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Published on: September 19, 2025

FOXO1 Promotes Mitophagy in Granulosa Cells by Targeting the METTL3/SMAD4 axis

Lan Luo1, Mi Tang2, Yanli Peng2

  • 1Department of TCM Gynecology, Hunan Provincial Maternal and Child Health Care Hospital, No.53, Xiangchun Road, Kaifu District, Changsha, 410008, Hunan, P.R. China. luolansci@126.com.

Cell Biochemistry and Biophysics
|August 14, 2026
PubMed

Insights

Forkhead box protein O1 (FOXO1) impairs fertility by promoting mitophagy and mitochondrial damage in ovarian granulosa cells. FOXO1 targets METTL3 to reduce SMAD4, affecting cell proliferation and apoptosis.

Area of Science:

  • Reproductive Biology
  • Cellular Biology
  • Molecular Endocrinology

Background:

  • Diminished ovarian reserve impacts fertility, with underlying mechanisms in ovarian granulosa cells needing elucidation.
  • Understanding the regulation of mitochondrial function is crucial for addressing fertility decline.

Purpose of the Study:

  • To investigate the role of FOXO1 in regulating mitochondrial function within ovarian granulosa cells.
  • To elucidate the molecular pathway involving FOXO1, METTL3, and SMAD4 in granulosa cell function.

Main Methods:

  • KGN cells were manipulated for FOXO1, METTL3, and SMAD4 expression.
  • Assays included proliferation (CCK-8, EdU), apoptosis (flow cytometry), molecular binding (immunoprecipitation), and reporter assays.
  • Mitochondrial function markers (ROS, MMP, ATP, mtDNA) and mitophagy proteins (DRP1, PINK1, parkin) were quantified.

Main Results:

  • FOXO1 overexpression reduced KGN cell proliferation and increased apoptosis, while SMAD4 knockdown had similar effects.
  • FOXO1 inhibited METTL3 transcription; METTL3 promoted SMAD4 N6-methyladenosine (m6A) modification.
  • FOXO1 repressed METTL3 and SMAD4 expression, whereas METTL3 upregulated SMAD4. Restoring METTL3 or SMAD4 counteracted FOXO1's negative effects on cell function and mitochondrial health.

Conclusions:

  • FOXO1 targets METTL3, leading to SMAD4 downregulation and promoting mitophagy and mitochondrial damage in granulosa cells.
  • This pathway contributes to diminished ovarian reserve and reduced fertility.
  • Targeting the FOXO1-METTL3-SMAD4 axis may offer therapeutic strategies for fertility preservation.
Keywords:
FOXO1Mitochondrial autophagyOvarian dysfunctionSMAD4m6A

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