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.