Genetic control of development in 2n/3n chimeric mouse embryos

用ICR或C57 BL/6 J精子与ICR卵受精，在5 μ g/ml细胞松弛素B存在下，体外培养获得三倍体胚胎。当在添加有100 μ M EDTA的改良Whitten培养基中培养时，约60%的这些三原核卵发育成胚泡。在8细胞期，用链霉蛋白酶去除其透明细胞后，每个三倍体胚胎与正常的二倍体ICR或FL（ICR x C57 BL）胚胎聚集。在2n（F1）/3 n（ICR）和2n（ICR）/3 n（F1）两对聚集胚胎中，单囊胚发育率分别为94.0%和89.5%。根据染色体核型分析，2n：3 n细胞比例约为4：6，2n（F1）/3 n（ICR）和2n（ICR）/3 n（F1）囊胚移植到假孕受体后，发育成活胚的比例分别为47.5%和34.4%。在2n（F1）/3 n（ICR）和2n（ICR）/3 n（F1）胚胎中，毛色嵌合率分别为26.2%和27.7%。这些比率显著低于2n/2n嵌合体胚胎衍生的对照幼仔。通过对毛色嵌合体小鼠尾部培养细胞的核型分析，发现尽管2n细胞比例较高，但至少有一部分是由2n和3 n细胞组成的。生殖细胞仅来源于2n/3 n嵌合体中的二倍体细胞。

Triploid embryos were developed from digynic ICR eggs fertilized with ICR or C57BL/6J spermatozoa in the presence of 5myg/ml cytochalasin B in vitro. About 60% of these tri pronuclear eggs developed into the blastocyst when.cultured in a modified Whitten medium supplemented with lOOmuM EDTA. At the eight cell stage, each of the triploid embryos was aggregated with a normal diploid ICR or FL(ICR x C57BL) embryos after removing their zona pellucida with pronase. The rate of development to a single blastocyst was 94.0% and 89.5% in the aggregated pairs of 2n(Fl)/3n(ICR) and 2n(ICR)/3n(Fl)embryos, respectively. The ratio of 2n:3n cells in these chimeric blastocysts was estimated to be about 4:6, based on the numbers of metaphase plates in karyotype analysis.After transfer to the pseudopregnant recipients, 47.5% and 34.4% of 2n(Fl)/3n(ICR) and 2n(ICR)/3n(Fl) blastocysts were developed into viable young. Coat color chimerism was observed in 26.2% and 27.7% of the young derived from 2n(Fl)/3n(ICR) and 2n(ICR)/3n(Fl) embryos, respectively. These rates were significantly lower than that of control young derived from 2n/2n chimeric embryos. By karyotyping of cultured cells from the tail of coat color chimeras, it has been suggested that at least some of them were composed of both 2n and 3n cells, although the proportion of 2n cells was predominantly high.All the offspring obtained from the chimeric mice showed the phenotype originated from diploid embryos, suggesting that the. germ cells were solely derived from the diploid cells in 2n/3n chimeras.