[Frontiers in Bioscience E4, 2631-2644, June 1, 2012]

P4 down-regulates Jagged2 and Notch1 expression during primordial folliculogenesis

Meng Guo1, Hua Zhang1, Fenghua Bian1, Ge Li1, 2, Xinyi Mu1, Jing Wen1, Guankun Mao1, Zhen Teng1, Guoliang Xia1, Meijia Zhang1

1State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, 100193, P.R. China, 2Guangdong Laboratory Animals Monitoring Institute

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. Materials and methods
3.1. Animal treatment
3.2. Real-time PCR
3.3. Hormone measurement
3.4. In vitro fetal ovary culture
3.5. Western blot
3.6. Immunohistochemistry
3.7. Oocyte and follicle counting
3.8. Hormone injection
3.9. RNA Interference (RNAi) on cultured fetal mouse ovaries
3.10. Statistical analysis
4. Results
4.1. The expression of Notch pathway genes in perinatal ovaries
4.2. Maternal P4 levels during midpregnancy inhibited Jagged2, Notch1 and Hey2 expression and primordial folliculogenesis
4.3. Suppression of Jagged2 and Notch1 by antibody exposure, and RNAi inhibited nest breakdown and primordial folliculogenesis in vitro
4.4. Localization of Jagged2 and Notch1 in the mouse ovary
4.5. RU486 inhibited Jagged2, Notch1, and Hey2 expression, and primordial folliculogenesis in vitro
5. Discussion
6. Acknowledgment
7. References

1. ABSTRACT

Nest breakdown and primordial folliculogenesis of the mouse ovary can be inhibited by progesterone (P4) and Notch signaling inhibitors. However, the relationship between these two signals during this process remains unknown. In the present study, transcript levels of Jagged2, Notch1, and their target, Hey2, increased markedly in ovaries during the beginning stage of folliculogenesis (17.5 days post coitus (dpc) to birth). Maternal P4 levels decreased simultaneously. We found that maternal midpregnancy P4 levels significantly inhibited Jagged2, Notch1, and Hey2 expression, and follicle formation in vitro. Maintaining high maternal P4 levels by daily injection also significantly suppressed the expression of Jagged2, Notch1, and Hey2, and follicle formation during late pregnancy. Based on immunohistochemistry, Jagged2 was localized in oocytes and Notch1 was strongly stained in pre-granulosa cells in 19.5 dpc ovaries. Suppression of their function by antibody addition and RNAi markedly inhibited nest breakdown and follicle formation. Taken together, these results demonstrate that maternal P4 levels during midpregnancy can inhibit the expression of Jagged2 and Notch1, which are involved in primordial folliculogenesis, in the mouse fetal ovary.