Summary of the regulatory code that control the entire expression of olSix3.2. (a) Early expression of olSix3.2 in the forebrain and eye depends on enhancers in module D and a silencer activity (activities) in module A. (b) olSix3.2 expression in the lens placode requires multiple elements distributed along modules D to H. (c) During organogenesis, correct olSix3.2 expression requires the activity of different enhancer arranged in a 5'to 3' mode within module I. The activity of I is repressed by module G, which, in turn, is neutralized initially by module H and at later stages (d) by the combined activity of the E and H silencers. Module A is necessary at all stages analyzed to prevent reporter expansion to caudal central nervous system.