Norris CR et al. (1998) East Coast Worm Meeting "Structure of the Developing Nerve Ring"

Hedgecock EM, Bazykina IA, Hall DH, Norris CR

[East Coast Worm Meeting, 1998]

In order to understand the cellular interactions that are important for the formation of pathways into the nerve ring, we have been examining embryos at the EM level. To date, we have reconstructed two stages of development: one when the amphid commissures are beginning to form but before axons enter the nerve ring proper (350'/start of elongation), and the other when the nerve ring contains axons and the lateral pathways are just forming (430'/1 and 2/3-fold elongation). We have been focusing on the development of 3 pathways from the lateral ganglion to the nerve ring: the amphid commissures, the lateral pathway, and the subdorsal pathway. Amphid commissural axons are the first to extend in C. elegans. Commissural axons cross to the ventral ganglion between muscle basal lamina and neuron SIBD, which transiently insinuates between muscle and hypodermis, forming a bridge between the lateral and ventral ganglion. Presumably, SIBD is an attractive/permissive substrate, and perhaps amphid axons are unable to traverse directly between muscle and hypodermis. (Although later commissural axons, such as motorneurons, grow directly between muscle and hypodermis.) Axons that enter the nerve ring via the lateral and subdorsal routes extend later. Interestingly, the timing of their outgrowth correlates with the separation of muscles into dorsal and ventral quadrants. We hypothesize that muscles may block access to a chemoattractant from the nerve ring. We have observed that axons in all these pathways extend in waves. For example, by the 1 and 2/3-fold stage, 8 amphid axons have reached the nerve ring via the amphid commissures, but the remainder of amphid axons have not yet crossed to the ventral ganglion. Similarly, AVA and ADL, which grow directly to the ring via a lateral route, have reached the ring, when other neurons destined to extend laterally have not initiated growth cones. We are unsure of the significance of this temporally distributed axon outgrowth, but have several hypotheses. We are processing more embryos of intermediate stages to fill in the developmental gaps, and are using laser ablations to test our ideas about cellular interactions important for guiding axons to the ring.

Norris CR et al. (1997) International C. elegans Meeting "Cellular Interactions Underlying Formation of the Nerve Ring."

Bazykina IA, Norris CR, Hedgecock EM, Hall DH

[International C. elegans Meeting, 1997]

In order to understand the cellular interactions that are important for the formation of pathways into the nerve ring, we have been reconstructing serially-sectioned embryos. We have focused on two stages of development: one when the amphid commissures are beginning to form but before axons enter the nerve ring proper (350'), and the other when the nerve ring contains many processes (430'). We are beginning to understand how head and neck muscles connect to the nerve ring. In mature worms, it appears as if muscles must extend long processes (arms) from their somas to the inner nerve ring (see White et. al., 1986). However, in the early neurula, head and neck muscles directly surround the pharynx where the nerve ring will form. During development then, muscle cell bodies themselves must migrate peripherally to the hypodermis, leaving behind an arm next to the pharynx. We hypothesize that muscle migration is also coordinated with the growth of amphid axons. The earliest amphid axons grow out when direct access to the nerve ring (or to GLRs) is blocked by muscles encircling the pharynx; these axons establish the amphid commissures. In mature worms, the commissures run between muscle and hypodermis and then join the ventral cord. During development, a neuron insinuated between muscles and hypodermis forms the substrate for the first commissural axons traversing from lateral ganglia to the ventral ganglion. We suggest this neuron (maybe SMDD) prevents or displaces muscle attachment as muscles migrate ventrally to the hypodermis, creating a pathway for the first commissural axons. As muscles separate during their dorsal and ventral migration to the hypodermis, direct access to the GLRs becomes available. Thus, the subdorsal and lateral pathways are available to amphids that extend later, after muscle migration. We are beginning to process more embryos of intermediate stages to fill in the developmental gaps.

Norris CR et al. (2000) European Worm Meeting "Extracellular matrix molecules and cell surface receptors in the C. elegans genome"

Hedgecock EM, Hutter H, Scheel JK, Proenca RB, Mastwal SS, Guo C-B, Plenefisch JD, Spieth J, Norris CR, Vogel BE, Zhu X

[European Worm Meeting, 2000]

