Identification and expression analysis of the zebrafish orthologues of the mammalian MAP1LC3 gene family

Combined treatment of melatonin and sodium tanshinone IIA sulfonate reduced the neurological and cardiovascular toxicity induced by deltamethrin in zebrafish

The pyrethroid insecticide deltamethrin has been reported to have an effect on vertebrate development and cardiovascular disease. Sodium tanshinone IIA sulfonate (STS) is considered to have cardioprotective effects and melatonin is known to regulate sleep-waking cycles. In this experiment, we used transgenic zebrafish Tg (kdrl:mCherry) and Tg (myl7:GFP) to investigate whether STS and melatonin could reverse the cardiovascular toxicity and neurotoxicity induced by deltamethrin. Zebrafish embryos were exposed to 25 μg/L deltamethrin at 10 hpf and treated with 100 mmol/L STS and 1 μmol/L melatonin showed that deltamethrin treatment affected normal cardiovascular development. In situ hybridization and qRT-PCR results showed that deltamethrin could interfere with the normal expression of cardiovascular development-related genes vegfr2, shh, gata4, nkx2.5, causing functional defects in the cardiovascular system. In addition, deltamethrin could affect the sleep-waking behavior of larvae, increasing the activity of larvae, decreasing the rest behavior and the expression of hcrt, hcrtr, aanat2 were down-regulated. The addition of melatonin and STS can significantly alleviate cardiovascular toxicity and sleep-waking induced by deltamethrin, while restoring the expression of related genes to normal levels. Our study demonstrates the role of STS and melatonin in protecting cardiovascular and sleep-waking behavior caused by deltamethrin.

Evaluating expression of autophagy-related genes in oriental river prawn Macrobrachium nipponense as potential biomarkers for hypoxia exposure

Autophagy, a crucial process for maintaining cellular homeostasis, is under the control of several autophagy-related (ATG) proteins, and is highly conserved in most animals, but its response to adverse environmental conditions is poorly understood in crustaceans. Herein, we hypothesised that autophagy acts as a protective response to hypoxia, and Beclin 1, ATG7 and ATG8 in oriental river prawn (Macrobrachium nipponense) were chosen as potential biomarkers under hypoxia exposure; thus, their full-length cDNA sequences were cloned and characterised. Open reading frames (ORFs) of 1281, 2076 and 360 bp, encoding proteins of 427, 692 and 120 amino acid residues, respectively, were obtained. Phylogenetic analysis demonstrated the three M. nipponense proteins do not form a clade with vertebrate homologs. Protein and mRNA levels were investigated in different tissues and developmental stages, and all three were significantly upregulated in a time-dependent manner in the hepatopancreas following hypoxia stress. Biochemical and morphological analysis of hepatocytes revealed that hypoxia increased the abundance of hepatic autophagic vacuoles and stimulated anaerobic metabolism. RNA interference-mediated silencing of ATG8 significantly increased the death rate of M. nipponense juveniles under hypoxia stress conditions. Together, these results suggest that Beclin 1, ATG7 and ATG8 contribute to autophagy-based responses against hypoxia in M. nipponense. The findings also expand our understanding of the potential role of autophagy as an adaptive response against hypoxia toxicity in crustaceans. The results showed that hepatic ATG8 levels may be directly indicative of acute hypoxia in prawns, and provide insight into the time at which hypoxia exposure occurs. Autophagy-related genes expression pattern seems to be sensitive and good biomarkers of acute hypoxia exposure.

Wnt/β-catenin signaling regulates VE-cadherin-mediated anastomosis of brain capillaries by counteracting S1pr1 signaling

Canonical Wnt signaling is crucial for vascularization of the central nervous system and blood-brain barrier (BBB) formation. BBB formation and modulation are not only important for development, but also relevant for vascular and neurodegenerative diseases. However, there is little understanding of how Wnt signaling contributes to brain angiogenesis and BBB formation. Here we show, using high resolution in vivo imaging and temporal and spatial manipulation of Wnt signaling, different requirements for Wnt signaling during brain angiogenesis and BBB formation. In the absence of Wnt signaling, premature Sphingosine-1-phosphate receptor (S1pr) signaling reduces VE-cadherin and Esama at cell-cell junctions. We suggest that Wnt signaling suppresses S1pr signaling during angiogenesis to enable the dynamic junction formation during anastomosis, whereas later S1pr signaling regulates BBB maturation and VE-cadherin stabilization. Our data provides a link between brain angiogenesis and BBB formation and identifies Wnt signaling as coordinator of the timing and as regulator of anastomosis.

