AKT1-FOXO4 AXIS RECIPROACLLY REGULATES HEMOCHORIAL PLACENTATION

ABSTRACT Hemochorial placentation involves the differentiation of specialized cells called invasive trophoblast cells possessing the capacity to exit the placenta and invade into the uterus where they restructure the vasculature. Invasive trophoblast cells arise from a well-defined compartment within the placenta, referred to as the junctional zone in the rat and the extravillous trophoblast cell column in the human. In this study, we investigated roles for AKT1, a serine/threonine kinase, in placental development using a genome-edited/loss-of-function rat model. Disruption of AKT1 resulted in placental, fetal, and postnatal growth restriction. Forkhead box O4 ( Foxo4 ), which encodes a transcription factor and known AKT substrate, was abundantly expressed in the junctional zone and invasive trophoblast cells of the rat placentation site. Foxo4 gene disruption using genome-editing resulted in placentomegaly, including an enlarged junctional zone. AKT1 and FOXO4 regulate the expression of many of the same transcripts expressed by trophoblast cells; however, in opposite directions. In summary, we have identified AKT1 and FOXO4 as part of a regulatory network that reciprocally controls critical indices of hemochorial placenta development. SUMMARY STATEMENT Genome-edited rat models were utilized to investigate roles for AKT1 and FOXO4 in hemochorial placentation. AKT1 and FOXO4 possess reciprocal actions in regulating development of the hemochorial placenta.