Toth, Marton et al. (2013) International Worm Meeting "Fructose accelerates neuronal aging in C. elegans."

Toth, Marton, Shah, Leena, Driscoll, Monica

[International Worm Meeting, 2013]

Dietary sugar intake has significantly increased in the human population as monosaccharides like glucose and fructose are used in large quantities to sweeten food products. However, there are profound differences between the physiological effects of glucose and fructose. In higher organisms, glucose can be metabolized in every cell and most of it is converted into inert glycogen until broken down in glycolysis to cover cellular energy demand. In contrast, fructose can only be metabolized in the liver and it is converted into lipid droplets and VLDLs. High fructose turnover may cause liver and muscle insulin resistance. Using morphological assays to score aging of individual neurons, we found that excess glucose can be neuroprotective in C. elegans. However, even modest additional fructose intake can accelerate the onset of morphological aging features in neurons. We will discuss genetic requirements for fructose toxicity. Our results call attention to the differential effects of dietary sugars and provide clear evidence that underscores concerns about the use of fructose as a food source.

Toth, Marton et al. (2013) International Worm Meeting "Calcium Exerts Critical Functions in Adult Neuronal Maintenance."

Kim, Steven, Zhang, Wenying, DuBose, Camisha, Driscoll, Monica, Patel, Saurabh, Gaul, Kelli, Toth, Marton, Xue, Jian, Ganihong, Ivana, Patel, Khushboo

[International Worm Meeting, 2013]

Human brain aging and cognitive decline are associated with synaptic changes and aberrant sprouting, rather than neuronal death. We have had a long-term interest in the genes and environmental factors that influence healthy tissue aging, using the facile experimental model C. elegans to decipher the basic biology of healthspan (the period of healthy maintenance prior to detectable functional or structural decline). Our initial study of how C. elegans tissues age indicated that, like in human brain aging, neither neuronal death nor axon degeneration is a significant feature of the aging nematode nervous system. However, specific C. elegans neuronal types can exhibit dramatic morphological changes (novel branching from processes, new outgrowth from cell bodies, wavy appearance) that increase in frequency with age. We have also shown that synaptic structures deteriorate in the aging C. elegans nervous system. Our findings support that C. elegans is a relevant model in which to study basic questions of nervous system aging, with anticipated findings likely informative on conserved mechanisms. The calcium-binding EF Hand motif can be found in a large number of protein families. This protein domain confers calcium regulation of proteins functions that include cytoplasmic calcium buffering, signal transduction, and muscle contraction. In a recent screen for genes that can influence the maintenance of adult neuronal integrity we discovered several previously uncharacterized EF Hand motif proteins with either neuroprotective or neurotoxic roles. RNAi knockdown of EF hand gene expression could accelerate or decrease neuronal aging up to 8 times, measured by our recently established branching and outgrowth markers of neuronal aging. We propose that EF Hand motif proteins and calcium play a substantial role in the maintenance of neuronal integrity in aging neurons.

Toth, Marton et al. (2015) International Worm Meeting "Novel gene interactions that modulate morphological aging of neurons in C. elegans."

Harinath, Girish, Guasp, Ryan, Toth, Marton, Xue, Jian, Patel, Khushboo, Gaul, Kelli, Zhang, Wenying, Driscoll, Monica, Ganihong, Ivana

[International Worm Meeting, 2015]

Aging neurons in C. elegans and humans can experience dramatic morphological restructuring. In a recent screen for genes encoding proteins that maintain adult neuronal integrity we discovered a group of relatively poorly characterized EGF-like motif proteins. Systemic RNAi knockdown of these predicted calcium binding protein genes limited age-associated dendritic branching in touch neurons as much as 4 fold. Interestingly, for some genes, cell autonomous inactivation exacerbated morphological neuronal aging. Furthermore, we found some genes with cell non-autonomous actions on touch neuron maintenance. We found that systemic inactivation of certain EGF-like motif genes increase life- and healthspan, via a mechanism distinct from dietary restriction. These genes have conserved functions in cell adhesion and can thus serve as models with which to investigate crosstalk between the regulation of aging and tissue integrity, potentially assigning an entirely new function to this protein family.