The extracellular matrix (ECM) has important roles in many developmental processes such as cell adhesion, migration (including axonal guidance) and differentiation. With the complete sequence of the C. elegans genome available we can for the first time get an idea about the complexity of the ECM in molecular terms. We searched the database of predicted C. elegans genes for putative extracellular or cell surface proteins using representative insect or mammalian proteins or their fragments. We analysed the domain organisation of these proteins and grouped them into families and superfamilies. Among those proteins we found homologs of known extracellular matrix (ECM) and cell adhesion molecules (CAM) as well as a number of novel proteins combining various old and new protein modules. A common theme is that none of the ECM and CAM superfamilies has substantially expanded within the nematode lineage. E.g. there are thirteen cell surface proteins with Immunoglobulin- and Fibronectin III modules, nine of which have homologs in other animal phyla. We predict the various new IgCAMs have yet undiscovered homologs in other animals. This molecular simplicity reflects the small cell number and simple anatomy of C. elegansand is in striking contrast to other protein families like lectins which have expanded to several hundert members within the nematode lineage. We found more than 40 ancient (i.e. predating metazoan radiation) protein motifs in the extracellular domains of C. elegans proteins. Some of them, like the EGF-module, occur in numerous, structurally different proteins, whereas others, like the Laminin-N-terminal-Motif, occur in only a few proteins. Certain motifs that are promiscous in vertebrates are found in only a few different contexts in C. elegans and vice versa, indicating that different animal phyla found different protein motifs useful for the generation of novel proteins. Some extracellular motifs present in vertebrates are missing in C. elegans. On the other hand we could define some 20 new protein motifs so far only present in C. elegans proteins, indicating that novel protein modules have been invented throughout evolution. Among the ECM and CAM molecules we identified in the genome we expect to find signalling molecules and receptors important for axonal guidance and synaptic target recognition. In order to identify such genes we are currently screening these proteins for a potential role in neuronal development. To this end we generate transient knock-outs using RNAi and score progeny for various behavioural, axonal outgrowth and cell migration defects. Progress will be reported.

Kowaltowski AJ (2011) Redox Rep "Caloric restriction and redox state: does this diet increase or decrease oxidant production?"

Kowaltowski AJ

[Redox Rep, 2011]

Calorie restriction (CR) is well established to enhance the lifespan of a wide variety of organisms, although the mechanisms are still being uncovered. Recently, some authors have suggested that CR acts through hormesis, enhancing the production of reactive oxygen species (ROS), activating stress response pathways, and increasing lifespan. Here, we review the literature on the effects of CR and redox state. We find that there is no evidence in rodent models of CR that an increase in ROS production occurs. Furthermore, results in Caenorhabditis elegans and Saccharomyces cerevisiae suggesting that CR increases intracellular ROS are questionable, and probably cannot be resolved until adequate, artifact free, tools for real-time, quantitative, and selective measurements of intracellular ROS are developed. Overall, the largest body of work indicates that CR improves redox state, although it seems improbable that a global improvement in redox state is the mechanism through which CR enhances lifespan.

Calvert S et al. (2015) Aging Cell "A network pharmacology approach reveals new candidate caloric restriction mimetics in C. elegans."

Sharifi S, Tacutu R, Ghosh P, de Magalhaes JP, Teixeira R, Calvert S

[Aging Cell, 2015]

Caloric restriction (CR), a reduction in calorie intake without malnutrition, retards aging in several animal models from worms to mammals. Developing CR mimetics, compounds that reproduce the longevity benefits of CR without its side effects, is of widespread interest. Here, we employed the Connectivity Map to identify drugs with overlapping gene expression profiles with CR. Eleven statistically significant compounds were predicted as CR mimetics using this bioinformatics approach. We then tested rapamycin, allantoin, trichostatin A, LY-294002 and geldanamycin in Caenorhabditis elegans. An increase in lifespan and healthspan was observed for all drugs except geldanamycin when fed to wild-type worms, but no lifespan effects were observed in eat-2 mutant worms, a genetic model of CR, suggesting that life-extending effects may be acting via CR-related mechanisms. We also treated daf-16 worms with rapamycin, allantoin or trichostatin A, and a lifespan extension was observed, suggesting that these drugs act via DAF-16-independent mechanisms, as would be expected from CR mimetics. Supporting this idea, an analysis of predictive targets of the drugs extending lifespan indicates various genes within CR and longevity networks. We also assessed the transcriptional profile of worms treated with either rapamycin or allantoin and found that both drugs use several specific pathways that do not overlap, indicating different modes of action for each compound. The current work validates the capabilities of this bioinformatic drug repositioning method in the context of longevity and reveals new putative CR mimetics that warrant further studies.

