For successful reproduction, most species of animals require the production of mature ova. An essential feature of egg formation is the acquisition of yolk, which serves as a nutrient supply during early development. In many species, the proteins used for yolk are produced elsewhere, transported to the ovaries through the blood and acquired by the developing egg via a process called "receptor-mediated endocytosis." This process involves membrane bound receptor molecules specific for the relevant proteins, allowing them to be concentrated far beyond their concentration in the blood. For insects which require a blood meal for yolk formation, an elegant story has emerged describing how each meal triggers hormonally controlled support for a single round of egg formation. However, there are myriad species in which several sequential rounds of egg production are occurring simultaneously. How do these species regulate the stages of egg development, particularly, the onset of yolk formation? It has recently been shown for species from six different insect orders that yolk formation is controlled by a signal sent to the egg from its surrounding epithelial cells. Transmission appears to be through small cell-to-cell channels called gap junctions. These channels are recognized across the animal kingdom as providing "semi-private" communication among cells. The present research is based on data suggesting that the epithelial cell-to-oocyte signal may be a 17,000 molecular weight protein called Calmodulin, and the study is designed to assess this hypothesis. What is surprising is that Calmodulin is 5-8 times the size of substances previously known to transit gap junctions, although its elongated shape could explain this phenomenon. The possibility that such large but elongated molecules can pass through gap junctions may have implications to understand for cell-to-cell communications in general, as gap junctional communication may be possible for other large but elongate molecules which regulate and integrate cell physiologies throughout organisms. This project will also support the education and training of undergraduate students.
