Follicle loss and PTEN/PI3K/mTOR signaling pathway activated in LepR-mutated mice

Abstract

Female mice (Y123F) with substitution mutations introduced through homologous gene targeting, replacing the three tyrosine residues of LepR, Tyr985, Tyr1077, and Tyr1138 with phenylalanine, could induce infertility. This study aimed to describe the reproductive alteration and to explore its mechanism. We compared the reproductive characteristics in the female homozygous (HOM) Y123F mice and wild-type (WT) littermates, analyzing the expression of downstream molecules of LepR, like protein kinase B (Akt)/mammalian target of rapamycin (mTOR), phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and insulin receptor substrate (IRS) in the ovaries. The results showed that 10-week old female Y123F HOM exhibited no reproductive periods, declined anti-mullerian hormone (AMH) levels in the serum and ovaries, reduced primordial follicles, primary follicles, secondary follicles, antral follicles and hardly no corpus lutea (all p < .05). The phosphorylation of downsream Akt, mTOR, S6K1 and eIF4B of LepR were all elevated in the ovaries of the mutated female mice. They also presented a decreased phosphorylation of IRS-1, IRS-2, and PTEN, and a strengthened phosphorylation of FOXO-3A in the ovaries. In conclusions, LepR mutation could result in follicle loss and activation of PTEN/PI3K/Akt/mTOR pathway in adult female mice, independent of insulin signaling pathway.

摘要

雌性小鼠(Y123F)通过同源基因靶向引入替代突变, 用苯丙氨酸替代瘦素受体的三个酪氨酸残基Tyr985、Tyr1077、Tyr1138, 可导致不育。本研究旨在描述生殖改变及其机制。我们比较了纯合子(HOM) Y123F小鼠和野生型(WT) 同窝出生仔鼠的生殖特性, 分析了瘦素受体下游分子的表达, 如蛋白激酶B (Akt)/哺乳动物雷帕霉素靶蛋白(mTOR)、10号染色体(PTEN)上缺失的磷酸酶和tensin同源物(IRS)以及卵巢中的胰岛素受体底物(IRS)。结果显示, 10周龄女性Y123F纯合子无生育周期, 血清和卵巢抗苗勒氏激素(AMH)水平下降, 原始卵泡、初级卵泡、次级卵泡、窦卵泡减少, 几乎无黄体(p<0.05)。瘦素受体的下游分子Akt、mTOR、S6K1和eIF4B的磷酸化在突变的雌鼠卵巢中均升高。同时其卵巢中IRS-1、IRS-2和PTEN磷酸化降低, FOXO-3A磷酸化增强。综上所述, 瘦素受体突变可导致成年雌性小鼠的卵泡丢失和PTEN/PI3K/Akt/mTOR通路的激活, 其独立于胰岛素信号通路。

Keywords:

• Leptin receptor
• primordial follicle
• AMH
• mTOR
• PTEN

Acknowledgements

We thank Prof. Huijuan Shi for kindly providing adult heterozygous Y123F mice.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The financial support of this study was from Youth Foundation of Shanghai Municipal Health Bureau (20164Y0178) to He-xia Xia.