Early development and X‐chromosome inactivation in mouse parthenogenetic embryos

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Abstract
Early development and X‐chromosome inactivation were studied in ethanol‐induced mouse parthenogenones. About 24% of oocytes transferred to 0.5‐day pseudopregnat recipients successfully implanted. However, only 49%, 20%, and 16% of implanted parthenogenones survived 5, 6, and 7 days later, respectively. Abnormal development was evident in every parthenogenone as early as 5 days after activation with the degenerating polar trophectoderm. These embryos were destined to become either small disorganized embryos or embryonic ectoderm vesicles bounded by the visceral endoderm. Only 2 of 51 representative 6‐ to 8‐day parthenogenones sectioned had morphology of the normal egg cylinder, although growth retardation was evident. Spontaneous LT/Sv parthenogenones shared similar morphological features. In late blastocysts, the frequency of cells with an apparently inactivated X chromosome was lower in parthenogenones than in fertilized embryos. The failure of X‐inactivation in the trophectoderm seems to contribute to the defective development of parthenogenones.