Law, Wenjing et al. (2015) International Worm Meeting "Heterologous Expression in Remodeled C. elegans: A Platform for Monoaminergic Agonist Identification and Anthelmintic Screening."

Law, Wenjing, Komuniecki, Patricia, Komuniecki, Richard, Hapial, Vera, Ortega, Amanda, Wuescher, Leah

[International Worm Meeting, 2015]

Monoamines, such as 5-HT and tyramine (TA), paralyze both free-living and parasitic nematodes when applied exogenously and serotonergic agonists have been used to clear Haemonchus contortus infections in vivo. Since nematode cell lines are not available and animal screening options are limited, we have developed a screening platform to identify monoamine receptor agonists. Key receptors were expressed heterologously in chimeric, genetically-engineered Caenorhabditis elegans, at sites likely to yield robust phenotypes upon agonist stimulation. This approach potentially preserves the unique pharmacologies of the receptors, while including nematode-specific accessory proteins and the nematode cuticle. Importantly, the sensitivity of monoamine-dependent paralysis could be increased dramatically by hypotonic incubation or the use of bus mutants with increased cuticular permeabilities. We have demonstrated that the monoamine-dependent inhibition of key interneurons, cholinergic motor neurons or body wall muscle inhibited locomotion and caused paralysis. Specifically, 5-HT paralyzed C. elegans 5-HT receptor null animals expressing either nematode, insect or human orthologues of a key Galphao-coupled 5-HT1-like receptor in the cholinergic motor neurons. Importantly, 8-OH-DPAT and PAPP, 5-HT receptor agonists, differentially paralyzed the transgenic animals, with 8-OH-DPAT paralyzing mutant animals expressing the human receptor at concentrations well below those affecting its C. elegans or insect orthologues. Similarly, 5-HT and TA paralyzed C. elegans 5-HT or TA receptor null animals, respectively, expressing either C. elegans or H. contortus 5-HT or TA-gated Cl- channels in either C. elegans cholinergic motor neurons or body wall muscles. Together, these data suggest that this heterologous, ectopic expression screening approach will be useful for the identification of agonists for key monoamine receptors from parasites and could have broad application for the identification of ligands for a host of potential anthelmintic targets.

Dames SA et al. (1997) International C. elegans Meeting "Mortality Kinetics of Large Populations of C. elegans"

Johnson TE, Dames SA

[International C. elegans Meeting, 1997]

We are currently examining multiple aspects of C. elegans mortality. Previous research using both heterogenous and homogenous genetic populations (180,000 total animals) has demonstrated that C. elegans exhibits an age-specific (post reproductive) mortality increase predicted by the Gompertz Law. Originally proposed in 1825 as an empirical model for human aging, the Gompertz Law states that as population increases in age, mortality rates increase exponentially. Recent studies using large populations (up to 1,000,000 animals) of C. capitata (medfly) and D. melanogaster indicate that the Gompertz Law may not accurately predict mortality rates of these exceedingly large populations. These populations display an initial Gompertz-like mortality rate until very late in life when the last few of the surviving animal's mortality rates appear to level off. Human census data has also introduced concerns as to the ability of the Gompertz Law to predict the mortality rates in contemporary human populations (which appear to level off at age 85). We have assessed the mortality kinetics of >500,000 genotypically identical "wild type" C. elegans hermaphrodites in a standard environment. The results are indicative of a two-stage Gompertz-like mortality rate. We will be performing multiple mortality kinetics experiments using large populations (>100,000) of the long-lived strain age-1 to determine how this mutation affects mortality kinetics. In future experiments, we intend to alter environmental conditions (population density, food resources, temperature) to obtain differences in the overall mortality kinetics of C. elegans. We are especially interested in how the overall "wild type" mortality rate function is influenced by these limiting conditions. Experiments will be performed with a variety of strains (including males) to observe if the general C. elegans mortality function is altered by genotype. This may prove useful in predicting the mortality rates of large heterogenic populations (such as humans).

Dames SA et al. (1996) West Coast Worm Meeting "MORTALITY KINETICS IN C. ELEGANS: THE MILLION WORM PROJECT."

