RGS12 as a Novel Maternal-Effect Gene Causes Arrest at the Pronuclear Stage of Human Zygote

Abstract Background: Early embryonic arrest is one of the major causes of female infertility after in vitro fertilization (IVF), but the causal gene of arrest at the pronuclear (PN) zygote stage is largely unknown. Results: To understand this process, we recruited a family characterized by recurrent PN arrest during IVF cycles and performed whole-exome sequencing. The missense variant c.C1630T (p.R544W) in RGS12 was responsible for a phenotype characterized by paternal transmission. RGS12 controls Ca2+ oscillation, which is required for oocyte activation after fertilization. Single-cell transcriptome profiling of PN-arrest zygotes revealed defective established translation, RNA processing and cell cycle, which explained the failure of complete oocyte activation. Furthermore, we identified proximal genes involved in Ca2+ oscillation–cytostatic factor–anaphase-promoting complex (Ca2+ oscillation–CSF–APC) signaling, including upregulated CaMKII, ORAI1, CDC20, and CDH1 and downregulated EMI1 and BUB3. The findings indicated abnormal spontaneous Ca2+ oscillations leading to oocytes with prolonged low CSF and high APC level, which resulted in defective nuclear envelope breakdown and DNA replication. The changes in levels of critical genes were confirmed by examining other independent PN-arrest zygotes. However, the PN-arrest zygote phenotype was not consistent with that of RGS12-deficient mice, thereby indicating species-specific functions between human and mouse. Conclusion: Our findings expand our knowledge of the genetic determinants of human early embryonic arrest at the PN stage and provide guidance for selecting clinically infertile individuals with PN-arrest zygotes for Ca2+ intervention.