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Title: THE TURKEY TRANSCRIPTIONFACTOR PIT-1GHF-1 CAN ACTIVATE THE TURKEY PROLACTINAND GROWTH HORMONE GENE PROMOTERS IN VITRO BUT IS NOT DETECTABLE IN LACTROTROPHS IN VIVO

Author
item WEATHERLY, K - VIRGINIA TECH
item RAMESH, R - 1265-10-00
item STRANGE, H - VIRGINIA TECH
item WAITE, K - VIRGINIA TECH
item Proudman, John
item WONG, E - VIRGINIA TECH

Submitted to: General and Comparative Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2001
Publication Date: 10/15/2001
Citation: Weatherly, K.L., Ramesh, R., Strange, H., Waite, K.L., Proudman, J.A., Wong, E.A. The turkey transcriptionfactor pit-1ghf-1 can activate the turkey prolactin and growth hormone gene promoters in vitro but is not detectable in actrotrophs in vivo. GEN. COMP. ENDOCRINOL. 123:244-253, 2001.

Interpretive Summary: Hormones produced and secreted by the pituitary are critical factors in regulating growth and reproduction. The production of these hormones is regulated, in part, by transcription factors, which are proteins produced in the nucleus of the cell that bind to the hormone genes to increase or decrease the synthesis of the messenger RNA (RNA) d for hormone synthesis. In mammals, a transcription factor known as Pit-1 is found in three different cell types, and is required for synthesis of prolactin (Prl), growth hormone (GH), and thyroid stimulating hormone. In this study, we investigated the ability of turkey Pit-1 to regulate the turkey Prl gene, the turkey GH gene, and the rat Prl gene. We also examined pituitary tissue sections for the presence of Pit-1 in the nucleus of lactotrophs (which produce Prl) and somatotrophs (which produce GH). We found that turkey Pit-1 will stimulate the production of Prl and GH mRNA in cultured pituitary cells, but that Pit-1 is not detectable in turkey lactotrophs but is abundant in somatotrophs. These results indicate that the mechanism for regulating Prl gene expression in birds is different from that in mammals, but that Pit-1 probably regulates GH synthesis in both birds and mammals. These findings will be used by scientists to further study the genetic factors which regulate growth and reproduction in poultry.

Technical Abstract: The transcription factor Pit-1/GRF-1 plays an important role in regulating the prolactin (Prl) and growth hormone (GH) genes in mammals. In this study, the role that Pit-1 plays in regulating the prolactin and growth hormone genes in avian species was examined using cotransfection assays and immunofluorescence staining of pituitary sections. In cotransfection assays, turkey Pit-1 activated the turkey Prl, turkey GH, and rat Prl promoters 3.8-fold, 3.7-fold, and 12.5-fold, respectively. This activation was comparable to rat Pit-1 activation of these same promoters. A point mutation in the turkey Pit-1 cDNA, which changed leu-219 to ser-219, resulted in a 2-fold, 2-fold, and 10-fold reduction in the activation of the turkey Prl, turkey GH, and rat Prl promoters, respectively. Unexpectedly, coexpression of tPit-1 (leu-219) and tPit- 1(ser-219) led to a 2.5- and 2.9-fold increase in activation of the turkey Prl and rat Prl promoters, respectively, but had no effect on the turkey GH promoter. Dual label immunofluorescence analysis of turkey pituitary sections revealed that Pit-1 was not detectable in prolactin- staining cells but was found in GH-staining cells. Taken together these data indicate that in the domestic turkey, Pit-1 can activate the turkey Prl promoter in vitro, but does not appear to play a role in regulating Prl gene expression in vivo. Pit-1, however, still likely plays a role in regulating GH gene expression.