Toth, Marton et al. (2011) International Worm Meeting "Neurite Sprouting and Synapse Deterioration are Features of the Aging C. elegans Nervous System."

Ibanez-Ventoso, C, Toth, Marton, Bhanot, G, Hall, D, Bhatia, A, Herndon, L, Lu, K, Naji, H, Shah, L, Ghose, P, Rongo, C, Driscoll, Monica, Talwar, A, Melentijevic, I, Jevince, A

[International Worm Meeting, 2011]

C. elegans is a powerful model for analysis of the conserved mechanisms that modulate healthy aging, from organismal to molecular levels. As animals age, tissues deteriorate at different rates. Neuronal death and/or detectable loss of processes, however, are not readily apparent in the aging C. elegans nervous system. Because dendrite restructuring and loss of synaptic integrity are hypothesized to contribute to human brain decline and dysfunction, we combined whole neuron fluorescence microscopy and electron microscopy to screen for nervous system changes in aging C. elegans at high resolution. We report two major aspects of morphological change in the aging C. elegans nervous system: 1) accumulation of novel outgrowths from specific neurons; and 2) decline in synaptic integrity. Novel outgrowth phenotypes, including branching from the main dendrite or new growth from somata, appear at a high frequency in some aging neurons, but not all. Lowered DAF-2 InsR signaling confers robust maintenance of touch neuron structural integrity into old age. Both DAF-16/FOXO and heat shock factor transcription factor HSF-1 exert protective functions in maintaining neuronal architecture. EM evaluation in synapse-rich regions revealed a decline in synaptic presynaptic vesicle numbers and a dimunition of presynaptic density size. Interestingly, animals that maintain locomotory prowess into old age exhibit less synaptic decline than same age decrepit animals, suggesting synaptic integrity correlates with locomotory healthspan. Our data reveal similarities between the aging C. elegans nervous system and mammalian brain, suggesting conserved neuronal responses to age. Dissection of neuronal aging mechanisms in C. elegans may thus influence development of anti-brain aging therapies.

Toth, Marton L. et al. (2009) International Worm Meeting "HSF-1 is an Essential Downstream Mediator of Resveratrol-induced, SIR-2.1-dependent Longevity in C. elegans."

Soti, Csaba, Toth, Marton L., Csermely, Peter, Dancso, Balazs

[International Worm Meeting, 2009]

Major longevity assurance mechanisms include the heat-shock response governed by the heat-shock transcription factor (HSF-1) and the metabolic stress response, exemplified by the Sir2 deacetylase. Sir2, and recently HSF-1 have been implicated in the life-span extending effect of dietary restriction. Resveratrol, a polyphenol from red wine, is a dietary restriction mimetic that induces longevity and displays an impressive therapeutic potential against various degenerative diseases via Sir2. Resveratrol has also been shown to induce the heat-shock response in mammalian cells. In this study, we have asked how the heat-shock response is involved in resveratrol-induced/Sir2-related longevity in C. elegans. We find that resveratrol specifically induces chaperone expression, thermotolerance and longevity depending on both SIR-2.1 and HSF-1. Moreover, we show that SIR-2.1 is a potent activator of HSF-1-dependent thermotolerance. Finally, we identify HSF-1 as an essential downstream effector of resveratrol-induced, SIR-2.1-dependent longevity in C. elegans. Thus, our results demonstrate a direct interaction of metabolic and proteotoxic stress responses in life-span regulation and indicate that the robustness of the heat-shock response may determine the therapeutic response to resveratrol. Marton Toth''s current address: Rutgers, The State University of NJ, Molecular Biology & Biochemistry, Piscataway, NJ.

Marton L. Toth et al. (2007) International Worm Meeting "Longevity pathways converge on autophagy genes to extend lifespan in Caenorhabditis elegans."

