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Joan W. Witkin, Ph.D.

Research Scientist

E-mail: jww3@columbia.edu

Development and aging in neuroendocrine systems:

picture This research is focused on the gonadotropin releasing hormone (GnRH) system in developing, mature and aging animals. The GnRH system is central to both hormonal and behavioral aspects of reproductive function. The hypothalamic neurons that drive reproduction are a small population of cells (GnRH neurons) that differentiates within the olfactory placode and migrates into the central nervous system (CNS). This highly unusual developmental history offers the opportunity to investigate problems of early development related to cellular differentiation and migration and of the later establishment of neuronal investigate problems of early development related to cellular differentiation and migration and of the later establishment of neuronal interactions and how these change in differing reproductive states. We are interested in: pathways and guidance cues during this migration; how and when these neurons establish their functional relationships to the CNS and to the vasculature of the hypophyseal portal system; what changes underlie the alterations in hormone production and secretion accompanying puberty; the events that drive cyclicity in the female; and finally, how the GnRH system changes during reproductive aging. The tools and methods used in this research are immunocytochemistry for light and electron microscopy and confocal imaging. We have perfected quantitative ultrastructural methods for measuring and comparing synaptic input and glial ensheathment of GnRH neurons. Using these methods we have characterized some of the morphological changes underlying the maturation of the GnRH system, the effects of the gonadal steroid environment, and how the ultrastructural milieu of the GnRH neuron is altered in aging. We are currently using techniques of molecular biology to investigate the onset of GnRH expression in the embryonic chick.

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Selected publications

Wang G, Witkin JW, McGraw TE, Baldini G. 2001. A novel type of Glut4 redistribution induced by cAMP (submitted).

Witkin JW. 1999. Anatomical evidence for synchronized neuronal networks: GnRH system Microscopy Research and Technique. 44:11-18.

Mulrenin EM, Witkin JW, Silverman A-J 1999. Embryonic development of the gonadotropin-releasing hormone (GnRH) system in the chick: a spatio-temporal analysis of GnRH neuronal generation, site of origin, and migration. Endocrinology. 140: 422-433.

Koticha DK, Huddleston SJ, Witkin JW, Baldini G 1999. Role of the cysteine-rich domain of the t-SNARE component, Syndet, in membrane binding and subcellular localization. J. Biol. Chem. 274:9053-9060.

Jung H, Carmel P, Witkin JW, Bentele KHP, Westphal M, Piatt JH, costa ME, Cornea A, Ma YJ, Ojeda SR 1999. Some hypothalamic hamartomas contain transforming growth factor alpha, a puberty-induced growth factor, but not luteinizing hormone-releasing hormone neurons. J. Clin. Endocrinol. Metab. 84 (12): 4695-4701. Joan W. Witkin's Medline citations

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Last modified on August 7, 2001