The pituitary gland stimulates cycles of ovarian follicle maturation through its production and subsequent release of follicle-stimulating hormone (FSH). FSH is secreted in two """"""""peaks"""""""" across the human menstrual cycle and this pattern of release is governed by endocrine hormones hypothalamic releasing peptides and paracrine growth factors that converge on pituitary gonadotrope cells to stimulate or inhibit FSH production. The projects described in this proposal concern the mechanisms of action of one class of regulatory factors, the activins. Activins, produced within gonadotropes, stimulate the production of one of the two protein subunits that comprise FSH, the FSHbeta subunit. Activins bind to cell-surface receptors that activate intracellular signaling proteins in the SMAD family. Specifically, activins stimulate SMAD2 and SMAD3 phosphorylation and nuclear translocation. Once in the nucleus, SMAD3 stimulates transcription of the FSHbsubunit gene. Early indications were that SMAD2 was not involved in this process; however, it is clear that SMAD3 alone cannot account for activin's stimulation of FSHbeta.
In Specific Aim 1, SMAD2-dependent signal transduction will be antagonized and the resulting effects on activin-stimulated FSHbeta transcription examined. SMAD3 binds a cis-acting regulatory element in the FSHbeta promoter. This site is necessary but not sufficient for activin and SMAD3-stimulated gene expression. Another region in the more distal promoter is also required for the transcriptional response. The position of this regulatory region will be mapped and the transcription factors acting there will be identified. To demonstrate an in vivo role for SMAD3 in FSHa expression, a conditional transgenic mouse model will be produced in Specific Aim 2. Here, the tetracycline-inducible system will be used to express a dominant negative (dn-) form of SMAD3 in gonadotropes of adult mice. The effects of dn-SMAD3 on FSH synthesis and secretion as well as estrous cyclicity and fertility will be examined. Finally, FSHbeta is expressed within gonadotropes, but not in other cell types of the body. The mechanisms controlling this cell-restricted gene expression are not understood. SMAD3, in concert with a zinc-finger transcription factor, GATA-2, stimulates basal FSHbeta transcription in cells that under other circumstances do not express this gene.
In Specific Aim 3, the mechanisms controlling the synergistic effects of GATA-2 and SMAD3 will be elucidated and the necessity for GATA-2 in basal FSHb expression examined. Collectively, the results of these experiments will shed new light on the mechanisms controlling basal and activin-stimulated FSHbeta expression. Given the critical importance of FSH for fertility in women, these results may aid in the design of novel contraceptives or may pinpoint causes of infertility that have thus far eluded our detection.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD047794-04
Application #
7269834
Study Section
Reproductive Endocrinology Study Section (REN)
Program Officer
Lamar, Charisee A
Project Start
2004-07-15
Project End
2009-06-30
Budget Start
2007-07-01
Budget End
2009-06-30
Support Year
4
Fiscal Year
2007
Total Cost
$188,762
Indirect Cost
Name
Mcgill University
Department
Type
DUNS #
205667090
City
Montreal
State
PQ
Country
Canada
Zip Code
H3 0-G4
Lamba, Pankaj; Fortin, Jérôme; Tran, Stella et al. (2009) A novel role for the forkhead transcription factor FOXL2 in activin A-regulated follicle-stimulating hormone beta subunit transcription. Mol Endocrinol 23:1001-13
Bak, Beata; Carpio, Laura; Kipp, Jinjing L et al. (2009) Activins regulate 17beta-hydroxysteroid dehydrogenase type I transcription in murine gonadotrope cells. J Endocrinol 201:89-104
Stevenson, T J; Lynch, K S; Lamba, P et al. (2009) Cloning of gonadotropin-releasing hormone I complementary DNAs in songbirds facilitates dissection of mechanisms mediating seasonal changes in reproduction. Endocrinology 150:1826-33
Ho, Catherine C; Bernard, Daniel J (2009) Bone morphogenetic protein 2 signals via BMPR1A to regulate murine follicle-stimulating hormone beta subunit transcription. Biol Reprod 81:133-41
Fortin, Jerome; Lamba, Pankaj; Wang, Ying et al. (2009) Conservation of mechanisms mediating gonadotrophin-releasing hormone 1 stimulation of human luteinizing hormone beta subunit transcription. Mol Hum Reprod 15:77-87
Stevenson, Tyler J; Bernard, Daniel J; Ball, Gregory F (2009) Photoperiodic condition is associated with region-specific expression of GNRH1 mRNA in the preoptic area of the male starling (Sturnus vulgaris). Biol Reprod 81:674-80
Wang, Ying; Fortin, Jerome; Lamba, Pankaj et al. (2008) Activator protein-1 and smad proteins synergistically regulate human follicle-stimulating hormone beta-promoter activity. Endocrinology 149:5577-91
Lamba, Pankaj; Hjalt, Tord A; Bernard, Daniel J (2008) Novel forms of Paired-like homeodomain transcription factor 2 (PITX2): generation by alternative translation initiation and mRNA splicing. BMC Mol Biol 9:31
Lamba, Pankaj; Khivansara, Vishal; D'Alessio, Ana C et al. (2008) Paired-like homeodomain transcription factors 1 and 2 regulate follicle-stimulating hormone beta-subunit transcription through a conserved cis-element. Endocrinology 149:3095-108
Ge, Ren-Shan; Chen, Guo-Rong; Dong, Qiang et al. (2007) Biphasic effects of postnatal exposure to diethylhexylphthalate on the timing of puberty in male rats. J Androl 28:513-20

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