I am interested in how animals move salts across epithelial cell layers and how epithelial salt transport is regulated. My lab uses a variety of approaches to investigate salt transport ranging from whole animal studies through molecular techniques. A variety of invertebrate model organisms are used. Two main areas of current interest are:

1) Regulation of calcium transport in the freshwater crayfish Procambarus clarkii. In collaboration with Michele Wheatly at Wright State University, my lab is looking at molecular mechanisms of calcium transport during the molt cycle and cold acclimation in crayfish. The molt cycle is an outstanding model for studying calcium transport because large vectorial movements of calcium occur during the premolt and postmolt periods. Calcium is transported from the cuticle into storage sites during the premolt, then moved back into the new cuticle during the postmolt period. These periods of rapid calcium transport are in contrast to the intermolt period where there is no net calcium transport. As expected, expression of plasma membrane calcium transporters is increased during premolt and postmolt. We are now investigating expression of calcium transporters and other proteins involved in calcium homeostasis during cold acclimation, because cold acclimation has been shown to affect cellular calcium homeostasis. We also are seeking to express these cloned genes in tissue culture cells to investigate their functional properties. By comparing the results of expression changes during the molt cycle and cold acclimation, we hope to develop a more precise understanding of how the genes involved in calcium transport are regulated.

Recent reference: White*, A.J., M.J. Northcutt*, S.E. Rohrback*, R.O. Carpenter*, M.M. Niehaus-Sauter*, Y. Gao, M.G. Wheatly, and C.M. Gillen. Characterization of sarcoplasmic calcium binding protein (SCP) variants from freshwater crayfish Procambarus clarkii. Comparative Biochemistry and Physiology Part B 160: 8–14, 2011.

2) Effect of body size on the physiology of the tobacco hormworm, Manduca sexta. This project is in collaboration with Harry Itagaki and Drew Kerkhoff (Kenyon Biology) and Judy Holdener and Brad Hartlaub (Kenyon Mathematics). Manduca larvae are a terrific model for investigating how size affects biological function, because they grow about 10,000 fold over a three week period without any gross changes in morphology and individual animals can be followed throughout their entire growth. A major consequence of increased size is that surface area to volume ratio decreases. In the absence of compensatory mechanisms, it is thus predicted that larger larvae will have less surface area per gram of body weight. A particularly important surface area is the gut epithelium, which transports large amounts of solute and it the site of nutrient uptake. We are testing the hypothesis that large animals have compensated for their reduced surface area by increasing the expression of membrane transport proteins. To this end, we have characterized a cation-chloride cotransport protein, masBSC, that is expressed on the luminal membrane of gut epithelial cells. Real-time PCR and Western blotting are being used to investigate the expression pattern of this gene in larvae of different sizes.

Recent reference: Gillen, C.M.; Somple, M.*; Heilman, N.R.*; Watson, N.*; Blair, C.R.*; Stulberg, M.*; Thombre, R.*; Gillen, K.; Itagaki, H. The cation chloride cotransporter, masBSC, is widely distributed in Manduca sexta. Journal of Insect Physiology 52: 661-668, 2006.