Ludewig AH et al. (2013) WormBook "Ascaroside signaling in C. elegans."

Ludewig AH, Schroeder FC

[WormBook, 2013]

Over the past 10 years, the relevance of small-molecule signaling for many aspects of C. elegans development and behavior has become apparent. One prominent group of small-molecule signals are the ascarosides, which control dauer entry and exit as well as a variety of sex-specific and social behaviors, including male attraction, hermaphrodite repulsion, olfactory plasticity, and aggregation. This wide range of biological functions is facilitated by a great diversity of ascaroside chemical structures. These are based on the sugar ascarylose, which is linked to fatty acid-like side chains of varying lengths and often decorated further with building blocks derived from amino acids, folate, and other primary metabolites. Different ascarosides or combinations of ascarosides mediate different phenotypes, and even small differences in chemical structures are often associated with strongly altered activity profiles. Additional complexity arises from concentration-dependent effects and synergism between different ascarosides. The ascarosides are sensed by several types of chemosensory head neurons, including the ASK, ASI, and ADL neurons as well as the male-specific CEM neurons. Ascaroside perception is mediated by diverse families of G-protein coupled membrane receptors that act upstream of conserved signal transduction pathways, including insulin/IGF-1 signaling and transforming growth factor beta (TGF-) signaling. Biosynthesis of the ascarosides appears to integrate input from several primary metabolic pathways, including peroxisomal -oxidation of long-chain fatty acids and amino acid catabolism. Life stage, sex, as well as food availability and other environmental factors affect ascaroside biosynthesis, suggesting that ascaroside signaling communicates detailed information about life history and metabolic state.

Ludewig, A. et al. (2019) International Worm Meeting "Molecular mechanisms underlying pheromone-mediated lifespan regulation in C. elegans."

Pulido, C., Schroeder, F., Ludewig, A.

[International Worm Meeting, 2019]

Previous studies demonstrated that both C. elegans sexes excrete pheromones that alter development and lifespan in the worms. Hermaphrodites produce the dauer-inducing pheromones ascr#2 and ascr#3 which have been shown to increase C. elegans lifespan and stress resistance (Ludewig et al., 2013), whereas males produce compounds that shorten lifespan in both sexes (Gems et al., 2000, Maures et al., 2014) including the ascaroside ascr#10 and the recently identified nacq#1, a representative of a new class of pheromones derived from acylated amino acids (Ludewig et al., in revision). Here we aim to unravel the molecular mechanisms underlying lifespan regulation mediated by ascarosides signaling. We provide evidence that changes in lifespan after exposure to asccr#2, #3 and #10 required G-protein coupled receptors srbc-64 and srbc-66 as well as intact ASK and ASI amphid neurons. Downstream of chemosensory perception, we show that several sirtuins are required for ascaroside-mediated changes of lifespan. Sirtuins are a family of NAD+ dependent histone deacetylases that are involved with regulation of stress responses and longevity in many organisms. Sensing of lifespan-increasing ascarosides results in a sirtuin-dependent transient increase of reactive oxygen species (ROS) levels in the mitochondria. Furthermore, we show that ascaroside-mediated lifespan increase requires the transcription factor skn-1/Nrf, a key regulator of responses to oxidative stress, consistent with a model in which sirtuin-dependent increase of mitochondrial ROS triggers skn-1-activated longevity pathways. In addition, we present the effect of tissue-specific expression of sir-2.1 in neuronal and intestinal cells on C. elegans lifespan. As part of a broader screen for targets of ascaroside signaling, we identified 35 genes differentially expressed in worms after treatment with asrc#3 and ascr#10 by RNAseq. References: Ludewig AH et al. PNAS 2013;110(14):5522-5527. doi:10.1073/pnas.1214467110 Gems D, Riddle DL. Genetics. 2000;154(4):1597-1610. Maures TJ et al. Science. 2013;343(6170):541-544. doi:10.1126/science.1244160

Ludewig AH et al. (2000) European Worm Meeting "Identification of DAF-12 interaction partners"

