Protection against nonylphenol-induced cell death by DJ-1 in cultured Japanese medaka (Oryzias latipes) cells

Complex molecular changes induced by chronic progestogens exposure in roach, Rutilus rutilus

In our previous study, we measured 0.23-13.67ng/L progestogens (progesterone, drospirenone, levonorgestrel) in natural waters in the catchment area of the largest shallow lake of Central Europe, Lake Balaton. Progestogen contaminations act as potent steroids with mixed progestagenic, androgenic and mild estrogenic effects that is why our aim was to investigate the morphological and molecular effects of mixture of progesterone, drospirenone, and levonorgestrel in environmentally relevant (10ng/L) and higher (50 and 500ng/L) exposure concentrations in common roach, Rutilus rutilus. Steroids (e.g. progestogens) and the protein deglycase DJ-1 chaperon molecule aim the same target molecules in cells, therefore, we hypothesized that a relationship may exist between progestogens and DJ-1. Furthermore, our other aim was to follow the changes of signal molecules of different biological function due to progestogen treatment in serum and brain. Adult roaches were exposed to 10, 50 and 500ng/L of mixture of progestogen for 42 days and their somatic indices (brain-somatic, liver-somatic, gonadosomatic and kidney-somatic) were measured. Vitellogenin (VTG) expression (estrogen effect) or inhibition (androgen effect) in fish is a widely used biomarker so we measured its changes in liver by ELISA. To determine the quantity and to map the spatial distribution of DJ-1 chaperon protein the brain and liver tissues were analyzed by ELISA and immunohistochemistry. Furthermore, we also studied molecular alterations: a) in the serum by measuring cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL) and triglyceride concentrations and b) in brain homogenate using a cell stress array kit (26 protein). The somatic index of liver and kidney significantly in all the treated groups, whereas the gonadosomatic index of 500ng/L treated group showed significant decrease compared to control animals. VTG level increased significantly in 500ng/L progestogen treated group. Since the concentration of DJ-1 significantly increased in brain and liver in all progestogen treatment groups, the DJ-1 protein could be able to a more sensitive marker than VTG. Serum LDL and cholesterol levels of exposed fish were significantly decreased. DJ-1 was mediated through the stimulation of the expression of LDL-receptor which facilitates reuptake subsequently. In summary, our observations unfolded new data about molecular alterations induced by the combined action of environmental progestogens. In addition, the DJ-1 chaperon protein as a possible biomarker helped to trace the abiotic chemical environmental contaminations, like progestogens in the freshwater ecosystems.

Loss of DJ-1 elicits retinal abnormalities, visual dysfunction, and increased oxidative stress in mice

DJ-1/PARK7 mutations or deletions cause autosomal recessive early onset Parkinson's disease (PD). Thus, DJ-1 protein has been extensively studied in brain and neurons. PD patients display visual symptoms; however, the visual symptoms specifically attributed to PD patients carrying DJ-1/PARK7 mutations are not known. In this study, we analyzed the structure and physiology of retinas of 3- and 6-month-old DJ-1 knockout (KO) mice to determine how loss of function of DJ-1 specifically contributes to the phenotypes observed in PD patients. As compared to controls, the DJ-1 KO mice displayed an increase in the amplitude of the scotopic ERG b-wave and cone ERG, while the amplitude of a subset of the dc-ERG components was decreased. The main structural changes in the DJ-1 KO retinas were found in the outer plexiform layer (OPL), photoreceptors and retinal pigment epithelium (RPE), which were observed at 3 months and progressively increased at 6 months. RPE thinning and structural changes within the OPL were observed in the retinas in DJ-1 KO mice. DJ-1 KO retinas also exhibited disorganized outer segments, central decrease in red/green cone opsin staining, decreased labeling of ezrin, broader distribution of ribeye labeling, decreased tyrosine hydroxylase in dopaminergic neurons, and increased 7,8-dihydro-8-oxoguanine-labeled DNA oxidation. Accelerated outer retinal atrophy was observed in DJ-1 KO mice after selective oxidative damage induced by a single tail vein injection of NaIO3, exposing increased susceptibility to oxidative stress. Our data indicate that DJ-1-deficient retinas exhibit signs of morphological abnormalities and physiological dysfunction in association with increased oxidative stress. Degeneration of RPE cells in association with oxidative stress is a key hallmark of age-related macular degeneration (AMD). Therefore, in addition to detailing the visual defects that occur as a result of the absence of DJ-1, our data is also relevant to AMD pathogenesis.

