The pioneer transcription factor FoxA2 represses Nanog promoter and blocks its induction by AKT in embryonic stem cells

ROVNER, FEDERICO ARIEL; ROBERTI, SABRINA LORENA; FRANCIA, MARCOS GABRIEL; DIAZ, MARIA CANDELARIA; VERNERI, PAULA; COZZA, LUCAS HELIO; ARANOVICH, MELANIE; GARCÍA, MORA RENEÉ; ORSINGHER, VICTOR; LEVI, VALERIA; GUBERMAN, ALEJANDRA SONIA

Valparaíso

Congreso; Latin American Developmental Biology Conference; 2024

Embryonic stem cells (ESCs) are an invaluable model for development research. We have previously found that AKT1 induces the expression of Nanog, a central pluripotency transcription factor (TF), in pluripotency contexts, yet the molecular mechanism remains elusive.Through the cross-matching analysis of the AKT1 phosphorylation targets present in the proteomes and transcriptomes of pluripotent contexts, where AKT1 induces Nanog, and missing in a non-pluripotent cellular environment, where AKT1 lacks this effect, we identified the pioneer TF FoxA2 as a potential mediator of AKT1 effect on Nanog expression. Notably, FoxA2, known for its role in differentiation, is regulated by AKT1 in other scenarios. Previous studies in hepatocytes and cancer cells showed that AKT1 interferes with FoxA2 activity through a mechanism involving its nuclear exclusion and transcriptional inhibition. Our hypothesis posits FOXA2 as the mediator of Nanog gene induction by AKT1. We propose that FOXA2 represses Nanog expression, and that AKT1-mediated nuclear exclusion of FOXA2 is responsible for the upregulation of Nanog in ESCs.Here, we confirmed the presence of FoxA2 in ESCs through immunofluorescence and RT-qPCR, which revealed low albeit detectable levels of FoxA2 in undifferentiated ESCs, with a significant increase during early differentiation. We next studied the effect of FoxA2 on Nanog expression through a luciferase assay and found that FoxA2 represses Nanog promoter activity. Remarkably, the overexpression of this TF completely blocked the induction of Nanog promoter exerted by AKT1, even the enhanced induction produced by the hyperactive E17K-AKT1 mutant, present in some cancers.These results suggest FoxA2´s potential role as the mediator in AKT1-induced Nanog expression. Our ongoing investigations aim to determine whether AKT1 modulates FoxA2 localization in ESCs, providing insights into the regulatory mechanisms governing pluripotency and differentiation. Unraveling this interplay may have implications for controlling pluripotent stem cell fate, especially in regenerative medicine and cancer therapeutics.