Gonzales, Patrick K et al. (2011) International Worm Meeting "Mitochondrial Fission Protects C. elegans from Amyloid-Beta Toxicity."

Link, Christopher D, Gonzales, Patrick K

[International Worm Meeting, 2011]

Alzheimers disease (AD) is a late-onset age-dependent, neurodegenerative disorder affecting 5.3 million Americans. Current evidence points to amyloid beta (Ab), a peptide derived from the amyloid precursor protein (APP), as playing a central role in AD pathogenesis, but mechanisms of Ab toxicity remain unclear. One possible mechanism of Ab toxicity is mitochondrial dysfunction. Amyloid beta induces mitochondrial dysfunction in many AD model systems. Evidence of abnormal mitochondria morphology is present in AD post mortem brain tissue, APP over-expressing neuroblastoma cells, and our Ab expressing transgenic worm. Mitochondria morphology is controlled by a number of fission and fusion genes. Fission and fusion genes are abnormally expressed upon induction of Ab in neuronal cell lines. In this study, we explored the effect of fission and fusion genes on Ab toxicity in a transgenic Ab (1-42) producing worm. We found increased mitochondrial fragmentation in response to Ab induction. We also report that RNAi knockdown of fission genes drp-1 and fis-1 result in increased toxicity, while RNAi of fusion gene eat-3 protects against Ab toxicity. Our results suggest that mitochondrial fission is a protective mechanism against Ab toxicity. Currently, we are exploring autophagy as a potential mechanism for mitochondrial fissions protection against Ab toxicity.

Lavigne JP et al. (2006) Pathol Biol (Paris) "[Caenorhabditis elegans: in vivo study model of bacterial virulence]"

O'Callaghan D, Bourg G, Blanc-Potard AB, Lavigne JP, Sotto A

[Pathol Biol (Paris), 2006]

The nematode Caenorhabditis elegans presents many advantages as a model system. The worm has recently emerged as a potentially useful tool for the study of host-pathogen interactions. This paper presents advantages and inconveniences of this model, the variety of bacterial pathogens studied, and its use to monitor virulence of Extraintestinal Escherichia coli strains.

Wood, Michael L et al. (2011) International Worm Meeting "Transgenic Caenorhabditis elegans expressing Alzheimer's pathway proteins to produce b-amyloid toxicity."

Hart, Anne, Wood, Michael L

[International Worm Meeting, 2011]

Neuronal degeneration in Alzheimer's disease (AD) has been associated with intraneuronal aggregation of b-amyloid (Ab). It has been previously shown that neuronal expression of Ab in Caenorhabditis elegans results in intraneuronal accumulation of the peptide along with phenotypes indicating toxicity including, defects in learning behaviors, chemotaxis deficits and hypersensitivity to serotonin (Link, 2006; Wu et al, 2006). Ab is derived from a much larger precursor protein APP which undergoes two cleavage events in the amyloidogenic pathway. Our aim is to create transgenic C. elegans that generate Ab precursor proteins within their neurons. This should lead to the aggregation of Ab and neurodegeneration. We hope this approach will closely mimic the normal pathway of Ab generation in an invertebrate model.

Yuan Luo et al. (2008) C.elegans Aging, Stress, Pathogenesis, and Heterochrony Meeting "Heat Shock Treatment Reduces Beta Amyloid Toxicity In Vivo By Diminishing Oligomers"

William Klein, Zhiming Cao, Yuan Luo, Yanjue Wu

[C.elegans Aging, Stress, Pathogenesis, and Heterochrony Meeting, 2008]

Heat shock response, mediated by heat shock proteins, is a highly conserved physiological process in multicellular organisms for maintenance of cellular homeostasis. Expression of heat shock factors and subsequent heat shock protein plays a role in protection against proteotoxicity in invertebrate and vertebrate models. Proteotoxicity due to b-amyloid peptide (Ab) oligomerization has been linked to the pathogenesis of Alzheimer''s disease. In a transgenic C. elegans model of AD, intracellular expression of human Ab is associated with elevated oxidative stres, accumulation of Ab aggregation and progressive paralysis behavior. Small heat shock protein HSP16.2 has been reported to co-localize with Ab in the transgenic C. elegans, and its over expression suppressed the paralysis. Heat shock response in C. elegans is a neuronal controlled behavior. Transcription factor HSF-1, which regulates heat shock response by up regulation of heat shock proteins in C. elegans, has been coupled to normal aging and age-related diseases. Recently, it also has been associated with dietary restriction and insulin-like signaling in protection against proteotoxicity. However, the functional link between sHSP and Ab on protection against Ab toxicity remains unknown. Previously, we demonstrated that progressive paralysis induced by expression of human Abin transgenic C. elegans was alleviated by Ab oligomer inhibitors ginkgo biloba extract and its constituents (Wu, et al., J. Neurosci 2006, 26:13102-13). In this study, we apply a protective heat shock treatment (2h, 35C) to Ab C. elegans and reveal a significant decrease of Ab toxicity and Ab oligomers in the transgenic worms. This data is consistent with the view that co-expression of HSP16.2 in Ab C. elegans lessened Ab toxicity in these worms. In addition, it provides new insight into the role of non-invasive physical treatment and endogenous chaperone proteins in regulation of Ab aggregation and toxicity.

