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

在5myg/ml细胞松弛素B存在的条件下，用ICR或C57BL/6J精子与digyic ICR卵进行体外受精，获得三倍体胚胎。约60%的三原核卵发育成囊胚。在添加了lOOmuM EDTA的改良Whitten培养基中培养。在8细胞期，每个三倍体胚胎在用pronase去除透明带后与正常的二倍体ICR或FL（ICR × C57BL）胚胎聚集。2n(Fl)/3n（ICR）和2n(ICR)/3n（Fl）胚胎聚集对的囊胚发育率分别为94.0%和89.5%。根据核型分析的中期板数，估计嵌合囊胚中2n:3n细胞的比例约为4:6。移植到假妊娠受体后，2n(Fl)/3n（ICR）和2n(ICR)/3n（Fl）囊胚发育成活仔的比例分别为47.5%和34.4%。2n(Fl)/3n（ICR）胚和2n(ICR)/3n（Fl）胚的幼胚毛色嵌合率分别为26.2%和27.7%。这些比率显著低于由2n/2n嵌合胚胎产生的对照幼崽。通过对毛色嵌合体尾部培养细胞的核型分析表明，至少有一部分细胞是由2n和3n细胞组成的，尽管2n细胞的比例占主导地位。从嵌合小鼠获得的所有后代均显示出来自二倍体胚胎的表型，这表明。生殖细胞完全来源于2n/3n嵌合体的二倍体细胞。

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.