Molecular regulation of germ cell number and fate in the nematode Caenorhabditis elegans

The C. elegans germ line provides an optimal model system to examine the genes involved in patterning a field of developing cells. Germline cells make two types of cell fate decisions: (1) proliferation versus differentiation and (2) sperm versus oocyte differentiated fate. To address the proliferation versus differentiation decision, I examined an fbf-controlled sub-network that regulates the size of the proliferation region maintained in adult gonads. I also sought to identify GLP-1/Notch targets in the germ line, and I attempted to generate a germline expressing GLP-1/Notch reporter. To address the sperm versus oocyte differentiated fate decision, I examined how the number of hermaphrodite sperm is determined during larval development.;Notch/GLP-1 signaling and two nearly identical RNA binding proteins, FBF-1 and FBF-2, promote germline proliferation. Our experiments show that the fbf-1 and fbf-2 genes are largely redundant for promoting mitosis, but they have opposite roles in fine-tuning the size of the mitotic region. Consistent with gene-specific roles, fbf-2 expression is limited to the distal germ line, while fbf-1 expression is broader. The fbf-2 gene, but apparently not fbf-1, is controlled by GLP-1/Notch signaling. The abundance of FBF-1 and FBF-2 proteins is limited by reciprocal 3'UTR repression. We propose that the divergent fbf genes and their regulatory sub-network control the size of the mitotic region.;A second project investigated the patterning of cell fates during larval development, focusing on the role of FOG-1 in sperm specification. FOG-1 is necessary, but not sufficient for sperm specification. The amount of time that FOG-1 is expressed during larval development correlates with the number of hermaphroditic sperm. We also explored how genes in the sex determination pathway regulate FOG-1 expression. We find that the fem genes and tra-1 regulate FOG-1, while fog-3 does not.;The genes examined in this study are conserved across phyla, and we suspect the functions and regulatory mechanisms are too. Thus, this investigation advances our general knowledge about how cell fate decisions are made during development.