomal RNA, several of which occurred in highly conserved regions of the gene and were present in patients with moderate-to-severe ototoxicity after exposure to aminoglycosides.

Improvements in DNA microarray technology have resulted in the generation of data on a scale that, for the first time, permits detailed scrutiny of the human genome. These data provide the foundation for understanding not only the connections between genes and the purpose of genes in the human genome, but also the molecular basis of genetic defects. These advances have the potential to significantly improve healthcare management by improving disease diagnosis and specifically targeting molecular therapy. Herein, the current state of the technology is reviewed, the commercial platforms used by the biopharmaceutical industry are compared and contrasted, and recent efforts in cross-platform data integration are explored.