T2-family acidic endoribonucleases are represented in all genomes. A physiological role for RNase T2 has yet to be defined for metazoa. RNASET2 mutation in humans is linked with a leukoencephalopathy that arises in infancy characterized by cortical cysts and multifocal white matter lesions. We now show localization of RNASET2 within lysosomes. Further, we demonstrate that loss of rnaset2 in mutant zebrafish results in accumulation of undigested rRNA within lysosomes within neurons of the brain. Further, by using high field intensity magnetic resonance microimaging, we reveal white matter lesions in these animals comparable to those observed in RNASET2-deficient infants. This correlates with accumulation of Amyloid precursor protein and astrocytes at sites of neurodegeneration. Thus we conclude that familial cystic leukoencephalopathy is a lysosomal storage disorder in which rRNA is the best candidate for the noxious storage material.

Plastic pollution, especially by nanoplastics (NPs), has become an emerging topic due to the widespread existence and accumulation in the environment. The research on bioaccumulation and toxicity mechanism of NPs from polyethylene terephthalate (PET), which is widely used for packaging material, have been poorly investigated. Herein, we report the first use of high-resolution magic-angle spinning (HRMAS) NMR based metabolomics in combination with toxicity assay and behavioural end points to get systems-level understanding of toxicity mechanism of PET NPs in intact zebrafish embryos. PET NPs exhibited significant alterations on hatching and survival rate. Accumulation of PET NPs in larvae were observed in liver, intestine, and kidney, which coincide with localization of reactive oxygen species in these areas. HRMAS NMR data reveal that PET NPs cause: (1) significant alteration of metabolites related to targeting of the liver and pathways associated with detoxification and oxidative stress; (2) impairment of mitochondrial membrane integrity as reflected by elevated levels of polar head groups of phospholipids; (3) cellular bioenergetics as evidenced by changes in numerous metabolites associated with interrelated pathways of energy metabolism. Taken together, this work provides for the first time a comprehensive system level understanding of toxicity mechanism of PET NPs exposure in intact larvae.

Purpose: To assess the development of β‐amyloid (Aβ) plaques in the brain with age in the transgenic mouse model of Alzheimer's disease (AD) pathology by in vivo magnetic resonance microimaging (μMRI).Materials and Methods: Live transgenic mice (Tg2576) and nontransgenic littermates (control) were studied at regular intervals between the ages of 12 and 18 months. Plaques were visualized using a T₂‐weighted rapid acquisition with relaxation enhancement (RARE) sequence. Changes in T₂ relaxation times were followed using a multislice multiecho (MSME) sequence. Plaque load and numerical density in MR images were calculated using SCIL image software.Results: Aβ plaques were clearly detected with the T₂‐weighted RARE sequence in the hippocampal and cortical regions of the brain of Tg2576 mice but not in control mice. Following the plaque development in the same animals with age showed that plaque area, number, and size increased markedly, while T₂ relaxation time showed a decreasing trend with age.Conclusion: These results demonstrate that μMRI is a viable method for following the development of Aβ plaques in vivo, and suggest that this method may be feasible for assessing the effect of therapeutic interventions over time in the same animals. J. Magn. Reson. Imaging 2006.

Aflatoxin B1 (AFB1) is a widespread contaminant of grains and other agricultural crops and is globally associated with both acute toxicity and carcinogenicity. In the present study, we utilized nuclear magnetic resonance (NMR), and specifically high-resolution magic angle spin (HRMAS) NMR, coupled to the zebrafish (Danio rerio) embryo toxicological model, to characterize metabolic profiles associated with exposure to AFB1. Exposure to AFB1 was associated with dose-dependent acute toxicity (i.e., lethality) and developmental deformities at micromolar (≤ 2 µM) concentrations. Toxicity of AFB1 was stage-dependent and specifically consistent, in this regard, with a role of the liver and phase I enzyme (i.e., cytochrome P450) bioactivation. Metabolic profiles of intact zebrafish embryos exposed to AFB1 were, furthermore, largely consistent with hepatotoxicity previously reported in mammalian systems including metabolites associated with cytotoxicity (i.e., loss of cellular membrane integrity), glutathione-based detoxification, and multiple pathways associated with the liver including amino acid, lipid, and carbohydrate (i.e., energy) metabolism. Taken together, these metabolic alterations enabled the proposal of an integrated model of the hepatotoxicity of AFB1 in the zebrafish embryo system. Interestingly, changes in amino acid neurotransmitters (i.e., Gly, Glu, and GABA), as a key modulator of neural development, supports a role in recently-reported neurobehavioral and neurodevelopmental effects of AFB1 in the zebrafish embryo model. The present study reinforces not only toxicological pathways of AFB1 (i.e., hepatotoxicity, neurotoxicity), but also multiple metabolites as potential biomarkers of exposure and toxicity. More generally, this underscores the capacity of NMR-based approaches, when coupled to animal models, as a powerful toxicometabolomics tool.

β-methylamino-L-alanine (BMAA) has been linked to several interrelated neurodegenerative diseases. Despite considerable research, specific contributions of BMAA toxicity to neurodegenerative diseases remain to be fully resolved. In the present study, we utilized state-of-the-art high-resolution magic-angle spinning nuclear magnetic resonance (HRMAS NMR), applied to intact zebrafish (Danio rerio) embryos, as a model of vertebrate development, to elucidate changes in metabolic profiles associated with BMAA exposure. Complemented by several alternative analytical approaches (i.e., in vivo visualization and in vitro assay), HRMAS NMR identified robust and dose-dependent effect of BMAA on several relevant metabolic pathways suggesting a multifaceted toxicity of BMAA including: (1) localized production of reactive oxygen species (ROS), in the developing brain, consistent with excitotoxicity; (2) decreased protective capacity against excitotoxicity and oxidative stress including reduced taurine and glutathione; (3) inhibition of several developmentally stereotypical energetic and metabolic transitions, i.e., metabolic reprogramming; and (4) inhibition of lipid biosynthetic pathways. Matrix-assisted laser desorption time-of-flight (MALDI-ToF) mass spectrometry further identified specific effects on phospholipids linked to both neural development and neurodegeneration. Taken together, a unified model of the neurodevelopmental toxicity of BMAA in the zebrafish embryo is presented in relation to the potential contribution of BMAA to neurodegenerative disease.