Agarwal, Priti et al. (2021) International Worm Meeting "Distal tip cell-specific mRNA profiling sheds light on the molecular mechanism of gonad morphogenesis"

Zaidel-Bar, Ronen, Rechavi, Oded, Anava, Sarit, Gingold, Hila, Antonova, Olga, Agarwal, Priti

[International Worm Meeting, 2021]

Cell motility is essential for the normal development and physiology of an organism. In C. elegans, the stereotypical U-shaped gonad is formed by the directional chemotactic movement of two somatic cells, known as Distal-Tip Cells (DTCs), whose movement is divided into three phases. In phase I (early L3 larval stage) they move along the ventral surface. Phase II (late L3 stage) involves two 90° turns, and finally in phase III (early L4 larval stage) the DTCs move along the dorsal surface towards the midbody of the worm. Migration halts during the late L4 stage. While multiple genetic screens have identified general regulators of gonad morphogenesis, a DTC-specific role has remained largely unexplored. To address this, we isolated GFP-labelled DTCs from different stages of development and performed RNA-sequencing, to characterize and compare the transcriptome of migratory DTCs (late L3 and early L4 stage) with non-migratory DTCs (late L4 and adult stage). We identified between 1700 to 3000 genes that are upregulated in each of the larval and adult stage DTC relative to other cell types. We confirmed the identification of the few DTC-specific transcripts known in the literature. The overlap between the genes we found upregulated in DTCs and the published germline-enriched genes (Reinke et al., 2004) is only 0.9 to 6.4%. Furthermore, we found that among the 99 genes identified in a genome-wide RNAi screen (Cram et al., 2006) to have a role in DTC migration, 43 genes are enriched in the migratory early L4 stage DTC transcriptome, while only 7 genes are present in the immobile adult stage DTCs. Taken together, it appears our dataset of cell-specific and stage-specific DTC transcripts is highly accurate. A bioinformatic functional analysis of the migratory DTC transcripts revealed enrichment of genes related to neuronal guidance, cytoskeleton, signaling, and membrane trafficking. Currently, we are performing a DTC-specific RNAi screen to identify the novel cell-autonomous regulators of DTC migration which in turn guides gonad morphogenesis. Identifying these regulators will help us to decipher the molecular mechanisms of DTC migration deployed in a three-dimensional microenvironment, which will eventually give insight into the mechanism of gonadogenesis.