Dames SA, Duhon SA, Johnson TE, Tedesco PM

[West Coast Worm Meeting, 1996]

Predicting the mortality rates of large populations is of significant economic importance. In the United States, over 20 percent of the population will be 65 years of age or older. Estimates off as little as one or two percent could have suboptimal economic implications by 2020. Using C. elegans and its obvious advantages in expense and speed will be useful in predicting the mortality kinetics of large populations. We are currently examining multiple aspects of C. elegans mortality. Previous research using both heterogenous and homogenous genetic populations (180,000 total animals) has demonstrated that C. elegans exhibits an age-specific (post reproductive) mortality increase predicted by the Gompertz Law. Originally proposed in 1825 as an empirical model for human aging, the Gompertz Law states that as population increases in age, mortality rates increase exponentially, and can be represented mathematically as: m(t) = Aeat Where "m(t)" is the mortality rate at time "t"; "A" is the mortality rate at reproductive maturity; and "a" is the Gompertz exponent which describes the rate of accelera- tion of age specific mortality with chronological age. Recent studies using large populations (up to 1,000,000 animals) of C. capitata (medfly) and D. melanogaster indicate that the Gompertz Law may not accurately predict mortality rates of these exceedingly large populations. These populations display an initial Gompertz-like mortality rate until very late in life when the last few of the surviving animal's mortality rates appear to level off. Human census data has also introduced concerns as to the ability of the Gompertz Law to predict the mortality rates in contemporary human populations (which appear to level off at age 85). We are in the process of determining the mortality rate of at least 1,000,000 genotypically identical animals in order to look for late stage alterations in mortality rates. We intend to alter environmental conditions (population density, food resources, temperature) to obtain differences in the overall mortality kinetics of C. elegans. We are especially interested in how the overall "wild type" mortality rate function is influenced by these conditions. Experiments will be performed with a variety of strains (including males) to observe if the general C. elegans mortality function is altered by genotype. This may prove useful in predicting the mortality rates of large heterogenic populations (such as humans).

Schilling, T. et al. (2019) International Worm Meeting "Non-Mendelian Inheritance in C. elegans: a Violation of the Law of Independent Assortment."

Severson, A. F., Schilling, T.

[International Worm Meeting, 2019]

Mendel's laws of inheritance can predict typical genotypic frequencies in subsequent generations. The second law, the Law of Independent Assortment, states that alleles determining different traits are inherited independently of each other. However, in C. elegans males, it has been previously observed that extrachromosomal DNA arrays and chromosomes containing integrated multicopy DNA arrays segregate away from the single male X chromosome, appearing more frequently in male than hermaphrodite offspring. For example, we observed that 80% of progeny inheriting a patroclinous copy of chromosome III balancer qC1[nIs281], are males and 20% are hermaphrodites instead of the expected 50% of each sex as predicted by Mendel's laws. A future goal is to perform FISH to visualize this unusual dependent assortment of chromosomes III and X. We also performed several crosses with different extrachromosomal and integrated arrays (oxEx229, mIs10, ccIs4251, syIs44) and analyzed the inheritance patterns in the offspring to demonstrate that the effects of non-Mendelian inheritance are not specific to the qC1[nIs281] balancer. The largest deviations from expected Mendelian frequencies resulted from crosses in which the array contained X chromosome homology. Finally, we are performing a forward genetic screen to identify mutations that disrupt non-Mendelian inheritance of the qC1[nIs281] balancer, shifting its transmission back to the expected ratio of 50% males and 50% hermaphrodites. Mutated pha-1/qC1[nIs281] males were crossed with pha-1 hermaphrodites and males fathering progeny in equal male and hermaphrodite proportions were considered candidates for having mutations resulting in expected inheritance patterns. Identifying genes required for non-Mendelian inheritance will define mechanisms that drive evolutionary change.

Zhang, Bi et al. (2015) International Worm Meeting "Environmental temperature differentially modulates C. elegans longevity through a thermosensitive channel."

Xiao, Rui, He, Yongqun, Xu, X.Z. Shawn, Ronan, Elizabeth A., Zhang, Bi, Liu, Jianfeng

[International Worm Meeting, 2015]

Temperature profoundly affects aging in both poikilotherms and homeotherms. A general belief is that lower temperatures extend lifespan while higher temperatures shorten it. Though this "temperature law" has been widely accepted, it has not been extensively tested. Here, we carefully evaluated the role of temperature in lifespan regulation in C. elegans. We found that while exposure to low temperatures at the adult stage promotes longevity, low temperature treatment at the larval stage surprisingly reduces lifespan. Interestingly, this differential effect of temperature on lifespan in larvae and adults is mediated by the same thermosensitive channel TRPA-1 that signals to the transcription factor DAF-16/FOXO, a master regulator of lifespan. DAF-16/FOXO and TRPA-1 act in larvae to shorten lifespan, but extend lifespan in adulthood. Notably, DAF-16/FOXO differentially regulates gene expression in larvae and adults in a temperature-dependent manner. Our results uncover unexpected complexity underlying temperature modulation of longevity, demonstrating that temperature differentially regulates lifespan at different stages of life.