Gendreau SB et al. (1994) Dev Biol "The potential to differentiate epidermis is unequally distributed in the AB lineage during early embryonic development in C. elegans."

Rothman JH, Moskowitz IPG, Gendreau SB, Terns RM

[Dev Biol, 1994]

In the early Caenorhabditis elegans embryo most of the ectoderm arises from the AB blastomere, one of the six founder cells. We report that nonequivalent blastomeres are generated at the third division round in the AB lineage. Each AB granddaughter divides to produce one cell that has the potential to make abundant epidermis and one that instead produces primarily nervous system. This unequal distribution of the potential to make epidermis occurs in an AB granddaughter that is isolated by laser-ablation of all other cells or during the development of an isolated AB blastomere in culture. The fidelity of this event is normally masked by a signal from the MS founder cell, which induces mesoderm in particular AB descendants. When MS induction is prevented by laser cell-ablation or by a mutation in the glp-1 gene, the epidermal fate map of the AB great granddaughters becomes left-right symmetrical. Cell lineage analyses demonstrate that, in fact, the AB lineage becomes entirely left-right symmetrical in the absence of MS induction. This accounts for the extra epidermal cells previously observed in a glp-1 mutant. Our results suggest that epidermal differentiation in the nematode may be controlled by a cell-autonomous mechanism that differentially allocates epidermal potential during AB development and that MS induction generates the left-right asymmetry in the fates of AB descendants in part by overriding this potential.

McColl G et al. (2012) Mol Neurodegener "Utility of an improved model of amyloid-beta (A) toxicity in Caenorhabditis elegans for drug screening for Alzheimer's disease."

Roberts CM, Cherny RA, Kenche VB, Bush AI, Ryan TM, Masters CL, Link CD, Pukala TL, McColl G, Roberts BR, Barnham KJ

[Mol Neurodegener, 2012]

BACKGROUND: The definitive indicator of Alzheimer's disease (AD) pathology is the profuse accumulation of amyloid-B (AB) within the brain. Various in vitro and cell-based models have been proposed for high throughput drug screening for potential therapeutic benefit in diseases of protein misfolding. Caenorhabditis elegans offers a convenient in vivo system for examination of AB accumulation and toxicity in a complex multicellular organism. Ease of culturing and a short life cycle make this animal model well suited to rapid screening of candidate compounds. RESULTS: We have generated a new transgenic strain of C. elegans that expresses full length AB. This strain differs from existing AB models that predominantly express amino-truncated AB. The AB is expressed in body wall muscle cells, where it oligomerizes, aggregates and results in severe, and fully penetrant, age progressive-paralysis. The in vivo accumulation of AB also stains positive for amyloid dyes, consistent with in vivo fibril formation. The utility of this model for identification of potential protective compounds was examined using the investigational Alzheimer's therapeutic PBT2, shown to be neuroprotective in mouse models of AD and significantly improve cognition in AD patients. We observed that treatment with PBT2 provided rapid and significant protection against the AB-induced toxicity in C. elegans. CONCLUSION: This C. elegans model of full length AB expression can now be adopted for use in screens to rapidly identify and assist in development of potential therapeutics and to study underlying toxic mechanism(s) of AB.

Schonegg S et al. (2014) Genesis "Timing and mechanism of the initial cue establishing handed leftright asymmetry in Caenorhabditis elegans embryos."

Schonegg S, Wood WB, Hyman AA

[Genesis, 2014]

By the six-cell stage, embryos of Caenorhabditis elegans are morphologically LR asymmetric with an invariant handedness that persists throughout development. We used intracellular markers to ask whether breaking of LR symmetry could be observed at earlier stages. Observation of two- to three-cell embryos carrying intracellular markers indicated that LR symmetry is broken concomitantly with establishment of DV axis polarity during division of the anterior AB cell. The AB cleavage furrow initiates asymmetrically and always from the left, suggesting LR differences in the AB cell cortex. An invariantly handed cortical rotation observed earlier during first cleavage implies that the one-cell embryo has an intrinsic chirality. We propose that LR differences in the cortex could result from mechanical forces on asymmetric components of a chiral cortical network during the off-axis elongation of the AB-cell spindle prior to AB cleavage.

