PARENT SESSION
Follicular Development

THE EFFECTS OF POSTNATAL GRANULOSA CELL EXPRESSION OF A DOMINANT-NEGATIVE FGFR2IIIb RECEPTOR ON OVARIAN FUNCTION.

Marciani, Karina¹, Koos, Robert¹, ¹

ABSTRACT- Growth factor-mediated cell interactions are important for follicle growth and functional differentiation. It seems likely that FGF-7 and/or FGF-10, which are expressed in the ovary, are involved in these interactions. This study was designed to test the hypothesis that FGF-7 and/or FGF-10, acting through the FGFR2IIIb receptor, play a role in follicle development. Transgenic mice were made that carry a dominant-negative FGFR2IIIb receptor (DNR) gene under the direction of the proximal -180 bp Mullerian Inhibiting Substance promoter. Transgene expression was verified by RT-PCR and the extent to which the DNR inhibited endogenous receptor (enR) function was assessed by culturing preantral follicles (100-300 mm) from wild type (WT) and homozygous (+/+) transgenic mice in the presence or absence of FGF-7. DNR impact on WT, heterozygous (+/-), and +/+ female fertility was determined. DNR expression was detected in the testes and ovaries but not in brain, kidney, heart, lung, liver or uterus. Follicle culture experiments confirmed that enR function was inhibited in +/+ follicles. In the presence of 100 ng/ml FGF-7, WT follicles grew significantly (4.9 ± 1.1% by day 1, 10.6 ± 2.2% by day 2, and 14.2 ± 3.0% by day 3), while +/+ follicles did not (1.6 ± 0.7% day 1, 3.5 ± 1.1% day 2, and 5.2 ± 1.4% day 3). FSH caused follicles from both WT and +/+ mice to grow significantly (by 23-24%). There was no significant difference between the average number of pups per litter, or the average number of litters born between WT, +/-, or +/+ females. WT females (n = 7) had an average 8.8 ± 0.4 pups per litter while +/- females (n = 4) had 9.5 ± 0.6 and +/+ females (n = 7) had 8.9 ± 0.4 pups per litter. Over the 21 week period, wild type females gave birth to 4.9 ± 0.3 litters, while +/- females had 5.3 ± 0.3 litters, and +/+ females had 4.6 ± 0.4 litters. In conclusion, the DNR was capable of inhibiting FGF-7 stimulated preantral follicle growth in vitro, which supports a role for FGFR2IIIb ligands in this process. The inhibitory effects of the DNR can apparently be overcome or bypassed, however, as evidenced by the ability of +/+ follicles to grow in response to FSH in vitro and the unimpaired fertility of +/+ mice. Nevertheless, this model may prove useful for the in vitro study of specific aspects of follicle growth and development. Supported by NIH HD07170 and HD36207.

KEY WORDS: FGF-7 and FGF-10, dominant-negative receptor, mouse, ovary