The Influence of the Uterine Environment on the Development of Mouse Eggs

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Abstract
Oviducal segmented eggs of the mouse, when transferred beneath the kidney capsule, give rise to trophoblast and extra-embryonic membranes only. Uterine blastocysts transferred to a similar position develop into embryos. Mouse eggs prevented from entering the uterus develop into blastocysts that are morphologically normal. These tube-locked blastocysts, however, that have been denied the uterine environment, do not develop into embryos when transferred to the kidney. -day-old tube-locked blastocysts develop into normal embryos if restored to the uterus. Eggs retained in the oviduct for days, although they appear normal, do not subsequently develop when transferred to the uterus. Oviducal, pre-blastocyst-stage eggs, transferred for a time to the uterus prior to transplantation to the kidney, develop into trophoblast and extra-embryonic membranes only. It is concluded that a blastocyst, to realize totipotency, must be subjected to the uterine environment to days after copulation. The substance producing this effect is termed the ‘uterine factor’. The action of the ‘uterine factor’ and the egg’s limited period of competence to react to it are discussed. A comparison between the potency of tubal mouse eggs and the tubal eggs of other mammals is made.