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Lhx8 regulates primordial follicle activation and postnatal folliculogenesis.

Ren Y, Suzuki H, Jagarlamudi K, Golnoski K, McGuire M, Lopes R, Pachnis V, Rajkovic A - BMC Biol. (2015)

Bottom Line: The conditional deficiency of Lhx8 in the oocytes of primordial follicles leads to massive primordial oocyte activation, in part, by indirectly interacting with the PI3K-AKT pathway, as shown by synergistic effects on FOXO3 nucleocytoplasmic translocation and rpS6 activation.However, LHX8 does not directly regulate members of the PI3K-AKT pathway; instead, we show that LHX8 represses Lin28a expression, a known regulator of mammalian metabolism and of the AKT/mTOR pathway.Our results indicate that the LHX8-LIN28A pathway is essential in the earliest stages of primordial follicle activation, and LHX8 is an important oocyte-specific transcription factor in the ovary for regulating postnatal folliculogenesis.

View Article: PubMed Central - PubMed

Affiliation: Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, PA, 15213, USA. yur4@pitt.edu.

ABSTRACT

Background: The early stages of ovarian follicle formation-beginning with the breakdown of germ cell cysts and continuing with the formation of primordial follicles and transition to primary and secondary follicles-are critical in determining reproductive life span and fertility. Previously, we discovered that global knockouts of germ cell-specific transcriptional co-regulators Sohlh1, Sohlh2, Lhx8, and Nobox, cause rapid oocyte loss and ovarian failure. Also factors such as Nobox and Sohlh1 are associated with human premature ovarian failure. In this study, we developed a conditional knockout of Lhx8 to study oocyte-specific pathways in postnatal folliculogenesis.

Results: The conditional deficiency of Lhx8 in the oocytes of primordial follicles leads to massive primordial oocyte activation, in part, by indirectly interacting with the PI3K-AKT pathway, as shown by synergistic effects on FOXO3 nucleocytoplasmic translocation and rpS6 activation. However, LHX8 does not directly regulate members of the PI3K-AKT pathway; instead, we show that LHX8 represses Lin28a expression, a known regulator of mammalian metabolism and of the AKT/mTOR pathway. LHX8 can bind to the Lin28a promoter, and the depletion of Lin28a in Lhx8-deficient oocytes partially suppresses primordial oocyte activation. Moreover, unlike the PI3K-AKT pathway, LHX8 is critical beyond primordial follicle activation, and blocks the primary to secondary follicle transition.

Conclusions: Our results indicate that the LHX8-LIN28A pathway is essential in the earliest stages of primordial follicle activation, and LHX8 is an important oocyte-specific transcription factor in the ovary for regulating postnatal folliculogenesis.

No MeSH data available.


Related in: MedlinePlus

Lin28a deficiency rescues Lhx8flx/flxGdf9Cre-induced PFA. a–d Representative histology of control (Lhx8flx/flx), Lhx8 conditional knockout (Lhx8flx/flxGdf9Cre), Lin28a conditional knockout (Lin28flx/flxGdf9Cre), and double Lhx8/Lin28a conditional knockout (Lhx8flx/flxLin28flx/flxGdf9Cre) ovaries. Double Lhx8/Lin28a conditional knockouts show a diminished number of activated primordial follicles. Anti-Nobox antibodies were used to label oocyte nuclei (dark brown). PF: primordial follicle; aPF: activated primordial follicle. e The Lin28flx/flxGdf9Cre (Lin28G9cKO) mice have a similar phenotype as control (Ctrl) mice and the primordial follicle count is expressed as the percentage of total follicles. f Quantitation of activated primordial follicles in control, Lhx8 conditional, and double Lhx8/Lin28a conditional knockouts. The percentage of primordial follicles (PF) and activated primordial follicles (aPF) is shown. Three pairs of ovaries from Lhx8 conditional knockout and double Lhx8/Lin28a conditional knockouts mice were serially sectioned, and every fifth section was counted. g AKT phosphorylation is diminished in double Lhx8/Lin28a conditional knockouts. We quantitated by fluorescence p-AKT (T308) expression in the primordial and activated primordial follicles of the Lhx8flx/flxGdf9Cre (G9cKO) and Lhx8flx/flxLin28aflx/flxGdf9Cre (G9dKO) ovaries at PD7. There was a significant decrease in AKT phosphorylation in Lhx8flx/flxLin28aflx/flxGdf9Cre primordial and activated primordial follicles compared to Lhx8flx/flxGdf9Cre. Student’s t-test was used to calculate P values. *P < 0.05, **P < 0.01. Scale bars: 50 μm (A–D)
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Fig5: Lin28a deficiency rescues Lhx8flx/flxGdf9Cre-induced PFA. a–d Representative histology of control (Lhx8flx/flx), Lhx8 conditional knockout (Lhx8flx/flxGdf9Cre), Lin28a conditional knockout (Lin28flx/flxGdf9Cre), and double Lhx8/Lin28a conditional knockout (Lhx8flx/flxLin28flx/flxGdf9Cre) ovaries. Double Lhx8/Lin28a conditional knockouts show a diminished number of activated primordial follicles. Anti-Nobox antibodies were used to label oocyte nuclei (dark brown). PF: primordial follicle; aPF: activated primordial follicle. e The Lin28flx/flxGdf9Cre (Lin28G9cKO) mice have a similar phenotype as control (Ctrl) mice and the primordial follicle count is expressed as the percentage of total follicles. f Quantitation of activated primordial follicles in control, Lhx8 conditional, and double Lhx8/Lin28a conditional knockouts. The percentage of primordial follicles (PF) and activated primordial follicles (aPF) is shown. Three pairs of ovaries from Lhx8 conditional knockout and double Lhx8/Lin28a conditional knockouts mice were serially sectioned, and every fifth section was counted. g AKT phosphorylation is diminished in double Lhx8/Lin28a conditional knockouts. We quantitated by fluorescence p-AKT (T308) expression in the primordial and activated primordial follicles of the Lhx8flx/flxGdf9Cre (G9cKO) and Lhx8flx/flxLin28aflx/flxGdf9Cre (G9dKO) ovaries at PD7. There was a significant decrease in AKT phosphorylation in Lhx8flx/flxLin28aflx/flxGdf9Cre primordial and activated primordial follicles compared to Lhx8flx/flxGdf9Cre. Student’s t-test was used to calculate P values. *P < 0.05, **P < 0.01. Scale bars: 50 μm (A–D)

