We use progenitors of the C. elegans reproductive system as a model for defining the genetic determinants of multipotency. The two somatic gonadal precursors (SGPs) are multipotent progenitors that generate all somatic tissues of the reproductive system. Each SGP is the product of a cell division that produces one SGP and one differentiated cell, the head mesodermal cell (hmc). Therefore, in this single cell division the potential to generate all of the somatic gonadal types is differentially segregated into one daughter cell. We have used fluorescence-activated cell sorting (FACS) to isolate SGPs and hmcs from the same worms and performed RNA sequencing to identify genes that are differentially expressed in the two cell types. We found a surprisingly large number of differentially expressed genes (~6000) when comparing these two sister cells. GO term enrichment analysis of our dataset provided interesting insights. Genes with higher expression in SGPs are enriched for GO terms related to transcription and translation, as might be expected for a multipotent progenitor cell preparing to undergo multiple cell divisions; among these are 175 of the 934 C. elegans transcription factors. Interestingly, genes with higher expression in the hmc are enriched for GO terms related to neuronal function, such as "synaptic vesicle exocytosis" and "calcium mediated signaling". To date, the function of the hmc has not been determined, and our data strongly suggest that it may have neuronal signaling properties, an idea that is consistent with its neuron-like cellular morphology. Our ultimate goal is to identify determinants of multipotency in SGPs, as well as genes that promote the terminal differentiation of the hmcs. To this end, we have begun to screen the SGP-biased transcription factors for roles in the SGP/hmc cell fate decision using RNA-mediated interference to knock down gene function. We score animals at the first larval stage and assess cell fates using a strain containing markers for SGPs (red fluorescence) and hmcs (green fluorescence). We will report on our progress at the meeting.

Affiliation:
- Department of Pharmacology & Toxicology, Virginia Commonwealth University, Richmond, VA