The role of IGFs in the regulation of ovarian follicular growth in the brushtail possum (Trichosurus vulpecula).
IGFs are known to be key regulators of ovarian follicular growth in eutherian mammals, but little is known regarding their role in marsupials. To better understand the potential role of IGFs in the regulation of follicular growth in marsupials, expression of mRNAs encoding IGF1, IGF2, IGF1R, IGF-binding protein 2 (IGFBP2), IGFBP4 and IGFBP5 was localized by in situ hybridization in developing ovarian follicles of the brushtail possum. In addition, the effects of IGF1 and IGF2 on granulosa cell function were tested in vitro. Both granulosa and theca cells synthesize IGF mRNAs, with the theca expressing IGF1 mRNA and granulosa cell expressing IGF2 mRNA. Oocytes and granulosa cells express IGF1R. Granulosa and theca cells expressed IGFBP mRNAs, although the pattern of expression differed between the BPs. IGFBP5 mRNA was differentially expressed as the follicles developed with granulosa cells of antral follicles no longer expressing IGFBP5 mRNA, suggesting an increased IGF bioavailability in the antral follicle. The IGFBP protease, PAPPA mRNA, was also expressed in granulosa cells of growing follicles. Both IGF1 and IGF2 stimulated thymidine incorporation but had no effect on progesterone production. Thus, IGF may be an important regulator of ovarian follicular development in marsupials as has been shown in eutherian mammals.
Wallaceville Animal Research Centre, AgResearch, Upper Hutt 5140, New Zealand AgResearch Ltd, Invermay Agricultural Centre, Puddle Alley, Mosgiel 9053, New Zealand. jenny.juengel@agresearch.co.nz
Jennifer L
JL
Juengel
Lisa J
LJ
Haydon
Brigitta
B
Mester
Brian P
BP
Thomson
Michael
M
Beaumont
Douglas C
DC
Eckery
D000818:Animals; D001483:Base Sequence; D005260:Female; D006107:Granulosa Cells / Q000166:cytology / Q000502:physiology*; D017403:In Situ Hybridization / Q000662:veterinary; D018969:Insulin-Like Growth Factor Binding Proteins / Q000235:genetics / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000502:physiology*; D007335:Insulin-Like Growth Factor II / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D006080:Ovarian Follicle / Q000166:cytology / Q000254:growth & development / Q000502:physiology*; D011266:Pregnancy-Associated Plasma Protein-A / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics; D017526:Receptor, IGF Type 1 / Q000235:genetics / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D017422:Sequence Analysis, DNA; D048330:Trichosurus / Q000502:physiology*
D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D017526:Receptor, IGF Type 1; D011266:Pregnancy-Associated Plasma Protein-A