Regulation of genes encoding steroidogenic factor-1 (SF-1) and gonadotropin subunits in the ovine pituitary gland

• Published in: Domestic animal endocrinology 2003-07, Vol.25 (1), p.121-131
• Main Authors: Baratta, M., Turzillo, A.M., Arreguin-Arevalo, A., Clay, C.M., Nett, T.M.
• Format: Article
• Language: English
• Subjects: Animals; Binding Sites; DNA-Binding Proteins - genetics; DNA-Binding Proteins - physiology; Female; Follicle Stimulating Hormone, beta Subunit - genetics; Fushi Tarazu Transcription Factors; gene expression regulation; Gene Expression Regulation - drug effects; genes; gonadotropic cells; Gonadotropin; gonadotropin-releasing hormone; Gonadotropin-Releasing Hormone - pharmacology; Gonadotropin-Releasing Hormone - secretion; gonadotropins; Gonadotropins - genetics; Homeodomain Proteins; hormonal regulation; hormone receptors; hypothalamic-pituitary-gonadal axis; Luteinizing Hormone, beta Subunit - genetics; messenger RNA; Ovariectomy; Pituitary; pituitary gland; Pituitary Gland - metabolism; Pituitary Gland, Anterior - chemistry; Rats; Receptors, Cytoplasmic and Nuclear; RNA, Messenger - analysis; Sheep; steroidogenesis; Steroidogenic Factor 1; transcription factors; Transcription Factors - genetics; Transcription Factors - physiology
• ISSN: 0739-7240; 1879-0054
• DOI: 10.1016/S0739-7240(03)00051-1

Steroidogenic factor-1 (SF-1) is a transcription factor originally characterized as a mediator of gene expression in steroidogenic tissues. Studies in SF-1 knockout mice revealed that SF-1 has additional roles at multiple levels of the hypothalamic–pituitary–gonadal axis, including regulation of gene expression in pituitary gonadotropes. Specific binding sites for SF-1 have been demonstrated in several pituitary genes with essential roles in gonadotropin synthesis, including α subunit, LHβ subunit, and GnRH receptor. In studies aimed at identifying physiological factors controlling pituitary expression of SF-1, GnRH has been implicated as a co-regulator of SF-1 and gonadotropin subunit genes. In both rats and ewes, elevated endogenous secretion of GnRH following ovariectomy was associated with increased amounts of SF-1 mRNA in the anterior pituitary gland. Conversely, removal of GnRH input to the pituitary gland by hypothalamic–pituitary disconnection (HPD) in ovariectomized (OVX) ewes reduced SF-1 expression. Despite these changes, however, treatment of OVX ewes with GnRH following HPD only partially restored levels of SF-1 mRNA in the pituitary gland. Therefore, it is possible that regulation of SF-1 gene expression by GnRH during the estrous cycle may involve ovarian hormones or other hypothalamic factors. Additional studies are required to further define the physiological roles of SF-1 in regulation of the hypothalamic–pituitary–gonadal axis in domestic ruminants.