Veerle Rottiers et al. (2005) International Worm Meeting "A multistep hormone biosynthetic pathway that regulates C. elegans development and dauer formation."

Birgit Gerisch, Veerle Rottiers, Adam Antebi, Kailly Harrell, Axel Bethke, Raha Nabbi, Anne Schadach, Harald Hutter

[International Worm Meeting, 2005]

During larval development, C. elegans evaluates environmental cues and must choose between reproductive growth or arrest at the dauer diapause. Insulin/IGF and TGF- signalling integrate neurosensory cues, and subsequently produce downstream secondary endocrines to coordinate tissues throughout the body. One such endocrine is proposed to be an unidentified lipophilic hormone that regulates the nuclear hormone receptor daf-12. Molecular genetic evidence suggests that in presence of this hormone, worms undergo reproductive development, whereas in its absence they enter the dauer diapause. The cytochrome P450 daf-9, is a major player in hormone production, but typically, such hormones are built by several enzymes. Accordingly, we previously reported that a novel Rieske-like oxygenase, daf-36, is also involved. daf-36 shares both dauer constitutive (Daf-c) and gonadal migration defect (Mig) phenotypes with daf-9 as well as daf-12 ligand binding domain mutants. However, daf-36 null mutant defects are weaker than daf-9 mutants, and both genes have non-overlapping expression patterns. This suggests a complex biosynthesis pathway involving several genes with distributed production sites, but the extent of this pathway is unknown. Here, we report a more detailed analysis of the hormone biosynthesis pathway. Using RNAi-enhancer screens of daf-36, we screened for Daf-c and Mig phenotypes, which are signatures of the hormone pathway. So far we have identified a dehydrogenase, another CYP450 and a nuclear hormone receptor. We are currently characterizing the phenotypes and epistasis patterns of these loci. A further prediction of the hormone hypothesis is that lipid extracts of worms should contain the daf-12 ligand. Indeed, we found that lipid extracts of wild type L3 worms can rescue the daf-9 and daf-36 mutant phenotypes, whereas each mutant cannot be rescued by its own extract. These results confirm the lipophilic nature of the hormone and demonstrate that these genes are involved in hormone production. We are currently performing cross-feeding experiments with mutant extracts to see whether the genes can be ordered relative to one another. This should allow us to dissect the biosynthetic pathway and facilitate the biochemical identification of the daf-12 hormone. In sum, these studies provide the first evidence for a multistep hormone biosynthetic pathway in C. elegans.

Yang, Jasper et al. (2021) International Worm Meeting "Differential expression analysis of migrating cells in C. elegans embryogenesis"

Yang, Jasper, Naik, Samuel, Kopf, Sarina, Praitis, Vida

[International Worm Meeting, 2021]

Cell migration drives morphogenesis, the developmental process in which cells become spatially organized to form tissues. An understanding of the molecular mechanisms and regulatory triggers behind cell migration has clinical relevance because it not only explains how embryos develop but offers insights into immune response and metastatic cancers. However, the mechanisms that regulate the transition between migratory and non-migratory states are not well understood, especially in vivo. In C. elegans, studies of cell migration have revealed some critical mechanisms, but classical genetic approaches have been limited in part because they miss redundant or pleiotropic genes. To look past these limitations, we conducted a comparative transcriptomic analysis using the scRNA-seq data published by Packer et al (2019), which mapped RNA transcriptomes of embryos onto C. elegans developmental lineages. We first identified cells of unambiguous lineage that undergo different types of embryonic cell migration. We then used the differential expression analysis workflow in Monocle 3 (Trapnell, 2019) to compare the transcriptomes of these migrating cells to their non-migrating cellular progenitors and progeny. In our analysis we identify 86 candidate genes from six migratory events, 46 of which come up as differentially expressed (DE) in more than one lineage. 30 of the candidates have known lethal phenotypes and 42 are associated with cell migration defects in C. elegans or in other systems. In comparing migrating lineages, we show that while no single set of mRNAs is associated with all migration events and each individual event has unique characteristics, there are some similarities within migration types. Clustering analysis reveals that cells undergoing intercalation and enclosure, which also share both lineage and fate, have DE gene patterns that are more similar to each other than to other migration types. Cells that ingress form a more diffuse cluster with other ingressing cells, with lineage playing an important role, a result supported by work from other labs (Harrell & Goldstein, 2011). Migrations of cells along the embryo surface also cluster, suggesting that despite differences in lineage and fate these migrating cells share some common mechanisms. Our analysis reveals that changes in gene expression associated with migrating cells are relatively complex but can be explored using DE analysis.