gvc@bu.edu

Cell Signaling and Gene Regulation Cancer Biology Endocrinology and Reproductive Biology Developmental Biology Cell and Molecular Neurobiology Neuroendocrinology

Professor of Biology
Ph.D., Rutgers University, 1964

Neuroendocrinology, reproductive and developmental endocrinology, estrogen biosynthesis and actions, gene regulation

Research in this laboratory focuses on the biosynthesis and actions of estradiol. In tissues where aromatase (P450arom, estrogen synthetase) and estrogen receptors (ER) are colocalized, estradiol has discrete, local actions (paracrine, autocrine) that differ from those exerted by the circulating hormone (endocrine). In one project we are investigating the structure, function and evolution of genes encoding P450arom and ER in neural tissues and the physiological and developmental consequences of estrogen formation in specific cells and circuits of the brain and retina. In a second project, we are studying the regulation of spermatogenesis by estrogen and the role of Sertoli cells as a source and target of intratesticular estrogen. Specifically, our aims are to identify estrogen-sensitive control points, target genes and physiological processes during spermatogenic development. A component of both projects is to elucidate the actions of environmental estrogens and other xenobiotics that disrupt normal endocrine and neuroendocrine mechanisms of reproduction. We use a wide range of animal models from fish to mammals and rely primarily on methods of cell biology (tissue culture, light and electron microscopy, image analysis), protein and steroid biochemistry (enzymology, receptor binding assays, SDS-PAGE and immunoblot analysis), and molecular biology (in situ and membrane hybridization, PCR-based methods of RNA & DNA analysis, cDNA and gene cloning & analysis).

Confocal microscopic image of a clone of male germ cells in early
(spermatogonial) stages of their develpment into spermatozoa.

Engel K.B., Callard G.V. 2006. Endocrinology of Leydig Cells in Nonmammalian Vertebrates. In: Payne A, Hardy M (eds)., The Leydig Cell in Health and Disease, Humana Press (in press).

Greytak S.R., Callard G.V. 2006. Cloning of three estrogen receptors (ER) from killifish ( Fundulus heteroclitus ): Differences in populations from polluted and reference environments. Gen Comp Endocrinol 148: 15pp (epub in advance of issue).

Tarrant, A. M., S. R. Greytak, G. V. Callard, and M. E. Hahn. 2006. Estrogen receptor-related receptors in the killifish Fundulus heteroclitus: diversity, expression, and estrogen responsiveness. Journal of Molecular Endocrinology 37:105-120.

Sawyer, S. J., K. A. Gerstner, and G. V. Callard. 2006. Real-time PCR analysis of cytochrome P450 aromatase expression in zebrafish: Gene specific tissue distribution, sex differences, developmental programming, and estrogen regulation. General and Comparative Endocrinology 147:108-117.

Greytak, S. R., D. Champlin, and G. V. Callard. 2005. Isolation and characterization of two cytochrome P450 aromatase forms in killifish (Fundulus heteroclitus): Differential expression in fish from polluted and unpolluted environments. Aquatic Toxicology 71:371-389.

Engel, K.B., Callard G.V. 2005. The testis and spermatogenesis. In: Jamieson B, Hamlett W (eds). Reproductive Biology and Phylogeny of Chondrichthyes: Sharks, Skates and Chimeras. Science Publishers, Inc., Enfield NH, pp. 171-200.

Tchoudakova A, Kishida M, Wood E, Callard GV. 2001. Promoter characteristics of two cyp19 genes differentially expressed in the brain and ovary of teleost fish. J Steroid Biochem Mol Biol. Nov;78(5):427-39.

Kishida M, McLellan M, Miranda JA, Callard GV. 2001. Estrogen and xenoestrogens upregulate the brain aromatase isoform (P450aromB) and perturb markers of early development in zebrafish (Danio rerio). Comp Biochem Physiol B Biochem Mol Biol. Jun;129(2-3):261-8.

Kishida M, Callard GV. 2001. Distinct cytochrome P450 aromatase isoforms in zebrafish (Danio rerio) brain and ovary are differentially programmed and estrogen regulated during early development. Endocrinology. Feb;142(2):740-50.

Tchoudakova A, Pathak S, and Callard G.V. 1999. Molecular cloning of an estrogen receptor §-subtype from the goldfish, Carassius auratus. Gen Comp Endocrinol 113:388-400.

Tchoudakova A, Callard G.V. 1998. Identification of multiple CYPl9 genes encoding different cytochrome P450 aromatase isozymes in brain and ovary. Endocrinology 139:2179-2189.

Betka M, Callard GV. 1997. Negative feedback control of the spermatogenic progression by testicular estrogen synthesis: insights from the shark testis model. In: Neoplastic Transformation of Testicular Germ Cells, Rajpert-DeMeyts E, Grigor KM, and Skakkebaek NE, eds., Acta Physiologica, Microbiologica, Immunologica Scandinavica 106:252-258.

Callard GV, Betka M, and Miller D. 1997. Unconventional models for toxicology research. In: Comprehensive Toxicology, Vol.10, Reproductive and Endocrine Toxicology, Section I. Male Reproductive Toxicology, K. Boekelheide, R. Chapin, P. Hoyer, Harris (eds), Elsevier, New York, pp. 235-247.

Callard GV, Kruger A, Betka M 1995. The goldfish as a model for studying neuroestrogen synthesis, localization and action in the brain and visual system. Envionmental Health Perspective 103(Suppl. 7):51-57

Callard GV, Jorgensen JC, and Redding MJ 1995. Biochemical analysis of programmed cell death during premeiotic stages of spermatogenesis in vivo and in vitro. Develop Genetics 16:140-147

Gelinas D, and Callard GV 1993. Evidence for aromatase in neurons of the retina, optic tectum and retinotectal pathways in goldfish. J Neuroendocrinology 5:635-641.

Questions and comments are always welcome.
Copyright © 1996, The Trustees of Boston University
This document was last modified on November 13, 2006.