Evolutionary scenario for the expression of <i>Dlx</i> genes at the neural plate border in chordates.

<p>Genes for which expression is known to be positive are written black while genes for which no expression has been recorded are indicated in grey. The blue circle represents the hypothetical apparition of <i>Dlx</i> expression in this structure and blue cross indicates loss of expression for both <i>Dlx</i> genes of a bigene cluster. Teleost duplicates in the zebrafish were pooled together to simplify the analysis.