Fig. 1.

Enhancer P7Ur8 activates reporter expression in a neural crest-like pattern. (A) VISTA plot of 12 kb from chicken chromosome 21, showing the percent identity (y-axis) between chicken-human (top) and chicken-mouse (bottom) sequences [conserved (>50% identity) non-coding peaks are highlighted in pink]. Position and relative size of 12 Pax7 upstream regions (P7Ur1 to P7Ur12) tested are numbered at the top of the plot. Each region was cloned in front of a weak promoter driving EGFP, and was co-electroporated with a ubiquitously expressed marker control (RFP). (B-E) P7Ur8-EGFP drives expression in a neural crest-like pattern. (B,C) P7Ur8-EGFP (green) is expressed as early as HH4-HH6 in the neural plate and neural plate border, but not in the NNE. (D) P7Ur8 is expressed in the neural plate, neural plate border and neural folds, but not in the NNE or somites through HH9. (E) By HH12, the oldest stage screened, P7Ur8 is no longer expressed. (F-I) Expression of Pax7 protein (green) is found in the neural plate border at HH5 (F) and later superimposes onto the neural folds (G-I). At HH9, somite expression of Pax7 is clearly visible (arrow, H). At HH12, Pax7 is expressed in the neural folds, somites (arrow) and presomitic mesoderm (I). np, neural plate; npb, neural plate border; nne, non-neural ectoderm; nf, neural folds; s, somites.