Ludewig AH, Antebi A

[European Worm Meeting, 2000]

The nuclear receptor daf-12 acts as a control gene at the intersection of heterochronic and dauer pathways. Conceivably, some of the proposed genetic interactions might be physical interactions. In addition, it is known that vertebrate nuclear receptors are part of large complexes that regulate transcription. We would like to identify similar and possibly new components of these complexes in C. elegans. As a first approach we performed a yeast 2-hybrid screen to identify putative DAF-12 interacting proteins. We constructed different DAF-12 bait fusion proteins, which were screened against mixed stage C. eleganscDNA libraries. In the first screen we used a version of DAF-12 bait lacking the DNA binding domain. We identified 3 reasonable, so far unknown candidate proteins for interaction. We are continuing screening with other libraries and other DAF-12 baits.

Ludewig, Andreas et al. (2009) International Worm Meeting "Ascaroside Signalling and Lifespan in C. elegans."

Pungaliya, Chirag, Malik, Rabia, Schroeder, Frank, Fox, Bennett, Ludewig, Andreas

[International Worm Meeting, 2009]

In the nematode Caenorhabditis elegans the endogenously produced ascarosides differentially regulate development and behaviour. At low concentrations, ascarosides act as mating signal (Srinivasan, 2008), whereas at higher concentrations, they induce developmental arrest at the dauer stage (Butcher, 2007, Butcher 2008). Here we report that the ascarosides ascr#2 and ascr#3 influence adult lifespan and stress tolerance of C. elegans. Combinations of ascr#2 and ascr#3 increased lifespan of wild type animals by 30 % and increased thermotolerance up to 70%. Thermotolerance and ageing assays in different mutant background revealed complex regulatory networks for the activity of ascr#2 and 3. Notably, only ascr#3-, but not ascr#2-, mediated heat stress and tolerance and longevity are abolished in reduced insulin signalling background indicating that ascr#2 and ascr#3 act through different pathways. Ascr#2 and ascr#3-mediated increases in ageing and thermotolerance are dependent on the histone deacetylases SIR2.1 and SIR2.3, which also mediate caloric restriction-dependent increases in lifespan. These studies provide the first examples for endogenous small molecules that strongly increase lifespan and thermotolerance.

Andreas Ludewig et al. (2007) International Worm Meeting "C. elegans - a model for studies of human diseases."

Andreas Ludewig, Hans Lehrach

[International Worm Meeting, 2007]

In the past few years, studies in C. elegans have been greatly expanded our knowledge of molecular mechanisms underlying human diseases as complex as cancer, diabetes and neurodegenerative diseases. In our present project, we aim for the establishment of suitable C. elegans models for detailed studies of human diseases. Importantly, this will be achieved in tight connection with collaboration partners exploring different aspects of the particular disease. By merging our results from C. elegans studies with data derived from cell culture assays, patient studies, mammalian animal models and bioinformatic approaches, we hope for new insight into molecular mechanisms of diseases. Initially, we focus on the effects of transient anoxia on C. elegans. Although the global neuronal structure differs widely in nematodes and mammals, there is good evidence that basic molecular circuits following neuronal damage are conserved throughout species. By examining the processes accompanying anoxia and recovery in C. elegans in molecular detail, we wish for a better understanding of the mechanisms promoting stroke and neuronal self-healing processes in men. In our preliminary studies, C. elegans wild type, adult hermaphrodites, when exposed to anaerobic atmosphere for 4 hours completely stopped moving. Re-exposure to oxygen reconstituted vitality of a large subset of animals. We currently determine global gene expression profiles and morphologic changes at different time points of anoxia and recovery. In a reciprocal approach, we explore C. elegans orthologs of mammalian genes that have been linked with stroke by our collaboration partners in a mouse stroke model (Nietfeld et al., unpublished). Currently, we score knock down strains of each C. elegans ortholog for differential gene expression, for morphologic changes and for changes in the survival- and motility rate under anoxic conditions.