Gene networks and toxicity pathways induced by acute cadmium exposure in adult largemouth bass (Micropterus salmoides)

Cadmium is a heavy metal that can accumulate to toxic levels in the environment leading to detrimental effects in animals and humans including kidney, liver and lung injuries. Using a transcriptomics approach, genes and cellular pathways affected by a low dose of cadmium were investigated. Adult largemouth bass were intraperitoneally injected with 20μg/kg of cadmium chloride (mean exposure level - 2.6μg of cadmium per fish) and microarray analyses were conducted in the liver and testis 48h after injection. Transcriptomic profiles identified in response to cadmium exposure were tissue-specific with the most differential expression changes found in the liver tissues, which also contained much higher levels of cadmium than the testis. Acute exposure to a low dose of cadmium induced oxidative stress response and oxidative damage pathways in the liver. The mRNA levels of antioxidants such as catalase increased and numerous transcripts related to DNA damage and DNA repair were significantly altered. Hepatic mRNA levels of metallothionein, a molecular marker of metal exposure, did not increase significantly after 48h exposure. Carbohydrate metabolic pathways were also disrupted with hepatic transcripts such as UDP-glucose, pyrophosphorylase 2, and sorbitol dehydrogenase highly induced. Both tissues exhibited a disruption of steroid signaling pathways. In the testis, estrogen receptor beta and transcripts linked to cholesterol metabolism were suppressed. On the contrary, genes involved in cholesterol metabolism were highly increased in the liver including genes encoding for the rate limiting steroidogenic acute regulatory protein and the catalytic enzyme 7-dehydrocholesterol reductase. Integration of the transcriptomic data using functional enrichment analyses revealed a number of enriched gene networks associated with previously reported adverse outcomes of cadmium exposure such as liver toxicity and impaired reproduction.

Oxidative stress regulation by DJ-1 in the retinal pigment epithelium

DJ-1 is a protein expressed in many tissues including the brain where it has been extensively studied due to its association with Parkinson's Disease (PD). DJ-1 was reported to function as an antioxidant, redox-sensitive molecular chaperone, and transcription regulator, which protected cells from oxidative stress by modifying signaling pathways that regulate cell survival. Here we discuss our progress toward characterization of the DJ-1 function in the protection of RPE to oxidative stress.

Quantitative proteomic analysis reveals the mode-of-action for chronic mercury hepatotoxicity to marine medaka (Oryzias melastigma)

Mercury (Hg) is a widespread persistent pollutant in aquatic ecosystems. We investigated the protein profiles of medaka (Oryzias melastigma) liver chronically exposed to different mercuric chloride (HgCl2) concentrations (1 or 10 μg/L) for 60 d using two-dimensional difference gel electrophoresis (2D-DIGE), as well as cell ultrastructure and Hg content analysis of the hepatic tissue. The results showed that Hg exposure significantly increased metal accumulation in the liver, and subsequently damaged liver ultrastructure. Comparison of the 2D-DIGE protein profiles of the exposed and control groups revealed that the abundance of 45 protein spots was remarkably altered in response to Hg treatment. The altered spots were subjected to matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry analysis, with the resultant identification of 33 spots. These proteins were mainly involved in cytoskeleton assembly, oxidative stress, and energy production. Among them, several proteins related to mitochondrial function (e.g. respiratory metabolism) were significantly altered in the treated hepatocytes, implying that this organelle might be the primary target for Hg attack in the cells. This study provided new insights into the molecular mechanisms and/or toxic pathways by which chronic Hg hepatotoxicity affects aquatic organisms, and also provided basic information for screening potential biomarkers for aquatic Hg monitoring.

