2018-04-21

Zygotic genome activation is transcriptional activation which begins during S/G2 phase of the first mitosis right after fertilization in pronuclear stage and extended to the peak during the 2-cell stage.12. At the primary stage of zygotic genome activation, S/G2 phage of zygote first mitosis, transcription level in the male pronucleus is significantly higher compared to the female pronucleus.3 Among the five PN stages, PN3 and PN4 embryos were mainly in S phage.2.5. Based on the immunofluorescence staining of DNA of PN stage embryo 5, pronuclear reached their maximum size at the PN3 stage and moved closer to each other from the two sides of the embryo at PN3 and PN4 stage (Fig 1). Around 80% embryo is in PN3 and PN4 stage 8h after fertilization (Fig. 2). Through getting rid of the PN2 embryo 8h after ICSI, we collect PN3-PN4 stage embryos one by one for later single-cell RNA sequencing (Fig.3).

Fig. 1

Fig. 2

Fig. 3 PN3 and PN4 stage embryo collected 8h after ICSI. Blue squared embryos were defined as the PN2 stage and being get rid of when collection.