Ludewig AH et al. (2019) Nat Chem Biol "An excreted small molecule promotes C. elegans reproductive development and aging."

Schroeder FC, Artyukhin AB, Aprison EZ, Panda O, Pulido DC, Burkhardt RN, Ruvinsky I, Gudibanda P, Zhang YK, Rodrigues PR, Ludewig AH

[Nat Chem Biol, 2019]

Excreted small-molecule signals can bias developmental trajectories and physiology in diverse animal species. However, the chemical identity of these signals remains largely obscure. Here we report identification of an unusual N-acylated glutamine derivative, nacq#1, that accelerates reproductive development and shortens lifespan in Caenorhabditis elegans. Produced predominantly by C. elegans males, nacq#1 hastens onset of sexual maturity in hermaphrodites by promoting exit from the larval dauer diapause and by accelerating late larval development. Even at picomolar concentrations, nacq#1 shortens hermaphrodite lifespan, suggesting a trade-off between reproductive investment and longevity. Acceleration of development by nacq#1 requires chemosensation and is dependent on three homologs of vertebrate steroid hormone receptors. Unlike ascaroside pheromones, which are restricted to nematodes, fatty acylated amino acid derivatives similar to nacq#1 have been reported from humans and invertebrates, suggesting that related compounds may serve signaling functions throughout metazoa.

Ludewig, A. et al. (2019) International Worm Meeting "An excreted small-molecule signal promotes C. elegans reproductive development and aging."

Gudibanda, P., Panda, O., Pulido, C., Burkhardt, R., Schroeder, F., Aprison, E., Zhang, Y., Artyukhin, A., Ruvinsky, I., Ludewig, A., Rodrigues, P.

[International Worm Meeting, 2019]

Excreted small-molecule signals can bias developmental trajectories and physiology in diverse animal species. However, the chemical identity of these signals remains largely obscure. Here we report identification of an unusual N-acylated glutamine derivative, nacq#1, that accelerates reproductive development and shortens lifespan in C. elegans. Produced predominantly by C. elegans males, nacq#1 hastens onset of sexual maturity in hermaphrodites by promoting exit from the larval dauer diapause and by accelerating late larval development. Because nacq#1 is produced and excreted upon reaching sexual maturity, this pheromone may indicate that sufficient resources are available to exit dauer and resume reproductive development. Therefore, nacq#1 may be considered as an "anti-dauer pheromone". Moreover, even at picomolar concentrations, nacq#1 shortens hermaphrodite lifespan, suggesting a trade-off between reproductive investment and longevity. Acceleration of development by nacq#1 requires chemosensation and depends on all three homologs of vertebrate steroid hormone receptors in C. elegans, including the little studied NHR-48. Dauer-inducing ascarosides antagonize the effects of nacq#1, suggesting that opposite activities of nacq#1 and dauer-inducing ascarosides may result from differential regulation of NHR signaling. Biosynthesis of nacq#1 is independent of ascaroside-related pathways and instead relies on mitochondrial fatty acid metabolism. Nacq#1 production is conserved in C. briggsae and other C. elegans relatives, whereby males consistently produce much larger amounts than hermaphrodites. Moreover, unlike ascaroside pheromones, which are restricted to nematodes, fatty acylated amino acid derivatives similar to nacq#1 have been reported from humans and invertebrates, suggesting that related compounds may serve signaling functions throughout Metazoa.

Ludewig, Andreas et al. (2011) International Worm Meeting "Identification of evolutionary conserved regulators of dietary restriction using the "Ortho2ExpressMatrix"."

