Fig. 4. Overexpression of Zic1 represses the expression of Cath1 and the Math1 enhancer in chick neural tubes. Control (A,C) and ^mycZic1 (B,D), both Myc tagged and in expression vector pMiWIII were electroporated into chick stage HH12-14 and assayed at 24 hours for endogenous levels of Cath1 (A,B) and for the Myc tag (A',B') by immunofluorescence. Arrowheads indicate the electroporated side of the neural tube. The graph shows the number of Cath1-expressing cells/section on the electroporated (gray bars) and non-electroporated (black bars) sides of the neural tube. At least three sections each from three embryos were counted for each construct. (C,D) Math1/lacZ transgene was co-electroporated with the different expression constructs into HH14-17 chick neural tubes and assayed at 24 hours by immunofluorescence for ß-gal (C,D) or Myc (C',D'). Scale bar: 50 µm.