Dicklow MB et al. (1993) Journal of Chemical Ecology "A novel streptomyces species for controlling plant-parasitic nematodes"

Dicklow MB, Acosta N, Zuckerman BM

[Journal of Chemical Ecology, 1993]

A novel species of Steptromyces isolated from nematode suppressive soils in Costa Rica was evaluated for efficacy in controlling plant-parasitic nematodes. This isolate, designated CR-43, was shown to inhibit reproduction of Caenorhabditis elegans in a laboratory assay. Greenhouse trials utilizing three different methods of treatment with CR-43 gave significant reductions of tomato root galling due to Meloidogyne incognita. In a field experiment in Puerto Rico, [West Indies] in soil naturally infested with M. incognita, CR-43-treated pepper showed significant reductions in root galling and significant increases in yield as compared to untreated controls. In a second experiment in Puerto Rico, a significant reduction in tomato root galling and a slight reduction in root galling on pepper occurred. In this trial, yields on both tomato and pepper were higher in CR-43 treatments, but these differences were not statistically significant. In both experiments populations of Rotylenchulus reniformis were reduced by CR-43 treatment. In a field trial on strawberry in Massachusetts, CR-43-treated plants had lower numbers of Pratylenchus penetrans within roots and showed a significant decrease in black root rot disease. Studies on sterile filtrates from CR-43 cultures indicated that a major determinant of CR-43 antinematodal activity was mostly thermostable macromolecules of molecular weight higher than 6000. Culture filtrates of CR-43 exhibited antifungal activity in vitro.

Liang Y et al. (2018) Sci Rep "Calorie restriction is the most reasonable anti-ageing intervention: a meta-analysis of survival curves."

Liu Q, Wang X, Liang Y, Dong Q, Zhang N, Wang Z, Liu C, Zhou J, Xiong W, Lu M

[Sci Rep, 2018]

Despite technological advances, the survival records from longevity experiments remain the most indispensable tool in ageing-related research. A variety of interventions, including medications, genetic manipulations and calorie restriction (CR), have been demonstrated to extend the lifespan of several species. Surprisingly, few systematic studies have investigated the differences among these anti-ageing strategies using survival data. Here, we conduct a comprehensive and comparative meta-analysis of numerous published studies on Caenorhabditis elegans and Drosophila. We found that CR and genetic manipulations are generally more effective than medications at extending the total lifespan in both models, and CR can improve the ageing pattern of C. elegans. We further analysed the survival variation for different anti-ageing medications and determined that hypoglycaemic agents and antioxidants are advantageous despite only moderately increasing the overall lifespan; therefore, these two types of medications are promising CR mimetics. Analysis of genetic manipulations also indicated that the genes or pathways that extend lifespan in a healthier pattern are associated with CR. These results suggest that CR or CR mimetics may be the most reasonable and potentially beneficial anti-ageing strategy.

Gerhard GS (2001) Journal of Anti-Aging Medicine "Caloric restriction in nonmammalian models."

Gerhard GS

[Journal of Anti-Aging Medicine, 2001]

The well-known effects of caloric restriction (CR) upon life span have been studied in a number of nonmammalian species, from yeast to fish. Early work focused on determining whether CR could prolong life span, which it does in most organisms thus far examined. More recently, studies done with invertebrates models, including yeast, Caenorhabditis elegans, and Drosophila, have suggested potential mechanistic commonalities with CR. In this review, a survey of data collected from the application of CR to a number of nonmammalian models is presented, as well as the potential molecular overlap arising from work done

Zhou G et al. (2020) Aging (Albany NY) "Methionine increases yolk production to offset the negative effect of caloric restriction on reproduction without affecting longevity in C. elegans."

Zhou G, Li L, Huang C, Wei Y, Jiang Y, Xing L

[Aging (Albany NY), 2020]

Caloric restriction (CR) or Dietary restriction (DR) is known to improve health and in many cases increases lifespan. However, its negative effect on reproduction has not been fully studied. Practicing CR/DR without adequate knowledge on its side effect may risk complications such as infertility, birth defect, or malnutrition. In this study, by using several CR strategies in <i>C. elegans</i>, we examine key functions of reproduction including embryonic development and larvae growth. We find that CR significantly decreases the survival of embryos and slows the growth of the offspring. We further determine that defect in oocyte but not sperm is responsible for the compromised reproduction under CR. Interestingly, adding methionine to the medium reverses the reproduction defects, but does not affect the long lifespan resulted from CR. The beneficial effect of methionine on reproduction requires the yolk protein vitellogenin. CR down-regulates vitellogenin expression, which can be reversed by supplementing methionine in the food. Lacking the yolk protein transport due to <i>rme-2</i> mutation blocks methionine's beneficial effects. Our study has revealed a novel, methionine-mediated genetic pathway linking nutrient sensing to reproduction and suggested methionine as a potential food supplement to mitigate the side effect of CR.

Hedgecock EM et al. (1997) Trends in Genetics "Netrins evoke mixed reactions in motile cells."

Norris CR, Hedgecock EM

[Trends in Genetics, 1997]

Like a molecular bulletin board, the extracellular matrix allows indirect communication between cells during development. For posting messages, soluble molecules from various sources are incorporated into more-or-less stable, matrix polymers surrounding tissues and individual cells. Integrins and other cell surface receptors tether these components and coordinate their assembly. Later, for reading messages, cells can express receptors for particular matrix components. In particular, motile cells and axons use matrix cues originating from path or target cells to control their direction and extent of migration.