Anderson, S.M. et al. (2019) International Worm Meeting "The fatty acid oleate is required for innate immune activation and pathogen defense in Caernohabditis elegans."

Peterson, N.D., Soukas, A.A., Anderson, S.M., Pukkila-Worley, R., Cheesman, H.K.

[International Worm Meeting, 2019]

Fatty acids affect a number of physiological processes, in addition to forming the building blocks of membranes and body fat stores. In this study, we uncover a role for the monounsaturated fatty acid oleate in the innate immune response of the nematode Caenorhabditis elegans. From an RNAi screen for regulators of innate immune defenses, we identified the two stearoyl-coenzyme A desaturases that synthesize oleate in C. elegans. We show that the synthesis of oleate is necessary for the pathogen-mediated induction of immune defense genes. Accordingly, C. elegans deficient in oleate production are hypersusceptible to infection with diverse human pathogens, which can be rescued by the addition of exogenous oleate. However, oleate is not sufficient to drive protective immune activation. Together, these data add to the known health-promoting effects of monounsaturated fatty acids, and suggest an ancient link between nutrient stores, metabolism, and host susceptibility to bacterial infection.

Foster, K.J. et al. (2019) International Worm Meeting "Olfactory neuron protein promotes intestinal immune homeostasis to ensure evolutionary fitness."

Liu, P., Pukkila-Worley, R., Cheesman, H.K., Foster, K.J., Peterson, N.D.

[International Worm Meeting, 2019]

Innate immune homeostasis is critically important for the health of metazoans, including C. elegans. Here, we demonstrate that control of innate immune activation via a signaling axis between sensory neurons and the intestine is required for reproductive fitness. We show that an olfactory neuron protein functions in the cell non-autonomous suppression of the canonical p38 MAP kinase PMK-1 immune pathway in the intestine. Immune de-repression in loss-of-function mutants causes constitutive activation of the p38 MAP PMK-1, hyperinduction of immune effector transcription and resistance to bacterial infection. Importantly, we demonstrate that regulation of the p38 MAPK PMK-1 pathway is required for healthy nematode development and reproduction. These data demonstrate that olfactory neurons regulate the p38 MAPK PMK-1 immune pathway in the intestine and indicate that maintenance of immune homeostasis is an evolutionarily ancient requirement for growth and reproduction of free-living organisms.

Phillips, Carolyn M. et al. (2009) International Worm Meeting "Characterization of the Transposon Silencing Machinery."

Phillips, Carolyn M., Ruvkun, Gary

[International Worm Meeting, 2009]

Small RNA-mediated gene silencing is a conserved mechanism used by nearly all eukaryotes as a way to regulate gene expression at both the transcriptional and post-transcriptional level. The double-strand RNA can be delivered from outside the cell or can be generated from endogenous transcription of coding and non-coding genomic loci. Some processes known to be regulated by RNAi include transposon silencing, defense against viral infection, and maintenance of heterochromatin. Transposon silencing is an important mechanism to prevent DNA damage and subsequent mutations in the germline. A subset of the genes shown to be involved in exogenous RNAi have also been shown to be involved in transposon silencing in the germline, including mut-2, mut-7, mut-14, mut-15, mut-16, and rde-2. When these genes are mutated, transposons can be excised, leaving a double-strand break (DSBs), which must be repaired by the cellular machinery, either through homologous recombination or non-homologous end joining. I am currently developing a strategy to visualize DSBs in the germline generated by unregulated transposons in the transposon silencing mutants. This assay will allow me to perform a small-scale cytological screen for new genes in the transposon silencing pathway. Additionally, I am generating fluorescently tagged proteins to perform localization analysis of both new and previously characterized genes in this pathway. Localization may identify particular cells where RNA based immunity is important or sub-cellular structures to which these proteins concentrate. Finally, to identify direct binding partners of these proteins and potentially identify additional components of the transposon silencing machinery, I will biochemically purify the components of this pathway. The tagged constructs that I am generating for cytology will include a modified version of the Tandem Affinity Purification (TAP) tag generated by Cheesman et al. (2004), which includes a fluorescent tag followed by a TEV protease cleavage site and the S peptide domain and is referred to as the Localization and Affinity Purification (LAP) tag. It allows for both visualization of the protein and its affinity purification. Interacting proteins will be identified by mass spectrometry. Any components identified through this strategy can be further characterized by mutational and localization analysis. These experiments will examine the relationship between the RNAi pathway and the maintenance of genome integrity, and further elucidate the mechanisms of transposon silencing in the germline.