Regulation of Neuronal APL-1 Expression by Cholesterol Starvation

Background: Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by the deposition of b-amyloid plaques composed primarily of the amyloid-b peptide, a cleavage product of amyloid precursor protein (APP). While mutations in APP lead to the development of Familial Alzheimer’s Disease (FAD), sporadic AD has only one clear genetic modifier: the e4 allele of the apolipoprotein E (ApoE) gene. Cholesterol starvation in Caenorhabditis elegans leads to molting and arrest phenotypes similar to loss-of-function mutants of the APP ortholog, apl-1 (amyloid precursor-like protein 1), and lrp-1 (lipoprotein receptor-related protein 1), suggesting a potential interaction between apl-1 and cholesterol metabolism. Methodology/Principal Findings: Previously, we found that RNAi knock-down of apl-1 leads to aldicarb hypersensitivity, indicating a defect in synaptic function. Here we find the same defect is recapitulated during lrp-1 knock-down and by cholesterol starvation. A cholesterol-free diet or loss of lrp-1 directly affects APL-1 levels as both lead to loss of APL-1::GFP fluorescence in neurons. However, loss of cholesterol does not affect global transcription or protein levels as seen by qPCR and Western blot. Conclusions: Our results show that cholesterol and lrp-1 are involved in the regulation of synaptic transmission, similar to apl-1. Both are able to modulate APL-1 protein levels in neurons, however cholesterol changes do not affect global apl-1 transcription or APL-1 protein indicating the changes are specific to neurons. Thus, regulation of synaptic transmission an

Mitochondrial Oxidative Stress Alters a Pathway in Caenorhabditis elegans Strongly Resembling That of Bile Acid Biosynthesis and Secretion in Vertebrates

Mammalian bile acids (BAs) are oxidized metabolites of cholesterol whose amphiphilic properties serve in lipid and cholesterol uptake. BAs also act as hormone-like substances that regulate metabolism. The Caenorhabditis elegans clk-1 mutants sustain elevated mitochondrial oxidative stress and display a slow defecation phenotype that is sensitive to the level of dietary cholesterol. We found that: 1) The defecation phenotype of clk-1 mutants is suppressed by mutations in tat-2 identified in a previous unbiased screen for suppressors of clk-1. TAT-2 is homologous to ATP8B1, a flippase required for normal BA secretion in mammals. 2) The phenotype is suppressed by cholestyramine, a resin that binds BAs. 3) The phenotype is suppressed by the knock-down of C. elegans homologues of BA–biosynthetic enzymes. 4) The phenotype is enhanced by treatment with BAs. 5) Lipid extracts from C. elegans contain an activity that mimics the effect of BAs on clk-1, and the activity is more abundant in clk-1 extracts. 6) clk-1 and clk-1;tat-2 double mutants show altered cholesterol content. 7) The clk-1 phenotype is enhanced by high dietary cholesterol and this requires TAT-2. 8) Suppression of clk-1 by tat-2 is rescued by BAs, and this requires dietary cholesterol. 9) The clk-1 phenotype, including the level of activity in lipid extracts, is suppressed by antioxidants and enhanced by depletion of mitochondrial superoxide dismutases. These observations suggest that C. elegans synthesizes and secretes molecules with properties and functions resembling those of BAs. These molecules act in cholesterol uptake, and their level of synthesis is up-regulated by mitochondrial oxidative stress. Future investigations should reveal whether these molecules are in fact BAs, which would suggest the unexplored possibility that the elevated oxidative stress that characterizes the metabolic syndrome might participate in disease processes by affecting the regulation of metabolism by BAs

DAF-12 Regulates a Connected Network of Genes to Ensure Robust Developmental Decisions

The nuclear receptor DAF-12 has roles in normal development, the decision to pursue dauer development in unfavorable conditions, and the modulation of adult aging. Despite the biologic importance of DAF-12, target genes for this receptor are largely unknown. To identify DAF-12 targets, we performed chromatin immunoprecipitation followed by hybridization to whole-genome tiling arrays. We identified 1,175 genomic regions to be bound in vivo by DAF-12, and these regions are enriched in known DAF-12 binding motifs and act as DAF-12 response elements in transfected cells and in transgenic worms. The DAF-12 target genes near these binding sites include an extensive network of interconnected heterochronic and microRNA genes. We also identify the genes encoding components of the miRISC, which is required for the control of target genes by microRNA, as a target of DAF-12 regulation. During reproductive development, many of these target genes are misregulated in daf-12(0) mutants, but this only infrequently results in developmental phenotypes. In contrast, we and others have found that null daf-12 mutations enhance the phenotypes of many miRISC and heterochronic target genes. We also find that environmental fluctuations significantly strengthen the weak heterochronic phenotypes of null daf-12 alleles. During diapause, DAF-12 represses the expression of many heterochronic and miRISC target genes, and prior work has demonstrated that dauer formation can suppress the heterochronic phenotypes of many of these target genes in post-dauer development. Together these data are consistent with daf-12 acting to ensure developmental robustness by committing the animal to adult or dauer developmental programs despite variable internal or external conditions

