Transcriptomic profiling of the oocyte-cumulus-granulosa cell complex from estrogen receptor β knockout mice

Objective

To study the role of estrogen receptor β in follicle development and maturation and the response to gonadotropin stimulation aiming at superovulation.

Design

Experimental study and transcriptomic analysis.

Setting

Karolinka Institutet, medical university.

Animal(s)

Healthy wild-type (WT) and estrogen receptor β knockout (Esr2-KO) female mice undergoing superovulation at 4 weeks, 7 weeks, and 6 months of age.

Intervention(s)

Not applicable.

Main Outcome Measure(s)

Oocyte yield after superovulation, transcriptomic profiling of cumulus-granulosa cell complexes and oocytes, and immunohistochemical analyses.

Result(s)

Superovulation of estrogen receptor β (ERβ) knockout mice resulted in reduced oocyte yield at 6 months of age compared with WT mice, but younger mice had similar yields. RNA-seq analysis of cumulus cells from superovulated WT and Esr2-KO mice identified genes and pathways associated with among others adhesion, proliferation, Wnt-signaling, and placed ERβ in bipotential granulosa cell cluster. Loss of ERβ increased expression of the other estrogen receptors Esr1 and Gper1.

Conclusion(s)

Our results show that ERβ has an important role in regulating ovulation in response to exogenous gonadotropins in 6-month-old mice, but not in younger mice. Our transcriptomic and immunohistochemical observations suggest a dysregulation of the granulosa cell communication and lack of tight coordination between granulosa cell replication and antrum expansion. A significant upregulation of other estrogen receptors may support a compensatory mechanism sustaining fertility during younger age in Esr2-KO mice.