Mentions: We performed ovarian morphometric analyses to determine the effects of the double knockout on PFA. No morphometric difference was observed between Lin28aflx/flxGdf9Cre and control females at PD7 (Fig. 5a, c, e). As expected, we observed significantly fewer activated primordial follicles in Lhx8flx/flxLin28aflx/flxGdf9Cre compared to Lhx8flx/flxGdf9Cre ovaries, but they were not completely normal compared with the control (Fig. 5a, b, d, f).Fig. 5


Lhx8 regulates primordial follicle activation and postnatal folliculogenesis.

Ren Y, Suzuki H, Jagarlamudi K, Golnoski K, McGuire M, Lopes R, Pachnis V, Rajkovic A - BMC Biol. (2015)

Lin28a deficiency rescues Lhx8flx/flxGdf9Cre-induced PFA. a–d Representative histology of control (Lhx8flx/flx), Lhx8 conditional knockout (Lhx8flx/flxGdf9Cre), Lin28a conditional knockout (Lin28flx/flxGdf9Cre), and double Lhx8/Lin28a conditional knockout (Lhx8flx/flxLin28flx/flxGdf9Cre) ovaries. Double Lhx8/Lin28a conditional knockouts show a diminished number of activated primordial follicles. Anti-Nobox antibodies were used to label oocyte nuclei (dark brown). PF: primordial follicle; aPF: activated primordial follicle. e The Lin28flx/flxGdf9Cre (Lin28G9cKO) mice have a similar phenotype as control (Ctrl) mice and the primordial follicle count is expressed as the percentage of total follicles. f Quantitation of activated primordial follicles in control, Lhx8 conditional, and double Lhx8/Lin28a conditional knockouts. The percentage of primordial follicles (PF) and activated primordial follicles (aPF) is shown. Three pairs of ovaries from Lhx8 conditional knockout and double Lhx8/Lin28a conditional knockouts mice were serially sectioned, and every fifth section was counted. g AKT phosphorylation is diminished in double Lhx8/Lin28a conditional knockouts. We quantitated by fluorescence p-AKT (T308) expression in the primordial and activated primordial follicles of the Lhx8flx/flxGdf9Cre (G9cKO) and Lhx8flx/flxLin28aflx/flxGdf9Cre (G9dKO) ovaries at PD7. There was a significant decrease in AKT phosphorylation in Lhx8flx/flxLin28aflx/flxGdf9Cre primordial and activated primordial follicles compared to Lhx8flx/flxGdf9Cre. Student’s t-test was used to calculate P values. *P < 0.05, **P < 0.01. Scale bars: 50 μm (A–D)
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4487509&req=5