Stephan R Goodwin et al. (2003) International Worm Meeting "A C. elegans population genetics lab."

Stephan R Goodwin, Scott E Baird

[International Worm Meeting, 2003]

Studying evolution with an investigative approach in introductory biology is difficult due to time, space and monetary limitations. Caenorhabditis elegans, however, provides an effective model organism to look at natural selection and population genetics within a manageable timeframe. We have developed a single-day C. elegans laboratory exercise to illustrate natural selection. In this exercise, mixed populations of fog-2 and dpy-11 fog-2 worms were initiated at four-day intervals starting thirty days prior to the scheduled laboratory date. Populations were bleached and L1 larvae collected five days prior to the lab. Starvation-arrest L1s were fed two days prior to the lab. Thus, students were required to score Dpy and wild-type phenotypes in synchronous populations of young adults. From frequencies of Dpy worms present at each time point students were required to determine dpy-11 (e224) allelic frequencies and observe the increase in calculated heterozygousity via the Hardy-Weinberg law. We found the optimal way to initiate populations was with 18 gravid dpy11 fog-2 females and two gravid fog-2 females. Starting with such populations we observed an exponential decay of the dpy11 (e224) frequency that reached zero by the last time point.

Bloniarz A E et al. (2010) Biology of the C. elegans Male, Madison, WI "Numerical methods for analyzing neural connectivity in the C. elegans nervous system"

Bloniarz A E, Emmons S W

[Biology of the C. elegans Male, Madison, WI, 2010]

The connectome of the posterior nervous system of the C. elegans male consists of a complex network of interacting nerve cells. We utilize concepts from the mathematical field of graph theory to describe the properties of the network. The connectome is modeled as a graph in which neurons and synapses are represented by vertices and edges, respectively, and the edge weights are determined by the total number and sizes of presynaptic densities. The pattern of connections is described by an adjacency matrix for the graph. Taken together, the network of chemical and electrical interactions form a mixed graph, consisting of both directed and undirected edges. The degree of a vertex is the number of edges incident to that vertex, representing the number of pre- or postsynaptic partners of a neuron. It has been suggested that many biological neural networks form a scale-free topology, in which the degree distribution follows a power law. Utilizing a most-likelihood estimator, we test the hypothesis that the degree distribution of the male connectome follows a power law. Also, the clustering coefficient is a property of a graph which gives the probability that two vertices are connected to each other by an edge, given that they both have an edge to a common vertex. We calculate the clustering coefficient and average shortest path length of the graph to analyze the small-world properties of the network. We identify neurons with high connectivity – so-called 'hub' neurons – which may synchronize the activity of large groups of neurons. We also calculate the betweenness centrality of neurons, which measures how often a neuron is involved in a shortest path between two other neurons. Neurons with high betweenness centrality may define common pathways of information flow that support specific substeps of male copulating behavior. We also take a more statistical approach to analyzing the male connectome. The connectivity of each neuron can be thought of as a point in high dimensional space, in which each dimension of the data point of a neuron represents the input from or output to another neuron or group of neurons. We can quantify the degree of similarity between neurons by defining a distance metric on this space. We use the cosine distance to capture correlations in the connectivity of two neurons. After grouping left/right pairs in the data points, we see that most pairs have a statistically significant degree of similarity, suggesting an overall symmetry in the wiring of the nervous system. We can also utilize a nearest-neighbor method in this distance metric to classify neuron processes which cannot be traced to a cell body. Finally, this metric is used to create a hierarchical clustering of neurons which may reveal biologically significant groupings in this high dimensional space.

Le, Son Tho et al. (2013) International Worm Meeting "Testing for non-Mendelian assortment of chromosomes in Caenorhabditis."

