Lao, R.X. et al. (2019) International Worm Meeting "Understanding Argonaute/Small RNA-based intercellular communication."

Buck, A.H., Claycomb, J.M., Wadi, L., Lao, R.X., Seroussi, U., Maity, T., Blaxter, M., Abreu-Goodger, C.

[International Worm Meeting, 2019]

Cells have many ways to regulate gene expression, one of which is by using small RNAs (sRNAs) and sRNA pathway effectors, called Argonautes (AGOs). Studies in plants and worms point to sRNA mediated communication between cells in a single organism (e.g., systemic RNAi; Winston et al., Science 2002). Perhaps even more exciting is the prospect that sRNA/AGO complexes could be used as a means of communication between organisms (Buck et al., Nat Comm. 2014, Cai et al., Science 2018). The discovery that sRNAs exist extracellularly in conjunction with AGOs is particularly important for host/parasite or pathogen relationships. For example, a parasitic nematode of mouse, H. polygyrus bakeri (Hb), secretes extracellular vesicles, which possess sRNAs and an extracellular AGO protein, exWAGO (extracellular Worm AGO). However, Hb is not genetically tractable, hence we have turned to C. elegans to study the functions of exWAGO. Although exWAGO is not present in the C. elegans genome, three homologs, SAGO-1, SAGO-2, and PPW-1 exist. We have engineered strains of C. elegans expressing exWAGO in various tissues to characterize its molecular function in sRNA pathways. In parallel, we engineered GFP-tagged strains of SAGO-1, -2, and PPW-1 using CRISPR-mediated gene editing. These three C. elegans AGOs share a common localization pattern to the apical gut membrane, where exWAGO is expressed in Hb. To further understand the roles of these intestinal secondary AGOs (iSAGOs), we immunoprecipitated the iSAGOs and performed sRNA sequencing and mass spectrometry analysis to identify sRNA and protein binding partners. Top hits from the IP/MS analysis included trafficking, secretory pathway, and membrane anchoring proteins, highlighting the potential for the iSAGOs to be secreted and act intercellularly in C. elegans. We are now in the midst of identifying the pathways that contribute to apical membrane anchoring of iSAGOs and determining what role the iSAGOs may play in systemic RNAi in C. elegans.

SAHMEDDINI, SOUDABEH et al. (2011) International Worm Meeting "Slimming Nematodes with Herbal Medicine: From pseudo-science to reality."

Sturzenbaum, Stephen, HYLANDS, PETER, SAHMEDDINI, SOUDABEH

[International Worm Meeting, 2011]

Obesity, defined as the abnormal accumulation of fat, is a key factor in a wide range of illnesses such as coronary heart disease and type II diabetes(1). Since western medication has struggled to identify effective but non-toxic anti-obesity drugs, East Asian medicine may offer promising new leads. Unfortunately, stringent scientific monitoring and post-treatment studies are rarely applied to herbal remedies. This shortcoming may possibly be addressed by exploiting the benefits of an invertebrate model organism such as Caenorhabditis elegans. The C. elegans genome is fully sequenced and has been shown to share many genes and pathways with mammals. In this study, Hoodia gordonii, an appetite suppressant extract from the South African cactus (2) was used as a target to study obesity. Age synchronized C. elegans (stage L1) were exposed to different doses of H. gordonii via the OP50 E. coli food source and maintained on nematode growth media (NGM). Size measurements (N=30 per condition) were determined using Image-Pro Express (Media Cybernetics) software. Data was analyzed statistically using Prism GraphPad5 (GraphPad Software, Inc.) software to assess statistical significance at p0.05. Nematodes exposed to H. gordonii were significantly affected resulting in a dose dependant reduction in body fat and size but also progeny number. In addition, pharyngeal pumping (food consumption) was modulated in an age dependent manner. Moreover, a genome-wide microarray analysis performed to identify novel genes involved in fat metabolic pathways in response to the anorectic H. gordonii. This may lead to characterization of abundant gene families which may have been neglected in obesity-related studies. H. gordonii exerts noticeable dose dependent effects on the nematode. At this stage it is not yet known if these are a direct consequence or side effect of exposure, a question that is currently being investigated at the molecular level. (1). Obesity and overweight, 2008, World Health Organization, [online], (updated February 2011), Available at: http://www.who.int/mediacentre/factsheets/fs311/en/ [Accessed on 3rd March 2011]. (2). Lao L, Zhang RX, Zhang G, Wang X, Berman BM, Ren K, 2004, Brain Res 1020 (1-2): pp1-11.