Fig. 7
From: TCF/Lef regulates the Gsx ParaHox gene in central nervous system development in chordates
Model for the mode of action of the Bf-Gsx-Up1 + 2b regulatory element. a In the presence of TCF/Lef binding, CNS expression is activated. Additional sequence beyond the Up1c minimal enhancer both increases the efficiency of CNS expression and reveals a partial division of function into the Up1c minimal enhancer nerve cord domain and the Up2b region sensory vesicle domain. The intermediate Up1a region contributes partially to both expression domains. b In the absence of TCF/Lef binding, a latent repressive function is unmasked, preventing expression, even of the reporter vector background domains (not illustrated; see text for details).