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

Abstract

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.

Keywords: Esr2; Estrogen; estrogen receptor β; granulosa cells; transcriptome.