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L Ellestad, Molecular and Cell Biology Program, University of Maryland, 20742, United States
S Malkiewicz, Department of Animal and Avian Sciences, University of Maryland, College Park, United States
H Guthrie, Animal Biosciences and Biotechnology Laborotory, United States Department of Agriculture, Agricultural Research Service, Beltsville, United States
G Welch, Animal Biosciences and Biotechnology Laborotory, United States Department of Agriculture, Agricultural Research Service, Beltsville, United States
T Porter, Molecular and Cell Biology Program, University of Maryland, 20742, United States

Correspondence: Tom Porter, Email: teporter{at}umd.edu

Abstract

The expression profile of glucocorticoid-induced leucine zipper (GILZ) in the anterior pituitary during the second half of embryonic development in the chick is consistent with in vivo regulation by circulating corticosteroids. However, nothing else has been reported about the presence of GILZ in the neuroendocrine system. We sought to characterize expression and regulation of GILZ in the chicken embryonic pituitary gland and determine the effect of GILZ overexpression on anterior pituitary hormone levels. Pituitary GILZ mRNA levels increased during embryogenesis to a maximum on the day of hatch, and decreased through the first week after hatch. GILZ expression was rapidly upregulated by corticosterone in embryonic pituitary cells. To determine if GILZ regulates hormone gene expression in the developing anterior pituitary, we overexpressed GILZ in embryonic pituitary cells and measured mRNA for the major pituitary hormones. Exogenous GILZ increased prolactin mRNA above basal levels, but not as high as that in corticosterone-treated cells, indicating that GILZ may play a small role in lactotroph differentiation. The largest effect we observed was a 2-fold increase in follicle-stimulating hormone beta subunit in cells transfected with GILZ but not treated with corticosterone, suggesting that GILZ may positively regulate gonadotroph development in a manner not involving glucocorticoids. In conclusion, this is the first report to characterize avian GILZ and examine its regulation in the developing neuroendocrine system. We have shown that GILZ is upregulated by glucocorticoids in the embryonic pituitary gland and may regulate expression of several pituitary hormones.

This article has been cited by other articles:

				E. Ayroldi and C. Riccardi Glucocorticoid-induced leucine zipper (GILZ): a new important mediator of glucocorticoid action FASEB J, November 1, 2009; 23(11): 3649 - 3658. [Abstract] [Full Text] [PDF]