Le, Son Tho, Kao, Chia-Yi, Wang, John

[International Worm Meeting, 2013]

Eukaryotic genome sizes range over 10,000-fold with a correlation between larger genomes and greater organismal size and complexity. In part, population genetic principles can explain this observation. Smaller organisms typically have larger population sizes which are more efficient at purging weakly deleterious mutations such as transposons and other insertions resulting in smaller genome sizes; larger organisms are the opposite. In contrast to the population genetic predictions, the reverse is observed for the species with known genome sizes within the Elegans group of the Caenorhabditis genus. Gonochoristic (male-female) species have larger genomes than hermaphroditic species despite the former predicted to have larger populations sizes than the latter. Why is this? Interestingly, Mendel's law of random chromosome assortment is violated in C. elegans males that are heterozygous for autosomal chromosomes of differing sizes whereby sons inherit the longer chromosome while the hermaphrodite daughters inherit the shorter chromosome, in a phenomenon which we call skew. Because a single hermaphrodite can start a new population, skew could explain how genomes of hermaphroditic species evolve to be smaller than the ancestral gonochoristic species. For this to be true, skew would be predicted to be a general property of the Caenorhabditis species. To this end, we are testing for the presence of skew in other Caenorhabditis species. We are also interested in understanding the mechanisms underlying skew and have initiated a forward genetic screen for genes that suppress skew.

Farris, Lily et al. (2009) International Worm Meeting "Open Science in Practice: C. elegans Researchers and Their Use of Open Access Resources."

Marden, Emily, Levy, Ed, Farris, Lily, Moerman, Don

[International Worm Meeting, 2009]

As integrated GE3LS (genomics, ethics, environment, economics, law and society) researchers with the C. elegans Gene Knockout Consortium we are exploring how publicly available data is accessed and used and how this process informs scientific advancement. Our survey asked researchers about their scientific resource use, sharing of information, and handling of information with proprietary potential. The results from this survey provide additional understanding of the relationship between the researcher''s use and exchange of information and their scientific innovation. Methods We invited researchers currently using C. elegans as a model organism who were 19 years of age or older to complete an online survey (www.wormsurvey.com) to provide information about their current use and exchange of research materials. Compiling a list of C. elegans researchers from the list of registered researchers in WormBase, we contacted a random sample of respondents five times in order to unsure higher response rates. The survey was fielded in October, 2008. We also requested that researchers circulate the survey to all members of their research team including graduate students, technicians, and research assistants who conduct any C. elegans related research. Preliminary Results Of the 349 respondents who conducted research with C. elegans, the majority supported the work of C. elegans Gene Consortium and supported the statement that their research would function differently if this resource was not available. Most respondents used WormBase on a daily or weekly basis and few respondents held patents. Overall, C. elegans researchers use and access a variety of resources with unrestricted access using these resources to produce both basic science and commercial innovation.

Iwasaki, Yuishi (2009) International Worm Meeting "Analysis of noise robustness in neural circuit of C. elegans."

Iwasaki, Yuishi

[International Worm Meeting, 2009]

Is a worm''s behavior, which seems to be random walk, deterministic or not? Noise or fluctuation sometimes plays an important role to organize decision or choice behavior. Neurons in C. elegans are believed to be non-spiking and communicate by graded synaptic transmission. In this meaning, the nervous system of C. elegans is not a "digital" control system but an "analogue" control system which seems to be sensitive to noise. In general, noises (fluctuations) are classified into two types. One is external noises for individuals such as environmental noises. For examples, concentration fluctuation in chemicals for chemotaxis and thermal fluctuation for thermotaxis. The other is internal noises in living organisms. For examples, fluctuation in a neuron''s membrane potential and noise in synaptic transmission. To analyze the noise robustness in neural circuit of C. elegans, simulation is carried out using a stochastic differential equation, so-called Langevin equation. As a neural circuit to simulate the dynamics, I focus on that of chemotaxis in this work. The number of chemical synapses and gap junctions is determined from the two databases of the neural connectivity (Oshio et al., 2003; Chen et al., 2006). I analyze the response of the neural circuit against the noises. If the additive noises are supposed to be uncorrelated each other, the law of large numbers naively says that the influence of the noises decreases as the number of connected neurons (elements) increases. In C. elegans, however, the number of connected neurons for a given neuron is not so large since the total number of neurons in the whole nervous system is 302. Therefore the influence of the noises does not sufficiently vanish. This work was supported by MEXT No. 20115004.