Boston University Department of Biology

Faculty Profiles

Current Research

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).

Courses Taught

• BI 554 Neuroendocrinology

Selected Publications

• Burnett KG, Bain LJ, Baldwin WS, Callard GV, Cohen S, Di Giulio RT, Evans DH, Gómez-Chiarri M, Hahn ME, Hoover CA, Karchner SI, Katoh F, MacLatchy DL, Marshall WS, Meyer JN, Nacci DE, Oleksiak MF, Rees BB, Singer TP, Stegeman JJ, Towle DW, Van Veld PA, Vogelbein WK, Whitehead A, Winn RN, Crawford DI. (2007). Fundulus as the Premier Teleost Model in Environmental Biology: Opportunities for New Insights Using Genomics. Comp. Physiol. Biochem., Part D: 257-286.
• Engel KB, Callard GV. (2007). Endocrinology of Leydig Cells in Nonmammalian Vertebrates. In: Payne A, Hardy M (eds), The Leydig Cell in Health and Disease, Humana Press, pp 207-224.
• Greytak SR, Callard GV. (2007). Cloning of three estrogen receptors (ER) from killifish (Fundulus heteroclitus): Differences in populations from polluted and reference environments. Gen. Comp. Endocrinol. 150, 174-188.
• Tarrant AM, Greytak SR, Callard GV, Hahn ME. (2006). Estrogen receptor-related receptors in the killifish Fundulus heteroclitus: diversity, expression, and estrogen responsiveness. Journal of Molecular Endocrinology 37, 105-120.
• Sawyer SJ, Gerstner KA, Callard GV. (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 SR, Champlin D, Callard GV. (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.
• 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, Callard GV. (1998). Identification of multiple CYPl9 genes encoding different cytochrome P450 aromatase isozymes in brain and ovary. Endocrinology 139, 2179-2189.