Fig5: Lin28a deficiency rescues Lhx8flx/flxGdf9Cre-induced PFA. a–d Representative histology of control (Lhx8flx/flx), Lhx8 conditional knockout (Lhx8flx/flxGdf9Cre), Lin28a conditional knockout (Lin28flx/flxGdf9Cre), and double Lhx8/Lin28a conditional knockout (Lhx8flx/flxLin28flx/flxGdf9Cre) ovaries. Double Lhx8/Lin28a conditional knockouts show a diminished number of activated primordial follicles. Anti-Nobox antibodies were used to label oocyte nuclei (dark brown). PF: primordial follicle; aPF: activated primordial follicle. e The Lin28flx/flxGdf9Cre (Lin28G9cKO) mice have a similar phenotype as control (Ctrl) mice and the primordial follicle count is expressed as the percentage of total follicles. f Quantitation of activated primordial follicles in control, Lhx8 conditional, and double Lhx8/Lin28a conditional knockouts. The percentage of primordial follicles (PF) and activated primordial follicles (aPF) is shown. Three pairs of ovaries from Lhx8 conditional knockout and double Lhx8/Lin28a conditional knockouts mice were serially sectioned, and every fifth section was counted. g AKT phosphorylation is diminished in double Lhx8/Lin28a conditional knockouts. We quantitated by fluorescence p-AKT (T308) expression in the primordial and activated primordial follicles of the Lhx8flx/flxGdf9Cre (G9cKO) and Lhx8flx/flxLin28aflx/flxGdf9Cre (G9dKO) ovaries at PD7. There was a significant decrease in AKT phosphorylation in Lhx8flx/flxLin28aflx/flxGdf9Cre primordial and activated primordial follicles compared to Lhx8flx/flxGdf9Cre. Student’s t-test was used to calculate P values. *P < 0.05, **P < 0.01. Scale bars: 50 μm (A–D)
Mentions: We performed ovarian morphometric analyses to determine the effects of the double knockout on PFA. No morphometric difference was observed between Lin28aflx/flxGdf9Cre and control females at PD7 (Fig. 5a, c, e). As expected, we observed significantly fewer activated primordial follicles in Lhx8flx/flxLin28aflx/flxGdf9Cre compared to Lhx8flx/flxGdf9Cre ovaries, but they were not completely normal compared with the control (Fig. 5a, b, d, f).Fig. 5

Bottom Line: The conditional deficiency of Lhx8 in the oocytes of primordial follicles leads to massive primordial oocyte activation, in part, by indirectly interacting with the PI3K-AKT pathway, as shown by synergistic effects on FOXO3 nucleocytoplasmic translocation and rpS6 activation.However, LHX8 does not directly regulate members of the PI3K-AKT pathway; instead, we show that LHX8 represses Lin28a expression, a known regulator of mammalian metabolism and of the AKT/mTOR pathway.Our results indicate that the LHX8-LIN28A pathway is essential in the earliest stages of primordial follicle activation, and LHX8 is an important oocyte-specific transcription factor in the ovary for regulating postnatal folliculogenesis.

View Article: PubMed Central - PubMed

Affiliation: Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, PA, 15213, USA. yur4@pitt.edu.

ABSTRACT

Background: The early stages of ovarian follicle formation-beginning with the breakdown of germ cell cysts and continuing with the formation of primordial follicles and transition to primary and secondary follicles-are critical in determining reproductive life span and fertility. Previously, we discovered that global knockouts of germ cell-specific transcriptional co-regulators Sohlh1, Sohlh2, Lhx8, and Nobox, cause rapid oocyte loss and ovarian failure. Also factors such as Nobox and Sohlh1 are associated with human premature ovarian failure. In this study, we developed a conditional knockout of Lhx8 to study oocyte-specific pathways in postnatal folliculogenesis.

Results: The conditional deficiency of Lhx8 in the oocytes of primordial follicles leads to massive primordial oocyte activation, in part, by indirectly interacting with the PI3K-AKT pathway, as shown by synergistic effects on FOXO3 nucleocytoplasmic translocation and rpS6 activation. However, LHX8 does not directly regulate members of the PI3K-AKT pathway; instead, we show that LHX8 represses Lin28a expression, a known regulator of mammalian metabolism and of the AKT/mTOR pathway. LHX8 can bind to the Lin28a promoter, and the depletion of Lin28a in Lhx8-deficient oocytes partially suppresses primordial oocyte activation. Moreover, unlike the PI3K-AKT pathway, LHX8 is critical beyond primordial follicle activation, and blocks the primary to secondary follicle transition.

Conclusions: Our results indicate that the LHX8-LIN28A pathway is essential in the earliest stages of primordial follicle activation, and LHX8 is an important oocyte-specific transcription factor in the ovary for regulating postnatal folliculogenesis.

No MeSH data available.


Related in: MedlinePlus