Tibor Vellai, Timea Sigmond, Krisztina Takacs-Vellai, Marton L. Toth, Attila L. Kovacs, Miklos Sass, Gyorgy Csikos, Peter Erdelyi, Eva Borsos

[International Worm Meeting, 2007]

Mutations decreasing insulin/IGF-1 (insulin-like growth factor-1) or TOR (target of rapamycin) kinase-mediated signalling, mitochondrial activity and food intake each extend lifespan in divergent animal phyla. Understanding how these genetically distinct mechanisms interact to control longevity is a fundamental and fascinating problem in biology. Here we show that mutational inactivation of autophagy genes, which are involved in the degradation of damaged cytoplasmic constituents accumulating in ageing cells, accelerates the ageing process and shortens lifespan in the nematode Caenorhabditis elegans. According to our results Drosophila flies deficient in autophagy also exhibit short-lived phenotype. Thus, autophagy is a cellular pathway that extends lifespan in both worms and insects. We also demonstrate that reduced activity of autophagy genes suppresses lifespan extension in dietary-restricted mutant nematodes as well as in worms with aberrant insulin/IGF-1 or TOR signalling and mitochondrial respiration. These findings suggest that the autophagy gene cascade functions downstream of and is inhibited by various longevity pathways in C. elegans, that is, their effects converge on autophagy to lengthen lifespan. Hence autophagy may act as a central regulatory mechanism of animal ageing.

Melentijevic, Ilija et al. (2013) International Worm Meeting "Neuronal Exophers: a Novel Mechanism for Removal of Neurotoxic Cytoplasm Components."

Driscoll, Monica, Melentijevic, Ilija, Toth, Marton, Neri, Christian

[International Worm Meeting, 2013]

We discovered a new, previously unknown feature of young adult C. elegans neurons-neurons can extrude substantial packets of cellular contents, which can include aggregated human neurodegenerative disease proteins or mitochondria, but no nuclear DNA. We currently call these extrusions "exophers". The ability to jettison cell contents appears to change with age, and extrusion is increased when protein turnover or autophagy is inhibited. Thus, this pathway may constitute a novel neuronal protection mechanism that serves to maintain protein/organelle homeostasis when other systems are compromised. We propose that the neuronal extrusion phenomenon constitutes a significant but currently unknown conserved pathway by which healthy neurons maintain their functions, and speculate that, in disease, this pathway may malfunction to promote spread of pathology. We will present the basic characterization of neuronal exopher production and our latest data on genetic influences on exopher generation.

Smart, Joelle et al. (2017) International Worm Meeting "Touch neurons can toss out mitochondria."

Arnold, Meghan, Toth, Marton, Melentijevic, Ilija, Driscoll, Monica, Harinath, Girish, Smart, Joelle, Guasp, Ryan

[International Worm Meeting, 2017]

Mitochondria provide energy, execute key steps of metabolism, control calcium, and modulate cellular decisions for life/death. Given these critical functions in cell, tissue, and organism health, it is not surprising that mitochondrial functionality plays an essential role in neuronal maintenance in everyday biology, aging, and late-onset neurodegenerative disease. Mitochondrial quality control is thought to be primarily executed through cell-internal elimination via mitophagy and lysosome degradation. However, the Driscoll lab has discovered, and recently published (Melentijevic, 2017 Nature 542:367) that mitochondria can be thrown out of neurons in large membrane bound vesicles we call exophers. Mitochondria in exophers budding from C. elegans touch neurons tend to have elevated oxidation of mitoROGFP reporters localized to the matrix. Genetic and pharmacological treatments that compromise mitochondria can increase numbers of exophers produced by touch neurons, suggesting that throwing away defective mitochondria may be a mechanism for neuronal quality control. Indeed, some mammalian neurons can throw out their mitochondria for degradation by neighboring astrocytes (Davis, PNAS 11:9633), suggesting relevance across phyla. In C. elegans, beautiful work on degradation of sperm mitochondria upon fertilization have been published (Sato, Science 334:1141). We will present data on our initial efforts to characterize mito-exopher production and the factors that prompt neurons to extrude mitochondria. Our hope is that our findings will be relevant to understanding neuronal maintenance and neuronal degeneration, especially as associated with perturbed mitochondrial quality as may occur in Parkinson's disease and many other human disorders.

