Developmental Biology

Putting on the Brakes

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Science  17 May 2013:
Vol. 340, Issue 6134, pp. 789
DOI: 10.1126/science.340.6134.789-c

Many mammals can delay embryo implantation in order to postpone pregnancy when conditions are unfavorable, or until later birthing seasons. Such embryonic diapause occurs when development is suspended in the blastocyst stage and implantation is prevented. Endocrine factors trigger diapause; however, the mechanism coordinating blastocyst dormancy and uterine quiescence remains unknown. Cha et al. show that the gene Msx1 is expressed when implantation is delayed, whether it occurs because of maternal lactation, ovariectomy, or the addition of antiestrogen. When implantation initiates, Msx1 expression is down-regulated. Further, genetic inactivation of Msx1 or Msx2 in the uterus results in the development of fewer blastocysts. In order for delayed implantation to occur, blastocyst dormancy must coincide with uterine quiescence. This work demonstrates a critical role of Msx1 in maternal regulation of embryonic diapause. The study finds that three distantly related mammalian orders—Rodentia (mouse), Carnivora (American mink), and Diprotodontia (Australian tammar wallaby)—display correlations between Msx expression and diapause, suggesting the presence of a conserved reproductive strategy across mammalian species.

Open Biol. 3, 10.1098/rsob.130035 (2013).

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