AUTHOR=Sun Penghao , Wang Hongliang , Liu Lingyun , Guo Kaimin , Li Xian , Cao Yin , Ko Chemyong , Lan Zi-Jian , Lei Zhenmin 

TITLE=Aberrant activation of KRAS in mouse theca-interstitial cells results in female infertility

JOURNAL=Frontiers in Physiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2022.991719

DOI=10.3389/fphys.2022.991719

ISSN=1664-042X

ABSTRACT=<p>KRAS plays critical roles in regulating a range of normal cellular events as well as pathological processes in many tissues mediated through a variety of signaling pathways, including ERK1/2 and AKT signaling, in a cell-, context- and development-dependent manner. The <italic>in vivo</italic> function of KRAS and its downstream targets in gonadal steroidogenic cells for the development and homeostasis of reproductive functions remain to be determined. To understand the functions of KRAS signaling in gonadal theca and interstitial cells, we generated a <italic>Kras</italic> mutant (<italic>tKrasMT</italic>) mouse line that selectively expressed a constitutively active <italic>Kras</italic><sup><italic>G12D</italic></sup> in these cells. <italic>Kras</italic><sup><italic>G12D</italic></sup> expression in ovarian theca cells did not block follicle development to the preovulatory stage. However, <italic>tKrasMT</italic> females failed to ovulate and thus were infertile. The phosphorylated ERK1/2 and forkhead box O1 (FOXO1) and total FOXO1 protein levels were markedly reduced in <italic>tKrasMT</italic> theca cells. <italic>Kras</italic><sup><italic>G12D</italic></sup> expression in theca cells also curtailed the phosphorylation of ERK1/2 and altered the expression of several ovulation-related genes in gonadotropin-primed granulosa cells. To uncover downstream targets of KRAS/FOXO1 signaling in theca cells, we found that the expression of bone morphogenic protein 7 (<italic>Bmp7</italic>), a theca-specific factor involved in ovulation, was significantly elevated in <italic>tKrasMT</italic> theca cells. Chromosome immunoprecipitation assays demonstrated that FOXO1 interacted with the <italic>Bmp7</italic> promoter containing forkhead response elements and that the binding activity was attenuated in <italic>tKrasMT</italic> theca cells. Moreover, <italic>Foxo1</italic> knockdown caused an elevation, whereas <italic>Foxo1</italic> overexpression resulted in an inhibition of <italic>Bmp7</italic> expression, suggesting that KRAS signaling regulates FOXO1 protein levels to control <italic>Bmp7</italic> expression in theca cells. Thus, the anovulation phenotype observed in <italic>tKrasMT</italic> mice may be attributed to aberrant KRAS/FOXO1/BMP7 signaling in theca cells. Our work provides the first <italic>in vivo</italic> evidence that maintaining normal KRAS activity in ovarian theca cells is crucial for ovulation and female fertility.</p>