Cytogenetic analysis and developmental assessment of mouse embryos derived from in vitro fertilization of oocytes reconstructed by meiosis-II chromosome transplantation.
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-II-t 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.
Mitsui
Akinori
A
Laboratory of Animal Breeding and Reproduction, Faculty of Agriculture, Utsunomiya University, Utsunomiya, Japan.
Yoshizawa
Midori
M
D000818:Animals; D001755:Blastocyst / Q000502:physiology; D002869:Chromosome Aberrations; D002875:Chromosomes / Q000235:genetics*; D020732:Cytogenetic Analysis; D004171:Diploidy; D047108:Embryonic Development / Q000235:genetics; D005260:Female; D005307:Fertilization in Vitro; D008297:Male; D008540:Meiosis; D051379:Mice; D008815:Mice, Inbred Strains; D009865:Oocytes / Q000502:physiology*; D008941:Spindle Apparatus / Q000235:genetics; D013696:Temperature