Meinel, Thomas, Doering, Frank, Ludewig, Andreas

[International Worm Meeting, 2011]

During the past decades, increasing amounts of data derived from high throughput approaches assaying all kinds of species, tissues and diseases have been accumulating into gigantic pools of data. However, the usability and the accessibility of these data for the generation of new scientific information is sometimes difficult. Here, we apply a novel developed bioinformatic tool - the Ortho2ExpressMatrix (Meinel et al., 2011) to summarize, compare and interpret gene expression data from various dietary restriction (DR) experiments performed in the model organisms mouse and C. elegans. We use the Ortho2ExpressMatrix to integrate complex gene family information, computed from sequence similarity with gene expression profiles of the two species exposed to DR and ad libidum feeding conditions. We come up with a comprehensive list of genes that are co- regulated in both species under DR. All in all, huge cohorts of data have been condensed to a list of 18 mouse genes and 24 assigned putative functional C. elegans orthologs, that can be directly used for experimental set ups further elucidating the molecular mechanisms that control DR related phenomena.

Andreas Ludewig et al. (2008) C.elegans Aging, Stress, Pathogenesis, and Heterochrony Meeting "Ascaroside Signalling and Lifespan in C. elegans"

Andreas Ludewig, Rabia Malik, Frank Schroeder, Chirag Pungaliya, Bennett Fox

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

Key developmental pathways in C. elegans appear to be regulated by several sets of endogenous small molecule signals. Recent analyses in our laboratory characterized eight C. elegans-produced glycosides of the dideoxysugar ascarylose. Among these, the three ascarosides ascr#1, ascr#2, and ascr#3 had previously been shown to induce dauer formation in C. elegans; in addition, ascr#2 and ascr#3 synergize with ascr#4 as sex pheromones (Kawano et al., 2005; Butcher et al., 2007, Srinivasan et al., in press). Identification of these endogenous compounds presents a unique opportunity by providing small-molecule tools for dissecting developmental pathways. Here, we show that ascarosides ascr#2 and ascr#3 strongly increase thermo tolerance in C. elegans. Wild type worms grown on NGM medium containing nanomolar concentrations of these ascarosides survived up to six times longer at 35degC compared to untreated controls. We also found that animals exposed to ascr#2 and ascr#3 on minimal growth medium had up to three-fold increased lifespan. Notably, 50 day old adult worms grown on minimal medium containing ascr#2 and ascr#3 carried small numbers of fully developed or over-developed embryos. When re-exposed to favourableconditions, these animals gave rise to few, but viable and reproductive progeny. We currently investigate the impact of these endogenous signaling molecules on thermotolerance and life span extension in a comprehensive set of mutant strains.

Ludewig AH et al. (2017) PLoS Genet "Larval crowding accelerates C. elegans development and reduces lifespan."

Ludewig AH, Thornton S, Doring F, Micikas RJ, Gimond C, Judkins JC, Braendle C, Pulido DC, Schroeder FC, Antebi A

[PLoS Genet, 2017]

Environmental conditions experienced during animal development are thought to have sustained impact on maturation and adult lifespan. Here we show that in the model organism C. elegans developmental rate and adult lifespan depend on larval population density, and that this effect is mediated by excreted small molecules. By using the time point of first egg laying as a marker for full maturity, we found that wildtype hermaphrodites raised under high density conditions developed significantly faster than animals raised in isolation. Population density-dependent acceleration of development (Pdda) was dramatically enhanced in fatty acid -oxidation mutants that are defective in the biosynthesis of ascarosides, small-molecule signals that induce developmental diapause. In contrast, Pdda is abolished by synthetic ascarosides and steroidal ligands of the nuclear hormone receptor DAF-12. We show that neither ascarosides nor any known steroid hormones are required for Pdda and that another chemical signal mediates this phenotype, in part via the nuclear hormone receptor NHR-8. Our results demonstrate that C. elegans development is regulated by a push-pull mechanism, based on two antagonistic chemical signals: chemosensation of ascarosides slows down development, whereas population-density dependent accumulation of a different chemical signal accelerates development. We further show that the effects of high larval population density persist through adulthood, as C. elegans larvae raised at high densities exhibit significantly reduced adult lifespan and respond differently to exogenous chemical signals compared to larvae raised at low densities, independent of density during adulthood. Our results demonstrate how inter-organismal signaling during development regulates reproductive maturation and longevity.