Snoek, L. Basten et al. (2009) International Worm Meeting "Natural variation reveals the autophagy gene unc-51 as a key connection between sex and death in C. elegans."

Vinuela, Ana, Kammenga, Jan E., Doroszuk, Agnieszka, Snoek, L. Basten, Riksen, Joost A.G., Gutteling, Evert W.

[International Worm Meeting, 2009]

The cost of reproduction, i.e. a decreased lifespan due to reproduction, is a crucial trade-off which drives life-history evolution in nearly all species, including humans. A key question in evolutionary and aging research is how this trade-off is regulated in natural populations. Although some induced mutations affecting lifespan also alter the reproductive state, detailed knowledge about the genetic control of the trade-off between lifespan and offspring in natural populations is scant. We combined life-history analysis and mapping of global gene transcription profiles in a C. elegans population of recombinant inbred lines (RILs) obtained from a cross between wildtypes N2 and CB4856. We found a trade-off between lifespan and offspring across the RILs and detected 27 gene transcripts that were highly correlated to both traits in an opposite way. These genes had 20% more eQTLs, i.e. were more regulated, than the less correlated genes. Using a candidate gene approach we show that knocking-down one of these genes, the autophagy gene unc-51, with RNAi increased offspring with 30% while decreasing lifespan with 15%. By introgressing a trans-acting CB4856 locus into N2 we show that the RNAi effect on the trade-off was modulated. Together our results demonstrate that the trade-off between lifespan and offspring can be highly regulated early in life and suggest that natural variation can tune C. elegans life-history by regulating unc-51 transcription during the L3 stage. Interestingly, the results also indicate that RNAi phenotypes depend strongly on the genetic background due to epistatic interactions and trans-acting loci.

Glater, Elizabeth E. et al. (2011) International Worm Meeting "The genetic basis of natural variation in food preference behavior in Caenorhabditis elegans."

Glater, Elizabeth E., Bargmann, Cornelia I.

[International Worm Meeting, 2011]

Our research focuses on the genetic basis of differences in the food preference behavior between two wild-type strains of the nematode Caenorhabditis elegans. We have found that C. elegans strains isolated from different locations around the world have distinct bacterial preferences. Specifically, in a bacterial choice assay between Serratia marcescens, a pathogenic soil bacteria, and Escherichia coli HB101, a common laboratory food source for C. elegans, the N2 Bristol strain had a stronger preference for Serratia than the CB4856 Hawaii strain did. Using N2-CB4856 recombinant inbred advanced intercross lines (RIAILs) (Rockman and Kruglyak, 2009), chromosome substitution strains (constructed by Man-Wah Tan and colleagues) and introgression lines (Doroszuk et al., 2009), we found that this variation in food preference behavior has a complex genetic basis, involving at least five quantitative trait loci (QTL). Based on genetic mapping and transgenic rescue, one of the QTLs appears to represent a divergent member of the F-box protein family. F-box proteins function as adapters between the E3 ubiquitin ligase complex and its ubiquitinated substrates. F-box proteins comprise one of the largest protein families in C. elegans, but few have known functions. In addition, we have begun to characterize the neural circuit that underlies food choice and found that one chemosensory neuron, AWCon, is important for discrimination between these two bacterial species. Understanding the genetic basis of this natural variation will provide insights into the mechanisms by which C. elegans tunes its responses to different complex stimuli, and more generally, into the relationship between the genome and behavior. References: Doroszuk, A., Snoek, L.B., Fradin, E., Riksen, J., and Kammenga, J. (2009). A genome-wide library of CB4856/N2 introgression lines of Caenorhabditis elegans. Nucleic Acids Res 37, e110. Rockman, M.V., and Kruglyak, L. (2009). Recombinational landscape and population genomics of Caenorhabditis elegans. PLoS Genet 5, e1000419.

