Differential expression of mRNAs encoding the putative inhibin co-receptor (betaglycan) and activin type-I and type-II receptors in preovulatory and prehierarchical follicles of the laying hen ovary

J Endocrinol. 2006 Feb;188(2):241-9. doi: 10.1677/joe.1.06525.

Abstract

Ovarian follicle development is primarily regulated by an interplay between the pituitary gonadotrophins, LH and FSH, and ovary-derived steroids. Increasing evidence implicates regulatory roles of transforming growth factor-beta (TGFbeta) superfamily members, including inhibins and activins. The aim of this study was to identify the expression of mRNAs encoding key receptors of the inhibin/activin system in ovarian follicles ranging from 4 mm in diameter to the dominant F1 follicle (approximately 40 mm). Ovaries were collected (n = 16) from mid-sequence hens maintained on a long-day photoschedule (16 h of light:8 h of darkness). All follicles removed were dissected into individual granulosa and thecal layers. RNA was extracted and cDNA synthesized. Real-time quantitative PCR was used to quantify the expression of mRNA encoding betaglycan, activin receptor (ActR) subtypes (type-I, -IIA and -IIB) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH); receptor expression data were normalized to GAPDH expression. Detectable levels of ActRI, -IIA and -IIB and the inhibin co-receptor (betaglycan) expression were found in all granulosa and thecal layers analysed. Granulosa ActRI mRNA peaked (P < 0.05) in 8-9.9 mm follicles, whereas ActRIIA rose significantly from 6-7.9 mm to 8-9.9 mm, before falling to F3/2; levels then rose sharply (3-fold) to F1 levels. Granulosa betaglycan mRNA expression rose 3-fold from 4-5.9 mm to 8-9.9 mm, before falling 4-fold to F3/2; levels then rose sharply (4-fold) to F1 levels. ActRIIB levels did not vary significantly during follicular development. Thecal ActRI mRNA expression was similar from 4-7.9 mm then decreased significantly to a nadir at the F4 position, before increasing 2-fold to the F1 (P < 0.05). Although thecal ActRIIB and -IIA expression did not vary significantly from 4 mm to F3, ActRIIB expression increased significantly (2-fold) from F3 to F1 and ActRIIA increased 2-fold from F2 to F1 (P < 0.05). Thecal betaglycan fell to a nadir at F6 after follicle selection; levels then increased significantly to F2, before falling approximately 50% in the F1. In all follicles studied expression of betaglycan and ActRI (granulosa: r = 0.65, P < 0.001, n = 144/group; theca: r = 0.49, P < 0.001, n = 144/group) was well correlated. No significant correlations were identified between betaglycan and ActRIIA or -IIB. Considering all follicles analysed, granulosa mRNA expression of betaglycan, ActRI, ActRIIA and ActRIIB were all significantly lower than in corresponding thecal tissue (betaglycan, 11.4-fold; ActRIIB, 5.1-fold; ActRI, 3.8-fold; ActRIIA, 2.8-fold). The co-localization of type-I and -II activin receptors and betaglycan on granulosa and thecal cells are consistent with a local auto/paracrine role of inhibins and activins in modulating ovarian follicle development, selection and progression in the domestic fowl.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Activin Receptors, Type I / analysis*
  • Activin Receptors, Type II / analysis*
  • Animals
  • Chickens / physiology*
  • Female
  • Follicular Phase / physiology
  • Glyceraldehyde-3-Phosphate Dehydrogenases / analysis
  • Granulosa Cells / physiology
  • Inhibins / analysis*
  • Ovarian Follicle / physiology*
  • Proteoglycans / analysis*
  • RNA, Messenger / analysis*
  • Receptors, Transforming Growth Factor beta / analysis*
  • Theca Cells / physiology

Substances

  • Proteoglycans
  • RNA, Messenger
  • Receptors, Transforming Growth Factor beta
  • betaglycan
  • Inhibins
  • Glyceraldehyde-3-Phosphate Dehydrogenases
  • Activin Receptors, Type I
  • Activin Receptors, Type II
  • activin receptor type II-A
  • activin receptor type II-B