(299) The Expression and Role of the Salt-inducible Kinases in Mouse Oocyte Meiotic Progression

Emily T. Hayes¹; Carlos Stocco¹ and Nicola Winston² 

1. Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, United States

2. Division of Reproductive Endocrinology and Infertility, Department of Obstetrics and Gynecology, University of Illinois at Chicago, Chicago, United States

 

Abstract Text:

The salt-inducible kinases (SIKs)—SIK1, SIK2, and SIK3—are a family of serine-threonine kinases with burgeoning, critical roles in female fertility. In vitro work using pan-SIK inhibitors revealed that SIK inhibition stimulates estradiol synthesis in human ovarian granulosa cells and can potentiate steroidogenic enzyme expression in granulosa cells from patients with ovarian causes of infertility. Further, SIK2 global and granulosa cell-specific knockout mice have a hyper-response to ovarian stimulation, ovulating three times as many oocytes as controls. Thus, SIK inhibition shows promise as a therapeutic strategy to stimulate ovarian function and oocyte yield in patients undergoing in vitro fertilization. However, it is unknown whether SIKs are expressed in the oocyte or if they control oocyte maturation. To determine how SIKs affect oocyte health and meiotic progression, we first characterized the expression of the SIKs via qPCR and immunocytochemistry in germinal vesicle (GV) and metaphase II (MII) mouse oocytes. SIK1 was undetectable at all stages. In contrast, SIK2 is expressed in the cytosol of GV oocytes and was found to be strongly associated with the meiotic spindle in MII oocytes. SIK3 expression and localization demonstrated maturation specific changes. Using an in vitro maturation approach to determine the effect of SIKs on meiotic progression, we showed that SIK inhibition does not affect the percentage of oocytes completing meiosis. SIK2’s striking localization at the spindle led us to study meiotic progression and spindle morphology in oocytes of SIK2 knockout mice. Interestingly, silencing SIK2 did not affect meiotic progression but caused significant morphological defects in the spindle. Further work is required to determine the targets of SIK2 at the spindle and how the spindle defects observed in SIK2 knockout mice affect oocyte fertilization. Together, this data reveals for the first time a role for SIKs in meiosis.