Melentijevic, Ilija et al. (2015) International Worm Meeting "Neuronal Exophers: a novel mechanism for the removal of neurotoxic cytoplasm components."

Driscoll, Monica, Arnold, Meghan, Parker, Alex, Guasp, Ryan, Toth, Marton, Neri, Christian, Harinath, Girish, Melentijevic, Ilija

[International Worm Meeting, 2015]

Combating late-onset neurodegenerative disease and age associated functional decline in brain are major health challenges of our time. For the effective design of interventions that protect the nervous system from disease-induced and/or age-associated deterioration, we must fully understand endogenous mechanisms for neuronal protection and how they might fail to enable disease promotion. Recently, it has come to be appreciated that neurodegenerative disease proteins/aggregates can be found outside of mammalian neurons, and when outside, can actually be taken up by neighboring cells. Transfer of offending molecules has been suggested to be a mechanism of pathogenesis spread for multiple neurodegenerative diseases, including the prevalent Alzheimer's and Parkinson's diseases.We discovered a novel capacity of young adult C. elegans neurons - neurons can extrude substantial packets of cellular contents, which can include aggregated human neurodegenerative disease proteins, mitochondria, or lysosomes, but no nuclear DNA. We currently call these extrusions "exophers". The ability to jettison cell contents appears to change with age, and extrusion is increased when protein turnover is impaired, autophagy is inhibited, or mitochondria are compromised. Moreover, exophers can selectively incorporate aggregation-prone proteins and mitochondria with elevated levels of an oxidized reporter. Thus, exopher-mediated extrusion may constitute a novel neuronal protection mechanism that serves to maintain protein/organelle homeostasis when other systems are compromised or overloaded. We propose that the neuronal extrusion phenomenon constitutes a significant but currently unknown conserved pathway by which healthy neurons maintain their functions, and speculate that, in neurodegenerative diseases, this pathway may malfunction to promote spread of pathology. We will present the basic characterization of neuronal exopher production and our latest data on genetic influences on exopher generation.

Vayndorf, Elena et al. (2015) International Worm Meeting "Protein homeostasis dysregulation is associated with aberrant morphology and reduced function of aging mechanosensory neurons."

Hunter, Skyler, Driscoll, Monica, Toth, Marton, Scerbak, Courtney, Taylor, Barbara, Neri, Christian, Parker, J. Alex, Vayndorf, Elena

[International Worm Meeting, 2015]

In both C. elegans and humans, the aging nervous system is characterized by decreased synaptic activity, deteriorating short-term and long-term memory, and altered neuronal morphology. Given the overwhelming evidence for proteostasis disruption in neuronal aging, we sought to explain the accumulation of neuronal morphological abnormalities by focusing on protein homeostasis in 6 mechanosensory neurons of aging C. elegans nematodes. We examined the effects of disrupted proteostasis on the integrity of neuronal cytoarchitecture using a transgenic model with an excessively high neuronal protein load, and RNAi knock down of specific genes involved in protein turnover. We found that animals expressing the first 57 amino acids of the human huntingtin gene and an expanded polyglutamine CAG tract (Q128) in mechanosensory neurons accumulate more aberrations that are distinct from those found in animals that express the non-toxic (Q19) number of repeats, or those that express no repeats. We scored and tallied these changes in both the soma and processes and found that they are sometimes associated with improved or reduced function. Next, we used an RNAi candidate gene approach to target genes involved in the maintenance of protein homeostasis in wild-type animals. We found that genes involved in protein turnover play an important role in maintaining the integrity of healthy neurons, and that their knockdown leads to distinct morphological changes in both the process and the soma of wild-type mechanosensory neurons. Taken together, these results suggest that protein homeostasis is critical for maintaining neuronal integrity and function, and that disrupted proteostasis contributes to morphological abnormalities that occur more frequently with advanced age.