Lake, Menesha et al. (2017) International Worm Meeting "Characterization of the transcriptional network that promotes gonadal development in Caenorhabditis elegans ."

Braun, Caleb J., Swann, Sellers, Lake, Menesha, Kreitz, Naden, Strickland, Kayman, Kroetz, Mary B.

[International Worm Meeting, 2017]

During embryogenesis, the C. elegans gonad originates as a primordium of cells consisting of two somatic gonadal cells that flank two germ line precursor cells. The gonadal primordium is morphologically identical in the two sexes. Midway through the first larval stage, the somatic gonadal cells divide and differentiate, and during the course of development they will ultimately form one of two dramatically different organs: either a single-armed testis in the male or two bilaterally symmetric ovotestes connected to a central uterus in the hermaphrodite. To help define genes responsible for promoting gonadal development, we identified transcripts enriched for expression in the developing somatic gonad compared to the whole animal using cell-specific RNA-seq (Kroetz and Zarkower, 2015). Additionally, transcripts that were expressed in a sex-biased manner in the gonad have also been identified. Sex-biased transcripts were defined as transcripts that were enriched in one sex of gonadal cells compared to the expression in the gonadal cells of the other sex. Of the more than 900 gonad-enriched transcripts, approximately 80 encode for proteins that are transcriptional regulators. Seventeen transcription factors are expressed in a male-biased manner, and nine transcription factors are expressed in a hermaphrodite-biased manner in the developing gonad. To better understand if and how these transcription factors are controlling expression of the gonad-enriched transcripts, we are characterizing the expression patterns of proteins whose transcripts show the strongest gonadal enrichment. We are using CRISPR-Cas to fuse GFP to the C-terminus of the endogenously expressed gonadal proteins. We then use loss-of-function mutations or RNAi against the sex-biased or gonad-enriched transcription factors to determine if the transcription factors are important for expression of the GFP-tagged genes. This work will better define the transcriptional networks controlling gonad development and give insights into how key genetic regulators promote sex-specific organogenesis.

Shih, Pei-Yin et al. (2019) International Worm Meeting "Extremophile nematodes from Mono Lake demonstrate adaptation to an arsenic-rich environment."

Sapir, Amir, Goetz, Elizabeth, Shih, Pei-Yin, Lee, James Siho, Sternberg, Paul, Badroos, Jean Marie, Shinya, Ryoji

[International Worm Meeting, 2019]

Extremophiles have much to reveal about the biology of resilience, yet their study has been limited by sampling difficulties and the shortage of lab-culturable extremophiles. The broad success and small size of nematodes make them advantageous for tackling these problems. We investigated Mono Lake (CA, USA), a basin that is arsenic-rich, alkaline, and hypersaline, for the presence of extremophile nematodes. Mono Lake was previously described to only contain microbes and two arthropod species. Here, we report the discovery of eight nematode species from the lake, including five new species. Phylogenetic and morphological analyses suggest that the nematodes originate from multiple colonization events, and that they cohabitate the lake with microbes and arthropods as microbe-grazers, parasites, and predators. One species, Auanema tufa n. sp., is culturable, and we found it to have an ovoviviparous life cycle (hatching of embryos inside the mother), a common and likely adaptive trait of extremophile nematodes. A. tufa is resistant to As(III) arsenite and As(V) arsenate-the primary forms of arsenic in the lake-and can survive prolonged exposure to 100,000-times the human lethal limit. A. tufa has higher arsenic resistance than Caenorhabditis elegans gain-of-function mutants of SKN-1/Nrf, the major arsenic response coordinator in C. elegans. Our findings expand the range of Mono Lake extremophiles, highlight nematodes for investigating extremophile biology, and provide a culturable organism for studying animal arsenic resistance.

Jodie F Wren et al. (2005) International Worm Meeting "Environmental Genomics of Fluoranthene Exposure"

Stephen R Sturzenbaum, Jodie F Wren, A John Morgan, Peter K Hankard, Nick Redshaw, Suresh C Swain, Claus Svendsen, Martijs J Jonker, David J Spurgeon

[International Worm Meeting, 2005]

Benzo(j)Fluoranthene, is a 5-ring polycyclic aromatic hydrocarbon (PAH), known to occur as a product of plant biosynthesis, but also as a byproduct of incomplete combustion of organic material. Fluoranthene has been identified in cigarette smoke, char-broiled foods, drinking water, lake sediments and ambient air. It is thought to interact with DNA, cause heritable genetic disorders and has been associated with lung, intestinal and pharyngeal cancer. Information regarding the toxicity of fluoranthene in C.elegans still remains scarce, a shortfall we are aiming to redress. Using GE-31 (an embryonic lethal TS mutant) an elaborate toxicity test identified a dose dependant slippery pharynx phenotype and effects on specific demographic endpoints, such as brood size, volumetric growth and life span. Exploiting whole genome oligo array technology, we are currently exploring the stage-specific toxic effects of fluoranthene at a transcriptional level.

