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The Wnt/β-catenin signaling pathway plays pivotal roles in axis formation during embryogenesis and in adult tissue homeostasis.Glutathione peroxidase 4(GPx4)is a selenoenzyme and participates in peroxides reduction.Its synthesis depends on the availability of element selenium.However,the roles of GPx4 in vertebrate embryonic development and underlying mechanisms are largely unknown.Here,we show that maternal loss of zebrafish gpx4b promotes embryonic dorsal organizer formation,whereas overexpression of GPx4b inhibits the development of the dorsal organizer.Depletion of GPx4/GPx4b increases,while GPx4/GPx4b overexpression decreases,Wnt/β-catenin signaling in vivo and in vitro.Functional and epistatic studies show that GPx4 functions at the Tcf/Lef level independently of selenocysteine activation.Mechanistically,GPx4 interacts with Tcf/Lefs and inhibits Wnt activity by preventing the binding of Tcf/Lefs to promoter of Wnt target genes,resulting in inhibitory action in the presence of Wnt/β-catenin signaling.Our findings unravel GPx4 as a suppressor of Wnt/β-catenin signals,suggesting a possible relationship between the Wnt/β-catenin pathway and selenium via the association of Tcf/Lef family proteins with GPx4.