Investigation of the Crustacean Molt-Inhibiting Hormone Receptor

University Of Alabama At Birmingham, Birmingham AL

Investigators

Abstract

A long-range goal of the research is to understand the mechanisms by which hormones control growth and development in crustaceans. The crustacean carapace (exoskeleton) restricts growth. Therefore, as crustaceans grow and develop the exoskeleton is periodically shed (molted) and replaced by a new and larger version. These cycles of growth and molting, and associated developmental processes including regeneration, are controlled by the crustacean endocrine system. The cellular events that lead to molting are stimulated by steroid hormones termed ecdysteroids. Ecdysteroids are secreted by paired endocrine glands, the Y-organs. The production of ecdysteroids by Y-organs is negatively regulated (inhibited) by a peptide hormone, molt-inhibiting hormone (MIH), produced by neurosecretory cells in the eyestalks. Thus, it is hypothesized that MIH inhibits Y-organs during much of the molting cycle, and that a molting sequence is initiated when MIH secretion diminishes. Recent progress has been made in understanding the structure of the MIH peptide and gene. Progress has likewise been made in understanding cell signaling pathways in Y-organs. However, a major gap in current understanding of the regulation of crustacean molting is lack of information on the MIH receptor. It is hypothesized that the effect of MIH on Y-organs is mediated by a cell surface receptor, but the MIH receptor has not been isolated or thoroughly characterized for any crustacean species. The specific aims of the current research are to (1) isolate a cDNA encoding the MIH receptor of the blue crab (Callinectes sapidus), (2) determine the tissue distribution of MIH receptor mRNA, (3) determine whether there occur changes in the level of receptor mRNA during a molt cycle, and (4) begin characterizing the native MIH receptor in Y-organ cell membranes. The aims will be achieved using methods of modern cellular and molecular biology and biochemistry, including recombinant DNA technology, nucleic acid blotting and hybridization, and protein cross-linking. The research will answer fundamental questions about the neuroendocrine regulation of growth and development in this abundant and economically important group of animals. In addition, study of the crustacean model system may provide conceptual insights into general questions about the regulation of steroidogenesis and the structure and function of neurosecretory cells. Finally, it is anticipated that the research will provide information that will enable development of methods for specifically manipulating growth and molting in crustaceans, a benefit to fisheries managers, the aquaculture industry, and consumers of shellfish.