Regulation and regulatory role of WNT signaling in potentiating FSH action during bovine dominant follicle selection

PLoS One. 2014 Jun 17;9(6):e100201. doi: 10.1371/journal.pone.0100201. eCollection 2014.

Abstract

Follicular development occurs in wave like patterns in monotocous species such as cattle and humans and is regulated by a complex interaction of gonadotropins with local intrafollicular regulatory molecules. To further elucidate potential mechanisms controlling dominant follicle selection, granulosa cell RNA harvested from F1 (largest) and F2 (second largest) follicles isolated at predeviation (PD) and onset of diameter deviation (OD) stages of the first follicular wave was subjected to preliminary RNA transcriptome analysis. Expression of numerous WNT system components was observed. Hence experiments were performed to test the hypothesis that WNT signaling modulates FSH action on granulosa cells during follicular waves. Abundance of mRNA for WNT pathway members was evaluated in granulosa cells harvested from follicles at emergence (EM), PD, OD and early dominance (ED) stages of the first follicular wave. In F1 follicles, abundance of CTNNB1 and DVL1 mRNAs was higher and AXIN2 mRNA was lower at ED versus EM stages and DVL1 and FZD6 mRNAs were higher and AXIN2 mRNA was lower in F1 versus F2 follicle at the ED stage. Bovine granulosa cells were treated in vitro with increasing doses of the WNT inhibitor IWR-1+/- maximal stimulatory dose of FSH. IWR-1 treatment blocked the FSH-induced increase in granulosa cell numbers and reduced the FSH-induced increase in estradiol. Granulosa cells were also cultured in the presence or absence of FSH +/- IWR-1 and hormonal regulation of mRNA for WNT pathway members and known FSH targets determined. FSH treatment increased CYP19A1, CCND2, CTNNB1, AXIN2 and FZD6 mRNAs and the stimulatory effect on CYP19A1 mRNA was reduced by IWR-1. In contrast, FSH reduced CARTPT mRNA and IWR-1 partially reversed the inhibitory effect of FSH. Results support temporal and hormonal regulation and a potential role for WNT signaling in potentiating FSH action during dominant follicle selection.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Blotting, Western
  • Cattle
  • Cells, Cultured
  • Female
  • Follicle Stimulating Hormone / pharmacology*
  • Gene Expression Regulation / drug effects*
  • Granulosa Cells / cytology
  • Granulosa Cells / drug effects
  • Granulosa Cells / metabolism*
  • Ovarian Follicle / cytology
  • Ovarian Follicle / drug effects
  • Ovarian Follicle / metabolism*
  • RNA, Messenger / genetics
  • Radioimmunoassay
  • Real-Time Polymerase Chain Reaction
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction / drug effects*
  • Wnt Proteins / genetics
  • Wnt Proteins / metabolism*

Substances

  • RNA, Messenger
  • Wnt Proteins
  • Follicle Stimulating Hormone

Grant support

P.S.P. Gupta was supported at Michigan State University by a Department of Biotechnology, Government of India CREST award. This project was supported by Agriculture and Food Research Initiative Competitive Grant no. 2009-65203-05700 from the USDA National Institute of Food and Agriculture to G.W.S., Chinese National Natural Science Fund Grant no. 31172211 to L. Lv, and funding from the Michigan State University Reproductive and Developmental Sciences Program and Michigan AgBioResearch. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.