S.C. Swain et al. (2006) European Worm Meeting "Environmental Genomics of Fluoranthene Exposure"

M Jonker, P Kille, S.R. Sturzenbaum, C Svendsen, D.J. Spurgeon, N. Redshaw, A.J. Morgan, S.C. Swain, J. Wren

[European Worm Meeting, 2006]

Benzo(j)Fluoranthene, is a 5-ring polycyclic aromatic hydrocarbon (PAH), known to occur as a product of plant biosynthesis, but also as a byproduct of incomplete combustion of organic material. Fluoranthene has been identified in cigarette smoke, char-broiled foods, drinking water, lake sediments and ambient air. It is thought to interact with DNA, cause heritable genetic disorders and has been associated with lung, intestinal and pharyngeal cancer. Information regarding the toxicity of fluoranthene in C.elegans still remains scarce, a shortfall we are aiming to redress. An elaborate toxicity test (using the embryonic lethal TS mutant cib-1) revealed a dose dependant slippery pharynx phenotype and effects on specific demographic endpoints, such as a reduction of egg-hatchability, brood size, volumetric growth and life span. In addition, whole genome oligo array analysis identified stage-specific (L1, L4 and adult) genes and pathways that are modulated at the transcriptional level in a dose-responsive manner. Here we present a summary of fluoranthene induced toxicosis ranging from the molecular and cellular level to effects on life history parameters.

Ralph Menzel et al. (2005) International Worm Meeting "Chemoattraction and whole genome transcriptional responses in the nematode Caenorhabditis elegans exposed to humic material"

Jana Kulas, Stephen Strzenbaum, Ralph Menzel, Anne Brenwaldt, Christian EW Steinberg

[International Worm Meeting, 2005]

Humic substances (HS) are complex organic molecules constituting the most abundant source of dissolved organic matter (DOM) in freshwater and soil ecosystems. To investigate whether HS display a potential to exert chemical cues, the nematode model organism Caenorhabditis elegans was chosen for clearly defined reasons. Firstly, C. elegans satisfies all typical criteria to function as an ecotoxicological test organism, secondly, exquisite molecular genetic tools are available, and, finally, the entire genome of C. elegans has been decoded. Here we present three approaches to investigate the effects of a natural DOM isolate from the Lake Fuchskuhle and a synthetic HS (HS1500) on the nematode. In detail they encompass: (i) a behavioral chemoattractant bioassay, (ii) a reproduction assay, and (iii) the analysis of whole genome transcriptional expression patterns. A simple attractant test was devised. Petri dishes were prepared containing alternating piles of bacteria around the peripheral region of the plate, lacking HS or supplemented with HS, respectively. Nematodes were placed in the centre of the petri dish and subsequent movements scored. As a result, the adults, but not the juveniles, preferentially moved to the food bacteria with HS. This phenomenological experiment provided evidence that HS exert distinct chemical cues. The reproduction test utilized age-synchronized L1 larvae. Brood size was calculated from the total number of second-generation juveniles exposed to control conditions (HS devoid) or either of four different concentrations of each HS. Only the highest concentration (100 mg/L DOC) resulted in a decrease in brood size, highlighting an overall intrinsic tolerance to HS. Finally, an oligonucleotide-based whole genome microarray was performed with Cy3/Cy5 labeled cDNAs, derived from RNA samples isolated from HS treated and non-treated worms. The cluster analysis (cut-off set to two-fold increase/decrease, p<0.05, n=5) revealed that 84 genes were significantly induced and 235 genes were significantly repressed. Notable transcriptional changes were identified in chemosensors, olfactory receptors, as well as enzymes of the biotransformation system (CYP, UGT and GST), thereby confirming that HS1500 as well as the natural HS Fuchskuhle are recognized as environmental signaling chemicals.