Date of Award
Dissertation - Restricted
Doctor of Philosophy (PhD)
Throughout the development of an organism, cells become specialized for specific functions, activities and the production of an array of biosynthetic molecules. As a result, this process of cellular differentiation and specialization leads to the formation of highly ordered structures and the construction of complex tissues. Cellular differentiation involves the selective, and temporally ordered expression of the genetic material in specific cells. Therefore, development is controlled both in time and space throughout the life cycle and is ultimately dependent upon the genetic repertoire of the organism. Consequently, a central issue in current biology
involves elucidating the mechanisms and controls that underlie the differential expression of the genetic material at the molecular level. From many recent studies it has become obvious that a combined biochemical and genetic approach will greatly facilitate understanding of the molecular mechanisms and controls involved in cellular differentiation and specialization.
Because of the wealth of genetic information on Drosophila melanogaster, the availability of mutants, and the genetic manipulations possible, this has been one of
the most studied organisms for addressing developmental processes. In Drosophila, a particular system which is currently being studied from a combined morphological, genetic, and molecular approach by several laboratories involves the production of the eggshell during oogenesis by the epithelial follicle cells surrounding the oocyte. Eggshell production is particularly suited for studying mechanisms underlying differential gene expression because large amounts of cell-specific gene products are produced that are easily identifiable and ,incorporated into, a well defined extracellular structure. The proteins constituting the major eggshell layers are produced in a sequential order (Petri et al., 1976; Waring and Mahowald, 1979; Fargnoli and Waring, 1982), making the eggshell synthesis program particularly attractive for studying differential gene expression in a well defined developmental pathway.
This study has been directed toward identifying the proteins and structural genes involved in the formation of the vitelline membrane, the first of two major eggshell layers to be synthesized by the somatic follicle cells in this developmental program.
The feasibility of these studies has been based on past and current investigations into the synthesis of the chorion, the outermost layer of the eggshell.