High-throughput profiling of caenorhabditis elegans starvation-responsive microRNAs

MicroRNAs (miRNAs) are non-coding RNAs of ~22 nucleotides in length that regulate gene expression by interfering with the stability and translation of mRNAs. Their expression is regulated during development, under a wide variety of stress conditions and in several pathological processes. In nature, animals often face feast or famine conditions. We observed that subjecting early L4 larvae from Caenorhabditis elegans to a 12-hr starvation period produced worms that are thinner and shorter than well-fed animals, with a decreased lipid accumulation, diminished progeny, reduced gonad size, and an increased lifespan. Our objective was to identify which of the 302 known miRNAs of C. elegans changed their expression under starvation conditions as compared to well-fed worms by means of deep sequencing in early L4 larvae. Our results indicate that 13 miRNAs (miR-34-3p, the family of miR-35-3p to miR-41-3p, miR-39-5p, miR-41-5p, miR-240-5p, miR-246-3p and miR-4813-5p) were upregulated, while 2 miRNAs (let-7-3p and miR-85-5p) were downregulated in 12-hr starved vs. well-fed early L4 larvae. Some of the predicted targets of the miRNAs that changed their expression in starvation conditions are involved in metabolic or developmental process. In particular, miRNAs of the miR-35 family were upregulated 6-20 fold upon starvation. Additionally, we showed that the expression of gld-1, important in oogenesis, a validated target of miR-35-3p, was downregulated when the expression of miR-35-3p was upregulated. The expression of another reported target, the cell cycle regulator lin-23, was unchanged during starvation. This study represents a starting point for a more comprehensive understanding of the role of miRNAs during starvation in C. elegans

Drug-Induced Progressive Multifocal Leukoencephalopathy: A Comprehensive Analysis of the WHO Adverse Drug Reaction Database

Objective To identify safety signals concerning the association between the use of various drug classes and the onset of progressive multifocal leukoencephalopathy (PML). Methods All reports containing suspected or interacting PML-related or leukoencephalopathy-related drugs, held in the World Health Organization spontaneous individual case safety reports database as at 1 September 2014, were retrieved.Weidentified safety signals by analysing the drug– reaction pairs, using the reporting odds ratio as a measure of disproportionality. A safety signal was defined if a drug was reported more than twice in PML cases with a reporting odds ratio[2 and a lower 95 % confidence limit[1. Results We retrieved 2452 reports associated with PML (N = 1612), leukoencephalopathy (N = 835) or both (N = 5), corresponding to 343 different drugs. PML was reported similarly in male and female adults (18–64 years), and almost 30 % of the cases had a fatal outcome. The most frequent Anatomical Therapeutic Chemical (ATC) classification groups concerned antineoplastic agents (23.5 %), antivirals for systemic use (10.1 %) or immunostimulants (4.6 %). Significant disproportionality was found for 88 drugs in the overall analysis (of cases with ‘progressive multifocal leukoencephalopathy’ or ‘leukoencephalopathy’ as the Preferred Term), and a new safety signal was identified for 59 active substances (e.g. muromonab-CD3, basiliximab and antithymocyte Ig), as no information on a possible risk of PML was acknowledged in their Summary of Product Characteristics documents. Some safety signals were confirmed also after sensitivity analysis adjustment for several confounding factors (underlying diseases and considering only ‘progressive multifocal leukoencephalopathy’ as the Preferred Term). Conclusion We report a possible association between several drugs and PML that has not been previously described. In addition, we have confirmed previously reported signals in a number of drugs. We highlight the need for follow-up by regulatory agencies

Mutation of C. elegans demethylase spr-5 extends transgenerational longevity

Complex organismal properties such as longevity can be transmitted across generations by non-genetic factors. Here we demonstrate that deletion of the C. elegans histone H3 lysine 4 dimethyl (H3K4me2) demethylase, spr-5, causes a trans-generational increase in lifespan. We identify a chromatin-modifying network, which regulates this lifespan extension. We further show that this trans-generational lifespan extension is dependent on a hormonal signaling pathway involving the steroid dafachronic acid, an activator of the nuclear receptor DAF-12. These findings suggest that loss of the demethylase SPR-5 causes H3K4me2 mis-regulation and activation of a known lifespan-regulating signaling pathway, leading to trans-generational lifespan extension