Efficient targeted mutagenesis in medaka using custom-designed transcription activator-like effector nucleases

Transcription activator-like effector nucleases (TALENs) have become powerful tools for targeted genome editing. Here we demonstrate efficient targeted mutagenesis in medaka (Oryzias latipes), which serves as an excellent vertebrate model for genetics and genomics. We designed and constructed a pair of TALENs targeting the medaka DJ-1 gene, a homolog of human DJ-1 (PARK7). These TALENs induced a number of insertions and deletions in the injected embryos with extremely high efficiency. This induction of mutations occurred in a dose-dependent manner. All screened G0 fish injected with the TALENs transmitted the TALEN-induced mutations to the next generation with high efficiency (44-100%). We also confirmed that these TALENs induced site-specific mutations because none of the mutations were found at potential off-target sites. In addition, the DJ-1 protein was lost in DJ-1(Δ7/Δ7) fish that carried a TALEN-induced frameshift mutation in both alleles. We also investigated the effect of the N- and C-terminal regions of the transcription activator-like (TAL) effector domain on the gene-disrupting activity of DJ1-TALENs and found that 287 amino acids at the N terminus and 63 amino acids at the C terminus of the TAL domain exhibited the highest disrupting activity in the injected embryos. Our results suggest that TALENs enable us to rapidly and efficiently establish knockout medaka strains. This is the first report of targeted mutagenesis in medaka using TALENs. The TALEN technology will expand the potential of medaka as a model system for genetics and genomics.

Long-term survival of hydrated resting eggs from Brachionus plicatilis

Background

Several organisms display dormancy and developmental arrest at embryonic stages. Long-term survival in the dormant form is usually associated with desiccation, orthodox plant seeds and Artemia cysts being well documented examples. Several aquatic invertebrates display dormancy during embryonic development and survive for tens or even hundreds of years in a hydrated form, raising the question of whether survival in the non-desiccated form of embryonic development depends on pathways similar to those occurring in desiccation tolerant forms.

Methodology/Principal Findings

To address this question, Illumina short read sequencing was used to generate transcription profiles from the resting and amictic eggs of an aquatic invertebrate, the rotifer, Brachionus plicatilis. These two types of egg have very different life histories, with the dormant or diapausing resting eggs, the result of the sexual cycle and amictic eggs, the non-dormant products of the asexual cycle. Significant transcriptional differences were found between the two types of egg, with amictic eggs rich in genes involved in the morphological development into a juvenile rotifer. In contrast, representatives of classical “stress” proteins: a small heat shock protein, ferritin and Late Embryogenesis Abundant (LEA) proteins were identified in resting eggs. More importantly however, was the identification of transcripts for messenger ribonucleoprotein particles which stabilise RNA. These inhibit translation and provide a valuable source of useful RNAs which can be rapidly activated on the exit from dormancy. Apoptotic genes were also present. Although apoptosis is inconsistent with maintenance of prolonged dormancy, an altered apoptotic pathway has been proposed for Artemia, and this may be the case with the rotifer.

Conclusions

These data represent the first transcriptional profiling of molecular processes associated with dormancy in a non-desiccated form and indicate important similarities in the molecular pathways activated in resting eggs compared with desiccated dormant forms, specifically plant seeds and Artemia.

Structural impact of three Parkinsonism-associated missense mutations on human DJ-1

A number of missense mutations in the oxidative stress response protein DJ-1 are implicated in rare forms of familial Parkinsonism. The best-characterized Parkinsonian DJ-1 missense mutation, L166P, disrupts homodimerization and results in a poorly folded protein. The molecular basis by which the other Parkinsonism-associated mutations disrupt the function of DJ-1, however, is incompletely understood. In this study we show that three different Parkinsonism-associated DJ-1 missense mutations (A104T, E163K, and M26I) reduce the thermal stability of DJ-1 in solution by subtly perturbing the structure of DJ-1 without causing major folding defects or loss of dimerization. Atomic resolution X-ray crystallography shows that the A104T substitution introduces water and a discretely disordered residue into the core of the protein, E163K disrupts a key salt bridge with R145, and M26I causes packing defects in the core of the dimer. The deleterious effect of each Parkinsonism-associated mutation on DJ-1 is dissected by analysis of engineered substitutions (M26L, A104V, and E163K/R145E) that partially alleviate each of the defects introduced by the A104T, E163K and M26I mutations. In total, our results suggest that the protective function of DJ-1 can be compromised by diverse perturbations in its structural integrity, particularly near the junctions of secondary structural elements.