Kleemann G A et al. (2010) Aging, Metabolism, Stress, Pathogenesis, and Small RNAs, Madison, WI "Longevity Differences Across N2 x CB4856 Recombinants Involves a Region of Chromosome IV That Interacts with Multiple Loci"

Murphy C T, KRUGLYAK L, Kleemann G A, Bloom J S

[Aging, Metabolism, Stress, Pathogenesis, and Small RNAs, Madison, WI, 2010]

Single-gene lesions with large effects have been useful for the rapid identification of major pathways influencing aging. However, our understanding of the ecological relevance and the physiological interactions of the known longevity pathways would be enhanced by studying natural polymorphisms in genes affecting longevity. In order to identify and characterize such polymorphisms, we are analyzing variation in longevity across CB4856 x N2 recombinant inbred advanced intercross lines (RIAILs) (Rockman and Kruglyak 2009). In the first phase of the project, we facilitated our analysis of the RIAILs by developing ""Chronos,"" a high-throughput longevity assay pipeline to count worms and estimate longevity curves. We identified long and short-lived RIAILs as well as a longevity-linked region of Chromosome IV, with the N2 genotype conferring higher longevity than the CB4856 genotype. While N2 and CB4856 longevity were similar, a number of the RIAIL life spans differed from either parent. This suggests that parental life span has converged, but hidden genetic variation is revealed when co-adapted alleles are separated. We are currently cloning the genetic locus under the linkage peak on Chr. IV. The initially identified region has been reduced by 60% using five different near isogenic lines (NILs) made by us and Doroszuk et al. (2009). The minimal region contains 40 SNPs with predicted functional changes. We are testing our best candidates with RNAi and transgenic lines. Additionally, a long-lived RIAIL QX203 and its sib-strain QX202 share ~70% of their genotype, but QX202 is not long-lived. Comparison of their genotypes reveals a polymorphism in the FOXO transcription factor daf-16. Microarray data for QX203 vs. QX202 reveals expression differences in known daf-16-regulated genes (Murphy et al. 2003). However, the two RIAILs do not have a genetic difference in the Chr. IV longevity-linked region. By investigating how natural variation influences longevity, gene expression and genetic interactions, we hope to gain insight into how longevity pathways interact under natural conditions.

Agnieszka Trzebiatowska et al. (2006) European Worm Meeting "TEN-1 is required for the Formation of the Somatic Gonad in Caenorhabditis elegans"

Krzysztof Drabikowski, Agnieszka Trzebiatowska, Ruth Chiquet-Ehrismann

[European Worm Meeting, 2006]

Agnieszka Trzebiatowska1, Krzysztof Drabikowski2, Ruth Chiquet-Ehrismann1. TEN-1 is a member of a novel family of transmembrane proteins named teneurins that have been characterized in Drosophila, zebrafish, chicken, mouse and man. Teneurins were shown to be mainly expressed in the developing and adult nervous system and to play a role in morphogenesis, cell migration and at sites of pattern formation. C. elegans TEN-1 was proposed to act as a receptor that signals directly to the nucleus. Its intracellular domain is cleaved and translocates to the nucleus where it may influence gene expression. Little is known, however, about the cleavage mechanism and possible target genes. C. elegans has a single teneurin orthologue, which is under control of alternative promoters. The upstream promoter is active in the somatic gonad, some muscle cells, the gut and in a number of neurons. The expression from the downstream promoter is mainly detected in the nervous system. TEN-1 is a type II transmembrane protein consisting of a short intracellular domain followed by a transmembrane domain and a long highly conserved extracellular part containing eight EGF-like repeats, a cysteine rich region and YD repeats.. In order to determine the function of TEN-1 in C.elegans, we investigated two loss-of-function mutants: ten-1(ok641) and ten-1(tm651). The former carries an in frame deletion of four EGF-like repeats and a part of the cysteine rich region; the latter has a deletion that removes the transmembrane domain and introduces a frameshift mutation resulting in the loss of the entire protein except for the first 194 aminoacids. In both mutants transcripts for the predicted truncated proteins could be detected on the level comparable to the wild type form. Both ten-1 mutants show a pleiotropic phenotype, similar to the phenotype observed after reduction of ten-1 expression by RNAi. Mutant worms are sterile due to various defects in the somatic gonad and ectopic germline formation in the proximity of the vulva. Time course analysis of germline development showed that these abnormalities may result from an early defect in the somatic gonad formation. We were able to partially rescue the phenotype of ten-1(ok641) mutant worms by injecting the cosmid F36A3 carrying the entire genomic region of the ten-1 gene. Since such an extrachromosomal array is likely to be silenced in the germline, gonadal defects appear to be the result of impaired signaling in the somatic gonad.