Cytogenetic Analysis and Developmental Assessment of Mouse Embryos Derived from In Vitro Fertilization of Oocytes Reconstructed by Meiosis-II Chromosome Transplantation

Abstract

Abstract. An electrofusion methodology for transferring meiosis-II chromosomes (M-II-t) has not been completely established. The present study compared the use of two temperatures (fusion at 37 C for Group A and 25 C for Group B) during an electrofusion procedure for mouse oocyte M-II-t and investigated the cytogenetic normality and developmental competence of embryos derived from in vitro fertilization using oocytes reconstructed by M-II-t. The M-II-t oocytes were fertilized in vitro and cultured to the blastocyst stage; the resultant embryos were analyzed cytogenetically. Subsequently, chromosomal normality of the resultant embryos at the prometaphase stage of first cleavage division and the integrity of the meiosis-II spindles of the reconstructed oocytes were analyzed. The success rate of electrofusion in Group B was 92.1%, which was significantly different from that in Group A (49.2%) (P<0.05). The fertilization rates (A, 80.7%; B, 77.2%) and development rates (A, 70.9%; B, 65.5%) in the M-II-t groups were significantly lower than those in the control group (95.0 and 92.2%, respectively) (P<0.05). The incidence of chromosomal abnormalities in the Group A embryos (20.5%) at the blastocyst stage was significantly higher than that in the control group embryos (8.5%) (P<0.05), but the incidence of chromosomal abnormalities in Group B (12.5%) was not significantly different compared with the other groups. A temperature of 25 C during the electrofusion procedure for M-IIt resulted in a good fusion rate, good development rate, and efficient production of chromosomally normal blastocysts. Furthermore, the incidence of chromosomal abnormalities in the first cleavage embryos at the prometaphase stage in Group B (9.6%) did not differ significantly from that in the control group (6.6%). The spindle morphology of the M-II-t oocytes in Group B was normal.

Overgrowth of mice generated from postovulatory‐aged oocyte spindles

“…9,11,36 However, without assessments of postnatal development, including growth and feed consumption, it is impossible to discuss the application of OST as a practical reproductive technology. 9,11,36 However, without assessments of postnatal development, including growth and feed consumption, it is impossible to discuss the application of OST as a practical reproductive technology.…”

“…Brain Liver the rate of development to term in mice. 9,11,36 However, without assessments of postnatal development, including growth and feed consumption, it is impossible to discuss the application of OST as a practical reproductive technology. In the absence of adequate evidence regarding the wholesomeness of OST individuals, the application of this technique in human reproduction would be hazardous.…”