Jagadeesan, Sakthimala et al. (2015) International Worm Meeting "Genome-wide screen identifies genes involved in gut immunity and homeostasis in C. elegans."

Hakkim, Abdul, Osmani, Aniqa, Jagadeesan, Sakthimala, LABED, sid ahmed, Ismail, Nidha, Ausubel, Fred

[International Worm Meeting, 2015]

Gut mucosal immunity plays a pivotal role in pathogen resistance in Caenorhabditis elegans. The mucosal barrier that is continuously exposed to pathogens and gut microbiota needs to identify and elicit an immune response only to invading pathogens but not to innocuous bacteria. Once, pathogens are detected and killed, it is also essential to resolve the epithelial damage caused by both infection and immune signaling. In humans, the lack of resolution often leads to chronic inflammation related diseases including inflammatory bowel diseases.C. elegans intestinal epithelial cells have similar anatomical features as their mammalian counterparts. Additionally, ~50% of C. elegans genes are homologous to human genes. Although, studies have shown that C. elegans employs evolutionarily conserved immune signaling pathways, not much is known about how pathogens are perceived and epithelial damage resolved by the host. To address this question, we developed an automated high-throughput genome wide screening platform to identify genes necessary for gut immunity and resolution. This led to the identification of both known as well as novel class of genes that are essential for mucosal immunity and healing.

L Wille et al. (1999) International C. elegans Meeting "The Anaphase-Promoting Complex is Required for Meiosis I Anaphase"

M Abdolrasulnia, L Wille, D Shakes

[International C. elegans Meeting, 1999]

The mitotic metaphase to anaphase transition in both yeast and vertebrates is driven by a multimeric E3 ubiquitin (Ub) ligase known as the anaphase promoting complex, APC. APC drives mitotic progression by sequentially targeting specific substrates for destruction, but its meiotic role is poorly characterized. To analyze APC's role during C. elegans meiosis, we are depleting maternal stores of APC components by RNA-mediated interference. Our goal is to analyze all APC genes in C. elegans , with initial studies focusing on APC1(BIME) and APC2. APC1 is postulated to be a negative regulator of mitosis since bimE mutants enter mitosis prematurely and can bypass a G2 or S phase arrest (Osmani et al., 1988), subsequently arresting in mitotic metaphase. RNAi of the APC1 C.elegans homolog (W10C6.1) resulted in fertilized oocytes which arrest in meiosis metaphase I (Chase et al., 1998). Later studies using a different RNA preparation, resulted in "weaker" phenotypes, including embryos with cytokinesis defects and hatching larvae which develop into sterile adults. Such adults are often severely GLP, but others have abnormal vulvals and small, highly disorganized gonads filled with differentiated gametes. We are currently testing whether the observed variability is dosage dependent. APC2 shares a conserved cullin domain with the G1-S Ub ligase component cdc53 which suggests that, like cdc53 , APC2 may interact directly with Ub conjugating enzymes (Yu et al., 1998). Consistent with its role as a core APC component, RNA-mediated interference of APC2 expression results in a strong 1-cell arrest phenotype in which maternal chromosomes lock in a prolonged meiosis metaphase I configuration. We have also observed weaker phenotypes, suggesting that APC2 RNAi effects are also dosage dependent. Our results suggest that APC function is not required for oocyte maturation, oocyte ovulation, fertilization, or the initial post-fertilization congression of the oocyte chromosomes. However APC function is critical during the meiosis I metaphase to anaphase transition, embryonic mitosis, and germline proliferation. Chase et al. (1998) WBG 15(4):45 Yu et al. (1998) Science 279: 1219-22 Osmani et al. (1988) Cell 52: 241-251