In brief: The regulation of AKT in the endometrium during many cellular processes such as apoptosis and cell survival is crucial during the estrous cycle to ensure fertility. This research shows the specific function of AKT isoforms in the mouse endometrium for litter size, estrous cyclicity and endometrial gland development.
Abstract: Apoptosis and cell survival regulation are crucial processes during the estrous cycle to prepare a receptive uterus during implantation for successful recognition of pregnancy. PI3K/AKT signaling has a crucial role during gestation, and AKT isoforms (1, 2 or 3) are regulated differently in the endometrium during the estrous cycle and embryo implantation. However, the specific roles of these isoforms are still unclear. We have previously shown that AKT isoforms expression during the rat estrous cycle and gestation is differently regulated. The present study aimed to establish the specific role of AKT isoforms in the mouse uterus. The hypothesis is that dysregulation of AKT isoforms expression could cause fertility-related issues in an isoform-specific manner. With four different mouse models and in-house crossbreeding, all isoforms KO combinations (single, double and triple) were obtained in progesterone receptor-expressing tissues. The results demonstrated that in absence of one or more AKT isoforms, female fertility was decreased. Mainly, we have observed smaller litter size, specifically in Akt1-2 KO mice. Additionally, we have found Akt1-2-3 KO mice to be fully infertile. Estrous cyclicity was also disrupted in Akt1-2 KO mice with longer diestrus stage. Moreover, the number of endometrial glands was decreased throughout the estrous cycle suggesting an important role in gland development for AKT1 and AKT2. Our results suggest not only specific roles between each isoform but also a partially redundant function of AKT1 and AKT2 in litter size, estrous cyclicity and endometrial gland development. This highlights the importance of AKT in the physiological regulation of mouse fertility.