Genetic Regulation of Peptidergic Signaling

University Of Oklahoma Norman Campus, Norman OK

Investigators

Abstract

Neuropeptides are chemical signals that are secreted by nerve cells to control the functioning of the brain and many other tissues. They are key regulators of diverse processes, including growth, reproduction, stress, sleep, body weight, pain, and circadian (daily) rhythms. Disruptions in neuropeptide signaling are associated with human diseases, such as obesity, diabetes and cancer. Thus, there is a critical need for basic research on neuropeptide systems. The major goal of this project is to understand complex molecular mechanisms underlying long-term regulation of neuropeptide secretion. To support normal signaling, peptidergic (neuropeptide-secreting) cells must develop the capacity to produce and store large quantities of neuropeptides. In mature cells, neuropeptide synthesis is regulated in response to diverse internal and external cues in order to adjust the strength of neuropeptide signaling. For many cell types, the genes and cell signaling pathways underlying these processes, and their physiological and developmental regulation, are almost completely unknown. With the powerful tools recently developed for the genetic manipulation of peptidergic cells in the fruit fly, Drosophila melanogaster, these mechanisms are now experimentally accessible. In previous work, the Drosophila gene dimmed (dimm) was shown to control accumulation and/or storage of secretory proteins in diverse peptidergic cells. This result suggests that dimm is an essential component of a cell signaling pathway controlling the robustness and timing of neuropeptide synthesis. To test this hypothesis, this project will address two key questions. First, what are the roles of dimm in developing versus mature cells? Second, what other proteins interact with Dimm, the protein product of the dimm gene, to control neuropeptide levels? To address the first question-what are the roles of dimm in developing versus mature cells-the first aim of this project is to define the contributions of the dimm gene in the regulation or maintenance of neuropeptide synthesis throughout the life cycle of the fly. Using transgenic animals, and a new temperature-dependent gene expression system, a re-introduced copy of the dimm gene will be turned on or off during specific stages of development. This system also allows peptidergic cell-type specific control over the expression of the dimm gene. Thus, transient and spatially restricted expression of the dimm gene will be used to determine the effects of post-embryonic increases in dimm expression on neuropeptide levels in dimm mutant and in normal cells. To address the second question-what other proteins interact with Dimm to control neuropeptide levels-the second aim of this project is to perform genetic screens to identify mutations of genes encoding other elements in the Dimm molecular signaling pathway. Genes will be identified by virtue of their ability to modify the effects of dimm misexpression in transgenic animals. Genetic interactions will be detected using two dimm-sensitive processes: molting and neuropeptide synthesis. Selected mutants then will be tested for effects on neuropeptide levels in developing and mature cells, and the mutated genes will be identified using standard Drosophila molecular cloning methods. Together, the proposed experiments will lay a foundation for defining key molecular pathways controlling neuroendocrine signaling. This project will continue to provide unique opportunities for several undergraduate and graduate students to participate in the research. Students in Oklahoma have few options for non-agricultural training in the sciences. This project provides hands-on experiences in molecular biology and genetics that are not otherwise readily available and that complement traditional lecture-format courses. These research experiences will continue to enable and inspire talented students from the State of Oklahoma to pursue professional careers in industry, medicine, and scientific research.