Roy-Bellavance, Catherine et al. (2011) International Worm Meeting "The R148.3 (OcaB) gene controls longevity and fat accumulation in the nematode C. elegans."

Roy-Bellavance, Catherine, Miard, Stephanie, Picard, Frederic, Rondeau, Evelyne

[International Worm Meeting, 2011]

OcaB (Oct co-activator from B cells) is a nuclear cofactor mainly expressed in immune B lymphocytes, where it regulates B cells development and function. Our lab has recently discovered that OcaB is expressed in white adipose tissue (WAT), and that the gene expression in WAT is very low in diet-induced obese mice but is increased upon aging. We used the genetic model C. elegans to assess the role of OcaB in fat accumulation and define its pathway in aging. GFP-reporter analysis indicated that R148.3 (OcaB closest homolog gene) is mainly expressed in the pharynx and pharyngeal neurons. mRNA quantification by qPCR analysis showed that R148.3 is mainly expressed in adult worm. Knockdown (KD) of the R148.3 gene was performed by RNAi feeding. R148.3-KD worms showed much higher lipid content than their wild-type counterparts, as evidenced by both Nile Red and Oil Red O staining, and this effect on lipid content tended to be age-dependent. In addition, R148.3-KD worms had a 40% shorter lifespan compared to wildtype nematodes. Using genetic mutants, we further found that the effect of R148.3 on longevity was abrogated in daf-2 and age-1 mutants, but not in daf-16 mutants. We also tested the capacity of R148.3KD worms to resist oxidative stress by soaking the worms in paraquat. We found that KD worms were more sensitive to paraquat and died earlier than wildtype nematodes. Taken together, these results suggest that R148.3 could possibly serve as a node linking fat accumulation to longevity and stress resistance. Study funded by CIHR (IAP-102233).

Legue, Marcela et al. (2017) International Worm Meeting "New triggers, old targets: Searching for bacterial small RNAs that elicit an interkingdom RNAi-based behavioral response."

Legue, Marcela, Caris, Carlos, Verdugo, Lidia, Martin, Alberto, Calixto, Andrea

[International Worm Meeting, 2017]

The host-microbe interaction depends on molecular patterns and damage signals that reciprocally modulate bacterial colonization and the host immune response, triggering changes in gene expression in both players. Bacterial small RNAs (sRNAs) are emerging actors of this inter-kingdom crosstalk, but many questions about the mechanisms by which they affect host transcriptomic profiles remain unanswered. Our group observed that C. elegans enters diapause, after two generations of feeding on P. aeruginosa PAO1 and S. Typhimurium MST1, as an RNAi-dependent defensive mechanism against infection. We hypothesize that bacterial sRNAs trigger this behavior by targeting host RNAs. Our aim is to identify which sRNAs from P. aeruginosa PAO1 sensed by C. elegans, are able to trigger an RNAi mediated transcriptomic change by targeting host RNAs. We compared the transcriptomic profiles of naive bacteria (never exposed to worms) with those residing in C. elegans intestine for one, and two generations, using simultaneous worm-bacteria RNAseq. Sequencing enriched for small RNAs was done using Illumina Truseq, yielding an average of 2,5 M reads from naive bacteria and 1,2 M reads from intestinal bacteria (bacteria-worm samples) trimmed and quality filtered (Q = 30; lenght = 17). After mapping (Bowtie, Bowtie2, Segemehl/Lack, Star) reads from bacteria-worm samples were separated in silico (Picard tools), counted, and annotated using NRDR database and SRF prediction (Structure RNA Finder). Differentially expressed genes between naive and experienced bacteria using Deseq2 identified 23 small RNAs from P. aeruginosa PAO1 overexpressed in contact with host (15 in F1, 19 in F2), far less than the 88 sRNAs from E. coli OP50 (61 in F1, 63 in F2). Targets were predicted by IntaRNA, RNA duplex, RNAplex, RNAup and PITA softwares, with 12956 RNA-RNA interactions consistently predicted by all five. Pre-miRNAs constituted the most frequent target class in the host (1214). Prediction of structure and target; analyzes of functional RNA motifs, sites and their homology (RegRNA 2.0), will clarify functional roles and specificity of sRNAs expressed in pathogens. In summary, there is a set of sRNAs uniquely overexpressed in pathogens, candidates of triggering a behavior response in host. We propose that there is a bidirectional dynamic interaction between bacteria and C. elegans that involves the activation of signaling pathways in the host, in which the RNAi machinery may play a central role. This work is the base for future validation studies.