1097-2765512000JanMol CellLeft-right asymmetric expression of lefty2 and nodal is induced by a signaling pathway that includes the transcription factor FAST2.354735-47The left-right (L-R) asymmetric expression of lefty2 and nodal is controlled by a left side-specific enhancer (ASE). The transcription factor FAST2, which can mediate signaling by TGF beta and activin, has now been identified as a protein that binds to a conserved sequence in ASE. These FAST2 binding sites were both essential and sufficient for L-R asymmetric gene expression. The Fast2 gene is bilaterally expressed when nodal and lefty2 are expressed on the left side. TGF beta and activin can activate the ASE activity in a FAST2-dependent manner, while Nodal can do so in the presence of an EGF-CFC protein. These results suggest that the asymmetric expression of lefty2 and nodal is induced by a left side-specific TGF beta-related factor, which is most likely Nodal itself.SaijohYYDivision of Molecular Biology, Osaka University, Japan.AdachiHHSakumaRRYeoC YCYYashiroKKWatanabeMMHashiguchiHHMochidaKKOhishiSSKawabataMMMiyazonoKKWhitmanMMHamadaHHengJournal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, P.H.S.