Maternal RNA binding protein with multiple splicing 2 (RBPMS2) is involved in mouse blastocyst formation through the bone morphogenetic protein pathway

Abstract

Research question: Is early embryo development in mice influenced by RNA binding protein with multiple splicing 2 (RBPMS2), a maternal factor that accumulates and is stored in the cytoplasm of mature oocytes?

Design: The expression patterns of RBPMS2 in mouse were analysed using quantitative real-time PCR (qRT PCR) and immunofluorescence staining. The effect of knockdown of RBPMS2 on embryo development was evaluated through a microinjection of specific morpholino or small interfering RNA. RNA sequencing was performed for mechanistic analysis. The interaction between RBPMS2 and the bone morphogenetic protein (BMP) pathway was studied using BMP inhibitor and activator. The effect on the localization of E-cadherin was determined by immunofluorescence staining.

Results: Maternal protein RBPMS2 is highly expressed in mouse oocytes, and knockdown of RBPMS2 inhibits embryo development from the morula to the blastocyst stage. Mechanistically, RNA sequencing showed that the differentially expressed genes were enriched in the transforming growth factor-β (TGF-β) signalling pathway. BMPs are members of the TGF-β superfamily of growth factors. It was found that the addition of BMP inhibitor to the culture medium led to a morula-stage arrest, similar to that seen in RBPMS2 knockdown embryos. This morula-stage arrest defect caused by RBPMS2 knockdown was partially rescued by BMP activator. Furthermore, the localization of E-cadherin to the membrane was impaired in response to a knockdown of RBPMS2 or inhibition of the BMP pathway.

Conclusion: This study suggests that RBPMS2 activates the BMP pathway and thus influences the localization of E-cadherin, which is important for early mouse embryo development during blastocyst formation.

Keywords: Blastocyst formation; E-cadherin; Maternal protein; Morula-stage arrest; RBPMS2; RBPMS2 knockdown.