Complex metazoans contain an incredible variety of cell types. Such variety reflects the specialized roles performed by different cells: the transport of oxygen by red blood cells, the generation of force by muscle cells, the transmission of electrical impulses by neurons. How does a single cell, the fertilized egg, give rise to such remarkable diversity? In large part, cellular differentiation is determined by the expression of cell-type-specific genes. Expression is restricted both spatially and temporally, with groups of genes required for a particular step or process induced in tissue and stage-specific patterns. The expression patterns are governed by the activity of transcription factors that typically function in a regulatory cascade. The goal of the proposed research is to understand the developmental program that governs sperm cell differentiation in the nematode Caenorhabditis elegans. This model system provides the opportunity to combine cytological and genetic studies with genome-wide analyses to understand the complex process of cellular differentiation at the molecular level. DNA microarray screens of nearly the complete genome have identified 1,343 genes that are induced during sperm production. Those spermenriched genes make the cell uniquely suited to its role and thus are the focus of further analysis. The proposed experiments are designed to divide those genes into groups on the basis of expression patterns, and to identify the different stages of sperm development at which those groups function. The strategy is to identify transcription factors that regulate expression of sperm-enriched genes; to isolate mutations in those transcription factors; and to characterize the defects in fertility, sperm cell development, and gene expression that result from those mutations.
The broader impact of this research is to provide insights into the fundamental mechanisms of cellular development. The assignment of functional roles to previously uncharacterized genes will suggest roles and avenues of investigation for homologs in other organisms. In addition, the proposed research will provide critical student training in the laboratory. The experiments are modular by design, and thus appropriate for undergraduate research projects (encompassing a single experiment) while remaining sufficiently comprehensive, when combined, for graduate/postdoctoral research projects.
