FOXO3 Is Expressed in Ovarian Tissues and Acts as an Apoptosis Initiator in Granulosa Cells of Chickens

Abstract

FOXO3, which encodes the transcription factor forkhead box O-3 (FoxO3), is a member of the FOXO subfamily of the forkhead box (FOX) family. FOXO3 can be negatively regulated by its phosphorylation by the PI3K/Akt signaling pathway and ultimately drives apoptosis when activated. In mammalian ovaries, the FOXO3 protein regulates atresia and follicle growth by promoting apoptosis of ovarian granulosa cells. Nonetheless, the specific effects of the FOXO3 protein on granulosa apoptosis of avian ovaries have not been elucidated. Therefore, we studied FOXO3 expression in follicles with different organization and at all hierarchical levels of chicken follicles. Via an immunofluorescence assay, the chicken follicular theca at all hierarchical levels were found to be strongly stained with an anti-FOXO3 antibody. In chicken primary ovarian granulosa cells, mRNA levels of proapoptotic factors BNIP3 and BCL2L11 decreased in the absence of FOXO3, and so did PARP-1 and cleaved caspase 3 protein levels. After treatment with a recombinant FOXO3 protein, PARP-1 and caspase 3 protein levels increased, along with mRNA levels of Bnip3 and BCL2L11 (significantly, p<0.05). In addition, FOXO3 was downregulated in chicken granulosa cells when different estradiol or FSH concentrations were applied. In conclusion, FOXO3 is expressed in chicken reproductive tissues, including follicles and ovarian granulosa cells, and promotes apoptosis of chicken ovarian granulosa cells.

Effects of RAC1 on Proliferation of Hen Ovarian Prehierarchical Follicle Granulosa Cells

“…GCs produce estradiol and progesterone as a reaction the inducement by gonadotropins (FSH and LH) respectively [31] and interacted with oocytes during follicular development and promoted oocyte development through nutrient exchange and information exchange [32]. In present…”

The Factors and Pathways Regulating the Activation of Mammalian Primordial Follicles in vivo

“…To prove this, FOXO3 was deleted from the oocytes of mouse primordial follicles, causing the global activation of dormant primordial follicles and the mutant female mice becoming infertile in young adulthood because of follicle depletion (Castrillon et al, 2003;Hosaka et al, 2004;Gallardo et al, 2008). In contrast, when the oocyte-specific FOXO3 was overexpressed in mice, the mice showed infertility caused by the retardation of oocyte growth and follicular development (Liu et al, 2007), indicating that FOXO3 suppressed the activation of ovarian follicles (Cui et al, 2019). Furthermore, constitutively active FOXO3 in oocytes could preserve the ovarian reserve in mice (Pelosi et al, 2013).…”

Expression Regulation and Physiological Role of Transcription Factor FOXO3a During Ovarian Follicular Development

“…Moreover, research on chicken primary ovarian granulosa cells indicated that in the absence of FOXO3, mRNA levels of proapoptotic factors BNIP3 and BCL2L11 decreased, along with poly [ADP-ribose] polymerase 1 (PARP-1) and cleaved caspase3 protein levels. After treatment with a recombinant FOXO3 protein, mRNA levels of BNIP3 and BCL2L11, as well as protein levels of PARP-1 and caspase3, were reportedly increased (Cui et al, 2019). Experiments in human ovarian granulosa-like tumor cells (KGN) have shown that expression of the proapoptotic factors FASLG and BCL2L11 is upregulated and cell death is induced by transfection of FOXO3 expression vectors (Matsuda et al, 2011).…”