Preeclampsia (PE) is a major hypertensive disorder of pregnancy, leading to serious maternal and fetal complications. Heritability of preeclampsia is estimated at 50% but genes directly involved in this disease are not numerous. The first identified is STOX1, a transcription factor, for which the disease state was associated with the presence of a variant (Y153H), affecting its binding site. In 2020, two new rare mutations were identified in Colombian women affected by the HELLP syndrome, a complication of preeclampsia. T188N affects the DNA binding domain, and R364X is predicted to truncate the protein. The purpose of the present research is to explore the molecular effects of the variant/mutations identified in human patients. We first generated two STOX1 knock-out BeWo-derived cell lines (a classical model of trophoblasts), and then created six stable cell lines overexpressing either the WT or each of the variants Y153H, T188N and R364X. These cell lines were characterized by transcriptomics, live cell imaging, secretion of hCG, and In silico structural analysis of the DNA-protein interaction surface in WT and mutant versions of STOX1.STOX1 knockout alters the response to oxidative stress, and the capacity of the cells to proliferate and fuse. Mutant versions of STOX1 triggered alterations of the gene profiles, in pathways pivotal in preeclampsia, as well as growth, fusion, and management of oxidative stress. The mutations affecting the binding site (Y153H and T188N) modified the affinity of the protein to its target DNA. Our results pinpoint for the first time an abnormal deregulation of the E2F3 transcription factor, a major gene of trophoblast proliferation expressed at the edge of the cell columns of the villous cytotrophoblast. We provide here the first extensive characterization of the effects of variants of STOX1 on trophoblast cells, thus contributing to elucidating how this gene impacts placental physiology.