Figure 1. Identification of a snail shadow enhancer.

The snail gene is expressed in the presumptive mesoderm, (top left in red). An intronic region in neighboring Tim17b2 was shown to be bound by transcription factors that regulate snail [13] and here is shown to drive expression of a lacZ fusion gene in the mesoderm in a pattern qualitatively similar to the endogenous gene (upper right panel). Below, schematic representations of the BAC constructs used in subsequent experiments are aligned to the gene model. In all figures, anterior is to left, dorsal is at top, unless indicated.