Serotonin signaling is required for Wnt-dependent development of the ciliated gastrocoel roof plate and leftward flow in Xenopus

Abstract

2003). In contrast to thismodel,whenFGFsignaling is inhibited, cyclopsand lefty1 are bilaterallyexpressed in thebrain even in the absenceof southpaw. Two transcription factors, six3b and six7, are required for repression of asymmetric lefty1 expression in the brain (Inbal et al., Neuron 2007). We have found that FGF signaling regulates expression of these transcription factors. Fromour results, we propose amodel for brain laterality,where FGF signaling activates six3b and six7,which in turn inhibits lefty1 expression in the brain. Here, southpaw, rather than initiating lefty1 and cyclops, inhibits the repressive activity of six3b and six7 in the left-side of the brain, acting as a permissive factor for normal lefty1 and cyclops expression.