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	About Me: I am a doctoral candidate in the Integrated Biosciences Program at UMD. I received a BS in Environmental Studies/Biology from Bemidji State University and MS in Marine-Estuarine Environmental Science from the University of Maryland at College Park, and worked in environmental consulting as an ecological toxicologist for several years. Recent economy-driven lay-offs encouraged my return to academia, where I am enjoying a new understanding of evolution through the molecular biology of endocrine and immune systems in a 500 million-year-old animal, the sea lamprey. ~Sally Mayasich
Introduction: Sea lampreys (Petromyzon marinus) are a natural species in ocean and estuarine ecosystems, however they are a destructive invasive species in the Great Lakes. They hatch in freshwater streams, and the filter-feeding larvae live in sediment for 5-7 years. Following metamorphosis, lampreys migrate into the lake or ocean to spend 12 to 18 months in the parasitic phase, returning to streams to spawn and then die. Males make nests and release a pheromone that attracts ovulating females to swim upstream. Arginine vasotocin is a nine-amino acid peptide hormone in all nonmammalian backboned animals that differs from mammalian vasopressin by one amino acid in the third position and from oxytocin by one amino acid in the eighth position. In mammals, three vasopressin receptor types and one oxytocin receptor, members of the same subfamily of Rhodopsin-like G-protein-coupled receptors (GPCRs), have been identified. The vasopressin receptors are classified as V1a, V1b, and V2. V1a- and V2-type receptors are found in all vertebrates studied, including fish. V1b receptors have only been found in tetrapods (amphibians, reptiles, birds and mammals). In addition to classical anti-diuretic and vaso-constriction functions mediated by the V2 receptor, the V1a and oxytocin receptors are involved in social and reproductive behaviors and functions in mammals. Studies in amphibians have demonstrated that vasotocin can induce pheromone discharge and mating responses. Vasotocin-mediated responses in fish appear subject to circadian rhythms due to interaction with melatonin, as established in mammals. AIMS Understanding the structures and expression of these receptors in sea lampreys gives us a better understanding of evolution and could lead to a way to block important functions, such as reproductive development or pheromone release, thus controlling this destructive species in the Great Lakes fisheries. Parasitic Phase Lamprey Tongue Action Lamprey Larvae Burrow in Sand
EVOLUTION OF NEUROENDOCRINE HORMONE-RECEPTOR SYSTEMS Utilizing Basic Local Alignment Search Tool (BLAST) queries of the sea lamprey draft genome (The Genome Institute at Washington University School of Medicine in St. Louis, ftp://genome.wustl.edu/pub/organism/Other_Vertebrates//Petromyzon_marinus/assembly/Petromyzon_marinus-3.0/) and reverse transcription-polymerase chain reaction (RT-PCR), I have so far identified and partially sequenced the vasotocin hormone precursor gene and five potential receptor genes. The structures of these receptors based on deduced amino acid sequence are similar to the vertebrate receptor types as shown in this phylogenetic tree, but do not fit into particular clades, and tend to highlight the intermediary evolutionary position of lampreys between invertebrates and vertebrates. The lamprey vasotocin receptors (VR) are tentatively numbered according to the contig number in the genome database.
I have shown expression patterns in tissues of parasitic and reproductively mature adult sea lampreys similar to and consistent with the functions of the receptor types in both higher vertebrates and invertebrates. Interesting and less well studied is the fact that neuropeptide hormones and receptors are also expressed in the immune system. Vasopressin is implicated in T-cell activation, primary antibody responses, and stress-induced immune suppression, and the V1a receptor affects signal transduction in B-cells in mammals. Estrogen levels in response to the menstrual cycle have been shown to affect oxytocin receptor expression in mammalian T-cells. These functions are important in a fit immune system, but over-expression of these receptors has been found to occur in leukemia and lymphoma cancers. The lamprey produces T- and B-lymphocyte-like cells, in which I have demonstrated expression of the vasotocin hormone and two receptors, and am currently working on determining how activation of these immune cells by pathogenic threats affects receptor expression, and how the receptors affect immune cell functions.
Sally A. Mayasich DMED Biomedical Sciences SMed 332 1035 University Dr Duluth, MN 55812 Email: maya0010@d.umn.edu