R. Douglas Watson

Research Description:

We're investigating the endocrine regulation of development using both invertebrate and vertebrate model systems. Our approach is multidisciplinary, drawing on the fields of physiology, biochemistry, and molecular biology. Current research is centered in two areas.

(1) We're investigating the neuroendocrine regulation of growth and molting in crustaceans. Crustacean growth and development are characterized by the periodic shedding (molting) and replacement of the exoskeleton. The cellular events that lead to molting are stimulated by steroid hormones (ecdysteroids) produced by paired endocrine glands, the Y-organs. Y-Organs are negatively regulated by a neuropeptide molt-inhibiting hormone (MIH) produced by neurosecretory cells in the eyestalks. From the standpoint of comparative physiology, the crustacean system is proving to be a useful model for study of the regulation of steroidogenesis and the structure and function of neurosecretory cells. Like vertebrate steroidogenic glands, Y-organs use cholesterol as a precursor for steroidogenesis and are controlled by a regulatory peptide. Y-Organs offer the advantage over vertebrate gonads and adrenal cortices of being structurally simple and histologically homogeneous; MIH provides the potentially insightful contrast of inhibiting steroidogenesis - the principal regulatory peptides of vertebrate glands stimulate steroidogenesis. In addition, the ready accessibility and experimental tractability of the X-organ/sinus gland complex have made it a useful model for study of the structure and function of neurosecretory cells. From the standpoint of applied science, manipulation of the crustacean endocrine system holds the prospect of providing a method for controlling growth and molting in these economically important organisms.

(2) My laboratory is also investigating aspects of the endocrine regulation of development in mosquitofish (Gambusia affinis), and the effects of environmental endocrine disruptors on these processes. We've developed an immunoassay for the egg yolk protein, vitellogenin, and studied the endocrine regulation of vitellogenin synthesis. We are testing the hypothesis that induction of vitellogenesis in male mosquitofish can serve as a useful marker for assessing the activity of candidate environmental estrogens.

Representative Publications:

Han, D.-W. and Watson, R.D. (2005) Trimericic G proteins in crustacean (Callinectes sapidus) Y-organs: occurrence and functional link to protein synthesis. Journal of Experimental Zoology 303A:441-447.

Angus, R.A., Stanko, J.P., Jenkins, R.L. and R.D. Watson (2005) Effects of 17 -ethynylestradiol on sexual development of male western mosquitofish (Gambusia affinis). Comparative Biochemistry and Physiology 140C:330-339

Han, D.-W., Patel, N. and Watson, R.D. (2006) Regulation of protein synthesis in Y- organs of the blue crab (Callinectes sapidus): Involvement of cyclic AMP. J. Exp. Zool. 305A: 328-334.

Zheng, J., Lee, C.-Y. and Watson, R.D. (2006) Molecular cloning of a putative receptor guanylyl cyclase from Y-organs of the blue crab, Callinectes sapidus. Gen. Comp. Endocrinol. 146:329-336.

Nakatsuji, T., Sonobe, H., and Watson, R.D. (2006) Molt-inhibiting hormone- mediated regulation of ecdysteroid synthesis in Y-organs of the crayfish (Procambarus clarkii): involvement of cyclic GMP and cyclic nucleotide phosphodiesterase. Molec. Cell. Endocrinol. 253:76-82.

Nakatsuji, T., Han, D.-W., Jablonsky, M.J., Harville, S.R., Muccio, D.D., and Watson, R.D. (2006) Expression of crustacean (Callinectes sapidus) molt-inhibiting hormone in Escherichia coli: Characterization of the recombinant peptide and assessment of its effects on cellular signaling pathways in Y-organs. Molec. Cell. Endocrinol. 253:96-104..

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