Regulation of genes encoding steroidogenic factor-1 (SF-1) and gonadotropin subunits in the ovine pituitary gland.
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 alpha subunit, LHbeta 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.
Baratta
M
M
Department of Veterinary Morphophysiology, University of Turin, Via Leonardo da Vinci 44, I-10095 Grugliasco, Turin, Italy, UE. baratta@veter.unito.it
Turzillo
A M
AM
Arreguin-Arevalo
A
A
Clay
C M
CM
Nett
T M
TM
D000818:Animals; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D005260:Female; D037201:Follicle Stimulating Hormone, beta Subunit / Q000235:genetics; D051717:Fushi Tarazu Transcription Factors; D005786:Gene Expression Regulation / Q000187:drug effects; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism / Q000494:pharmacology; D006062:Gonadotropins / Q000235:genetics*; D018398:Homeodomain Proteins; D037101:Luteinizing Hormone, beta Subunit / Q000235:genetics; D010052:Ovariectomy; D010902:Pituitary Gland / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000737:chemistry; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear; D012756:Sheep; D054339:Steroidogenic Factor 1; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology
D004268:DNA-Binding Proteins; D037201:Follicle Stimulating Hormone, beta Subunit; D051717:Fushi Tarazu Transcription Factors; D006062:Gonadotropins; D018398:Homeodomain Proteins; D037101:Luteinizing Hormone, beta Subunit; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D054339:Steroidogenic Factor 1; D014157:Transcription Factors; C515060:steroidogenic factor 1, rat; D007987:Gonadotropin-Releasing Hormone