Identification of autophagy related genes LC3 and ATG4 from yellow catfish Pelteobagrus fulvidraco and their transcriptional responses to waterborne and dietborne zinc exposure

Autophagy mediates the regulation of lipid metabolism. Moreover, our recent study indicated that waterborne and dietborne zinc (Zn) exposure differentially influenced lipid metabolism in a fish species of significance for aquaculture, yellow catfish Pelteobagrus fulvidraco, but further mechanism remained unknown. The hypothesis of the present study is that autophagy mediated the Zn-induced changes of lipid metabolism of yellow catfish subjected to different exposure pathways. To this end, we cloned key genes involved in autophagy in yellow catfish, explored their mRNA expressions in responses to different Zn exposure pathways. Full-length cDNA sequences of two LC3 subtypes and six ATG4 isoforms were isolated from yellow catfish. More ATG4 members were firstly identified in fish that might have arisen by teleost-specific whole genome duplication events. All of these members shared similar domain structure to their orthologous genes of vertebrates. Their mRNAs were widely expressed in various tissues, but at variable levels. Extra Zn addition in water or diets induced (P < 0.05) mRNA expression of ATG4Da, ATG4Db and LC3B. Considering their important roles of these genes in lipid metabolism, ATG4Da, ATG4Db and LC3B may mediate the changes of Zn-induced hepatic lipid metabolism of yellow catfish under different Zn exposure pathways. For the first time, we characterized the full-length cDNA sequences of six ATG4 isoforms and two LC3 subtypes, determined their tissue expression profiles and transcriptional responses to different Zn exposure pathways, which would contribute to our understanding of the molecular basis of autophagy, and also provide new insights into physiological responses to different Zn exposure pathways.

HS1BP3 negatively regulates autophagy by modulation of phosphatidic acid levels

A fundamental question is how autophagosome formation is regulated. Here we show that the PX domain protein HS1BP3 is a negative regulator of autophagosome formation. HS1BP3 depletion increased the formation of LC3-positive autophagosomes and degradation of cargo both in human cell culture and in zebrafish. HS1BP3 is localized to ATG16L1- and ATG9-positive autophagosome precursors and we show that HS1BP3 binds phosphatidic acid (PA) through its PX domain. Furthermore, we find the total PA content of cells to be significantly upregulated in the absence of HS1BP3, as a result of increased activity of the PA-producing enzyme phospholipase D (PLD) and increased localization of PLD1 to ATG16L1-positive membranes. We propose that HS1BP3 regulates autophagy by modulating the PA content of the ATG16L1-positive autophagosome precursor membranes through PLD1 activity and localization. Our findings provide key insights into how autophagosome formation is regulated by a novel negative-feedback mechanism on membrane lipids.

Autophagy must be tightly controlled at each step of the process. Here the authors show that HS1BP3 binds phosphatidic acid (PA) at autophagosome precursors and negatively regulates autophagosome formation by modulating the activity and localization of the PA-producing enzyme phospholipase D1.

Functionally conserved effects of rapamycin exposure on zebrafish

Mechanistic target of rapamycin (mTOR) is a conserved serine/threonine kinase important in cell proliferation, growth and protein translation. Rapamycin, a well‑known anti‑cancer agent and immunosuppressant drug, inhibits mTOR activity in different taxa including zebrafish. In the present study, the effect of rapamycin exposure on the transcriptome of a zebrafish fibroblast cell line, ZF4, was investigated. Microarray analysis demonstrated that rapamycin treatment modulated a large set of genes with varying functions including protein synthesis, assembly of mitochondrial and proteasomal machinery, cell cycle, metabolism and oxidative phosphorylation in ZF4 cells. A mild however, coordinated reduction in the expression of proteasomal and mitochondrial ribosomal subunits was detected, while the expression of numerous ribosomal subunits increased. Meta‑analysis of heterogeneous mouse rapamycin microarray datasets enabled the comparison of zebrafish and mouse pathways modulated by rapamycin, using Kyoto Encyclopedia of Genes and Genomes and Gene Ontology pathway analysis. The analyses demonstrated a high degree of functional conservation between zebrafish and mice in response to rapamycin. In addition, rapamycin treatment resulted in a marked dose‑dependent reduction in body size and pigmentation in zebrafish embryos. The present study is the first, to the best of our knowledge, to evaluate the conservation of rapamycin‑modulated functional pathways between zebrafish and mice, in addition to the dose‑dependent growth curves of zebrafish embryos upon rapamycin exposure.