Figure 1

Schematic comparison of the TCET and ICSI procedures. (a) The TCET group is established by in vivo fertilization after gonadotropin stimulation. After 2-cell embryo is obtained from the oviduct, the embryo is subsequently transferred into a pseudo-pregnant mouse. (b) The ICSI mice also begin with the injection of gonadotropin and end with transferring 2-cell embryo into surrogate mice. A primary difference between the two procedures is the manipulation and injection of occytes and culture for ICSI, while only in vivo fertilization for TCET. (Drawn by authors Q. Z and X. Q).