McColl, Gawain et al. (2011) International Worm Meeting "Improved Alzheimer's Disease Model of Ab1-42 toxicity."

Link, Christopher, Bush, Ashley, Pukala, Tara, Roberts, Christine, Roberts, Blaine, Gunn, Adam, Cherny, Robert, McColl, Gawain

[International Worm Meeting, 2011]

One of the hallmarks of Alzheimer's disease is the cerebral deposition of plaques composed of Amyloid-beta (Ab) peptide. Human Ab (e.g. in brain, CFS or plasma) is not found as a single species, but rather as diverse mixtures of various modified and truncated forms. Caenorhabditis elegans offers a simplified in vivo system in which to examine Ab accumulation, including sub-cellular localization, and toxicity. We determined that an earlier model of Ab expression in C. elegans accumulates Ab3-42 due to mis-cleavage of a synthetic signal peptide. To achieve correct signal peptide cleavage we inserted an extra Asp-Ala (DA) N-terminal to the hu-Ab sequence in the transgene construct The molecular identity of the Ab expressed was then determined via complimentary techniques. Using immunocapture and electrospray ionization mass spectrometry (ESI-MS) we determined the mono-isotopic molecular weight of the expressed Ab as 4511.2586 Da with an error of 2.5 ppm. This mass is consistent with full length Ab1-42 (expected mass 4511.2697 Da). The Ab1-42 is expressed in body wall muscle cells, where it aggregates and results in severe, and fully penetrant, age progressive-paralysis. The in vivo accumulation of Ab1-42 also stains positive for amyloid dyes, consistent with in vivo fibril formation. This C. elegans model of full length Ab expression can now be adopted to study underlying toxic mechanism(s) of Ab1-42.

Lavigne JP et al. (2006) Clin Microbiol Infect "Virulence genotype and nematode-killing properties of extra-intestinal Escherichia coli producing CTX-M beta-lactamases."

Bouziges N, Lavigne JP, O'Callaghan D, Blanc-Potard AB, Chanal C, Moreau J, Bourg G, Sotto A

[Clin Microbiol Infect, 2006]

This study evaluated the virulence potential of Escherichia coli isolates producing CTX-M beta-lactamases. During a 24-month period, 33 extended-spectrum beta-lactamase (ESBL)-producing E. coli, including 14 CTX-M-producers, were isolated from urinary tract infections at Nimes University Hospital, France. The prevalence of 14 major virulence factors (VFs) was investigated by PCR and compared with the prevalence in a group of 99 susceptible E. coli isolates. Ten VFs were less prevalent (p <0.05) in the ESBL isolates than the susceptible E. coli, while iutA and traT were more prevalent in ESBL isolates (p <0.05). Moreover, the CTX-M-producing isolates had significantly fewer VFs than TEM-producing isolates. A novel infection model using the nematode Caenorhabditis elegans was developed to assess the virulence properties of extra-intestinal pathogenic E. coli (ExPEC) strains in vivo. C. elegans infection assays, using 14 ESBL-producing E. coli and ten susceptible E. coli isolates, indicated that the ability to kill nematodes correlated with the presence of VFs, and that CTX-M-producing isolates had relatively low virulence in vivo. Overall, the results suggested that hospital-acquired CTX-M-producing E. coli, although adapted for survival in an antibiotic-rich environment such as the hospital milieu, have a relatively low intrinsic virulence potential.

Fujita M et al. (2012) PLoS One "Cell-to-cell heterogeneity in cortical tension specifies curvature of contact surfaces in Caenorhabditis elegans embryos."

Onami S, Fujita M

[PLoS One, 2012]

In the two-cell stage embryos of Caenorhabditis elegans, the contact surface of the two blastomeres forms a curve that bulges from the AB blastomere to the P blastomere. This curve is a consequence of the high intracellular hydrostatic pressure of AB compared with that of P. However, the higher pressure in AB is intriguing because AB has a larger volume than P. In soap bubbles, which are a widely used model of cell shape, a larger bubble has lower pressure than a smaller bubble. Here, we reveal that the higher pressure in AB is mediated by its higher cortical tension. The cell fusion experiments confirmed that the curvature of the contact surface is related to the pressure difference between the cells. Chemical and genetic interferences showed that the pressure difference is mediated by actomyosin. Fluorescence imaging indicated that non-muscle myosin is enriched in the AB cortex. The cell killing experiments provided evidence that AB but not P is responsible for the pressure difference. Computer simulation clarified that the cell-to-cell heterogeneity of cortical tensions is indispensable for explaining the pressure difference. This study demonstrates that heterogeneity in surface tension results in significant deviations of cell behavior compared to simple soap bubble models, and thus must be taken into consideration in understanding cell shape within embryos.