Expression of genes from the first candidate list within 133 mouse atlas SAGE libraries. Numbers on the X-axis depict each tag-sequence in the first candidate list, and the Y-axis depicts the number of the libraries in which a specific tag-sequence is present. Thus a low bar reflects high tissue specificity, and vice versa. The 8 genes from the 1st list exhibiting differential expression between foregut and hindgut by RT-qPCR as well as whole mount in situ hybridization have significantly lower bars. Names of these genes are provided on top of their respective bars. SPCs: Signaling Pathway Components; TFs: Transcription Factors.